“GREEN” COMPOSITES BASED ON RECYCLED PAPER PRODUCTS AND BIODEGRADABLE RESINS

INTRODUCTION

Composites

Composites play a crucial role in various everyday applications due to their customizable properties, making them essential in industries such as automotive, sports, healthcare, and construction Engineered for superior mechanical performance, these materials are integral to modern society, reflecting a high production rate to satisfy the demands of today's consumers.

A composite is a combination of two different materials, each contributing unique and desirable properties By merging these distinct materials, the resulting composite exhibits a range of enhanced characteristics tailored to specific applications This versatility in property customization is a key reason for the growing popularity of composites in various industries.

Resin, a moldable glue-like substance, is commonly used in composites, often combined with high-strength fibers or recycled paper products to enhance properties Traditionally, resin is derived from petroleum, with polypropylene being a prevalent choice This thesis aims to replace petroleum-based resins with eco-friendly alternatives by utilizing plant-based fibers By combining this sustainable resin with recycled paper products, a composite can be created that not only meets desired performance standards but also contributes to a more sustainable future.

Table 1.1 Mechanical Properties of Petroleum-based Resin and Composites [1]

Tensile Stress at Max Load (MPa)

Tensile Strain at Max Load (%)

The Limitations of Petroleum-based Composites

Society's daily reliance on composites has led to a significant dependence on petroleum By combining resins like epoxies and polyurethanes with fibers such as aramid, graphite, and glass, we achieve high-strength materials essential for various applications.

Advanced composites rely heavily on petroleum, which accounts for approximately 7-8% of its usage in producing materials like fibers and plastics Currently, nearly all resins and fibers are petroleum-based, raising significant concerns due to their non-biodegradable and environmentally harmful nature These factors highlight the urgent need to address the limitations of petroleum, particularly regarding resource scarcity, to ensure a sustainable future.

Petroleum is a non-renewable resource, with estimates suggesting it could be depleted in just 50 years due to excessive consumption, occurring at a rate 100,000 times faster than its natural production This impending scarcity poses significant challenges, including the inability to produce essential composites that society relies on, leading to increased prices and manufacturing costs As petroleum becomes more limited, dependence on countries that control the remaining supply grows, highlighting the urgent need for renewable resources that can provide sustainable alternatives and alleviate reliance on dwindling petroleum reserves.

The disposal of petroleum-based composites poses significant challenges due to their composition of two incompatible materials, making recycling and reuse difficult As these products reach the end of their life cycle, they do not decompose in typical environments and are primarily sent to landfills This accelerated consumption of such products leads to rapid landfill space depletion With the Earth's limited landfill capacity, the situation is becoming increasingly critical; for example, the number of landfills in the United States has drastically declined from 8,000 in 1988.

By 1998, only 2,314 landfills remained, highlighting a critical issue: the world is rapidly running out of landfill space Instead of seeking additional landfill sites, the focus should shift to minimizing landfill usage This can be effectively addressed by reducing the production of petroleum-based composites, which contribute significantly to waste accumulation.

Petroleum-based chemicals significantly contribute to the pollution of freshwater sources during the production of fibers, resins, and composites, further diminishing the already limited supply of potable water While the Earth is covered by 70% water, a mere 2.5% constitutes freshwater, with 70% of this frozen in glaciers and 29% trapped in inaccessible underground reservoirs Only about 1% of freshwater is available in rivers and lakes, translating to just 0.025% of the world's total water being usable Although desalination can convert salt water into freshwater, it currently meets only 0.25% of global water demands Thus, the combination of increasing water scarcity and pollution from petroleum-based chemicals exacerbates the challenges in accessing clean water.

The use of petroleum significantly contributes to rising carbon concentrations in the environment, primarily through the emission of carbon dioxide (CO2) when fossil fuels are burned Petroleum is a major source of CO2 emissions, which account for approximately 99% of greenhouse gases that contribute to global warming by trapping infrared radiation To combat this issue, it is crucial not only to reduce future CO2 emissions but also to implement strategies for removing existing CO2 from the atmosphere This process, known as carbon sequestration, can be effectively supported by natural fibers, which have the ability to both lower CO2 emissions and capture carbon, similar to the natural processes of plants.

The over-reliance on petroleum highlights the urgent need for sustainable alternatives that are renewable and non-exhaustive While solar and wind energy have emerged as viable replacements for petroleum in electricity generation, the challenge of finding non-petroleum-based materials remains Research into "Green" Composites is essential to develop materials that minimize dependence on petroleum and promote environmental sustainability.

"Truly green" composites are fully degradable materials sourced directly from plants, allowing them to return to the earth as compost without generating waste These eco-friendly composites possess the essential properties of traditional materials while avoiding the environmental issues associated with petroleum With an abundant supply of plants that can be sustainably grown worldwide, reliance on petroleum sources is diminished, leading to more affordable options Additionally, green composites can be composted, eliminating landfill waste and preventing pollution of limited resources Unlike their petroleum-based counterparts, these composites are produced without harsh chemicals, ensuring a safer environment for both the ecosystem and workers involved in their production.

"Green" composites, known for their environmentally-friendly attributes, offer versatile applications due to their impressive mechanical properties and customizable specifications These materials are suitable for various uses, including furniture such as desks and tables, sports equipment like tennis racquets and skateboards, transportation components such as car parts and airplane panels, as well as packaging solutions and housing elements like walls and floors.

CHATPER 2 LITERATURE REVIEW 2.1 Truly “Green” Composites

The increasing demand for sustainable and eco-friendly composites has spurred research and development in "green" composites, which are characterized by their biodegradable and environmentally-safe properties These innovative materials can be composted or disposed of without harming the environment They are versatile, suitable for applications ranging from short-term use to those with lifecycles of one to several years.

Research on "green" composites emphasizes the combination of natural fibers with biodegradable resins, which are preferred for their superior strength and modulus compared to metals The popularity of natural fibers stems from their global availability and unique hollow structure, which reduces density and enables the creation of lightweight composites This hollow structure also enhances acoustical and thermal insulation properties.

Recycling paper has gained significant attention from consumers and manufacturers worldwide, prompting concerns from governments and organizations about its environmental impact This focus has led to the creation of paper products from waste fiber and increased recycling behaviors among consumers There are three primary methods of recycling paper: mill broke, pre-consumer waste, and post-consumer waste Mill broke refers to waste from paper mills, pre-consumer waste includes paper that has not yet reached consumers, and post-consumer waste is paper that has been used and discarded The recycling process restores paper to its original wood pulp form, allowing for repeated manufacturing In contrast, alternatives like burying and burning paper contribute to landfill issues and air pollution, making recycling the more sustainable option for preserving the environment.

The integration of recycled paper in "green" composites represents a burgeoning area of research Investigating the economic implications of recycled paper is crucial, as highlighted by Pati et al [11], who analyzed the financial impact on paper manufacturing companies opting for recycled materials over virgin wood pulp While recycled paper may be low-cost or even free, associated expenses arise from collection, transportation, and processing Nevertheless, the study concluded that recycling proves more economically viable than using virgin wood pulp, primarily due to the scarcity of raw materials required for traditional paper production [11].

Therefore, using recycled paper products to manufacture “green” composites should have significant economic benefits as opposed to cultivating natural fibers.

Newspaper, a widely used paper product with single-use functionality, is discarded after its initial use, resulting in approximately 8.7 million tons consumed annually in the U.S This has sparked a creative movement among artists and innovators seeking to repurpose newspaper for various applications, such as wrapping paper, furniture, and jewelry While these endeavors reflect a growing consumer interest in reusing newspaper, the inherent properties of the material limit its practicality without reinforcements If newspaper could be enhanced to meet the necessary requirements for composite applications, the potential for practical recycled newspaper products would significantly increase.

Figure 2.2 Recycled Newspaper Products: (a) Newspaper Table and Chair [13], (b)

The Solution: “Green” Composites

Soy Protein Isolate (SPI) powder, specifically PRO-FAM ® 974, was sourced from Archer Daniels Midland Co in Decatur, IL Analytical grade glycerol was obtained from Fisher Scientific in Pittsburgh, PA, while Phytagel ® was acquired from Sigma-Aldrich Co in St Louis.

MO The starches used were Novastar – TG (pre-gelatinized tapioca starch with galacto mannen), Novastar – MG (pre-gelatinized maize starch with galacto mannen), Novastar –

Nova Transfers Pvt Ltd in Mumbai, India, supplied various pre-gelatinized starches, including PG (potato starch with galacto mann), Novastar – TGS (tapioca starch with glycol stearate as plasticizer), Novastar – MGS (maize starch with glycol stearate as plasticizer), and Novastar – PGS (potato starch with glycol stearate as plasticizer) Additionally, sorbitol was sourced from Sigma-Aldrich Co in St Louis, MO, while CMG (Carboxyl Methyl Gum), CMS (Carboxyl Methyl Starch), and CMT (Carboxyl Methyl Tamarind) were also provided by Nova Transfers Pvt Ltd.

Bounty® paper towels were sourced from Proctor & Gamble in Cincinnati, OH, while Georgia-Pacific Acclaim® and enMotion® paper towels were obtained from Georgia-Pacific in Atlanta, GA Additionally, Kleenex® Scottguard paper towels were purchased from Kimberly-Clark Corporation in Neenah, WI The Cornell Daily Sun newspaper was collected from the Cornell University campus in Ithaca, NY.

