Investigate Mechanical Properties Of Hdpe Composite Enhanced With Zno Nanoparticles In Injection Molding.pdf

TECHNOLOGY AND EDUCATIONMINISTRY OF EDUCATION AND TRAINING HO CHI MINH CITY UNIVERSITY OF INVESTIGATE MECHANICAL PROPERTIES OF HDPE COMPOSITE ENHANCED WITH ZNO NANOPARTICLES IN INJECT

INTRODUCTION

Overview of research in HDPE

High-Density Polyethylene (HDPE) is the full name of the HDPE material This plastic material is originally derived from polyethylene HDPE plastic is created by chaining the reactions of ethylene molecules together In Vietnam, HDPE is applied in many fields such as the food industry, mechanical engineering, etc In recent years, the domestic plastic industry has shown signs of strong growth with an annual increase of 16-18% per year Plastic products are used more and more in daily life and are the leading substitute for traditional materials in the field of industrial production Along with that, this market also has fierce competition with not only domestic competitors but also the penetration of foreign plastic companies Up to the present time, some of the big names in the industry are Binh Minh Plastic (BMP), Tien Phong Plastic (NTP), and recently emerging DEKKO, Hoa Sen has been at the forefront of manufacturing HDPE plastic [1]

Furthermore, Nguyen Thuy Chinh, et al (2019) conducted a study titled "Change of some characteristics of HDPE pipes tested in Nghe An province seawater" in the Journal of Science and Technology Development The study focuses on the change of some characteristics of high-density polyethylene (HDPE) pipes tested in Nghe An province seawater The investigated characteristics of HDPE pipe before and after testing are structural, morphological, crystal, thermal properties, and stability Infrared (IR) spectroscopy, scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) methods were used to evaluate the change in characteristics of PE pipes after 10 months of testing in Nghe An province seawater In addition, the change in weight and tensile properties of PE pipes after testing was also investigated The obtained results showed that the Nghe An province seawater influenced the structural, morphological, tensile, crystal, and thermal characteristics of PE pipes [2]

Research on HDPE has been conducted worldwide in various fields Moreover, some companies use novel technology is nanoparticles, which is an additive that makes the injecting process more efficient and better their mechanical abilities The standard definition of a nanoparticle or ultrafine particle is a material particle with a diameter of one to one hundred nanometers (nm) When referring to fibers and tubes that are smaller than 100 nm in only two orientations or larger particles up to 500 nm, the phrase is occasionally used Smaller metal particles are typically referred to as atom clusters at the lowest limit, which is smaller than 1 nm

Studies have examined the mechanical and physical effects of nanoparticles, such as durability and strength under strain, impact, high temperatures, and other conditions This study has improved the production process by providing crucial knowledge about it There are several scientific research studies on why they chose this method

A study on copper/carbon core-shell nanoparticles as an additive for natural fiber/wood plastic blends by Qinglin Wu et al focuses on copper/carbon core/shell nanoparticles (CCCSNs) that have recently been introduced as an industrial material In this paper, composites based on high-density polyethylene (HDPE), bamboo fiber,

CCCSNs, and a coupling agent (MAPE) were prepared by melt compounding The influence of CCCSN content on the resulting composites' mechanical, biological resistance, and thermal properties was investigated It was found that CCCSNs within the carbon black matrix were processed well with bamboo fiber-plastic blends through mixing and injection molding The materials enhanced composite strength and modulus- related properties Composites with CCCSNs and natural fibers reduced heat capacity and thermal diffusivity Composites with CCCSN materials also enhanced termite and mold performance Thus, the material can be used as an additive for plastics and other polymers to modify strength properties, biological resistance (e.g., mold and stain), and thermal conductivity properties [3]

Ubair Abdus Samada et al 2018 "Enhancing mechanical properties of epoxy/polyaniline coating with the addition of ZnO nanoparticles: Nanoindentation characterization." Epoxy/Polyaniline (PANI) coating from our previous work was modified with ZnO nanoparticles at 0.5 and 1.0 wt%, while the percentage of PANI was kept constant (0.78 wt%) ZnO nanoparticles were disseminated in an epoxy/PANI mixture using mechanical stirring and sonication with acetone as a facilitator for mixing The effects of ZnO on the mechanical and thermal properties of Epoxy/PANI were studied Mechanical characterizations of the samples were carried out using conventional techniques (i.e., pendulum hardness, scratch, and impact resistance) and nanoindentation Thermal characterization was performed using DSC and TGA to study the effect of ZnO nanoparticles on the Tg and thermal stability of the coatings The mechanical analysis results showed that nano hardness (from nanoindentation) and scratch resistance (scratch test) of the modified coating increased by a maximum of 15% compared to unmodified coatings On the other hand, the impact resistance and elastic modulus (from nanoindentation) were decreased The thermal analysis results showed that the addition of ZnO nanoparticles to the Epoxy/PANI matrix decreased the glass transition temperature (Tg) and thermal stability of the matrix [4]

Another study has focused on the effect of using nano-sized zinc oxide (ZnO) particles on the enhancement of the degradation resistance of wood-high-density polyethylene (HDPE) composite, which was investigated through artificial weathering Samples with different amounts of ZnO mixing ratio (0, 1, 2, and 3 %) were manufactured using an internal mixer followed by compression molding The prepared samples were then exposed to the artificial weathering process in a QUV weather meter The weathering behavior of samples was characterized using tensile strength, contact

4 angle analysis, colorimetry, ATR-FTIR spectroscopy, and FE-SEM The results indicated that the number of surface cracks, tensile strength loss, and contact angle changes decreased as a function of ZnO addition, while lightness changes were not affected Analysis of the functional groups at the composite surface by ATR-FTIR showed that the incorporation of nano-sized ZnO particles in the composite formulation changed the degradation mechanism of the composite to photocatalytic reactions, leading to the production of high levels of zinc carboxylate in the structure of the weathered composite [5].

Reason to choosing the topic

There are several reasons why we selected that subject First, the field of composite materials is expanding quickly This implies that there will be plenty of chances to conduct study in this field

To increase product quality and lower manufacturing costs, it is also vital to investigate the materials that affect how durable composite products made through injection molding are

Thirdly, this research may open up new research avenues in the field of composite materials and may also have applications in other industries, such as healthcare, energy, etc It may also assist companies who make composite products to improve their competitiveness in the market.

Topic objective

Investigate the change in materials of ZnO - NPs and HDPE, with nanoparticles additive to determine the effect of heat on the mechanical properties such as strength, ductility, melting temperature, etc

In this study, 2 different samples of composite, ZnO - NPs and HDPE were combined After that, put it in the granulating machine to create feedstock Go on to the injecting step, we put stock onto the injection molding machine to make the green part After injecting, detached by solvent debinding liquid Move on to the thermal step, heating the part The last thing to do is test it The data were analyzed and evaluated through the Taguchi method

Research methodology

The method is mainly based on theory, and experimental implementation, using suitable machines to create and collect research samples Analyze, compare, and contrast with analytical methods, and collect information from experiments on samples to evaluate results

OVERVIEW OF RESEARCH TOPIC

Introduction of HDPE (Polyethylene High-Density)

The thermoplastic polymer known as high-density polyethylene (HDPE) or polyethylene high-density (PEHD) is created from the monomer ethylene When used for HDPE pipes, it is referred to as "polyethylene" or "alkaline" at times HDPE has a high strength-to-density ratio and is used to make geomembranes, plastic lumber, corrosion-resistant pipework, and bottles HDPE is frequently recycled, and its resin identification code is "2"

