Anisotropy in thermoplastic elastomers.Anisotropy anisotropy /an·isot·ro·py/ (an?i-sot´rah-pe) the quality of being anisotropic. anisotropy (an´āsôt´r is defined as a dependence of physical properties and behavior of substances on direction. This effect is most common in crystals, but it may even be found in liquids. Polycrystalline Adj. 1. polycrystalline - composed of aggregates of crystals; "polycrystalline metals" crystalline - consisting of or containing or of the nature of crystals; "granite is crystalline" substances can be anisotropic Refers to properties that differ based on the direction that is measured. For example, an anisotropic antenna is a directional antenna; the power level is not the same in all directions. Contrast with isotropic. if the crystallites are not randomly oriented o·ri·ent n. 1. Orient The countries of Asia, especially of eastern Asia. 2. a. The luster characteristic of a pearl of high quality. b. A pearl having exceptional luster. 3. . Anisotropy is observed in electrical and thermal conductivity thermal conductivity A measure of the ability of a material to transfer heat. Given two surfaces on either side of the material with a temperature difference between them, the thermal conductivity is the heat energy transferred per unit time and per unit , elasticity, hardness, fracture fracture, breaking of a bone. A simple fracture is one in which there is no contact of the broken bone with the outer air, i.e., the overlying tissues are intact. In a comminuted fracture the bone is splintered. direction, thermal expansion thermal expansion Increase in volume of a material as its temperature is increased, usually expressed as a fractional change in dimensions per unit temperature change. and optical properties (ref. 1). Gurney gurney /gur·ney/ (gur´ne) a wheeled cot used in hospitals. gur·ney n. pl. gur·neys A metal stretcher with wheeled legs, used for transporting patients. and Gough (ref. 2) reported in the late 1940s that the molding of rubber materials might lead to anisotropy in the properties of a rubber item. The anisotropy effect of injection molding injection molding n. A manufacturing process for forming objects, as of plastic or metal, by heating the molding material to a fluid state and injecting it into a mold. of thermoplastics has been well studied (ref. 3). In a study by Gent on PE, processing temperatures have been shown to change the anisotropic nature of a material (ref. 4). Observations of degree of molecular orientation have been made by Lu in reference to shrinkage Shrinkage The amount by which inventory on hand is shorter than the amount of inventory recorded. Notes: The missing inventory could be due to theft, damage, or book keeping errors. measurements made on PE pipe (ref. 5). A review by Lavebratt (ref. 6) gives the following conclusions for anisotropy in rubber compounds: * Anisotropic behavior was due to orientation rather than to a difference in state of cure. * Vulcanization vulcanization (vŭl'kənəzā`shən), treatment of rubber to give it certain qualities, e.g., strength, elasticity, and resistance to solvents, and to render it impervious to moderate heat and cold. during flow was an important factor giving anisotropy. * The rate of vulcanization influences anisotropy. * The presence of carbon black enhances anisotropy. * Higher anisotropy was observed in injection molding than in compression molding Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, and heat . * An increase in injection speed reduces the anisotropy. The studies cited by Lavebratt concluded that the dominating factor giving rise to anisotropy is the orientation of the molecules during the mold-filling operation. Lavebratt's subsequent studies (ref. 7) confirmed the influence of mold mold, name for certain multicellular organisms of the various classes of the kingdom Fungi, characteristically having bodies composed of a cottony mycelium. The colors of molds are caused by the spores, which are borne on the mycelium. filling on the anisotropy. He also proved the existence of laminar laminar /lam·i·nar/ (lam´i-nar) 1. pertaining to a lamina or laminae. 2. laminated. 