Plastics Product Design Part 14 pot

500 Plastics Engineered Product Design inexpensive, and controllable large production method. They also paved the way for the overwhelming triumph of the polyolehs in subsequent years. All this is now changing to some degree, with the metallocene catalysts, Unlike the Z-N, the new generations of catalysts can provide very simplified production capabilities that produce improvements in properties, processability, and cost. Catalyst metallocene Catalyst Also called single site, Me and m. Metallocene catalysts achieve creativity and exceptional control in polymerization and molecular design permitting penetration of new markets and expand on of present markets. Chemists can model and predict plastic structure in a matter of days rather than years. Emphasis has been on the polyolefins (mPOs); others include PS, PE/PS, TPO, and EPDM. Uniformity of molecular weight effectively eliminates molecular extremes resulting in a range of property improvements that are targeted to include improved mechanical, physical, and chemical properties; provide processing advantages; and lower costs. Available are uniquely synergistic combinations of complementary abilities. As an example, mPE becomes an economical material competing with the properties of nylon and thermoplastic polyester plastics. Also one can produce mLLDPE film with the same strength at a lower gauge than conventional LLDPE because of its narrow molecular weight range. These Me catalysts are more accurate in characterizing plastics than today’s quality control instruments can verify. They produce plastics that are stronger and tougher; thus less plastic is required. They process in a different manner so one has to become familiar with the processing techniques. Target is to obtain a plastic with a specific molecular weight distribution (MWD), density, melt flow rate, tensile strength, flexural modulus, or a combination of other factors. Whatever the parameter, Me catalysts allow fabricators to alter reactor temperatures, pressures, and other variables to achieve their goal. Performancewise, mPO grades, regardless of density or comonomer, can combine softness and toughness, whereas conventional POs must trade off one for the other. These catalysts can make plastics that process well by knitting long branches into the carbon chains. They make plastics with uniform, narrow MWD, high comonomer content, very even comonomer distribution, and enormously wide choice of comonomers compared to multi-site Z-N catalysts. Comonomer choices include aromatics, styrene compounds, and cyclic olefins. Copolymers made with conventional Z-N catalysts favor ethylene and propylene. They incorporate only isolated amounts of more exotic monomers. The Me catalysts have been used to make different plastics such as PE homo-, co-, or ter-polymers from 0.865 to 0.96 density; isotactic, syndiotactic, and atactic PP; syndiotactic PS; and cyclic olefin copolymers. As an example, blown film extruders designed to process LLDPE can process mLLDPE generally without difficulty; torque, head pressure, and motor load limitations generally do not limit film productivity. However, it is important to understand the differences arising from the different Appendix B - Glossary 501 1 rheologies. The mLLDPE has a narrower MWD, and it thus exhibits lower shear sensitivity. The extruder would operate at higher temperatures and motor torque levels, while decreasing bubble stability and easing tensions on winding and draw down ratio. The Me with less chain branching would result in faster melt relaxation and less draw resonance. One with lower density would have greater elasticity, decreased specific rate in a grooved feed machine, and increased specific rate in a smoothbore machine, while harder to wind. All other things being equal, they are more viscous at typical extrusion shear rates than conventional LLDPE. There is a difference between shear rheology with the same screw/barrel. The mLLDPE will extrude at a higher melt temperature profile. This action may limit output on cooling- limited lines, but it may be possible to keep line speeds constant. Result is making a thinner film having the same performance because of the better properties offered by mLLDPE. Barrel cooling can be used to reduce mLLDPE melt temperatures but it may be more desirable to optimize the extruder screw for the plastic’s rheology. Catalyst summation The new polymerization catalysts with conventional commodity feedstocks have produced a wave of new plastics that became obvious early during the 1990s. The terms used with this new technology include metallocene, single-site, constrained-geometry, and syndiotactic. Center for Process Analytical Chemistry CPAC is an industry university consortium headquartered at the University of Washington. The team of faculty members, research staffers, visiting scientists, and graduate students conducts research at I 0 university nationwide and works with companies to develop technology. The charter focuses on chemometrics, sensors, spectroscopy, chromatography, and