HDPE is renowned for having a high strength-to-density ratio HDPE has a density of 930 to 970 kg/m 3 ISO 1183 part 2 (gradient columns) and ISO 1183 part 1 (MVS2PRO density analyzer) are the two accepted methods for testing plastic density Low branching in HDPE gives it better intermolecular forces and tensile strength (38 MPa against 21 MPa) than LDPE, despite the fact that HDPE's density is just slightly higher than LDPE's

HDPE can be fabricated for various industries such as packaging, manufacturing plastic products, plastic waves, plastic pallets, water pipes, drainage systems, toys, packaging, containers, discharge pipes, construction materials, and other engineering plastic products It can be reinforced with ZnO nanoparticles to increase its stiffness and strength, etc

Latent heat of fusion 178.6 kJ/kg

Specific heat capacity 1330 to 2400 J/kg K

Specific heat (solid) 1.9 kJ/kg °C

(C2H4)n High strength-to-density ratio, impact and chemical resistances, recyclable, high melting point, easily molded and worked

HDPE is easy to melt and cast, lightweight, resistant to corrosion, has a long life, is sustainable, has great waterproofing, and is simple to recycle It is used for packaging, household appliances, and weaving fabrics High-density polyethylene is used in the packaging industry for a variety of packaging applications, such as crates, trays, plastic pallets, milk and juice bottles, food packaging caps, drums, and industrial containers

HDPE is the material of choice for creating household and consumer items such as garbage cans, detergent containers, home appliances, ice bins, toys, etc because of its low cost and ease of handling

The great tensile strength of HDPE makes it a popular material in the garment industry for rope systems, fishing, and sports nets, agricultural nets, industrial and ornamental fabrics, etc HDPE is also used for pipes and accessories, including fuel tanks for cars, electrical wiring and cables for solar panels, telecommunications lines, and drainage pipes [6]

HDPE has a plastic identification code of number 2

Figure 2.2 HDPE plastic identification code [3]

Overview of nanoparticles

Zinc oxide (ZnO) NPs, which are, have been utilized as drug carriers, cosmetics ingredients, and medical filling materials ZnO NPs have advantages over Ag NPs, such as a low production cost, a white appearance, and UV-blocking properties ZnO NPs showed bactericidal effects on Gram-positive (S aureus) and Gram-negative (E coli) bacteria as well as the spores that are resistant to high temperature and high pressure (Azam et al., 2011) The exact mechanism of ZnO NPs’ antibacterial activity has not been well understood so far One proposed possibility is the generation of hydrogen peroxide as a main factor of the antibacterial activity It is also believed that the accumulation of the particles on the bacteria's surface because of the electrostatic forces could be another mechanism of the antibacterial effect of ZnO particles It was found that the bactericidal efficiency of ZnO NPs depended on concentration and surface area

ZnO NPs in higher concentrations and larger surface areas displayed better antibacterial activity [7]

2.2.2 The structure of Zinc Oxide

Zinc oxide nanoparticles are categorized among the materials that have potential applications in many areas of nanotechnology ZnO possesses one-, two- and three- dimensional structures 1D structure involves tubes, needles, ribbons, nanorods helixes, belts, combs, wires, rings, and springs The two-dimensional structure involves nanoplates and nanosheets that can give us zinc oxide However, the three-dimensional structure of zinc oxide includes snowflakes, coniferous, urchin-like flowers, and dandelions Zinc oxide gives greatly different particles among materials Also, zinc oxide in different shapes and structures can be seen

Figure 2.4 Different tructures and shapes of zinc oxide, (a) flower, (b) wire, (c, d) rod

The thermal conductivity of the composite materials based on the zinc oxide powders with different average particle sizes (micrometer, sub-micrometer, and nanometer) dispersed in the polymethylsiloxane (silicone oil) was measured using the radial heat flow method The thermal conductivity of the composite material based on the commercial ZnO micro powder with an average particle size of 50 mm was found to be 0.8 W/(m∙K) The thermal conductivity of the composite material based on ZnO

11 nano-powder with an average particle size of approximately 3 nm synthesized using the wet chemistry methods was found to be 2.5 W/(m∙K) The discovered enhancement of the above-mentioned parameter is considered a manifestation of the quantum size effects in heat transfer

The coefficients of thermal conductivity of the composite materials based on the zinc oxide powders with different grain size – 50 mm, less than 1 μm, and about 3 nm were determined by the radial heat flow method They were found to be equal to 0.8 W/(m∙K), 1.1 W/(m∙K) and 2.5 W/(m∙K) respectively The observed clear increase of the thermal conductivity of the thermal compound based on ZnO nano-powder instead of ZnO micro powder is explained by the ballistic conductivity, increase of the exciton thermal conductivity, and reduction of the contact thermal resistance

With its unique physical and chemical properties, such as high chemical stability, high electrochemical coupling coefficient, a broad range of radiation absorption, and high photostability, it is a multifunctional material in materials science, zinc oxide is classified as a semiconductor in group II-VI, whose covalence is on the boundary between ionic and covalent semiconductors A broad energy band (3.37 eV), high bond energy (60 meV), and high thermal and mechanical stability at room temperature make it attractive for potential use in electronics, optoelectronics, and laser technology The piezo- and pyroelectric properties of ZnO NPs mean that they can be used as a sensor, converter, energy generator, and photocatalyst in hydrogen production Because of its hardness, rigidity, and piezoelectric constant, it is an important material in the ceramics industry At the same time, its low toxicity, biocompatibility, and biodegradability make it a material of interest for biomedicine and in pro-ecological systems [9]

ZnO nanoparticles can be classified depending on physical and chemical properties; for instance, crystal structure, shape, surface area, size, and other properties change with size reduction This has risen to the improvement of methods to prepare mixtures, as well as mechanic and chemical procedures, the procedure of precipitation, surfactant precipitation, sol-gel, hydrothermal and solvothermal procedures, technique of microwave, emulsion, technique of microemulsion, CVD (Chemical vapor

12 deposition), MBE (Molecular beam epitaxy), spray method, laser ablation, among others

ZnO has different chemical and physical properties It can be used in numerous fields Zinc oxide is important in a wide range of applications, from medicine to agriculture, from paints to chemicals, and from tires to ceramics

Figure 2.5 Universal consumption of ZnO [6]

Zinc oxide NPs have certain properties that make them appropriate for applications associated with the central nervous system (CNS) and possibly with the improvement procedures of disease treatment over (mediating neuronal excitability) or (even the release of neurotransmitters) Several types of research have shown that zinc oxide influenced unalike tissues, cells, or functions, as well as neural tissue engineering and biocompatibility [10]

ZnO NPs have the potential to enhance the growth of food crops Seeds fixed by various ZnO-NPs concentrations improved seed propagation, seed strength, and plant growth ZnO-NPs were shown to be active in growing roots stems and seeds The importance of zinc oxide NPs in the biotechnology area was investigated by Paul and Ban They observed the effect of chemically prepared ZnO NPs on the biological system

Zinc oxide is also used at different concentrations (Streptococcus pneumonia, Bacillus subtitles, E Coli, and Pseudomonas aeruginosa) A quick rise of enzymatic activity was found through high concentrations of zinc oxide [11]

Electronics and electecnology industries Rubber Industrial

Fillers, activator of rubber compounds

Component of creams, powders, dental pastes etc., absorber of UV radiation

Used in: photoelectronics, field emitters, sensors, UV lasers, solar cells etc.

Used in: production of zinc silicates, typographical and offset inks, criminology, biosensor, process of producing and packing meat and vegetables products etc.