3. of, pertaining to, or being a streamlined, smooth fluid flow. structure in the EPDM EPDM Ethylene-Propylene-Diene-Monomer EPDM Enterprise Product Data Management EPDM Ethylene Propylene Dimonomer (industrial/commercial piping/plumbing components) EPDM Engineering Product Data Management material similar to that found in thermoplastics. A review of TPEs by Kresge (ref. 8) discusses the morphological mor·phol·o·gy n. pl. mor·phol·o·gies 1. a. The branch of biology that deals with the form and structure of organisms without consideration of function. b. nature of these materials. He felt that the elastic elastic Of or relating to the demand for a good or service when the quantity purchased varies significantly in response to price changes in the good or service. nature of the material depended strongly on the morphology morphology In biology, the study of the size, shape, and structure of organisms in relation to some principle or generalization. Whereas anatomy describes the structure of organisms, morphology explains the shapes and arrangement of parts of organisms in terms of such . He also felt that the morphology of the melt played a large role in rheological rhe·ol·o·gy n. The study of the deformation and flow of matter. rhe  o·log properties and
processability.In a study done by Handlos (ref. 9), a liquid crystalline Like a crystal. It implies a uniform structure of molecules in all dimensions. For example, phase change technology, widely used for rewritable optical discs, uses crystalline spots (bits) to reflect the laser beam. Amorphous, non-crystalline bits do not reflect light. polymer (TLCPs) was blended into PP to study the effect of extrusion blow molding, anisotropy and TLCPs. These materials generate improvements in properties; however, they caused extreme, two to ten times, difference in properties in the perpendicular and parallel directions. Blow molding was accomplished in this study to determine whether the TLCPs could be oriented in both directions, therefore decreasing the anisotropy in these materials. The crystalline nature of the first widely used thermoplastic elastomer Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) which consist of materials with both thermoplastic and elastomeric properties. (TPE TPE Thermoplastic Elastomer TPE Terminal de Paiement Electronique (French) TPE Total Power Exchange TPE Twisted Pair Ethernet TPE Tampines Expressway (Singapore) TPE Therapeutic Plasma Exchange ) has been shown in the literature for over 30 years. Technically, the first solid polyurethanes polyurethanes (pŏl'ēy  r`əthānz), group of plastics that may be either thermosetting or thermoplastic. Polyurethane can be made into both flexible and rigid foams. developed by Bayer were the
first TPEs on the market, around 1930. The urethanes consist of an
amorphous Unorganized or vague. A lack of structure. For example, the amorphous state of a spot on a rewritable optical disc means that the laser beam will not be reflected from it, which is in contrast to a crystalline state which will reflect light. See crystalline. polyester polyester, synthetic fiber, produced by the polymerization of the product formed when an alcohol and organic acid react. The outstanding characteristic of polyesters is their ability to resist wrinkling and to spring back into shape when creased. or polyether-based soft segment and a urethane-based
hard segment (ref. 7). Microphase segregation segregation: see apartheid; integration. of the hard segments into
semi-ordered regions provides the `pseudocrosslinking' necessary
for the development of strength, with the amorphous flexible soft
segments giving the copolymer copolymer: see polymer. its elastomeric nature. Longer annealing annealing (ənēl`ĭng), process in which glass, metals, and other materials are treated to render them less brittle and more workable. times produce higher levels of crystallinity Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. In a gas, the relative positions of the atoms or molecules are completely random. .The development of triblock materials styrene-isoprenestyrene heralds the real start of the TPE explosion. These became commercially available in 1965. The SIS- (or SBS-) based TPEs are block copolymers, in which the end blocks are hard polystyrene polystyrene (pŏl'ēstī`rēn), widely used plastic; it is a polymer of styrene. Polystyrene is a colorless, transparent thermoplastic that softens slightly above 100°C; (212°F;) and becomes a viscous liquid at around 185°C; , and the center block is soft polyisoprene or butadiene butadiene (by  t'ədī`ēn), colorless, gaseous hydrocarbon. There are two structural isomers of butadiene; they differ in the location of the two carbon-carbon double bonds in the (ref. 10). These two materials are