LITERATURE REVIEW

Truly “Green” Composites

The increasing demand for sustainable and eco-friendly composites has sparked significant research into "green" composites, which are characterized by their biodegradable properties and minimal environmental impact These materials can be composted or disposed of safely, making them a responsible choice for various applications Green composites are versatile, suitable for short-term use, one-time applications, and products with lifecycles ranging from one to several years.

Research on "green" composites emphasizes the combination of natural fibers with biodegradable resins, which are preferred for their superior strength and modulus compared to metals The popularity of natural fibers stems from their global availability and unique hollow structure, which reduces density and enables their use in lightweight composites This hollow structure also enhances acoustical and thermal insulation properties.

Recycled Paper Products

Recycling paper is increasingly important for consumers and manufacturers, as global concerns have prompted efforts to create paper products from waste fiber and encourage recycling habits There are three primary methods of recycling paper: mill broke, pre-consumer waste, and post-consumer waste Mill broke refers to waste recovered from paper mills, pre-consumer waste involves paper that has not yet reached consumers, and post-consumer waste consists of used paper products The recycling process transforms paper back into its original wood pulp form, allowing the manufacturing cycle to restart In contrast, alternative disposal methods like burying and burning lead to landfill issues and air pollution, making recycling the more sustainable and environmentally friendly choice.

The exploration of recycled paper in "green" composites is an emerging field, with significant research highlighting its economic implications Pati et al [11] examined the financial impacts of using recycled paper instead of virgin wood pulp in paper manufacturing, revealing that while recycled paper may be low-cost or free, it incurs additional expenses related to collection, transportation, and processing Nonetheless, the study concluded that recycling is economically advantageous compared to virgin wood pulp, primarily due to the scarcity of raw materials needed for traditional paper production [11].

Therefore, using recycled paper products to manufacture “green” composites should have significant economic benefits as opposed to cultivating natural fibers.

Newspapers are typically single-use products, with approximately 8.7 million tons consumed annually in the U.S This abundance has sparked creativity among artists and consumers seeking to repurpose newspapers for various projects, such as wrapping paper, furniture, and jewelry However, these creative applications often lack practicality due to the inherent properties of unreinforced newspaper If methods were developed to enhance the properties of recycled newspaper, it could lead to more viable composite applications, making it a valuable resource for sustainable projects.

Figure 2.2 Recycled Newspaper Products: (a) Newspaper Table and Chair [13], (b)

Newspaper, primarily made from pine tree wood pulp containing approximately 59.9% cellulose, 27.8% lignin, and 8.3% hemicellulose, plays a significant role in the scientific industry as a reinforcement for composites Research by Ashori et al demonstrated the effectiveness of recycled newspaper in wood fiber-plastic composites, where it was combined with high-density polyethylene (HDPE) and polypropylene (PP) The study found that integrating recycled newspaper with maleated polypropylene enhanced the mechanical properties of the composites compared to those without it However, despite their recyclability, these composites cannot be considered truly "green" due to the petroleum-derived fibers, which prevent full degradation in natural environments, highlighting the need for genuinely sustainable alternatives using recycled newspaper.

Recycled newspaper serves as a valuable resource not only for reinforcing composites but also for producing cellulose acetate, which finds applications in the textile and cigarette industries A study conducted by Filho et al demonstrated the successful production of cellulose acetate from recycled newspaper, highlighting its potential as a viable alternative to commercial cellulose acetate The research evaluated key properties, including thermal stability and water vapor flux, confirming that cellulose acetate derived from recycled newspaper is a competitive substitute in various applications.

Research indicates that recycled newspaper can serve various functions beyond its original purpose; however, previous studies often involved modifying its chemistry or using it solely as reinforcement This thesis focuses on utilizing newspaper as the primary reinforcing element in a composite, employing fully sustainable resins without any petroleum-based materials.

While recycled newspaper has been extensively studied for sustainable product development, there is a notable lack of research on other paper products like recycled paper towels Similar to newspaper, recycled paper towels are designed for single-use, making them a potential candidate for composite materials Despite the popularity of newspaper in composite applications due to its availability and intended one-time use, recycled paper towels possess unique properties that could enhance the production of resin-reinforced composites.

Paper towels are designed to be porous and absorbent, allowing them to effectively soak up liquids during cleaning tasks Unlike napkins and tissues, they are engineered for strength and durability, even when wet Their capacity to hold resins and enhance the mechanical properties of composites positions recycled paper towels as an excellent subject for research in composite materials.

While there have been no studies on the use of recycled paper towels in composite manufacturing, research on the recycled paper towel market has been conducted Srinivasan et al examined consumer willingness to buy recycled paper towels to support environmental efforts In the 1990s, paper towel companies began using ecolabels on their packaging to promote environmental safety Their findings revealed that consumers' environmental concerns significantly influenced their purchasing decisions regarding ecolabeled paper towels, indicating a growing interest in the reuse and recycling of not just newspapers, but also paper towels.

Soy Protein

Soy protein, extracted from soybeans, is utilized in various commercial products, including plywood adhesives, paper coatings, and printing ink binders While primarily used for animal feed in the United States, soy protein's excellent film-forming ability makes it suitable for sustainable films It is available in three forms: soy protein isolate (SPI), soy protein concentrate (SPC), and soy flour (SF), with SPI containing the highest protein percentage and superior mechanical properties, making it the preferred choice for resin applications in experiments.

Table 2.1 Composition of Commercial Soy Proteins [18]

Soy protein isolate (SPI) is increasingly favored for use in "green" composites due to its high availability and superior mechanical properties Although SPI is being explored for engineering applications and packaging materials, its mechanical properties currently fall short for these uses, prompting ongoing research aimed at enhancements The curing process facilitates cross-linking among soy protein chains, and recent modifications have introduced additional cross-links to the protein structure These advancements in cross-linking have demonstrated a positive impact on the mechanical properties of SPI, resulting from the strengthened linkages between SPI molecules.

SPI exhibits promising mechanical properties for engineering and packaging applications, but its brittleness when dry limits its usability This low fracture strain makes handling and processing challenging To enhance its applicability, SPI must be combined with other materials, such as paper products or natural fibers, to increase its fracture strain This improvement is essential to ensure that the SPI composite maintains superior mechanical properties without breaking before the accompanying materials.

To enhance the ductility of dried soy protein isolate (SPI) and increase fracture strain, plasticizers are incorporated into the SPI solution These small molecules improve material flexibility by introducing more ends compared to longer molecules, resulting in greater free volume within the system This increased free volume effectively lowers the glass transition temperature, making the material less rigid and more pliable.

“glassy”, which increases the strain.

Figure 2.3 Number of Ends in (a) One Long Molecule and (b) Several Small Molecules

To enhance the mechanical properties of soy protein isolate (SPI), various polyol-based plasticizers, including glycerol, propylene glycol, 1,2-butanediol, and 1,3-butanediol, have been incorporated Research by Mo et al revealed that glycerol and propylene glycol increased free volume and lowered the glass transition temperature of SPI Additionally, Wang et al identified glycerol as the most suitable plasticizer for SPI due to its non-toxic nature, in contrast to the more volatile propylene glycol Consequently, glycerol was selected as the plasticizer for SPI resin to effectively reduce brittleness.

2.3.3 Modification of SPI Using Phytagel ®

Phytagel ® is a biopolymer gellan derived from bacterial fermentation, capable of forming gels through hydrogen bonding Research by Lodha and Netravali explored the integration of Phytagel ® into soy protein isolate (SPI) resin, resulting in a highly cross-linked interpenetrating polymer network (IPN) that significantly enhanced the tensile properties of the modified SPI resins An IPN comprises two or more synthesized polymer networks, with Phytagel ® contributing to a robust and stable gel structure through cross-linking The improved mechanical properties achieved by incorporating Phytagel ® into SPI make this modified resin a valuable subject of study.

(a) (b) resin for “green” composites, these studies have used natural fibers in the composite,whereas this thesis uses recycled paper products.

Starch

Starch is an abundant, biodegradable, and renewable polymer, commonly found in natural products such as rice, maize, potatoes, tapioca, and beans Composed of repeated glucose chains, starch undergoes gelatinization when granules swell and cross-link in the presence of excess water, forming a three-dimensional matrix that enhances its stiffness This thickening property enables starch to be utilized effectively as a resin.

Figure 2.4 Chemical Structure of Starch: Repeated Glucose Units [28].

Recent research into the use of starch as a resin for eco-friendly composites highlights its advantages due to global availability and biodegradability This study focuses on tapioca, maize, and potato starches, examining their potential as primary resin components rather than mere additives to other resins Previous studies, such as those by Sailaja et al., demonstrated that incorporating tapioca starch into low-density polyethylene (LDPE) enhanced the mechanical properties of the resin; however, LDPE lacks biodegradability and sustainability In contrast, this research emphasizes starch as the main resin ingredient, combined with other sustainable materials to ensure both the resin and composite remain environmentally friendly.