Figure 2.6 Zinc oxide applications stated in the manuscript [7]

Properties and applications of ZnO NPs / HDPE composite

ZnO nanoparticles can be included in plastics to shield them from UV radiation and microbial flora ZnO is a safe material with appealing antibacterial capabilities; nevertheless, polyolefins and polar materials often don't get along well because PE lacks any polar groups in its backbone to interact with the ZnO surface for effective dispersion into the polymeric composite Instead of the aforementioned, the HDPE/ZnO nanocomposite is utilized for ultraviolet radiation protection

It has a rough Mohs hardness of 4.5, making it quite a soft substance It possesses excellent thermal conductivity, high refractive index, antimicrobial, and UV protection qualities for materials science applications Strong defense against UVA and UVB radiation is provided by nanoscale and micron sized ZnO

The melt mixing process, which involves combining treated nano-ZnO additive and molten HDPE pellets using a twin-screw extruder, was initially utilized to create ZnO/PE nanocomposite Nanocomposites were found to have good mechanical and spectral characteristics, making them a potential for uses where UV absorption is crucial, such as food packaging and UV shields, among many other uses.

Technical tested Figure of ZnO NPs / HDPE composite

The following is a table of tested mechanical properties Figures and microhardness values for ZnO-NPs / HDPE composite

2.4.1 Microhardness values for HDPE/nano-ZnO composite

Table 2.3 Vickers microhardness values for HDPE/bulk ZnO composite [1]

Overview of injection molding technology

Injection molding is a technological method of producing goods by injecting molten material into a mold Injection molding can be done on a wide range of materials, including metals (also known as pressure casting), glass, elastomers, mixes, and, most typically, plastics Heat, ductility, and thermosetting properties

Plastic molding machines can be classified in a variety of ways, including:

 Clamping force: 50, 100 , 8000 tons are available

 Max shot weight each cycle: 1, 5, 8, 10 , 56, 120 oz

 By piston or screw type

 Screw types include horizontal and vertical screw kinds

The Injection Molding Machine's Structure:

Figure 2.7 Horizontal Injection Molding Machine [8]

Figure 2.8 Vertical Injection Molding Machine [9]

A clamping system, a mold, an injection system, a hydraulic system, and a control system are the basic components of an injection molding machine

Figure 2.9 Structure of the Injection Molding Machine [10]

This system is in charge of opening and closing the mold, as well as moving it and creating adequate force to keep it in place during the filling and injection processes This system is linear system

Mechanical clamping, hydraulic clamping, and hybrid mechanical-hydraulic clamping systems are all common types of clamping systems

There are two main components: the fixed mold and the moving mold The moveable mold normally carries the core, while the fixed mold usually contains the cavity The major components of the mold are a cooling system and a runner system

The injection system is made up of three major components: the hopper, the heating cylinder, and the screw, which includes the screw head and nozzle Small plastic pellets are used to feed the substance The hopper holds these raw ingredients before they enter the heating cylinder The heating cylinder causes the substance to pour out in liquid form The thermoforming sheets heat it

The screw has three stages: the material feeding portion, which moves the raw material forward, and the melting part, which occurs at the end of this section

The compression section, located in the screw's center, is utilized to compress the liquid substance

The mixing zone in the metering portion homogenizes the material before injection into the mold

The nozzle is the component that joins the screw head to the mold sprue During the injection molding process, the nozzle must have an appropriate form for material flow and be tightly linked to the sprue

The hydraulic system is in charge of providing energy to open and close the mold, retaining the load while clamping the mold, spinning the screw shaft, and applying force to the injector pins to release the mold A hydraulic system consists of a pump, valves, a hydraulic motor, a piping system, and a storage system

The control system is in charge of assuring consistent and reproducible machine operation It controls and shows numerous characteristics such as temperature, pressure, injection speed position, screw shaft speed, and hydraulic system position

The injection molding method has a relatively quick processing time, often spanning from 2 seconds to 2 minutes, and comprises of five stages:

Figure 2.10 Clamping and Injection process

Before pumping plastic into the mold, the two mold parts, one fixed and one moveable, must be tightly fastened While the material is being injected into the mold, the hydraulic clamping mechanism presses the two mold halves together and provides enough force to keep the mold tightly closed

Process of injection, the plastic pellets are melted by heat and pressure during this procedure The heated plastic is then pumped quickly into the mold The shot is the amount of substance injected Although the injection time is difficult to measure precisely, it can be estimated using the shot volume, injection pressure, and injection power

Cooling, plasticization, and product Ejection phase

Figure 2.11 Cooling, plasticization, and product Ejection process [11]

The cooling process, as soon as the molten plastic inside the mold contacts the inside surface of the mold, it begins to cool As the plastic cools, it solidifies into the appropriate product shape However, the product may shrink throughout the chilling process The mold cannot be opened until it has completely cooled The cooling time may be affected by the product's maximum wall thickness

The plasticization process, while the part cools, the barrel screw retracts and automatically draws additional polymer resin from the material hopper into the barrel The heater bands keep the barrel temperature appropriate for the type of resin used to ensure proper molding

Process of Ejection, after enough cooling time, the product can be ejected from the mold using an ejection mechanism attached to the mold's back half The mold can be closed once the product has been discharged to begin the next cycle

In the context of injection molding technology, filling time is critical to the overall manufacturing process It refers to the time required during the injection molding cycle to fill the mold cavity with molten material

During the filling process, molten material, often plastic, is pumped at a controlled pace and pressure into the mold This technique guarantees that the material flows smoothly and uniformly throughout the mold cavity, creating the final product and taking the proper shape To obtain the desired quality, accuracy, and structural integrity of the molded item, the filling time is carefully estimated and optimized

Several factors influence injection molding filling time Some of the essential criteria that determine the time include the viscosity and temperature of the molten material, the design of the mold, the complexity of the component geometry, and the injection pressure Manufacturers seek to discover the appropriate filling time that assures effective material flow while reducing flaws such as air traps, voids, or uneven filling through intensive testing, analysis, and simulation

Mechanical Testing

A popular technique for assessing the mechanical characteristics of materials is the tensile test, often known as the tension test or tensile strength test To quantify a specimen's reaction to stretching or elongation, a pulling force is used during the test Static testing refers to the testing technique where the load is steadily increased or maintained constant Tensile testing, compression testing, shear testing, and hardness testing are some of the static testing techniques

Dynamic testing refers to testing techniques that include impact loads, fast loads, and alternating loads This includes evaluating components under operational loads, fatigue strength tests, and bending impact tests Static testing refers to testing procedures where the load is either maintained constant or gradually increased Tensile testing, compression testing, shear testing, and hardness testing are some of these testing techniques Tensile testing using D638-14 standard [8]

Table 2.5 Specimen Dimensions for Thickness, T, mm (in.) A [3]

A Thickness, T, shall be 3.2± 0.4 mm (0.13 ± 0.02 in.) for all types of molded specimens, and for other Types I and II specimens where possible If specimens are machined from sheets or plates, thickness, T, shall be the thickness of the sheet or plate provided this does not exceed the range stated for the intended specimen type For sheets of nominal thickness greater than 14 mm (0.55 in.) the specimens shall be machined to 14 ± 0.4 mm (0.55 ± 0.02 in.) in thickness, for use with the Type III specimen For sheets of nominal thickness between 14 and 51 mm (0.55 and 2 in.) approximately equal amounts shall be machined from each surface For thicker sheets both surfaces of the specimen shall be machined, and the location of the specimen with reference to the original thickness of the sheet shall be noted Tolerances on thickness less than 14 mm (0.55 in.) shall be those standards for the grade of material tested

B for the Type IV specimen, the internal width of the narrow section of the die shall be 6.00 ± 0.05 mm (0.250 ± 0.002 in.) The dimensions are essentially those of die