microflow analysis. The main objective is to develop real time measurement and relevant data handling techniques. Channel With the screw in the barrel, it is the space bounded by the interfaces of the flights, the root of the screw, and the bore of the barrel. This is the space through which the stock (melt) is conveyed and pumped. Chisolm’s law Anytime things appear to be going better, you have overlooked something. Chlorinated solvent Chlorinated solvents (CSs) were first produced over a century ago and came into common usage in the 1940’s. Chlorinated solvents are excellent degreasing agents and they are nearly non- flammable and non-corrosive. These properties have resulted in their widespread use in many industrial processes such as cleaning and degreasing rockets, electronics and clothing (used as dry-cleaning agents), plastics, and medical devices. Chlorinated solvent compounds and their natural degradation or progeny products have become some of the most prevalent organic contaminants found in the shallow groundwater of the USA. The most commonly used chlorinated solvents are perchloroethene (PCE), trichloroethene (TCE), 1, I, 1-trichloroethane (TCA), and carbon tetrachloride (CT). 502 Plastics Engineered Product Design Chromatography A technique for separating a sample material into constituent components and then measuring or identifylng the compounds by other methods. As an example separation, especially of closely related compounds, is caused by allowing a solution or mixture to seep through an absorbent such as clay, gel, or paper. Result is that each compound becomes adsorbed in a separate, often colored layer. Clean-area, fabricating Technology provides a milieu of artificial purity to protect sensitive products from air-laden particle contamination. Required measures include: (1) a workplace correctly designed for clean-air technology and suitable conduct by employees, (2) effective filtration of the air supply and carefully planned air ducting, (3) easily to clean surfaces throughout the clean-area, (4) a high degree of automation of all work operations, and (5) regular monitoring with the aid of suitable particle measuring technology. Cleaning equipment Different equipment requires cleaning on a periodical maintenance time schedule to ensure their proper operation. Available are cleaning devices for molds, extruder dies and screen changers, molded flash, etc. that operate economically and safely removing contaminated plastics. The routine techniques used include blow torches, hot plates, hand working, scraping, burn-off ovens, vacuum pyrolysis, hot sand, molten salt, dry crystals, high pressure water, ultrasonic chemical baths, heated oil, and lasers. Personnel have to be careful not to damage expensive tooling by spot annealing, mechanical abuse, etc. There are commercial cleaning systems used such as aluminum oxide beds (fluidized beds), salt baths, hot air ovens, and vacuum pyrolysis. As an example, the vacuum pyrolysis cleaner utilizes heat and vacuum to remove the plastic. Most of the plastic is melted and trapped. Remaining plastic is vaporized and appropriately collected in a trap. Cleaning plastic Different techniques are used to clean fabricated products. Included is solvent, ultrasonic, blasting with dry ice (carbon dioxide) pellets, toxic chemicals, and even PCFC-based solvents, particular medical devices. Cleanroom In the past clean rooms where left to a few, usually the larger plants or specialized operations concerned with medical or pharmaceutical products. In the mean time, processors have not been able to isolate themselves fiom the trend toward clean room production in order to achieve the necessary quality levels fiom the electronics and micro electronics industries, and lately, even fiom other industries such as automotive and entertainment. With carell planning, considerable savings can be made in investments and operating costs. The required degree of cleanliness, in particular, determines costs to a large extent and is directly influenced by a number factors such as the size of the room and contaminants. The worst enemy is dust that must be eliminated with the greatest producer are human beings. The smallest dust particles are less than 0.5pm. Moreover, the number of particles depends on the type and speed of any motions. Since the continued production of dust is unavoidable, measures must be taken to reduce the total particle count. The lower the permissible amount of dust in a planned production area, the greater the resultant costs. Cleanroom standard The US Federal Standard 209E, Airborne Particulate Cleanliness Classes in Clean-rooms and Clean Zones, is required for manufacturers who want to conform to quality system regulation. Via the industrial IS0 European Community, it has been integrated with ISO. Among the more important recent changes are metrication, revision of upper confidence level (UCL) requirement, provisions for sequential sampling, and an alternative verification procedure based on determination of the concept of ultra-fine particles known as