2.4.1 Plasticization of Starch Using Glycol Stearate

This study examined tapioca, maize, and potato starches with and without glycol stearate, a plasticizer that enhances ductility, making the starches less brittle for processing Research by Kumar et al indicated that adding water during gelatinization significantly reduced starch crystallinity, while glycol stearate facilitated the formation of crystalline regions within gelatinized starch Acting as a molecular adhesive, glycol stearate not only improved the mechanical properties of starch by increasing strain but also enhanced strength and stiffness through increased crystallinity.

2.4.2 Plasticization of Starch Using Sorbitol

Sorbitol serves as an effective plasticizer for starch, enhancing its properties by increasing free volume and lowering the glass transition temperature, which reduces brittleness and improves handling Research, including a study by Krogars et al., indicates that a mixture of sorbitol and glycerol can enhance the mechanical properties of starch resins However, unlike this thesis, which separately examines the effects of glycerol and sorbitol, previous studies often combined them Notably, McHugh et al found that sorbitol outperformed glycerol in producing superior mechanical properties in edible films made from starch Consequently, sorbitol was selected as the plasticizer for starch resin in this research.

2.4.3 Modification of Starch Using CMG, CMS and CMT

This study investigates the use of Carboxyl Methyl Gum (CMT), Carboxyl Methyl Tamarind (CMT), and Carboxyl Methyl Starch (CMS) to enhance the mechanical properties of starch-based resin These thickeners, derived from Carboxyl Methyl Cellulose (CMC), are known for their high viscosity and are commonly used in various applications, including food products like ice cream, as well as in toothpaste, paints, and detergents The research focuses on incorporating these thickeners to increase the viscosity of starch resin solutions, ultimately aiming to improve the mechanical properties of the resulting resin films while maintaining eco-friendly characteristics.

An Innovative Step in “Green” Composite Progress

This thesis explores innovative methods and materials for producing composites, focusing on the use of recycled paper products instead of traditional natural fibers While "green" composites have been previously examined, this study highlights the growing market demand for recycled paper products and presents a novel approach to integrating them into everyday applications.

Soy Protein Isolate (SPI) is increasingly recognized as a valuable biodegradable resin, particularly in the development of recycled paper product composites This study explores the potential of modified-SPI as a resin alternative and highlights the advantages of starch-based resins, which are more readily available and may offer superior properties compared to SPI for biodegradable applications.

Soy Protein Isolate (SPI) powder, specifically PRO-FAM ® 974, was sourced from Archer Daniels Midland Co in Decatur, IL For analytical purposes, glycerol was obtained from Fisher Scientific in Pittsburgh, PA, while Phytagel ® was acquired from Sigma-Aldrich Co located in St Louis.

Nova Transfers Pvt Ltd in Mumbai, India, supplied various pre-gelatinized starches, including PG (pre-gelatinized potato starch with galacto mannen), Novastar – TGS (pre-gelatinized tapioca starch with glycol stearate as plasticizer), Novastar – MGS (pre-gelatinized maize starch with glycol stearate as plasticizer), and Novastar – PGS (pre-gelatinized potato starch with glycol stearate as plasticizer) Additionally, sorbitol was sourced from Sigma-Aldrich Co in St Louis, MO, while CMG (Carboxyl Methyl Gum), CMS (Carboxyl Methyl Starch), and CMT (Carboxyl Methyl Tamarind) were also provided by Nova Transfers Pvt Ltd.

Bounty® paper towels were sourced from Proctor & Gamble in Cincinnati, OH, while Georgia-Pacific Acclaim® and enMotion® paper towels were obtained from Georgia-Pacific in Atlanta, GA Additionally, Kleenex® Scottguard paper towels were purchased from Kimberly-Clark Corporation in Neenah, WI The Cornell Daily Sun newspaper was collected from the Cornell University campus in Ithaca, NY.

3.2 Processing and Modification of Resins

3.2.1 Resin Preparation of Soy Protein Isolate (SPI) Resin Sheet

SPI resin was characterized by creating a resin sheet using a Teflon®-coated mold This mold was crafted from a square Teflon® sheet, which was cut to the required dimensions and affixed to a glass plate The edges of the sheet were folded inward by one inch on each side, effectively forming a box that contained the resin during the curing process.

The SPI resin was prepared through a pre-curing process, which involved adding a specific amount of SPI powder to a glass beaker To this, 20% of glycerol by total SPI weight was incorporated, followed by the addition of 15 times the weight of SPI in distilled water (15 mL per gram of SPI) The mixture was magnetically stirred at room temperature for 30 minutes to achieve a uniform dispersion Subsequently, it was transferred to a water bath at 80ºC and stirred for another 30 minutes.

This pre-cured solution was poured into the Teflon ® mold and placed in an oven at

The resin film was dried overnight at 50 ºC and subsequently removed from the Teflon ® mold It was then conditioned for two hours at 21ºC and 65% relative humidity, adhering to ASTM D 1776-98 standards After conditioning, the resin was sandwiched between two aluminum plates and cured through hot pressing at 120ºC under a pressure of 38,300 lbs for 15 minutes, utilizing a Carver Hydraulic hot press (model 3891-4PROA00) Following the curing process, the resin was placed back in the conditioning room for an additional three days.

Figure 3.1 Carver Hydraulic Hot Press for Curing Process

To enhance the mechanical properties of SPI resin, Phytagel® was incorporated during the pre-curing process The specified percentage of Phytagel® powder, based on the total weight of SPI, was combined with 50 times its weight in distilled water in a glass beaker This mixture was manually stirred with an aluminum stirrer to eliminate gel clumps formed during the mixing After achieving a smooth consistency, the Phytagel® solution was added to the SPI solution for pre-curing, optimizing the resin's performance.

3.2.3 Resin Preparation of Starch Resin Sheet

The preparation of the starch resin was consistent for all six starches (TG, MG,

In this experiment, various starch types (PG, TGS, MGS, and PGS) were utilized A specific amount of starch powder was measured and placed into a glass beaker, followed by the manual addition of sorbitol using an aluminum stirrer to ensure even dispersion of the powders Subsequently, 50 mL of distilled water was added for every gram of starch, resulting in a total of 50 times the weight of the starch The mixture was then magnetically stirred at room temperature for 30 minutes to achieve a homogenous blend.

30 minutes, the mixture was then transferred to a water bath at 80ºC and stirred for an additional 30 minutes.

The pre-cured resin solution was poured into a Teflon® mold and dried overnight in an oven at 45ºC The next day, the dried resin film was removed and conditioned at 21ºC with 65% relative humidity for about 30 minutes It was then cured through hot pressing at 110ºC under 38,300 lbs of pressure for 15 minutes, after which the resin was placed back in the conditioning room for three days.

The mechanical properties of MG and MGS starch resins were enhanced by modifying the plasticizer content Sorbitol was removed from the starch solution and replaced with CMG, CMS, and CMT thickeners The appropriate amount of thickener was added to the starch powder according to the desired starch weight percentage Subsequently, the starch and plasticizer powders were manually stirred to ensure even dispersion before proceeding with the starch resin preparation process.

The MGS starch resin was modified by incorporating 30% by weight of CMG to enhance its tensile strain To achieve this, sorbitol was added in powder form as a plasticizer, with its quantity determined by the desired percentage of starch weight The three powders were thoroughly combined by hand to ensure a uniform mixture before proceeding with the film preparation process as previously outlined for the starch resin.

Composites were fabricated using recycled paper products and either modified SPI resin or modified starch resin A schematic diagram of the composite fabrication process can be found in Figure 3.2.

Figure 3.2 Schematic Diagram of Composite Fabrication

3.3.1 Recycled Paper Products with SPI and Phytagel ® Resin

Composites were created using recycled paper products and SPI combined with Phytagel ® resin To fabricate the specimens, squares were cut from the paper and weighed, with the size and number of squares based on the required quantity Pre-cured SPI with 30% Phytagel ® resin was then applied to each paper sheet, ensuring thorough impregnation by hand on both sides The sheets were subsequently dried in an oven at 65ºC, and their weight was measured to assess the resin composition This impregnation process was repeated until the target resin composition by weight was achieved.

After drying, the paper sheets were conditioned at 21ºC and 65% relative humidity for 30 minutes A single impregnated paper sheet underwent hot-pressing, while multiple sheets were stacked and pressed at 120ºC under 38,300 lbs of pressure for 25 minutes to form a composite The aluminum plates used were either flat or corrugated, based on the desired composite shape Following the hot-pressing process, the samples were placed back in the conditioning room for three days.

3.3.2 Recycled Paper Products with Starch Resin

EXPERIMENTAL PROCEDURE

Materials

Soy Protein Isolate (SPI) powder, specifically PRO-FAM ® 974, was sourced from Archer Daniels Midland Co in Decatur, IL, while analytical grade glycerol was acquired from Fisher Scientific in Pittsburgh, PA Additionally, Phytagel ® was obtained from Sigma-Aldrich Co in St Louis.