C the Type V specimen shall be machined, or die cut to the dimensions shown, or molded in a mold whose cavity has these dimensions The dimensions shall be:

W-Width of narrow section = 3.18 ± 0.03 mm (0.125 ± 0.001 in.),

L-Length of narrow section = 9.53 ± 0.08 mm (0.375 ± 0.003 in.),

R-Radius of fillet = 12.7 ± 0.08 mm (0.500 ± 0.003 in.) The other tolerances are those in the Table

RO-Outer radius (Type IV)

D supporting data on the introduction of the L specimen of Test Method D1822 as the Type V specimen are available from ASTM Headquarters Request RR: D20-1038

E the tolerances of the width at the center Wc shall be +0.00 mm, −0.10 mm (+0.000 in.,

−0.004 in.) compared with width W at other parts of the reduced section Any reduction in W at the center shall be gradual, equally on each side so that no abrupt changes in dimension result F for molded specimens, a draft of not over 0.13 mm (0.005 in.) is allowed for either Type I or II specimens 3.2 mm (0.13 in.) in thickness See diagram below and this shall be considered when calculating width of the specimen Thus, a typical section of a molded Type I specimen, having the maximum allowable draft, could be as follows:

G overall widths greater than the minimum indicated are used for some materials in order to avoid breaking in the grips

H overall lengths greater than the minimum indicated are used for some materials to avoid breaking in the grips or to satisfy special test requirements

I test marks or initial extensometer span

J then self-tightening grips are used, for highly extensible polymers, the distance between grips will depend upon the types of grips used and may not be critical if maintained uniform once chosen [13]

Figure 2.15 Test method for tensile properties of plastics ASTM D638 [15]

A standardized specimen of the material is clamped at each end during the test, and a universal testing machine is used to progressively pull the specimen apart in opposite directions The specimen deforms as the force is applied, resulting in an expansion in length and a contraction in cross-sectional area Throughout the test, the applied force and the accompanying elongation or strain are noted

The ultimate tensile strength, yield strength, elongation at break, and modulus of elasticity of the material are all useful details revealed by the tensile test These characteristics reveal the material's mechanical strength overall, resistance to deformation, and capacity for pulling forces

Movable Cross Head Space for Compressive spacemen

Figure 2.16 Structure of Universal Compression Testing Machine [16]

Several uses for the tensile test results include material selection, quality assurance, design optimization, and research and development It aids engineers and scientists in comprehending the performance characteristics of the material and informing judgments about the material's mechanical qualities

The bottom and upper grips of the testing apparatus are used to clamp the tensile specimen at both ends The machine is then turned on, and the crosshead and upper grip slowly move upward, slowly delivering a tensile strain to the specimen The tensile specimen lengthens as a result of the load

Figure 2.17 The deformation of the tensile specimen [17]

Without experiencing considerable changes in cross-sectional area, the specimen elongates until it reaches the maximum tensile force The specimen then experiences substantial elongation at this point, undergoes necking in the middle, and ultimately fractures As the specimen necks down, the tensile force drops At the site of fracture, the tensile force is zero

Evaluation of the test result

The tensile force F and the accompanying elongation AZ are continually measured by a device throughout the tensile testing procedure The tensile force F and the cross- sectional area of the tensile specimen are used to determine the stress in the testing machine's units

The strain 𝜀� is calculated by the elongation:

Where F is the applied tensile force, 𝑆�0 is the original cross – sectional area of the specimen

Where ∆𝐿� is the change in length of the specimen and 𝐿�0 is the original length of the specimen

Hooke's Law is a mechanical principle in the field of materials that describes the linear relationship between stress and strain of an elastic material Hooke's Law is expressed as follows:

Hooke’s Law (linear), stress (𝜎�) is directly proportional to the strain (𝜀�) within the elastic deformation range of the material

Where E is the elastic modulus (Young’s modulus) of the materials, representing its stiffness

The yield strength is calculated by dividing the change in stress (∆𝜎�) by the change in strain (∆𝜀�) at the yield point:

The formula for tensile strength is as follows:

In this equation, the cross-sectional area of the specimen is referred to as the maximum load, which is the maximum force that was applied to it during the tensile test The maximum stress a material can endure before cracking or breaking under tension is known as tensile strength It is commonly represented in megapascals (MPa) or pounds per square inch (psi), which are measurements of force per unit area

2.6.3 ASTM D2240 standard and Shore hardness testing method

The American Society for Testing and Materials (ASTM) created the global standard known as ASTM D2240 It is frequently used in many different industries to gauge how tough rubber and elastomeric products are The Shore hardness testing method, a widely used and reliable method for determining the surface hardness of materials, is described in this standard

The Shore hardness test is performed in accordance with ASTM D2240, which details the circumstances, test methods, and essential tools The resistance of the material to indentation is measured with this technique using a measuring equipment with a specialized probe called a Shore hardness durometer The probe is applied to the surface of the material with a predetermined force, and the depth of penetration is measured

The Shore hardness scale is used to portray the test result as a numerical value There are two primary types of this scale, each with a different measurement range: Type

A for soft materials and Type D for tougher materials The physical characteristics of elastomeric materials, such as hardness, resilience, and impact resistance, are evaluated using the Shore hardness test results from ASTM D2240

Surface inspection using SEM

2.7.1 Overview of SEM (Scanning Electron Microscope)

SEM (Scanning Electron Microscopy) using electron beams and signals produced by the interaction of the electron beams with the sample, scanning electron microscopy, or SEM, is a technique for visualizing and examining the surface of materials SEM enables high magnification observations of incredibly minute details on a sample's surface, often ranging from a few hundred to thousands of times It is a crucial instrument for evaluating and researching materials

SEM creates images by scanning a material with a narrow electron beam and gathering the interaction signals These signals include X-ray emission, backscattered electrons, electron reflection, and electron emission from the material SEM can determine the sample surface's shape, structure, chemical composition, and physical characteristics by examining these signals

Applications for SEM can be found in a wide range of disciplines, including materials science, materials research, manufacturing technology, biology, medicine, and forensics As well as studying physical and chemical processes that take place on surfaces, it is used to examine the surface structures of materials, observe the morphological characteristics of samples, and analyze the formation and distribution of chemical components 36 on surfaces SEM is an effective method for investigating and getting more in-depth understandings of the surface characteristics and structure of materials and samples

Scanning Electron Microscope (SEM) Electron Gun

2.7.2 The history of Scanning Electron Microscope and EDS method

The history of Scanning Electron Microscope

The development of SEMs started with more of a whimper than a bang When the technology was first unveiled in 1935, a group of marketing professionals was asked to evaluate the new instrument's potential in the marketplace After polling the scientific community, the marketing experts weren't too optimistic They estimated a need for, at most, 10 of the devices worldwide As it turns out, the experts vastly underestimated the potential of SEMs, and thankfully, their dour outlook failed to deter further development of the technology As a result, more than 50,000 SEMs fill laboratories and businesses across the globe

For one thing, scientists had pushed optical microscopes to their limits Optical microscopes had been around for centuries, and while you can still find them in

44 classrooms across the country, their dependence on light had become a problem Light's tendency to diffract, or bend around the edges of optical lenses, limits the magnification capability and resolution of optical microscopes As a result, scientists began to develop new ways to examine the microscopic world around them and, in 1932, produced the world's first transmission electron microscope (TEM) This instrument directs a beam of electrons through the sample under observation and then projects the resulting image on a fluorescent screen TEMs, as you might guess, share a lot in common with SEMs, and it was only a matter of a few years before SEMs were developed