U descriptors. Cold flow It is creep at room temperature. Commodity & engineering plastics About 90wt% of plastics can be classified as commodity plastics, the others being engineering plastics. Commodity plastics are usually associated with the higher volume, lower priced plastics with low to medium properties. Used for the less critical parts where engineering plastics are not required. The five families of commodities LDPE, HDPE, PI', PVC, and PS account for about two thirds of all the plastics consumed. The engineering plastics such as nylon, PC, acetal, etc. are characterized by improved performance in higher mechanical properties, better heat resistance, higher impact strength, and so forth. Thus, they demand a higher price. About a half century ago the price per pound difference was at 20C; now it is above $ 1.00. There are commodity plastics with certain reinforcements and/or alloys with other plastics that put them into the engineering category. Many TSs and RPs are engineering plastics. Computer See Chapter 5. Computer science & algebra The symbolic system of mathematical logic called Boolean algebra represents relationships between entities; either ideas or objects. George Boole of England formulated the basic rules of the system in 1847. The Boolean algebra has been used extensively in the fields of chemistry and engineering associated with plastics and eventually became a cornerstone of computer science. Constant lead Also called uniform pitch screw. A screw with a flight of constant helix angle. Contamination Any unwanted or foreign body in a material or the processing area, including air, that affects or detracts from part's quality. Control, solid state This is the type of control system that superceded relay control. It is based on electronic components that have no moving parts and yet can, for example, provide switching action. Controlled motion Linear guides used in different equipment provide a means of low-friction precision linear motion through an assortment of rails (round or profile), contact elements (rollers, ball bearings, or full- contact sleeves), and mounting configurations. Many types of guides exist, 504 Plastics Engineered Product Design each engineered toward optimized performance in a specific range of applications. Therefore, various application criteria d effect Linear guide incorporation. These criteria can be summarized as follows: dynamic load capacity, envelope size, mounting configurations, life, travel accuracy, rigidity, speed/acceleration, cost, and environmental considerations. The priority of these items will determine the appropriate linear guide for application. Controller Any instrumentation such as pressures, temperatures, timers, etc. used to control and regulate the fabricating cycle. Corona resistance Among the factors contributing to the breakdown of insulating materials is dielectric heating at high frequencies and, in many instances, the effect of corona. Corona is usually described as the partial breakdown of insulation due to the concentration of electrical stress at sharp edges, or actual breakdown of insulation when placed in series with another insulation having a different dielectric constant. In use at DC potentials the average insulation has very little corona. However, at frequencies from 60 cycles up, the corona becomes apparent and is an important factor in the service life and breakdown of the dielectric. For use at high voltages and frequencies, for example, polyethylene is usually impregnated with insulating oil, such as silicone oil. However, corona discharge does occur in oil, and if the oil breaks down the corona will produce higher stresses and erode away the surface of the dielectric, thereby reducing its thickness and causing a breakdown. Most high plastic insulating materials, such as polyethylene, Mylar, polystyrene, nylon and silicone, have about the same resistance to corona. Kel-F and Teflon are particularly susceptible to the erosion effects of corona. At a frequency of 60 cycles per second, a 4.5 mil sample of polycthylcnc, strcsscd at 600 volts per mil, will average about 50 h before breakdown occurs. The time to breakdown for polystyrene is approxi- mately 75 h, while that of Teflon is only about 6 hours. Crack growth Crack growth behavior can be analyzed using fracture mechanics that can provide fracture toughness to prevent fracture. Fracture is a crack-dominated failure mode. For fracture to occur, a crack must somehow be created, then initiate, and finally propagates. The prevention of any of these events will prevent fracture. Cracks can be considered elastic discontinuities that can come fiom a variety of sources such as internal voids or dirt, and/or surface scratch, embrittlement, or weld line. Cracks can be consequences of faulty design, poor processing, and/or poor handling of raw material, assuming material arrived clean. Crazing See Stress whitening. Creep It is the time-dependent increase in strain in material, occurring under stress. Creep at room temperature is sometimes called cold flow. It is the change