Nova Transfers Pvt Ltd in Mumbai, India, supplied various pre-gelatinized starches, including PG (pre-gelatinized potato starch with galacto mann), Novastar – TGS (pre-gelatinized tapioca starch with glycol stearate as plasticizer), Novastar – MGS (pre-gelatinized maize starch with glycol stearate as plasticizer), and Novastar – PGS (pre-gelatinized potato starch with glycol stearate as plasticizer) Additionally, sorbitol was sourced from Sigma-Aldrich Co in St Louis, MO, along with CMG (Carboxyl Methyl Gum), CMS (Carboxyl Methyl Starch), and CMT (Carboxyl Methyl Tamarind), which were also provided by Nova Transfers Pvt Ltd.

Bounty® paper towels were sourced from Proctor & Gamble in Cincinnati, OH, while Georgia-Pacific Acclaim® and enMotion® paper towels were obtained from Georgia-Pacific in Atlanta, GA Additionally, Kleenex® Scottguard paper towels were purchased from Kimberly-Clark Corporation in Neenah, WI, and the Cornell Daily Sun newspaper was collected from the Cornell University campus in Ithaca, NY.

Processing and Modification of Resins

3.2.1 Resin Preparation of Soy Protein Isolate (SPI) Resin Sheet

SPI resin was characterized by creating a resin sheet using a Teflon®-coated mold This mold was crafted from a square Teflon® sheet, which was cut to the required dimensions and affixed to a glass plate The edges of the Teflon® sheet were folded inward by one inch on each side, forming walls that contained the resin during the curing process.

The SPI resin preparation began with a "pre-curing" process, where a specified amount of SPI powder was placed in a glass beaker To this, 20% glycerol by weight of the SPI was added, followed by 15 times the weight of SPI in distilled water (15 mL per gram) The mixture was magnetically stirred at room temperature for 30 minutes to achieve a uniform dispersion Subsequently, it was transferred to a water bath at 80ºC and stirred for an additional 30 minutes.

This pre-cured solution was poured into the Teflon ® mold and placed in an oven at

The dried resin film, initially processed at 50 ºC overnight, was removed from the Teflon® mold and conditioned at 21ºC and 65% relative humidity for two hours, adhering to ASTM D 1776-98 standards It was then sandwiched between two aluminum plates and cured through hot pressing at 120ºC under a pressure of 38,300 lbs for 15 minutes using a Carver Hydraulic hot press (model 3891-4PROA00) After the curing process, the resin remained in the conditioning room for an additional three days.

Figure 3.1 Carver Hydraulic Hot Press for Curing Process

SPI resin was enhanced by incorporating Phytagel® to boost its mechanical properties In the pre-curing phase, a specific percentage of Phytagel® powder, based on the total weight of SPI, was measured into a glass beaker To this, 50 mL of distilled water per gram of Phytagel® was added, and the mixture was manually stirred with an aluminum stirrer to eliminate gel clumps After thorough mixing, the resulting solution was integrated into the SPI resin for pre-curing.

3.2.3 Resin Preparation of Starch Resin Sheet

The preparation of the starch resin was consistent for all six starches (TG, MG,

In this experiment, various starch types (PG, TGS, MGS, and PGS) were utilized A specific quantity of starch powder was measured and placed into a glass beaker, followed by the addition of sorbitol, which was manually mixed using an aluminum stirrer for even dispersion Subsequently, 50 mL of distilled water was added for every gram of starch, resulting in a total of 50 times the weight of the starch The mixture was then magnetically stirred at room temperature for 30 minutes to ensure thorough blending.

30 minutes, the mixture was then transferred to a water bath at 80ºC and stirred for an additional 30 minutes.

The pre-cured solution was poured into a Teflon® mold and dried overnight in an oven at 45ºC The next day, the dried resin film was removed and conditioned at 21ºC with 65% relative humidity for about 30 minutes It was then cured through hot pressing at 110ºC under a pressure of 38,300 lbs for 15 minutes After curing, the resin was stored in the conditioning room for three days.

The mechanical properties of MG and MGS starch resins were enhanced by modifying the plasticizer content Sorbitol was removed from the starch solution and replaced with CMG, CMS, and CMT thickeners The appropriate amount of thickener was added to the starch powder according to the desired starch weight percentage Subsequently, the starch and plasticizer powders were mixed by hand to ensure an even distribution before proceeding with the starch resin preparation process.

The MGS starch resin was modified by incorporating 30% by weight of CMG to enhance its tensile strain To achieve this, sorbitol was introduced as a plasticizer in powder form The three powders were thoroughly combined by hand to ensure a uniform mixture, with the quantity of sorbitol determined by the desired starch weight percentage Following this, the film preparation process was executed as previously outlined for the starch resin.

Composite Fabrication

Composites were fabricated using recycled paper products and either modified SPI resin or modified starch resin A schematic diagram of the composite fabrication process can be found in Figure 3.2.

Figure 3.2 Schematic Diagram of Composite Fabrication

3.3.1 Recycled Paper Products with SPI and Phytagel ® Resin

Composites were created using recycled paper products and SPI combined with Phytagel® resin The process began by cutting and weighing squares from the paper, with dimensions based on the required quantity Pre-cured

After drying, the paper sheets were conditioned at 21ºC and 65% relative humidity for 30 minutes A single sheet of impregnated paper underwent hot-pressing, followed by the stacking and pressing of multiple sheets at 120ºC under 38,300 lbs of pressure for 25 minutes, resulting in a composite material The aluminum plates used were either flat or corrugated, based on the desired composite shape Following the hot-pressing process, the samples were placed back in the conditioning room for three days.

3.3.2 Recycled Paper Products with Starch Resin

Composites were created using Georgia-Pacific Acclaim® and enMotion® paper towels, along with Cornell Daily Sun newspaper, incorporating MGS resin with 30% CMG and varying percentages of sorbitol, resulting in six distinct composite formulations.

A square was cut from the paper product and weighed, with the size and quantity of squares based on the desired amount Pre-cured starch resin was poured onto the individual sheets, which were then hand-impregnated with resin The sheets were dried in an oven at 65ºC, and once dry, were weighed again to assess the resin composition This procedure was repeated until the resin made up 40-50% of the total composite weight.

After drying, the treated paper sheets were stored in a conditioning room at 21ºC and 65% relative humidity overnight The next day, the curing process was conducted using the same method as for the recycled paper products with SPI/30% Phytagel® For visual reference, images illustrating the different stages of the composite fabrication process are available in Figure 3.3.

Figure 3.3 Images of Paper Towel: (a) Dry; (b) After Resin Pre-Curing; (c) 7 Sheets After

Pre-Curing; (d) 7 Sheets After Curing Using Corrugated Mold

Characterization Techniques

The tensile properties of resins, composites, and paper products were evaluated following the ASTM D 882-02 standard Specimens were prepared as 1 cm wide strips and conditioned for three days at 21ºC and 65% relative humidity before testing An Instron universal testing machine (model 55-66, Instron Co., Canton, MA) was utilized to perform the tensile tests, with the machine calculating the tensile properties Relevant parameters used during testing are listed in Table 3.1, and the specimen dimensions are illustrated in Figure 3.5.

Figure 3.4 Instron Testing Machine Used to Determine Tensile Properties

Table 3.1 Instron Parameters for Tensile Testing

The moisture content of resins, composites, and paper products was assessed using the ASTM D 1576-90 procedure with a moisture/volatiles tester (model-SAS, C.W Brabender Instruments, Inc., South Hackensack, NJ) Specimens were conditioned at 21ºC and 65% relative humidity before tensile testing After weighing the specimen strips, they were subjected to drying at 105ºC for 24 hours The moisture content was calculated using the formula where A represents the weight of the original specimens and B denotes the weight after drying.

Figure 3.5 Dimensions of a Specimen Used for Tensile Testing

CHAPTER 4 RESULTS AND DISCUSSION 4.1 Soy Protein Isolate Modified with Phytagel ®

Phytagel® was incorporated into Soy Protein Isolate (SPI) to enhance its mechanical properties, with glycerol serving as a plasticizer at a concentration of 20% by weight of SPI Resin films were created by adding 10%, 20%, and 30% Phytagel® by weight of SPI The formulations included a SPI-based solution of 10g SPI, 2g glycerol, and 150 mL distilled water, alongside a Phytagel® solution with varying amounts (1.0g, 2.0g, or 3.0g) and corresponding volumes of distilled water These solutions were prepared separately before being combined Comparative results of these resins against SPI alone are detailed in Table 4.1, showcasing mean values with standard deviations indicated in italics.

Table 4.1 Effect of Phytagel ® on the Mechanical Properties of SPI Resin

Modulus (Young’s 0.4-2.1%) (MPa) SPI + 0% Phytagel ®

The incorporation of Phytagel ® into SPI resin significantly enhanced its mechanical properties The control sample, SPI with 0% Phytagel ®, exhibited low tensile stress and modulus alongside high tensile strain, which is not ideal for composite resins However, as the amount of Phytagel ® increased, the properties improved, with the optimal results achieved at 30% Phytagel ®, yielding a tensile stress of 20.29 MPa, a modulus of 552.08 MPa, and a reduced tensile strain of 19.42% This balance is crucial, as the lower strain indicates the resin can withstand stress without excessive deformation, making it suitable for applications requiring durability Consequently, SPI + 30% Phytagel ® was selected for the development of initial recycled paper product composites due to its superior mechanical characteristics.