Since development of TEMs was well under way by the time SEMs came along, the latter were initially considered unnecessary It took the unwavering resolution of C.W Oatley, a professor of engineering at Cambridge University, to move the newer microscope forward Working closely with several of his colleagues and graduate students, Oatley was able to demonstrate both the SEM's magnification potential and the astonishing 3-D quality of images it produced Today, SEMs are routinely used in tasks like inspecting semiconductors for defects or exploring how insects work

Energy Dispersive X-ray Spectroscopy or Energy Dispersive Spectroscopy is a technique for analyzing the chemical composition of a solid based on recording the X- ray spectrum emitted by a solid due to interaction with radiation (mainly radiation) high-energy electron beams in electron microscopes) In the scientific literature, this technique is often abbreviated as EDX or EDS from the English name Energy-dispersive X-ray spectroscopy

In order to capture images of the microstructure of solids, high-energy electron beams that interact with the solid are used in the EDX technique, which is mostly used in electron microscopes A solid object will have its atoms thoroughly penetrated when a high-energy electron beam is directed onto it, interacting with the inner electron layers of the atoms According to Mosley's rule, this interaction produces X-rays with a characteristic wavelength proportionate to the atomic number (Z) of the atom

In other words, the frequency of X-rays released is unique to each substance's atom present in the solid The chemical components contained in the sample and their relative quantities can be determined by recording the X-ray spectra emitted from a solid object (see more information on the X-ray generating technique)

Figure 2.22 Principal diagram of the EDX spectral signal recording system in TEM

While EDX analysis equipment is widely available, it was primarily created for use in electron microscopes, where analyses are carried out using high-energy electron beams and focused by a set of electron lenses With the aid of an energy dispersive spectrometer, the frequency (or X-ray photon energy) of the emitted X-ray spectrum may be examined to learn more about the elements and composition The EDX method was created in the 1960s and commercial equipment appeared in the early 1970s using

Si, Li, or Ge displacement detectors

Recording technique and accuracy of EDX

X-ray energy dispersive spectrum of thin film sample, recorded on FEI Tecnai TF20 transmission electron microscope

X-ray emitted from a solid body (due to interaction with electron beam) will have a wide range of variable energy, will be sent to a dispersion system, and recorded (energy) by a displacement detector (usually Si, Ge)., Li ) is cooled by liquid nitrogen, which is a small chip that generates secondary electrons by interacting with X-rays, which are then driven into a small anode X-ray intensity is proportional to the fraction of elements present in the sample The resolution of the analysis depends on the electron beam size and the sensitivity of the detector (the active region of the detector)

EDX accuracy is on the order of a few percent (usually detecting the presence of elements in the order of 3-5% or more) However, EDX proves to be ineffective against light elements (e.g., B, C ) and often occurs the effect of overlapping the X-ray peaks of different elements (an element that usually emits a lot of light) characteristic peaks

Kα, Kβ , and peaks of different elements can overlap making analysis difficult)

Figure 2.23 X-ray energy dispersive spectrum of thin film sample

2.7.3 The operating principle and image formation in SEM

The following steps make up the scanning electron microscope (SEM)'s working principle:

Electron Beam Generation: A high-energy electron beam is produced by an electron source, such as a heated filament or a field emission gun

Electron Beam Focusing: The electron beam is focused and shaped by magnetic lenses, such as condenser and objective lenses, to ensure its accuracy and resolution

Sample Interaction: The sample surface is targeted by the focused electron beam Different interactions take place when the beam interacts with the sample, leading to the emission of diverse signals

Signal Detection: The radiated signals are gathered by detectors that are placed above the sample The corresponding signals are recorded by secondary electron detectors, backscattered electron detectors, and X-ray detectors

Image Formation: The radiated signals are gathered by detectors that are placed above the sample The corresponding signals are recorded by secondary electron detectors, backscattered electron detectors, and X-ray detectors

Taguchi method

The Taguchi method of quality control is a technical approach that emphasizes the role of research and development, product design and development in reducing the occurrence of defective products and defects in manufactured goods export The method, developed by Japanese engineer and statistician Genichi Taguchi, argues that in quality control, design is more important than manufacturing process, in order to eliminate manufacturing variances before they can be happen

For example, if the product under consideration is a drill that needs to drill holes of exact and identical dimensions in all material surfaces, then part of the quality of that product is determined by how many the machine is different from those standards

At the heart of the Taguchi approach to quality control is to use research and design to ensure that every unit of product will closely meet designed specifications and function exactly as designed

Loss from adverse effects to society refers to whether the product's design could lead to an adverse effect For example, if the design of a drill makes its operation possible to injure the operator, the quality of the product is reduced

According to the Taguchi method, the work done during the design phase of product creation is aimed at minimizing the likelihood that the drill will be built in such a way that its use could cause injury to the operator onion

From a higher perspective, the Taguchi method will also try to reduce costs to society in using the product, such as designing goods that work more efficiently instead of creating waste For example, drills can be designed to minimize the need for routine maintenance

Genichi Taguchi began formulating the Taguchi method while developing a telephone switching system for a Japanese company in the 1950s He aimed to improve the quality of manufactured goods using statistics

By the 1980s, Taguchi's ideas were beginning to gain influence in the Western world, making him famous in the United States, following his successes in Japan Well- known global companies such as Toyota, Ford, Boeing, and Xerox Holdings have adopted his approach

Taguchi’s methodology features and formulas

Features of the Taguchi method:

1 The Taguchi method complements 2 methods of whole experimental planning (TNT) and partial experimentation (TRT)

2 The Taguchi method is based on a pre-constructed orthogonal empirical matrix and a method for analyzing and evaluating results

3 Possible factors 2, 3, 4, 5 8 levels of value

4 The Taguchi method is best used with the number of survey factors from 3 to 50, the number of interactions is small, and when only a few factors are significant

The Taguchi method uses a signal-to-noise ratio of S/N converted from the loss function

L = k (y - m) 2 , where L is the loss due to a deviation from the desired response value m, k is constant The S/N ratio is constructed and converted to calculate for 3 main cases:

If the value that meets yi needs to reach "Greater than better" then:

If the value that meets yi needs to reach "Less than better", then:

If the response value needs to meet the "Assessment of the influence of factors", then:𝑦 𝑖

Where are the number of iterative experiments, standard deviation, and mean, respectively? In any case, the larger the ratio, the better the characteristic received Because it does not use all combinations of experiments, the Taguchi method does not give an exact number of the effects of a certain input parameter (factor) on the output but is only oriental However, judging by ratios helps technologists know trends and how each technological parameter affects outputs These identifications will help researchers quickly find out the technological parameters and scope to impact to get the best output efficiency On the basis of individual impact assessment, parameters can be found the optimal combination of technological parameters for the desired outcome characteristic results.𝑛, 𝑠, 𝑦‾S/NS/N

Many studies and applications since the 1970s have shown that the Taguchi method can be used for academic research, as well as for manufacturing applications, and is particularly suitable for those with limited understanding of statistics The Taguchi method is carried out in the following 7 basic steps:[1,2,3]

1 Select independent factors (Factors), control variables (Control Variable) and response variables (Response - output parameters), target functions (Objective Function)

2 Identify the domain of values of factors affecting the goal (response), the relationships that exist between factors (degrees of freedom) and distribute the entire domain of values of factors into levels

Table 2.8 Factors and value scoops [6]

1 Cutting tool working length (cm) L x 1

3 Create (select) an experimental planning matrix depending on the number of factors and the number of value levels, for example L9 as Table 2.8.2: columns are factors, rows are experiments (n) on Section 2.8.2, depending on the number of value levels and the number of factors

4 Conduct experiments to collect data on response values (output parameters) In some cases, in each experiment we repeat it Statistical analysis of empirical data.𝑛