in dimensions of a plastic under a given stress/load and temperature over a period of time, not including the initial instantaneous elastic deformation. Appendix B - Glossary 505 - Crystallinity and orientation When crystallites already exist in the amorphous matrix, orientation will make these crystallites parallel. If a plastic crystallizes too far in the melt, it may not contain enough amorphous matrix to permit orientation, and will break during stretching. (Most partially crystalline plastics can be drawn 4 to 5 times.) The degree of crystallinity is influenced by the rate at which the melt is cooled. This is utilized in the fabrication operations to help control the degree of crystallinity. The balance of properties can be slightly altered in this manner, allowing some control over such parameters as container volume, stiffness, warpage, and brittle- ness. Nucleating agents are available that can promote more rapid crystallization resulting in faster cycle times. Curing It is basically to change properties of a plastic material by chemical polycondensation or addition reactions; generally refers to the process of hardening a plastic. More specifically it refers to the changing of the physical properties of a material by chemical reactions usually by the action of heat (includes dielectric heat, etc.) and/or catalyst with or without pressure. It is the process of hardening or solidification involving cross- linking, oxidizing, and/or polymerization (addition or condensation). The term curing, even though it is applied to thermoset and thermoplastic materials, is a term that refers to a chemical reaction (cross-linking) or change that occurs during its processing cycle. This reaction occurs with TS plastics or TS elastomers as well as cross-linked TPs that become TSs. Decompression Injection and blow molding machines are fitted with decompression or suck-back. After the screw has finished rotating, it is drawn back so as to suck material away from the nozzle tip. This facility allows the use of an open nozzle. Keep the amount of suck-back as small as is practicable as the introduction of air can cause problems with some materials, for example, with PA 66 where processing temperatures are high. Definition It is important to define words or terms, as well as abbreviations, in order to ensure that proper communication exists. Many times there can be more than one definition in order to meet different requirements as setup by different organizations, industries, legal documents, etc. In fact the definitions could have opposite or completely different meanings. Definition, art of Providing written, graphics, etc. definitions throughout all industries (designers, fabricators, societies, trade organizations, etc.) to legal regulations (local, state, federal, worldwide, etc.) are extremely important. As an example, to enforce a law FDA, court trial, and others are obligated to interpret the language of the law. Inevitably it will sometimes stretch definitions rather “far” (as is done with the US constitution). The challenge for FDA and others is to keep them within the bounds of reason. Thus, care and a concentrated effort is required to ensure that your definition is specific, complete, concise, and not subject to change. Deflashing Technique of removing flash from a plastic product, usually a molding. Several different methods are employed that include low temperatures of dry ice and cryogenic. 506 Plastics Engineered Product Design Deformation, plastic Plastics have some degree of elasticity so as long as the plastic stretches within its elastic limit, it will eventually return to its original shape. When overstressed it reaches what is known as plastic deformation where the plastic will not return to its original shape. Denier It is the number that represents the weight in grams of 9000 meters of yarn, and is a measure of linear density. An alternative unit is the tex, representing the weight in grams of 1000 meters. Yam linear density is sometimes expressed in decitex where 1 dtex = 0. 1 tex. Design source reduction This generally defines the design, manufacture, purchase, or use of materials or products to reduce the amount of material used before they enter the municipal solid waste stream. Because it is intended to reduce pollution and conserve resources, source reduction should not increase the net amount or toxicity of waste generated throughout the life of the product. The EPA has established a hierarchy of guidelines for dealing with the solid waste situation. Their suggestions logically include source reduction, recycling, waste-to-energy gains, incineration, and landfill. The target is to reduce the quantity of trash. Design verification DV refers to the series of procedures used by the product development group to ensure that a product design output meets its design input. It focuses primarily on the end of the product development cycle. It is routinely understood to mean a thorough prototype testing of the final product to ensure that it is acceptable for shipment to the customers. In the context