Figure 4.1 Effect of Phytagel ® on the Mechanical Properties of SPI

4.2 Recycled Paper Product Composites with SPI Resin

A variety of paper products were tested for composite fabrication using SPI Resin and 30% Phytagel®, focusing on porous materials without existing resin films, such as those found on glossy papers Samples were sourced from Cornell University's campus and local grocery and craft stores Initial trials with several brands of napkins and toilet paper failed due to their fragility when resin-impregnated, leading to their exclusion from the study Similarly, craft papers like construction and mulberry scrap paper were deemed unsuitable due to insufficient porosity for effective resin absorption, resulting in their removal from consideration.

Recycled paper products such as Bounty®, Georgia-Pacific Acclaim®, Georgia-Pacific enMotion®, Kleenex® Scottfold paper towels, and the Cornell Daily Sun newspaper were identified as suitable materials for creating composites due to their high strength and porous structure These paper products, particularly paper towels and newspapers, are effective when combined with SPI resin to produce durable composite materials.

Before the paper products were impregnated with SPI resin, their mechanical properties were evaluated using an Instron machine, as detailed in section 3.4.1 The findings, including the mean results and standard deviations in italics, are presented in Table 4.2 A graphical comparison of these mechanical properties is illustrated in Figure 4.3 Prior to testing, the paper products were conditioned at 21ºC and 65% relative humidity for three days.

Table 4.2 Mechanical Properties of Dry Paper Products

Modulus (Young’s 0.4-2.1%) (MPa) Bounty ® Paper Towels 2.28

4.2.2 Bounty ® Paper Towel and SPI Composite

Bounty® paper towels demonstrated a significant ability to absorb SPI resin, achieving a composition of 60% SPI resin and 40% Bounty® paper towel after just two impregnations The study involved curing a single sheet through hot-pressing, as well as curing 14 sheets together to create a composite The mechanical properties of both the Bounty® paper towel and the SPI composite were evaluated in comparison to dry Bounty paper towels and an SPI + 30% Phytagel® resin film, with detailed results presented in Table 4.3.

4.2.3 Georgia-Pacific Acclaim ® Paper Towel and SPI Composite

The GP Acclaim ® paper towels consist of 55% SPI resin and 45% paper towel after undergoing three impregnations, making them a highly absorbent product despite requiring one more impregnation than Bounty ® paper towels Both a single sheet and 14 stacked sheets were cured to create a composite material For a detailed comparison of the mechanical properties of the GP Acclaim ® paper towel and SPI composite with the dry GP Acclaim ® paper towel and SPI + 30% Phytagel ® resin film, refer to Table 4.4.

4.2.4 Georgia-Pacific enMotion ® Paper Towel and SPI Composite

The GP enMotion ® paper towels demonstrated significant absorbency, achieving a composition of 57% SPI resin and 43% paper towel after three impregnation cycles Both a single sheet and a composite of 11 sheets were cured for testing The mechanical properties of the GP enMotion ® paper towel and SPI composite were compared to those of the dry GP enMotion ® paper towel (without resin) and the SPI film containing 30% Phytagel ® resin, as detailed in Table 4.5.

4.2.5 Kleenex ® Scottfold Paper Towel and SPI Composite

Kleenex® Scottfold paper towels demonstrate significant absorbency, similar to other paper towel composites After three impregnation processes, a final composition of 60% SPI resin and 40% paper towel was achieved Additionally, a single sheet was successfully cured during the experiment.

The mechanical properties of the composite formed by 11 sheets of Kleenex® Scottfold paper towel and SPI were compared to those of the dry Kleenex® Scottfold paper towel without resin and the SPI film with 30% Phytagel® resin, as detailed in Table 4.6.

4.2.6 Cornell Daily Sun Newspaper and SPI Composite

The Cornell Daily Sun (CDS) newspaper exhibited lower absorbency compared to paper towels, requiring eight impregnations to achieve a composition of 65% SPI resin and 35% newspaper This reduced absorbency is anticipated, as paper towels are specifically designed for liquid absorption, while the newspaper lacks this purpose and is less porous.

The mechanical properties of the CDS newspaper and SPI composite, consisting of 15 bonded sheets, were analyzed and compared to the dry CDS newspaper without resin and the SPI film containing 30% Phytagel® resin, as detailed in Table 4.7.

4.2.7 Comparison of Recycled Paper Product Composites with SPI Resin

The mechanical properties of composites made from recycled paper products and SPI resin are detailed in Table 4.8 and illustrated in Figure 4.4 All five paper products produced satisfactory "green" composites, with GP Acclaim ® paper towels, GP enMotion ® paper towels, and CDS newspaper exhibiting superior mechanical properties These composites demonstrated the highest tensile stress and modulus results, while also showing lower tensile strain, indicating they would deform less under stress Consequently, the GP Acclaim ®, GP enMotion ®, and CDS newspaper composites were selected for further research involving starch resins, while the Bounty ® paper towels and Kleenex ® Scottfold paper towels were excluded from additional studies.

Table 4.3 Mechanical Properties of Bounty ® Paper Towels and SPI + 30% Phytagel ®

Modulus (Young’s 0.4-2.1%) (MPa) SPI + 30% Phytagel ® Resin Film 20.29

Table 4.4 Mechanical Properties of GP Acclaim ® Paper Towels and SPI + 30% Phytagel ®

GP Acclaim ® Paper Towels (No

GP Acclaim ® Paper Towels with

Table 4.5 Mechanical Properties of GP enMotion ® Paper Towels and SPI + 30%

Phytagel ® Tensile Stress at Max Load (MPa)

GP enMotion ® Paper Towels with 55% SPI Resin – 1 Sheet

GP enMotion ® Paper Towels with 55% SPI Resin – 11 Sheets

Table 4.6 Mechanical Properties of Kleenex ® Paper Towels and SPI + 30% Phytagel ®

Kleenex ® Scottfold Paper Towels w/ 60% SPI Resin – 1 Sheet

Table 4.7 Mechanical Properties of CDS Newspaper and SPI + 30% Phytagel ®

Table 4.8 Comparison of Recycled Paper Product Composites with SPI Resin

Modulus (Young’s 0.4-2.1%) (MPa) Bounty ® Paper Towel w/

GP Acclaim ® Paper Towels w/ 55% SPI Resin – 14

Figure 4.3 Mechanical Properties of Paper Products

Figure 4.4 Mechanical Properties of Recycled Paper Product Composites Reinforced with SPI + 30% Phytagel® Resin

RESULTS AND DISCUSSION

Soy Protein Isolate Modified with Phytagel ®

Phytagel ® was incorporated into Soy Protein Isolate (SPI) to enhance its mechanical properties, with glycerol serving as a plasticizer at a concentration of 20% by weight of SPI Resin films were created by adding 10%, 20%, and 30% Phytagel ® (by weight of SPI) to the SPI resin The formulations included a SPI-based solution consisting of 10g SPI, 2g glycerol, and 150 mL distilled water, alongside a Phytagel ® solution with varying amounts of Phytagel ® (1.0g, 2.0g, or 3.0g) and corresponding volumes of distilled water (50mL, 100mL, or 150mL) These solutions were stirred separately before being combined, as detailed in section 3.2.2 The comparative results of these resins versus SPI alone are presented in Table 4.1, which includes mean values and standard deviations in italics.

Table 4.1 Effect of Phytagel ® on the Mechanical Properties of SPI Resin

Modulus (Young’s 0.4-2.1%) (MPa) SPI + 0% Phytagel ®

The addition of Phytagel ® significantly enhances the mechanical properties of SPI resin The control sample, containing 0% Phytagel ®, exhibited low tensile stress and modulus, coupled with high tensile strain, which is not ideal for composite resins However, increasing the Phytagel ® content improved these properties, with the optimal formulation being SPI + 30% Phytagel ®, which achieved the highest tensile stress of 20.29 MPa, a modulus of 552.08 MPa, and the lowest tensile strain at 19.42% These results, illustrated in Figures 4.1 and 4.2, demonstrate that while higher tensile strain can enhance ductility, the strain in SPI + 30% Phytagel ® is sufficient to prevent brittleness, allowing the resin to deform adequately before fracture This lower strain is advantageous for applications requiring minimal deformation under stress Consequently, SPI + 30% Phytagel ® was selected for developing initial recycled paper product composites due to its superior mechanical properties.

Figure 4.1 Effect of Phytagel ® on the Mechanical Properties of SPI

Recycled Paper Product Composites with SPI Resin

A diverse range of paper products was tested for composite fabrication using SPI Resin combined with 30% Phytagel ®, focusing on porous materials that lacked a resin film, as seen in glossy papers like magazines Samples were sourced from Cornell University's campus facilities and purchased from local grocery and craft stores Initial trials with various brands of napkins and toilet paper proved unsuccessful due to their fragility when resin-impregnated, leading to their exclusion from the study Additionally, craft papers such as construction paper and mulberry scrap paper were found to be insufficiently porous to absorb the necessary resin, resulting in their removal from consideration as well.

Recycled paper products, particularly paper towels and newspapers, have been identified as effective materials for creating composites due to their high strength and porous structure The specific paper products utilized in the composite development with SPI resin include Bounty® paper towels, Georgia-Pacific (GP) Acclaim® paper towels, GP enMotion® paper towels, Kleenex® Scottfold paper towels, and the Cornell Daily Sun newspaper.