inherently incompatible incompatible adj. 1) inconsistent. 2) unmatching. 3) unable to live together as husband and wife due to irreconcilable differences. In no-fault divorce states, if one of the spouses desires to end the marriage, that fact proves incompatibility, and a divorce , which gives rise to a tendency to form separate
phases. The polystyrene end blocks agglomerate agglomerateLarge, coarse, angular rock fragments associated with lava flow that are ejected during explosive volcanic eruptions. Although they may appear to resemble sedimentary conglomerates, agglomerates are igneous rocks that consist almost wholly of angular or rounded into domains that are dispersed dis·perse v. dis·persed, dis·pers·ing, dis·pers·es v.tr. 1. a. To drive off or scatter in different directions: The police dispersed the crowd. b. in a continuous phase. Li thoroughly explains phase separation of neat, prepared blocks of P [Alpha] MeSt - PIB-P [Alpha] MeSt. The phase separation is shown through TEM TEM 1. transmission electron microscope. 2. triethylenemelamine. 3. transmissible encephalopathy of mink. photomicrographs, DSC (1) (Digital Signal Controller) A microcontroller and DSP combined on the same chip. It adds the interrupt-driven capabilities normally associated with a microcontroller to a DSP, which typically functions as a continuous process. See microcontroller and DSP. and DMA (1) (Digital Media Adapter) See digital media hub. (2) (Document Management Alliance) A specification that provides a common interface for accessing and searching document databases. . Since the samples were compression molded mold 1 n. 1. A hollow form or matrix for shaping a fluid or plastic substance. 2. A frame or model around or on which something is formed or shaped. 3. Something that is made in or shaped on a mold. , no analysis was accomplished on the possible anisotropy (ref. 12). The introduction of the olefin-based partially vulcanized vul·ca·nize tr.v. vul·ca·nized, vul·ca·niz·ing, vul·ca·niz·es To improve the strength, resiliency, and freedom from stickiness and odor of (rubber, for example) by combining with sulfur or other additives in the presence of heat TPEs in 1972 and the fully vulcanized TPEs in 1980 led to a third class of materials. Common interpretation is that these materials possess a cured domain of a rubbery material surrounded sur·round tr.v. sur·round·ed, sur·round·ing, sur·rounds 1. To extend on all sides of simultaneously; encircle. 2. To enclose or confine on all sides so as to bar escape or outside communication. n. by a plastic material. The most commonly used type is EPDM rubber EPDM rubber (ethylene propylene diene monomer rubber) is an elastomer which is characterized by wide range of applications. EPDM rubber is used in vibrators and seals; glass-run channel; radiator, garden and appliance hose; tubing; washers; belts; and electrical insulation. in a polypropylene polypropylene (pŏl'ēprō`pəlēn), plastic noted for its light weight, being less dense than water; it is a polymer of propylene. It resists moisture, oils, and solvents. phase. Some other researchers have proposed other types of morphology when different blends of rubber/plastic are used, including co-continuous phases. Of critical interest to the compounder of these materials is the influencing factor of additives on these materials. In most cases, significant amounts of fillers, 10-50%, can be added to these materials, and the materials' ability to form the necessary crystalline domains is not compromised. Compare this phenomenon to inorganic inorganic /in·or·gan·ic/ (in?or-gan´ik) 1. having no organs. 