of design control, however, DV starts when a product’s specification or standard has been established and is an on-going process. The net result of DV is to conform with a high degree of accuracy that the final product meets performance requirements and is safe and effective. According to standards established by ISO-9000, DV should include at least two of the following measures: (a) holding and recording design reviews, (b) undertaking qualification tests and demonstrations, (c) carrying out alternative calculations, and (d) comparing a new design with a similar, proven design. Deviation It refers to the variation from a specified dimension or design requirement, usually defining the upper and lower limits. The mean deviation (MD) is the average deviation of a series of numbers from their mean. In averaging the deviations, no account is taken of signs, and all deviations whether plus or minus, are treated as positive. The MD is also called the mean absolute deviation (MAD) or average deviation (AD). Deviation, root-mean-square RMS is a measure of the average size of any measurable item (length of bar, film thickness, pipe thickness, coiled molecule, etc.) that relates to the degree of accuracy per standard deviation measurement. Devolatilization It is an important operation in the processing of plastics into products without contaminants. Since contaminants in most cases are volatile relative to their plastic, they are removed from the condensed phase by evaporation into a contiguous gas phase. Such separation Appendix B - Glossary 507 - -* processes are commonly referred to as devolatilization (DV). The plastic to be devolatilized may be in the form of a melt or particulate solid. Separation is effected by applying a vacuum or by using inert substances, such as purging with nitrogen gas or steam. Basically one or more volatile components are extracted from the plastic. It can be either in a solid or molten state. Two types of actions occur: (1) volatile components diffuse to the plastic-vapor interface (called diffusional mass transport) and (2) volatile components evaporate at the interface and are carried away (called convective mass transport). If (1) is less then (2), the process is diffusion-controlled. This condition represents most of the plastic devolatilization processes because plastic diffusion constants are usually low. The important relationship in diffusional mass is Fick‘s law. It states that in diffusion the positive mass flux of component A is related to a negative concentration of ingredients. This law is valid for constant densities and for relatively low concentrations of component A in component B. The term binary mixture is used to describe a two-component mixture. A binary diffusivity constant of one component is a binary mixture. The diffusional mass transport is driven by a concentration gradient, as described by Fick’s law. This is very familiar with Fourier’s law, which relates heat transport to a temperature gradient. It is also very similar to Newton’s law that relates momentum transport to a velocity gradient. Because of the similarities of these three laws, many problems in diffusion are described with similar equations. Also several of the dimensionless numbers used in heat transfer problems are also used in diffusion mass transfer problems. Die See Tool. Differential scanning calorimetry DSC is a method in which the energy absorbed or produced is measured by monitoring thc difference in energy input (energy changes) into the material and a reference material as a function of temperature. Absorption of energy produces an endothermic reaction; production of energy results in an exothermic reaction. Its use includes studying processing behavior of the melting action, degree of crystallization, degree of cure, applied to processes involving a change in heat capacity such as the glass transition, loss of solvents, etc. Dilatant Basically a material with the ability to increase its volume when its shape is changed. A rheological flow characteristic evidenced by an increase in viscosity with increasing rate of shear. The dilatant fluid, or inverted pseudoplastic, is one whose apparent viscosity increases simultaneously with increasing rate of shear; for example, the act of stirring creates instantly an increase in resistance to stirring. Anisotropic construction One in which the properties are different in different directions along the laminate flat plane; a material that exhibits different properties in response to stresses applied along the axes in different directions. Directional terminology 508 Plastics Engineered Product Design Balanced construction In woven RPs, equal parts of warp and fill fibers exist. Construction in which reactions to tension and compression loads result in extension or compression deformations only, and which in flexural loads produce pure bending of equal magnitude in axial and lateral directions. It is an RP in which all laminae at angles other than 0" and 90" occur in -c pairs (not necessarily adjacent) and are symmetrical around the central