5 Numerical data analysis, depending on the goal of "Higher-the-better", "Lower-the- better" or "Evaluate the influence of factors" we use Formula (7.1) to (7.3) Then determine the optimal experimental values of the factors S/N

To determine the influence of factors on outputs, we use Analysis of Mean (ANOM) and Analysis of Variance (ANOVA), to determine the degree of influence of factors on outputs

Table 2.10 Factors affecting momentum parameters [8]

The average S/N ratio for the value meets the value levels

Note: Take the average value that meets the factors of the same value (Level) The average value of the tợ numbers for each level of value of each factor is determined by the formula: 𝜂 m S/N

Where p is the number of elements of the same value as the factor j

Deviations can be assessed by different quantities, which can be done in 3 ways for the second factor:

 Total average deviation of value levels:

 The sum of the average squares of deviations of the value levels: s j = ∑ n u=1

 The sum of the squares of the average deviation between value levels s j = (𝜂 ml − 𝜂 m2 ) 2 + (𝜂 m2 − 𝜂 m3 ) 2 + (𝜂 m3 − 𝜂 ml ) 2 + ⋯

The degree of influence of each factor is evaluated as a percentage between the deviation of that factor and the total deviation of all factors (with the number of factors):S j k

6 Recalculate the target function according to the optimal set of factor values and test it experimentally This is an additional step since step 5 considers the influence of ratio-based factors.S/N

The Taguchi method is simple, the number of experiments is small, it can be quantitative or qualitative However, the method has drawbacks:

 Due to discrete data, the plan receives near-optimal expenditure

 Failed to introduce binding conditions

 Solve the single-target problem

EXPERIMENT AND SELECTION PROCESS

Experiment

At first, we set up a scale to a specific weight with the weight of the Becher After that, we calculate the percentage of ZnO-NPs are 0%, 1%, 2% 3% of 2 kg HDPE, which are about 0g, 20g, 40g and 60g

Figure 3.1 Material prepared before injection molding

We use a digital scale to calculate the weights of HDPE and ZnO-NPs

Figure 3.9 Calculating the weight of HDPE and ZnO-NPs 3.1.2 Mixing composites

To mix the composite, we use the mixing machine

First, we add 2kg of HDPE then add ZnO-NPs

Figure 3.10 Adding HDPE then ZnO-NPs

Second, close the lid and set up the heating flow The heat has to correct so that ZnO-NPs can hold the HDPE beads without melting the plastic In this case, we set up to 150 degrees Celsius

Figure 3.11 Setting up the heating flow

Third, click the start button so that the machine starts twirling round automatically We will wait for 1 hour

Finally, after finishing the work, take out the composite and continue with 2% and 3% ZnO-NPs respectively

We use 4 boxes to classified 0%, 1%, 2% and 3% HDPE - ZnO-NPs composites and noted their names on it Using desiccant bags to avoid steam

Figure 3.13 Box of ZnO-NPs

Even though it is carefully preserved, it is inevitable that the plastic particles will more or less absorb moisture In order for the pressed product to meet the requirements, the group must dry it before pressing

We dry the HDPE granules for 3 hours in 100 degrees Celsius

 Cycle Delay: Time to run automatically when taking out the product

During the product pressing process, we keep one parameter fixed without changing:

 Journey of the mobile plate

Mold size: The composite is put into the press and pressed at a temperature higher than the melting temperature of the plastic Advantages: Mass production, high productivity

First, use three mold cranes to move to the plastic injection machine and install the mold in the correct position, then proceed with bolting to ensure the mold is installed accurately and securely

After testing and adjusting the mold, we proceed to injecting the product on the

MA 1200III plastic injection machine at HAITAIN room, Ho Chi Minh City University of Technical Education

After injecting the product, we test the flexural and tensile strength of the product on a tensile machine

Test the ultimate tensile strength (UTS)

For tensile testing we use clamping mechanism with upper mobile clamp and lower fixed clamp

Turn on the CB inside the electrical box

Step 1: Select number 1 to turn the machine ON

Step 2: Select numbers 2 and 3 to set the force and displacement values to 0

Step 3: Enter number 11 to select pulling speed (maximum 10,000)

Step 4: Select number 4 (Jog Up) or select number 5 (Jog Down) to move to the pull sample position

Step 5: After setting the pattern, select number 6 (Set Home)

B6: Select number 4 (Jog Up) to break the sample, let the machine run about 10 mm more and select number 7 (Set End)

Step 7: Choose number 8 (Go Home)

Step 8: Choose number 9 (Create new file)

Step 9: Select number 10 (Go end) to drag and get data tensile test

After fixing the sample, press Jog up to drag the sample `

After dragging the sample, take it out and continue the next one

For flexural testing we use the bending jig with U-shaped bottom base and V- type upper base

Figure 3.15 Bending jig with sample

The operation is the same as tensile testing.

Selection

The extraction of samples by injection molding

Haitian International uses the Mars III series of plastic molding equipment The Haitian International MA 1200 III model is the specific plastic molding machine that is employed

HDPE and ZnO - NPs plastic is the material used for molding The group uses the following six parameters to guide its numerous stages of plastic

To ensure the sample can be correctly molded, without any resin shortages or typical molding defects like burrs or flash, a trial molding is first carried out to determine the set of parameters that provide the lowest values

We begin by setting values at six levels, starting with the simplest set of parameters

We discovered six distinct values at six distinct levels using the data mentioned above

The group has determined the parameters after performing the molding test with HDPE – NPs

Table 3.1 The minimum value table for the parameter set of HDPE at normal temperature

Filling time 3 Filling pressure 800 Packing time 8 Packing pressure 50 Melt temperature 220

From the above value table, the group has established a univariate value table for HDPE

Table 3.2 Univariate value table for HDPE – ZnO composite

Parameter Level 1 Level 2 Level 3 Level 4 Level 5

Based on the data above, a first table was created

Table 3.3 Five levels of utilization in the univariate table

(bar) Packing pressure (bar) Melt temp (°C)

We have obtained 100 cases, each with 4 different percentage values

(from 0 to 3%) Each percentage we have 5 cases Each case we have 5 samples

The sampling process is conducted with the following quantity At the beginning of the molding, around 2 initial samples are discarded to stabilize the plastic

Test samples after injection molding will be tested for Tensile strength

Figure 3.26 The sample before and after dragging

After conducting tensile testing on 5 samples for each case in the univariate value table, a total of 100 samples were tested, resulting in the following tensile data table

Table 3.4 Strength testing data of ZnO 0%, 1%, 2%, 3%

0% Max stress (MPa) Break strain (%)

Based on the charts and experimental data obtained from sampling, the team draws the graphs of two parameters, filling pressure and packing pressure, had under-expected quality and were not suitable Therefore, to optimize the analysis, our group decided to exclude this chart and introduce a new one, mold temperature This parameter proved to be appropriate for further research and analysis Therefore, we will use a new parameter table with 4 parameters and 5 different levels The test results for the two types of plastic using the new parameter set are as follows With the three existing parameters, filling pressure, packing pressure, and melting temperature, there are little change compared to

67 the old table The new one that has been modified into univariate The second table show univariate comparison after using Taguchi’s method:

Filling pressure (bar) Packing pressure (bar) Melt temp (°C)

Conclusion: Multivariate comparison has a lot of advantages over the traditional A/B comparison Although it has a lot in common, like both involve splitting live traffic to different design variations and both measure conversions However, in multi-variation testing, you test every possible combination of those variations That way we can determine what change or combination of changes will have the greatest impact

ANALYSIS AND EVALUATION OF THE RESULT

Results before and after parameter selection

Table 4.1 Five levels of utilization in the univariate table

(bar) Packing pressure (bar) Melt temp (°C)