Before the paper products were impregnated with SPI resin, their mechanical properties were assessed using an Instron machine, as detailed in section 3.4.1 The findings are presented in Table 4.2, which includes the mean results accompanied by standard deviations in italics A comparative graph of these mechanical properties is illustrated in Figure 4.3 Prior to testing, the paper products were conditioned at 21ºC and 65% relative humidity for three days.

Table 4.2 Mechanical Properties of Dry Paper Products

Modulus (Young’s 0.4-2.1%) (MPa) Bounty ® Paper Towels 2.28

4.2.2 Bounty ® Paper Towel and SPI Composite

Bounty® paper towels demonstrated a high absorption capacity for SPI resin, achieving a composition of 60% SPI resin and 40% Bounty® paper towel by weight after just two impregnations The curing process involved both a single sheet and a composite of 14 sheets, which were hot-pressed For a detailed comparison of the mechanical properties of the Bounty® paper towel and SPI composite against the dry Bounty paper towel and an SPI + 30% Phytagel® resin film, please refer to Table 4.3.

4.2.3 Georgia-Pacific Acclaim ® Paper Towel and SPI Composite

The GP Acclaim ® paper towels achieved a composition of 55% SPI resin and 45% paper towel after three impregnations, demonstrating significant absorbency despite one additional impregnation compared to Bounty ® paper towels Both a single sheet and 14 stacked sheets were cured to create a composite, with mechanical properties detailed in Table 4.4, comparing the GP Acclaim ® paper towel and SPI composite to the dry GP Acclaim ® paper towel and SPI with 30% Phytagel ® resin film.

4.2.4 Georgia-Pacific enMotion ® Paper Towel and SPI Composite

The GP enMotion® paper towels demonstrated significant absorbency, achieving a composition of 57% SPI resin and 43% paper towel after three impregnations Both a single sheet and a composite of 11 sheets were cured for analysis The mechanical properties of the GP enMotion® paper towel and SPI composite were compared to the dry GP enMotion® paper towel (without resin) and the SPI + 30% Phytagel® resin film, as detailed in Table 4.5.

4.2.5 Kleenex ® Scottfold Paper Towel and SPI Composite

Kleenex® Scottfold paper towels demonstrate strong absorbency, similar to other paper towel composites After three impregnation cycles, a composite material was achieved, consisting of 60% SPI resin and 40% paper towel Additionally, a single sheet of this composite was successfully cured.

A composite was created by curing 11 sheets together, allowing for a comparison of mechanical properties between the Kleenex® Scottfold paper towel, the SPI composite, the dry Kleenex® Scottfold paper towel (without resin), and the SPI film combined with 30% Phytagel® resin, as detailed in Table 4.6.

4.2.6 Cornell Daily Sun Newspaper and SPI Composite

The Cornell Daily Sun (CDS) newspaper demonstrated lower absorbency compared to paper towels, requiring eight impregnations to achieve a composition of 65% SPI resin and 35% newspaper This outcome aligns with the inherent design of paper towels, which are specifically manufactured to absorb liquids effectively, unlike newspapers that are less porous and not intended for such purposes.

The mechanical properties of the composite formed by 15 sheets of CDS newspaper and SPI were analyzed and compared to those of dry CDS newspaper without resin and a film made of SPI combined with 30% Phytagel® resin, as detailed in Table 4.7.

4.2.7 Comparison of Recycled Paper Product Composites with SPI Resin

The mechanical properties of composites made from recycled paper products and SPI resin are summarized in Table 4.8 and illustrated in Figure 4.4 All five paper products resulted in acceptable "green" composites, but the GP Acclaim ® paper towels, GP enMotion ® paper towels, and CDS newspaper exhibited superior mechanical properties These composites showed the highest tensile stress and modulus results compared to Bounty ® paper towels and Kleenex ® Scottfold paper towels, while also demonstrating lower tensile strain, indicating less deformation under stress Consequently, the GP Acclaim ®, GP enMotion ®, and CDS newspaper composites were selected for further experimentation with starch resins, leading to the exclusion of Bounty ® and Kleenex ® Scottfold paper towels from the study.

Table 4.3 Mechanical Properties of Bounty ® Paper Towels and SPI + 30% Phytagel ®

Table 4.4 Mechanical Properties of GP Acclaim ® Paper Towels and SPI + 30% Phytagel ®

GP Acclaim ® Paper Towels (No

GP Acclaim ® Paper Towels with

Table 4.5 Mechanical Properties of GP enMotion ® Paper Towels and SPI + 30%

Phytagel ® Tensile Stress at Max Load (MPa)

GP enMotion ® Paper Towels with 55% SPI Resin – 1 Sheet

GP enMotion ® Paper Towels with 55% SPI Resin – 11 Sheets

Table 4.6 Mechanical Properties of Kleenex ® Paper Towels and SPI + 30% Phytagel ®

Kleenex ® Scottfold Paper Towels w/ 60% SPI Resin – 1 Sheet

Table 4.7 Mechanical Properties of CDS Newspaper and SPI + 30% Phytagel ®

Table 4.8 Comparison of Recycled Paper Product Composites with SPI Resin

Modulus (Young’s 0.4-2.1%) (MPa) Bounty ® Paper Towel w/

GP Acclaim ® Paper Towels w/ 55% SPI Resin – 14

Figure 4.3 Mechanical Properties of Paper Products

Figure 4.4 Mechanical Properties of Recycled Paper Product Composites Reinforced with SPI + 30% Phytagel® Resin

Starch Resins

Starch-based resins were initially created using TG, MG, PG, TGS, MGS, or PGS without a plasticizer, incorporating 50 times the amount of starch to distilled water (50mL per 1g of starch) However, these resin films proved to be extremely brittle, leading to the formation and propagation of cracks, which rendered them unsuitable for testing The presence of cracks indicated that the specimens were already compromised, preventing accurate measurements during testing with the Instron Furthermore, some resin films could not withstand the pressure during the curing process (hot-press) and fractured into multiple pieces Consequently, it was concluded that the inclusion of a plasticizer was essential for enhancing the performance of these resins.

In the pre-curing process of starch resins, 10% glycerol was added by weight to enhance flexibility However, the addition of glycerol did not improve the brittleness of the starch resins, which continued to crack during the hot-press process and exhibited flaws in specimen strips during tensile tests Consequently, glycerol was excluded as a plasticizer for starch resins, as it failed to enhance the tensile strain of the resin films.

To enhance the durability of starch resins, the plasticizer was switched to sorbitol, and adjustments were made to the hot-press parameters The hot-press temperature was lowered from 120ºC to 110ºC, and the pressing time was reduced from 25 minutes to 15 minutes These modifications successfully minimized cracking in the resin film during curing, enabling the production of crack-free specimens suitable for tensile testing As a result, multiple starch resin samples were successfully formed without any cracks.

Table 4.9 presents the tensile results for six starches with different sorbitol concentrations, displaying the mean values alongside standard deviations in italics Due to the brittleness and pre-existing cracks in many resin strips before testing, only a limited number of results are deemed reliable The reliable results, which showed no cracks prior to tensile testing, are highlighted in bold.

Table 4.9 Mechanical Properties of Starch Resins with Sorbitol

Note: (NA) indicates not available

In Table 4.9, the asterisk indicates that the modulus referenced is the automatic modulus, not Young's modulus, as the tensile strain in these samples was too low to measure Young's modulus due to brittleness, occurring when strain remained below 0.4-2.1% Furthermore, MGS + 30% sorbitol and PGS + 20% sorbitol could not be tested; MGS + 30% sorbitol failed to create a resin that could endure the hot-press, as it adhered to the metal plates and had to be discarded, likely due to excessive plasticizer Similarly, PGS + 20% sorbitol did not form correctly during oven drying, potentially due to miscibility issues that resulted in holes throughout the resin samples.

It is crucial to highlight that TG + 20% sorbitol and PG + 30% sorbitol lack standard deviations due to the testing of only one strip for each resin As previously noted, these specimens faced challenges in forming without holes, indicating miscibility issues Despite this, the samples were cured, and a strip meeting the required gauge length was tested However, the absence of standard deviations means these results cannot be deemed significant.

The samples TG + 0% sorbitol, TG + 20% sorbitol, PG + 0% sorbitol, TGS + 0% sorbitol, TGS + 10% sorbitol, and PGS + 0% sorbitol exhibited insufficient tensile strain to calculate a modulus, indicating their brittleness This lack of ductility prevents accurate measurement of their mechanical properties using the Instron machine, suggesting these resins are unsuitable for handling and packaging Consequently, the significance of the tensile results remains challenging to analyze without this critical mechanical property.

The specimens highlighted in bold in Table 4.9 achieved satisfactory tensile test results using the Instron machine, which are summarized in Table 4.10 and Figure 4.6 for comparison The results are presented as mean values, with standard deviations italicized Notably, some results exhibited brittleness, indicated by the use of automatic modulus rather than Young’s modulus, marked with an asterisk Despite their brittle characteristics, these results were considered acceptable due to the potential for improved ductility through the addition of plasticizer However, the remaining starch and sorbitol resins were excluded from the study due to their failure to produce acceptable resin films.