line. Biaxial load A loading condition in which a specimen is stressed in two different directions in its plane, i.e., a loading condition of a pressure vessel under internal pressure and with unrestrained ends. Bidirectional construction An RP with the fibers oriented in various directions in the plane of the laminatc usually idcntifics a cross laminate with the direction 90" apart. Isotropic construction RPs having uniform properties in all directions. The measured properties of an isotropic material are independent on the axis of testing. The material will react consistently even if stress is applied in different directions; stress-strain ratio is uniform throughout the flat plane of the material. Isotropic transverse construction Refers to a material that exhibits a special case of orthotropy in which properties are identical in two orthotropic dimensions but not the third. Having identical properties in both transverse but not in the longitudinal direction. Nonisotropic construction A material or product that is not isotropic; it does not have uniform properties in all directions. Orthotropic construction Having three mutually perpendicular planes of elastic symmetry. Quasi-isotropic construction It approximates isotropy by orientation of plies in several or more directions. Unidirectional construction Refers to fibers that are oriented in the same direction, such as unidirectional fabric, tape, or laminate, often called UD. Such parallel alignment is included in pultrusion and filament winding applications. Z-axis construction In RP, the reference axis normal (perpendicular) to the X-Y plane (so-called flat plane) of the RP. Disc feeder Horizontal, flat, grooved discs installed at the bottom of a hopper feeding a plasticator to control the feed rate by varying the discs speed of rotation and/or varying the clearance between discs. A scraper is used to remove plastic material fiom the discs. Dispersive mixing. A mixing process in which an intrinsic change takes place in the physical character of one of the components. Agglomerates are reduced in size by fracture due to stresses generated during mixing. Distributive mixing. Reducing the composition non-uniformity where the ingredients do not exhibit a yield stress. Downtime See Processing line. Appendix B - Glossary 509 Dry cycle Number of cycles the machine can perform in 1 minute, with a mold installed, but ignoring injection, plasticizing, and dwell time. The following phases are performed by the machine during a dry cycle rate measurement: (1) mold closing and clamping, (2) nozzle-to-mold approach, (3) nozzle retraction from mold, and (4) mold opening. Elastomer An elastomer is a rubberlike material (natural or synthetic) that is generally identified as a material that at room temperature stretches under low stress to at least twice its length and snaps back to approximately its original length on release of the stress (pull) within a specified time period. The term elastomer is often used interchangeably with the term plastic or rubber; however, certain industries use only one or the other. Although rubber originally meant a natural thermoset elastomeric (TSE) material obtained from a rubber tree (hevea braziliensis), it identifies a TS elastomer (TSE) or thermoplastic elastomer (TPE) material. They can be differentiated by how long a material deformed requires to return to its approximately original size after the deforming force is removed and by its extent of recovery. Different properties also identify the elastomers such as strength and stiffness, abrasion resistance, solvent resistance, shock and vibration control, electrical and thermal insulation, waterproofing, tear resistance, cost-to-performance, etc. Elastomer terminology per ASTM D 1418 is shown in Table B-l on page 487. The natural rubber materials have been around for over a century. They will always be required to meet certain desired properties in specific products. TPEs principally continue to replace traditional TS natural and synthetic rubbers (elastomers). TPEs are also widely used to modify the properties of rigid TPs usually by improving their impact strength. Natural rubber provides the industry worldwide with certain material properties that to date are not equaled by synthetic elastomers. They followed a process that ensures producing products. Examples include tires (with its heat build-up resistance), certain type vibrators, etc. However both synthetic TSE and TPE have made major inroads to product markets previously held by natural rubber and also expanded into new markets. The three basic processing types are conventional (vulcanizable) elastomer, reactive type, and thermoplastic elastomer. Overall an elastomer may be defined as a natural or synthetic material that exhibits the rubberlike properties of high extensibility and flexibility. It identifies any thermoset elastomer (TSE) or thermoplastic elastomer (TPE) material. Such synthetics as neoprene, nitrile, styrene butadiene, and polybutadiene are grouped with natural rubber (NR) that are TSEs. The term’s “rubber” and “elastomer” are used interchangeably. Elastomer embrittlement The temperature at which elastomers lose their rubbery properties varies widely among elastomers. Basically, the rubbery state is maintained until the glass transition temperature (T,) of the base polymer is reached, although in practice, elastomers become leathery as T, is approached. Perhaps the most usehl method of determining the lowest [...]