Table 4.1 Five levels of multivariate table

Filling pressure (bar) Packing pressure (bar) Melt temp (°C)

Tensile testing analysis

4.2.1 Experimental chart effect of each percentage of ZnO-NPs to tensile strength

Figure 4.8 Tensile stress of 0% ZnO-NPs

4.2.2 Effect of ZnO-NPs to the Ultimate Tensile Strength and Elastic Modulus of HDPE

Figure 4.12 Graph of effect of Nano-ZnO percentage on Ultimate tensile strength

Conclusion: In the above experiment, it shows that the influence of changing additive on the tensile strength of the material is insignificant When changing the nano ZnO from 0% to 3%, the tensile stress of the material only changes slightly, ranging from 7.12 to 7.19 (MPa) This can be explained as follows, in the range of ZnO-NPs from 0% to 3%, the stress range that the composite can withstand is about 7 MPa and there is also a slight change fluctuating ±0.07 MPa, there is no strong impact in the range of changes of ZnO-NPs on the tensile stress in the experimental domain If compared with the tensile stress of the base plastic (HDPE plastic) with an optimal tensile stress of 7.12 (MPa) when adding additive such as ZnO-NPs, the mechanical properties change very small with the amplitude of change is about 0.18 (MPa) Thereby it can be explained that the strongest impact of additives on the tensile stress of the composite is 2% and it is possible that when increasing the amount of additive to a certain level, the tensile strength will not be affected

Graph of Effect of Nano-ZnO percentage on ultimate tensile strength

Figure 4.13 Graph of Effect of Nano-ZnO percentage on Tensile Elastic Modulus

Conclusion: Young's elastic modulus implies measure of bond strength between atoms It can be altered either by substituting or adding of ZnO-NPs at lattice points It is clear from table above that the elastic modulus increased from 0 to 3% nanocomposites sample (1798.9, 1822.18, 1827.49 and 1846.87 respectively) The modulus results are associated with the dispersion of the ZnO nanoparticles in the HDPE base Good dispersion achieved for ZnO 1, 2, 3% samples, resulted in improving in the modulus compared with pure HDPE

Graph of Effect of Nano-ZnO percentage on

Figure 4.14 Graph of Effect of Nano-ZnO percentage on Elongation

Conclusion: When changing the amount of ZnO-NPs, the mechanical properties of the material also change in many different trends In terms of elongation of the material, when increasing the additives amount from 0% to 1%, the elongation of the composite increases This can be explained because when the additive amount is increased, the bonds of the plastic are not intercepted much by the additive, making the bonds in the composite less likely to break than pure plastic However, at the composite stage, increasing the amount of nano ZnO 1%, the composite has a relatively similar elongation compared to itself from 0% to 1% This can also be explained as follows, when at a certain level of ZnO, the compatibility between ZnO and plastic is closely linked and harmonious, then the composite is no longer subject to major elongation mainly from the properties of plastic but purely from the elongation of a new material that is the optimal combination of plastic and ZnO-NPs.

Flexural strength analysis

4.3.1 Experimental chart effect of each percentage of ZnO-NPs to flexural strength

ZnO-NPs 0% a) Case 1 b) Case 2 c) Case 3 d) Case 4 e) Case 5

Figure 4.8 Flexural stress of ZnO-NPs 0%

ZnO-NPs 3% a) Case 1 b) Case 2 c) Case 3 d) Case 4 d) Case 5

4.3.2 Effect of ZnO-NPs to the Elongation of HDPE

Figure 4.12 Graph of effect of Nano-ZnO percentage on Flexural strength

Conclusion: Through experiments, it has been shown that the resistance of materials tends to increase gradually from 0% to 2% This can be explained because the existence of nano ZnO mixed with the base plastic will combine the two inherent mechanical properties of the two basic materials: the flexibility of the plastic and the solidity of the additives, so then the material will be subjected to gradually increasing load variations as the nano ZnO additive increases, specifically in the experiment the highest flexural strength is 74.07 MPa, an increase of nearly 2 MPa compared to the optimal strength of the HDPE plastic base material

Figure 4.13 Graph of Effect of Nano-ZnO percentage on deformation

Conclusion: The influence of nano ZnO additive on material deformation occurs with a significant decreasing trend from 0% to 1% (from 0.316 to only 0.308) Plastic deformation during the composite process is limited by the presence of nano-ZnO additive Increasing the amount of nano-ZnO additive (from 1 to 3%) will reduce the interparticle spacing of the additive Therefore, an increase in strain index as well as Vickersmicro hardness is observed as the nano-ZnO additive loading increases

Graph of Effect of Nano-ZnO percentage on deformation

Figure 4.14 Graph of Effect of Nano-ZnO percentage on Flexural Elastic Modulus

Conclusion: Through experiments, it has been shown that the elastic modulus of the material will gradually change when increasing the amount of additive, specifically from 0% to 3% This can be explained by the original properties of the additive, nano ZnO, which has high mechanical properties and good load resistance, so when combined with a substrate of HDPE plastic, it will create a composite composition with high specific hardness in experiments The highest flexural modulus of elasticity is 1691.78 MPa, an increase of nearly 400 MPa compared to the optimal flexural modulus of HDPE plastic (1338.6 MPa)

Conclusion: After three experimental surveys of ZnO-NPs to mechanical properties of materials, the following conclusions were drawn:

• Flexural strength gradually increases when the nano ZnO additive is from 0 to 2%

• Nano ZnO additive has small impact on the deformation of the material

• Nano-ZnO additive gradually increases the elasticity of plastic materials.

SEM and DSC analysis

The SEM images captured at the fracture positions of each type of plastic are shown as follows:

Figure 4.15 The structure of HDPE within ZnO-NPs

Figure 4.16 A close-up view of ZnO-NPs on sample

Figure 4.17 ZnO-NPs scattered above HDPE structure

Figure 4.18 SEM of HDPE ZnO-NPs 1%

Figure 4.19 SEM of HDPE ZnO-NPs 2% and 3%

Conclusion: When taken under a scanning electron microscope, cases with nano ZnO additive from 1% to 3% are tightly bonded to the plastic molecules, with no signs of cracking two components On the SEM-imaged film background, the ZnO nano particles are white, distributed relatively evenly in the plastic surface and have similar sizes This is proven when measuring and receiving results after many times, drawing the following conclusions:

 1% nano ZnO additive, size recorded after measurement is 177.8445 nm

 2% nano ZnO additive, size recorded after measurement is 167.4521 nm

 3% nano ZnO additive , size recorded after measurement is 194.3254 nm

The measurement results show that the nano ZnO additive varies quite a lot, but the distribution of Zno-NPs on the plastic base is very uniform, showing good compatibility between the base material and additive as well as the heating process when mixing them together goes well and there are no cases of underheating or overheating requirements

DSC studies show that the typical endothermic crystallization peak of HDPE corresponds to 131.8°C during heating; The exotermic crystallization peak was observed at 131.8°C during melting temperature at 123.4°C The difference between melting temperatures is based on the figure Thermomechanical history of the samples The properties of the polymer are determined during processing (mixing and injecting), which significantly affects the organization of the crystalline phase The presence of ZnO nanoparticles in the polymer does not affect this temperature The melting peak of HDPE and of all composites is asymmetric and bimodal during sample heating This may indicate the presence of more than a crystalline fraction of polyethylene in the material The parameters can vary in their thickness and orientation, spherical crystal structure, presence of interphases or unit cell structure

In this expression, ΔHm is the melting temperature due to equal to DSC and ΔHm o is the reference for the heat of fusion For HDPE, this reference value is 178.7 J/g This gives an estimated percentage crystallinity of 73.9% for the HDPE