Table 4.10 Mechanical Properties of Acceptable Starch Resins with Sorbitol

PG + 20% Sorbitol 13.06 (3.82) 2.00 (0.45) 912.92 (96.81) TGS + 20% Sorbitol 4.18 (0.38) 15.45 (2.46) 163.36 (15.29) TGS + 30% Sorbitol 2.11 (0.26) 11.14 (2.34) 69.51 (12.90) MGS + 0% Sorbitol 21.42 (6.95) 1.57 (0.42) 1793.90 (248.83)* MGS + 10% Sorbitol 5.65 (2.50) 1.13 (0.44) 635.77 (46.33)* MGS + 20% Sorbitol 2.70 (0.27) 5.42 (1.00) 130.00 (10.27) PGS + 10% Sorbitol 12.69 (2.42) 1.21 (0.25) 1316.17 (112.89)* PGS + 30% Sorbitol 2.30 (0.46) 10.80 (4.10) 93.42 (18.54)

The mechanical properties of MG + 20% sorbitol and MGS + 0% sorbitol were found to be superior, exhibiting the highest tensile stress and modulus compared to SPI + 30% Phytagel ® resin, as detailed in Table 4.11 and Figure 4.7 Further analysis focused on MG + 20% sorbitol and MGS + 0% sorbitol, with their stress vs strain curves illustrated in Figure 4.5, while other resins were excluded from additional study.

Table 4.11 Desired Starch Resins Compared to SPI + 30% Phytagel ®

Figure 4.5 Stress vs Strain Curves of: (a) MG + 20% Sorbitol and (b) MGS + 0%

Figure 4.6 Mechanical Properties of Acceptable Starch Resins with Various Amounts of Sorbitol

Figure 4.7 Comparison of Preferred Starch Resins to SPI + 30% Phytagel ®

The SPI + 30% Phytagel® resin demonstrated comparable tensile stress to MG + 20% sorbitol and MGS + 0% sorbitol, but starch-based resins exhibited significantly higher modulus, making them more desirable While SPI-based resin showed a higher tensile strain, leading to increased deformation, MGS + 0% sorbitol outperformed MG + 20% sorbitol in mechanical properties due to its superior tensile stress and modulus Nevertheless, both starch-based resins are currently too brittle for composite production, necessitating the addition of a plasticizer This plasticizer will reduce tensile stress and modulus slightly, yet enhance tensile strain, allowing for better handling without breakage.

4.3.1 Starch Resins Modified with Thickeners

CMG, CMS, and CMT thickeners were incorporated into MG and MGS starch resins, which exhibited superior mechanical properties compared to other tested starches The thickeners were added in varying amounts of 10%, 20%, and 30% by weight of the starch, following a specific recipe: 7.0g of starch combined with 0.7g, 1.4g, or 2.1g of thickener, along with 350mL of distilled water To ensure proper mixing, the dry starch and thickener powders were thoroughly combined before adding water, as the thickeners would gel upon hydration, complicating dispersion The addition of water resulted in a thick gel, making it challenging to evenly distribute the resin during the pre-curing phase Although the gel clumps remained intact at room temperature, stirring in an 80ºC water bath reduced the viscosity, leading to a uniformly dispersed resin.

The incorporation of CMG significantly enhanced the mechanical properties of the starch resin, while the addition of CMT and CMS proved ineffective, resulting in unacceptable resin films Specifically, CMS failed to fully dissolve in the starches, leading to persistent gel formation and the presence of holes in the oven-dried films Despite hot-pressing curing these defects, the resulting samples were brittle and unsuitable for tensile testing, necessitating the exclusion of CMS from further research Although the addition of CMT produced better films than CMS, they still exhibited holes and brittleness Cracks formed in the tensile strips for all CMT increments, except for MGS with 30% CMT, which was subsequently selected for further study due to its relatively better performance The mechanical properties of the CMT-added samples were compromised, as indicated by the results from the Instron machine, which could not accurately assess the samples due to pre-existing cracks.

Table 4.12 Mechanical Properties of MG and MGS with the Addition of CMT

CMG proved to be an effective thickener for MG and MGS resins, although CMS and CMT were not viable options Tensile testing results indicated that the addition of 10% CMG to MG resulted in excessive brittleness, preventing the samples from being cut into strips for testing While 20% CMG in MG and 10% CMG in MGS yielded acceptable mechanical properties, both samples remained too brittle, with MGS + 10% CMG being particularly untestable for modulus Although the samples of MG + 20% CMG and MGS + 10% CMG showed no cracks, only a limited number of strips without cracks were obtained, leading to the exclusion of MG + 10% CMG, MG + 20% CMG, and MGS + 10% CMG from further investigation.

Table 4.13 Mechanical Properties of MG and MGS with the Addition of CMG

The MG + 10% CMG and MG + 20% CMG samples were excluded from testing due to excessive brittleness, with the latter producing cracked strips Additionally, the MG + 30% CMG sample demonstrated unsatisfactory mechanical properties, characterized by a low modulus of stiffness and a high standard deviation, indicating inconsistency Consequently, MG + 30% CMG was also omitted from further analysis The remaining starch resin samples eligible for use in paper composites are detailed in Table 4.14 and are compared to SPI + 30% Phytagel ®, with results illustrated in Figure 4.10.

Table 4.14 Mechanical Properties of Starch Resins Compared to SPI + 30% Phytagel ®

The mechanical properties of MGS + 30% CMG were found to be superior, as illustrated in Table 4.14 and Figure 4.10 The stress vs strain curve for this composite is depicted in Figure 4.9, showing a tensile stress of 19.01 MPa, which is lower than that of SPI + 30% Phytagel®, MG + 20% sorbitol, or MGS without a plasticizer However, the modulus of MGS + 30% CMG, measuring 1951.43 MPa, is significantly higher than that of the other resin films.

Recycled Paper Products with Starch-based Resins

The mechanical properties analysis revealed that GP Acclaim® paper towels, GP enMotion® paper towels, and Cornell Daily Sun newspaper are the top choices for resin-reinforced composites These paper products were utilized to create composites with two different formulations: MGS + 30% CMG + 5% sorbitol and MGS + 30% CMG + 10% sorbitol Detailed mechanical properties of the dry paper towels can be found in Table 4.2.

The number of impregnations required to achieve the desired starch resin composition has increased with the SPI + 30% Phytagel® resin due to the addition of more water to the starch resin solution This increase in water aimed to reduce viscosity for better processability, which inadvertently lowered the resin concentration Despite this challenge, the target composition was ultimately achieved after additional impregnations.

4.4.1 Georgia-Pacific Acclaim ® Paper Towel and Starch-based Composite

The GP Acclaim ® paper towel composite was developed using a formulation of MGS + 30% CMG + 5% sorbitol, resulting in a final composition of 45% resin and 55% paper towel after four impregnation cycles Both a single sheet and a composite of seven sheets were cured to evaluate their mechanical properties For a detailed comparison of these properties against the dry GP Acclaim ® paper towel and the MGS + 30% CMG + 5% sorbitol resin film, refer to Table 4.16.

After impregnating GP Acclaim ® paper towels with MGS + 30% CMG and varying sorbitol concentrations, a composite with 45% resin and 55% paper towel was achieved Curing tests revealed that while some sheets adhered together, they did not fully bond, particularly with the addition of 10% sorbitol, leading to uneven breaks during mechanical testing In contrast, the composite with 5% sorbitol exhibited better cohesiveness and broke uniformly This indicates that the formulation with 10% sorbitol resulted in less desirable mechanical properties compared to the 5% sorbitol variant Detailed mechanical properties are available in Table 4.16 for further comparison.

4.4.2 Georgia-Pacific enMotion ® Paper Towel and Starch-based Composites

The GP enMotion® paper towel was developed with a formulation of MGS, 30% CMG, and 5% sorbitol resin, resulting in a composition of approximately 46% resin and 54% paper towel after four impregnation processes Both a single sheet and a composite of seven sheets were cured, allowing for a comparison of their mechanical properties Detailed comparisons between the GP enMotion® paper towel with resin and the dry version, as well as the MGS + 30% CMG + 5% sorbitol resin film, can be found in Table 4.17.

Following the impregnation of GP enMotion ® paper towels using MGS + 30%CMG + 5% sorbitol, GP enMotion ® paper towels were impregnated using MSG + 30%

The study investigated the effects of different sorbitol concentrations on the cohesiveness and mechanical properties of composites made from CMG and paper towels After four impregnations, a composition of 46% resin and 54% paper towel was achieved While a single sheet and a composite of seven sheets were successfully cured and adhered well after hot-pressing, the Instron testing revealed that the composite with 10% sorbitol did not break as evenly as anticipated, contrasting with the 5% sorbitol composite, which maintained better cohesiveness Detailed mechanical properties of the composites, including GP enMotion® paper towels and various resin formulations, are summarized in Table 4.17, highlighting the differences in performance based on resin concentration.