... of ethylene forms a 528 Plastics Engineered Product Design polyethylene plastic or condensation of phenol and formaldehyde (with production of water) forms phenol-formaldehyde plastics A polymer is a pure material; they are NEAT plastics To fabricate products practically all polymers include additives, fillers, and/or reinforcements; they are than called plastics or resins Polymer, addition Also called... to a molding along the parting lines, fins at holes or openings, etc Flight land The surface of the radial extremity of the flight constituting the periphery or outside diameter of the screw 51 6 Plastics Engineered Product Design Flow mark Molding can cause product surface melt flow marks Major contributor to the markings is the melt flow speed Foamed plastic Practically all plastics can be made into... in fabricating parts Usually they are not a problem in the finished product However, with excess stresses, the product could be damaged quickly or after in service from a short to long time depending on amount of stress and the environmental conditions around the product Responsibility The responsibilities of those involved in the World of Plastics encompass all aspects to producing products as well... fouled up, anything done to improve it makes it worst Fines They are very small particles, usually under 200 mesh, accompanying larger forms of molding powders, developed when granulating plastics When plastics are extruded and pelletized, varying amounts of oversized pellets and strands are produced, along with fines When the plastics are dewatered/dried or pneumatically conveyed, more fines, fluff, and... elastomers (TSEs) TPEs offer a combination of strength and elasticity as well as exceptional processing versatility They present creative designers with endless new and unusual product opportunities 51 2 Plastics Engineered Product Design e Quite large elastic strains are possible with minimal stress in TPEs TPEs have two specific characteristics: their glass transition temperature (Tg) is below that... (see Chapter 3) 51 8 Plastics Engineered Product Design - I Graft polymer It is a polymer comprising of molecules in which the main backbone chain of atoms has attached to it at various points side chains containing different atoms or groups from those in the main chain The main chain may be a copolymer or may be derived from a single monomer Green strength During the processing of plastics even though... prime objective is to keep the screw and barrel centerlines coincident meeting the production line height requirement Installation is a multi-step procedure that consists of building a foundation, setting and leveling the machine supports, and aligning the machine components to each other 520 Plastics Engineered Product Design Machines not alike Just like people, not all machines may be created equal... be pushed through a set orifice with various conditions controlled (basically 522 Plastics Engineered Product Design temperature, time, pressure) It represents the “flowability” of a material The higher numbers indicate the easier flow Metrology The science of measurement Modulus of elasticity Most materials, including plastics and metals, have deformation proportional to their loads below the proportional... properties of plastics With MW differences of incoming material, the fabricated product performance can be altered; the more the difference, the more dramatic change occurs in the product Melt flow rate (MFR) tests are used to detect degradation in products where comparisons, as an example, are made of the MFR of pellets to the MFR of products MFR has a reciprocal relationship to melt viscosity This relationship... terminated (frozen) downstream of a stretching operation when a cold enough temperature is achieved Reversing this operation occurs when the product is subjected to a sufficient high temperature This reheating results in the product shrinking Use for these products includes part assemblies, tubular or flat communication cable wraps, hrniture webbing, medical devices, wire and pipe fitting connections or joints, . engineering plastics. Commodity plastics are usually associated with the higher volume, lower priced plastics with low to medium properties. Used for the less critical parts where engineering plastics. product, usually a molding. Several different methods are employed that include low temperatures of dry ice and cryogenic. 506 Plastics Engineered Product Design Deformation, plastic Plastics. quantity of trash. Design verification DV refers to the series of procedures used by the product development group to ensure that a product design output meets its design input. It focuses