Created with NETZSCH Proteus software

Sample : Reference : Material : Corr./temp.cal : Sens.file :

HDPE , 8 mg none,0 mg HDPE / 11-01-2022 13:57 11-01-2022 13:45

Range : Sample car./TC : Mode/type of meas : Segments : Crucible :

40°C/10.0(K/min)/250°C DSC 214 Corona sensor / E DSC / Sample 1/1 Concavus Pan Al, slide-in lid

N2, 40.0ml/min / N2, 60.0ml/min 059/5000 àV

Instrument : NETZSCH DSC 214 Polyma DSC21400A-1082-L File : E:\Tien\20231208\HDPE.ngb-sdg

Peak: 132.1 °C, 3.271 mW/mg Peak: 132.1 °C, 3.271 mW/mg

Figure 4.21 DSC of HDPE ZnO-NPs 1%

HDPE-1%ZnO, 8.2 mg none,0 mg HDPE-1%ZnO / 11-01-2022 13:57 11-01-2022 13:45

N2, 40.0ml/min / N2, 60.0ml/min 059/5000 àV

Instrument : NETZSCH DSC 214 Polyma DSC21400A-1082-L File : E:\Tien\20231208\HDPE-ZnO1%.ngb-sdg

N2, 40.0ml/min / N2, 60.0ml/min 009/5000 àV

Instrument : NETZSCH DSC 214 Polyma DSC21400A-1082-L File : E:\Tien\20231208\HDPE-ZnO 2%.ngb-sdg

Main 2023-12-11 15:01 User: lms HDPE-ZnO 2%.ngb-odg

N2, 40.0ml/min / N2, 60.0ml/min 059/5000 àV

Instrument : NETZSCH DSC 214 Polyma DSC21400A-1082-L File : E:\Tien\20231208\HDPE-ZnO 3%.ngb-sdg

Figure 4.24 Estimated percentage of crystalinity in DSC analysis of HDPE with ZnO-

Taguchi mehod analysis

Estimated percentage of crystalinity in DSC analysis of HDPE with ZnO-NPs

7.41 - 0.0042 ZnO (%) – 0.0312 Filling pressure (bar) + 0.0356 Packing pressure (bar)

Table 4.3 Coefficients for tensile strength

Term Coef SE Coef T-Value P-Value VIF

Table 4.4 Model Summary for tensile strength

S R-sq R-sq(adj) R-sq(pred)

Table 4.5 Analysis of Variance for tensile strength

Source DF Adj SS Adj MS F-Value P-Value

Table 4.6 Fits and diagnostics for Unusual Observations for tensile strength

Obs UTS Fit Resid Std Resid

Table 4.7 Response Table for Signal to Noise for tensile strength

Level ZnO (%) Filling pressure (bar) Packing pressure (bar) Melt temp

Table 4.8 Response Table for Means for tensile strength

Figure 4.25 Main effects plot for means

Figure 4.26 Main effects plot for SN ratio

Table 4.9 Prediction for tensile strength

Table 4.10 Settings for tensile strength

ZnO (%) Filling pressure (bar) Packing pressure

By using Taguchi method, we have conclusions:

Filling pressure has the greatest influence on tensile strength results, and the least influence on tensile strength is percentage of ZnO-NPs

The most appropriate pressing plan is:

- Predicted tensile strength is 7.44 MPa if the most appropriate option is used

Flexural strength Table 4.11 Coefficient for flexural strength

- 0.193 Packing pressure (bar) + 0.026 Melt temp (°C)

Term Coef SE Coef T-Value P-Value VIF

Table 4.12 Model summary for flexural strength

S R-sq R-sq(adj) R-sq(pred)

Table 4.13 Analysis of Variance for flexural strength

Source DF Adj SS Adj MS F-Value P-Value

Table 4.14 Fits and diagnostics for Unusual Observations of flexural strength

Obs UTS Fit Resid Std Resid

Table 4.15 Response Table for Signal to Noise of flexural strength

Table 4.16 Response Table for Means of flexural strength

Figure 4.27 Main effects plot for means

Figure 4.28 Main effects plot for SN ratio

Table 4.17 Prediction for flexural strength

Table 4.18 Settings for flexural strength

ZnO (%) Filling pressure (bar) Packing pressure

Packing pressure has the greatest influence on flexural strength results, and the least influence on flexural strength is filling pressure

The most appropriate pressing plan is:

The flexural strength is predicted to be 75.619 MPa if the most appropriate option is used.

Hardness result

Table 4.19 Result of hardness testing (shore D)

Case 1 Case 2 Case 3 Case 4 Case 5 Case 1 Case 2 Case 3 Case 4 Case 5

Figure 4.29 Hardness of samples measured by shore D

ZnO-NPs percentage (%)Hardness of samples measured by shore D

Conclusion: After hardness test proceed by using shore D, we can see that HDPE is ranked extra hard in shore D scale The effect of ZnO-NPs is not considerable With the hardness property we measured, HDPE is suitable for making safety equipment, durable tools, and mechanical materials

CONCLUSION AND RECOMMENDATION

Conclusion

After implementing the project, the team has known the tasks in each stage of this project Start by choosing the type of plastic and additives based on their quantity and mechanical properties

Use a mixer to mix HDPE plastic with ZnO nano additives in each percentage (in order from 0% to 3%), thereby understanding how to operate the mixer and the specific temperature for the additive to adhere to plastic beads

Use a drying machine to dry the resin mixture, thereby knowing the appropriate temperature for the resin to dry without overheating

Use the Haitien Mars III plastic injection machine to mold plastic into test products From there, experience is gained in operating the machine, appropriate pressing parameters as well as planning product production with the best quantity and quality

Through the tensile-flexing test to measure the durability of the sample, we learned how to use the tensile testing machine and process parameters after testing

Using the Taguchi processing method, we learn how to use software to calculate, predict, and give optimal results during the pressing process and find the pressing case that is suitable for tensile-flexural strength and image composition most affects the tensile-flexural strength

Through the process of analysis, statistics, and parameter processing, our team has learned how to compare cases with each other through charts and graphs to find trends in the effects of additives on materials, and which cases affect the material the most

Expand the scope of materials research: Research can continue to explore the effects of different materials on the durability of composite products It can consider testing and comparing the effects of new materials, recycled materials, or composite materials to evaluate their mechanical and tensile properties as well as flexural strength

Optimizing the Synthetic Formula: Research may focus on optimizing the synthetic formula to achieve maximum strength By varying the ratio and type of

101 material, layer structure, and manufacturing process, the ideal combination of strength and other mechanical properties of a composite product can be found

Application and field expansion: Research results can be applied in many different industrial fields Further research into the application of composites in industries such as transportation, aerospace, architecture, shipbuilding, and green energy will create new growth opportunities and broaden the impact of this thesis

By continuing to research and expand these development directions, this graduation thesis will contribute to understanding the influence of materials on the durability of composite products after injection molding and bring practical value in the field of injection molding composite production and application

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Tiêu đề	Investigate Mechanical Properties Of HDPE Composite Enhanced With Zno Nanoparticles In Injection Molding
Tác giả	Nguyen Hoang Thanh Long, Do Cao Anh Khoa, Nguyen Quoc Nam
Người hướng dẫn	Ph. D Nguyen Van Thuc
Trường học	Ho Chi Minh City University of Technology and Education
Chuyên ngành	Mechanical and Manufacture Engineering
Thể loại	Graduation Project
Năm xuất bản	2024
Thành phố	Ho Chi Minh City

Định dạng
Số trang	130
Dung lượng	12,7 MB