4.4.3 Cornell Daily Sun Newspaper and Starch-based Composite

The CDS newspaper composite was developed using a mixture of MGS, 30% CMG, and 5% sorbitol resin, achieving a final composition of 43% resin and 57% newspaper after five impregnation cycles Initially, a single sheet was cured, followed by the curing of seven additional sheets together to create a composite The mechanical properties of the CDS newspaper composite, along with the MGS, 30% CMG, and 5% sorbitol resin film, are detailed in Table 4.18, allowing for a comparison with the dry CDS newspaper that contains no resin.

After impregnating CDS newspaper with MGS + 30% CMG + 10% sorbitol, a composite was formed with a composition of 43% resin and 57% paper towel following five impregnations Curing was conducted on both a single sheet and seven sheets together; however, the individual sheets did not adhere as expected, revealing a lack of cohesion in the composite when the outer layers were peeled back Furthermore, during Instron testing, the composite failed to break evenly, indicating poor cohesiveness similar to previous composites using 10% sorbitol The mechanical properties of the CDS newspaper and MGS + 30% CMG + 10% sorbitol are detailed in Table 4.18, highlighting the performance differences compared to the composite made with MGS + 30% CMG + 5% sorbitol and the CDS newspaper without resin.

Table 4.16 Mechanical Properties of GP Acclaim ® Paper Towels with Starch Resin

Modulus (Young’s 0.4-2.1%) (MPa) MGS + 30% CMG

Table 4.17 Mechanical Properties of GP enMotion ® Paper Towels with Starch Resins

Table 4.18 Mechanical Properties of CDS Newspaper with Starch Resin

4.4.4 Comparison of Recycled Paper Product and Starch-based Resin Composites

The study evaluated composites made from recycled paper products and MGS + 30% CMG with varying sorbitol concentrations It was found that composites with 5% sorbitol exhibited valid cohesion, while those with 10% sorbitol lacked sufficient bonding between sheets, indicating that 10% sorbitol is not effective for desirable composite formation A comparison of composites created using GP Acclaim ® paper towels, GP enMotion ® paper towels, and CDS newspaper, all with MGS + 30% CMG + 5% sorbitol, demonstrated excellent mechanical properties, as illustrated in Table 4.19 and Figure 4.13 Notably, GP enMotion ® paper towels delivered superior performance with the highest tensile stress of 48.98 MPa and a modulus of 2100.06 MPa, making them the most effective choice among the tested materials.

Table 4.19 Comparison of Recycled Paper Products with MGS + 30% CMG + 5%

The stress versus strain curves for various materials reveal distinct properties: (a) GP Acclaim® Paper Towels, combined with MGS + 30% CMG + 5% Sorbitol, demonstrate unique performance characteristics; (b) GP enMotion® Paper Towels, also formulated with MGS + 30% CMG + 5% Sorbitol, exhibit similar traits; and (c) the Cornell Daily Sun Newspaper, utilizing the same blend of MGS + 30% CMG + 5% Sorbitol, showcases its own specific stress-strain behavior.

Comparison of Composites Produced with Modified SPI and Modified Starch

The mechanical properties of modified starch resins were found to be superior to those of modified SPI resins, as detailed in section 4.3 Both types of resins were utilized to create recycled paper product composites, with comparative data presented in Table 4.20 and Figure 4.15 Notably, the modified starch resin exhibited a higher modulus and a lower tensile strain compared to the modified SPI resin While tensile stress remained relatively similar for both composites, there was a slight inclination towards increased tensile stress in the modified starch resin Overall, the findings indicate that recycled paper product composites made with modified starch resin possess the most favorable mechanical properties.

Table 4.20 Comparisons of Recycled Paper Product Composites with Modified SPI

Resin and Modified Starch Resin

GP Acclaim ® Paper Towels/SPI

GP enMotion ® Paper Towels/SPI

Figure 4.15 Comparison of Recycled Paper Products with Modified SPI or Modified Starch Resins

This research focuses on the development of environmentally-friendly, sustainable "green" composites made from recycled paper products and modified starch resins, incorporating 30% CMG with MGS resins Additionally, composites utilizing recycled paper and modified Soy Protein Isolate (SPI) resin were created with 30% Phytagel® The study thoroughly examined the mechanical properties of the resin films, paper products, and their composite forms, leading to significant conclusions about their performance characteristics.

1 The tensile stress and the modulus of SPI resin film both increased with the increasing amounts of Phytagel ® , from 0% to 30% Additionally, the tensile strain significantly decreased with this addition This confirmed the results of earlier studies in that the addition of Phytagel ® improves the mechanical properties of SPI resin.

2 The paper products that were able to be fabricated into composites were both porous and had acceptable strength The paper products that were too porous broke when impregnated with the resin solution and the paper products that had a higher strength did not absorb significant amounts of resin.

3 Based on the recycled paper products used in this study, the recycled paper products fabricated into composites with the best mechanical properties areGeorgia-Pacific Acclaim ® paper towels, Georgia-Pacific enMotion ® paper towels and the Cornell Daily Sun newspaper This was determined by the composites created using SPI + 30% Phytagel ® resin.

4 Starch resin films were able to form without cracks with the addition of sorbitol as a plasticizer, but not with the addition of glycerol as a plasticizer This confirmed the results of earlier studies in that the use of sorbitol as a plasticizer in starches is preferred to the use of glycerol.

5 Based on the mechanical properties of the six different starch-based resins produced, it was determined that the maize starches (MG and MGS) produce the preferred resin films when compared to the tapioca starches (TG and TGS) and the potato starches (PG and PGS).

6 Based on the mechanical properties of the maize starches, it was determined that the addition of glycol stearate, as seen in MGS, enhanced the properties of the maize starch.

7 CMS and CMT were unable to be used as thickeners to enhance the mechanical properties of the maize starches due to their inability to form resin films without cracks.

8 The tensile stress, tensile strain and modulus of the MGS resin all increased with the increasing amounts of CMG, from 10% to 30%.

9 When sorbitol is added to MGS + 30% CMG, the optimal results are obtained when using 5% resin due to having a higher tensile strain than lesser amounts of sorbitol and higher tensile stress and modulus than greater amounts of sorbitol.

10 The preferred modified starch resins produced in this study had a higher modulus and lower tensile stress than the modified SPI resin, while the tensile stress of these resins were similar

11 The tensile stress, tensile strain and modulus of MGS + 30% CMG + 5% sorbitol resin were: 15.57 MPa, 2.38% and 1111.33 MPa, respectively.

12 The increasing amount of plasticizer in a resin decreases the ability of a composite to cohesively form This is based on the ability of MGS + 30% CMG with 5% sorbitol to form cohesive composites and the inability of this resin with 10% sorbitol to form a cohesive composite.

13 The Georgia-Pacific Acclaim ® paper towels, Georgia-Pacific enMotion ® paper towels and the Cornell Daily Sun Newspaper produce composites of desirable properties when fabricated with MGS + 30% CMG + 5% sorbitol.

14 The Georgia-Pacific enMotion ® paper towels with MGS + 30% CMG + 5% sorbitol produced the composite with the best mechanical properties, as compared to the other paper product composites studied The tensile stress, tensile strain and modulus of this composite were: 48.98 MPa, 10.79% and 2100.06 MPa, respectively.

15 When the resin used in recycled paper product composites was changed from modified SPI to modified starch, the tensile stress and modulus increased while the tensile strain decreased.

This thesis concludes that "green" composites made from recycled paper products and modified starch resin exhibit mechanical properties that make them viable alternatives to petroleum-based composites.

The mechanical properties of these composites can be tailored to meet various application requirements, rather than being fixed At the end of their lifecycle, the components can be easily separated for disposal or composted into organic soil, resulting in zero waste Further research is needed to explore the degradability of these composites, their lifecycle duration, and their responses to environmental changes The composites examined in this thesis represent significant advancements in the "green" composite sector, showcasing their potential for diverse applications.

CONCLUSIONS

This thesis explores the potential of utilizing recycled paper products combined with biodegradable resins to develop sustainable composites that can serve as alternatives to petroleum-based materials While the study highlights the mechanical properties of these innovative composites, it also identifies substantial opportunities for future research, particularly in the selection and characterization of the paper products used in the creation of these environmentally friendly composites.

When selecting paper products, it's essential to consider two key factors: mechanical properties and environmental impact Different types of paper exhibit varying mechanical characteristics, while prioritizing eco-friendliness involves choosing products that are 100% post-consumer recycled, chlorine-free, and handcrafted Adhering to these criteria not only enhances the sustainability of the materials but also contributes to the development of greener composites, aligning with the primary objective of this research area.

Enhancing the characterization of paper products used in composite fabrication is crucial for improving their performance Key factors to consider include fiber length, paper strength, and porosity, as these elements influence resin absorption By analyzing changes in these characteristics, researchers can evaluate the final composite's quality Advancements in paper product characterization pave the way for further exploration of recycled paper-based "green" composites, building on the foundational research presented in this thesis.

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Tiêu đề	Green Composites Based On Recycled Paper Products And Biodegradable Resins
Tác giả	Alexandra J. Sonis
Người hướng dẫn	Professor Anil N. Netravali
Trường học	Cornell University
Chuyên ngành	Fiber Science
Thể loại	thesis
Năm xuất bản	2009
Thành phố	Ithaca

Định dạng
Số trang	90
Dung lượng	8,05 MB