2. not of organic origin. in·or·gan·ic n. 1. crystals, some of which significantly lose their strength with ppm (Pages Per Minute) The measurement of printer speed. See gppm. PPM - Portable Pixmap levels of contamination. Materials evaluated All the materials evaluated are commercially available materials in the Shore A hardness range of 51-86. The majority of them have moderate levels of fillers, plasticizers plasticizers mostly triaryl phosphates, such as tricresyl, triphenyl phosphates, which are poisonous. See also triorthocresyl phosphate. or inorganics. None of the materials have fiber or other crystalline reinforcements reinforcements reinforce npl (Mil) → renfort(s) m(pl) . Two of the materials, #3 and #4, have little or no filler fill·er 1 n. One that fills, as: a. Something added to augment weight or size or fill space. b. A composition, especially a semisolid that hardens on drying, used to fill pores, cracks, or holes in wood, plaster, addition. Sample #4 is a metallocene catalyzed polyoctene, so therefore does not meet the true definition of a rubber, since its elasticity retention is small. The materials, their type, their suppliers, and hardness values are listed in table 1. Table 1 - materials Designation TPE-1 TPE-2 Material name Santoprene 8211-75 Santoprene 101-73 Type TPV-PP/EPDM TPV-PP/EPDM Supplier Adv. Elas. Systems Adv. Elas. Systems Hardness, Shore A 75 73 Designation TPE-3 TPE-4 TPE-5 Material name Pellethane Engage 8003 Alcryn Type Polyurethane Metallocene MPR Supplier Upjohn Dow Chemical DuPont Hardness, Shore A 58 86 67 Designation TPE-6 TPE-7 TPE-8 Material name Softflex grey XL-0117-5 XL-0117-22 Type Proprietary SEBS SEBS Supplier Diamond Polymers M.A. Hanna M.A. Hanna Hardness, Shore A 71 59 64 Designation TPE-9 TPE-10 TPE-11 Material name XL-0117-31 XL-1020-7 4180B Type SEBS SEBS TPV-PP/EPDM Supplier M.A. Hanna M.A. Hanna DSM Hardness, Shore A 55 51 76 Specimen preparation The materials were molded using the conditions listed in table 2. The injection molder mold·er v. mold·ered, mold·er·ing, mold·ers v.intr. To crumble to dust; disintegrate. v.tr. To cause to crumble. See Synonyms at decay. used was a Cincinnati Milacron Vista 33-ton molder. The mold used was a 4" x 4" plaque plaque (plak) 1. any patch or flat area. 2. a superficial, solid, elevated skin lesion. attachment plaques mold with a gate at the top corner. A drawing of the mold is shown in figure 1. The samples were died out either parallel to the flow, or perpendicular to the flow. [Figure 1 ILLUSTRATION OMITTED] Table 2 - extrusion conditions Designation TPE-1 TPE-2 TPE-3 TPE-4 Zone #1, C 182 182 124 182 Zone #2, C 188 188 130 188 Zone #3, C 200 200 133 200 Die, C 205 205 140 205 Melt temperature, [degrees] C 196.7 206.3 120.4 Designation TPE-5 TPE-6 TPE-7 TPE-8 Zone #1, C 170 149 149 149 Zone #2, C 175 159 159 159 Zone #3, C 180 160 160 160 Die, C 180 170 170 170 Melt temperature, [degrees] C 179 174 173 175.5 Designation TPE-9 TPE-10 TPE-11 Zone #1, C 149 149 n/a Zone #2, C 159 159 n/a Zone #3, C 160 160 n/a Die, C 170 170 n/a Melt temperature, [degrees] C 174 174 n/a The materials were extruded using the conditions listed in table 3. The extruder was a conical conical /con·i·cal/ (kon´i-k'l) cone-shaped. con·i·cal or con·ic adj. Of, relating to, or shaped like a cone. counter-rotating twin screw screw, simple machine consisting essentially of a solid cylinder, usually of metal, around which an inclined plane winds spirally, either clockwise or counterclockwise. driven by a Haake Rheocord. All samples were extruded into a water bath and were fully cooled prior to being coiled coil 1 n. 1. a. A series of connected spirals or concentric rings formed by gathering or winding: a coil of rope; long coils of hair. b. . The extrusion die was 1" x 0.250". The samples were died out parallel to the flow of the extruder. Due to the small size of the sample, we were unable to take specimens perpendicular to the flow or prepare specimens for tear properties. Table 3 - injection molding conditions Designation TPE-1 TPE-2 TPE-3 TPE-4 Nozzel, C 210 210 210 204 Zone #1, C 204 204 204 204 Zone #2, C 199 199 199 199 Zone #3, C 193 193 193 193 Injection time, mm/sec. 25.4 25.4 25.4 25.4 Pack time, sec. 1 3 3 3 Hold time, sec. 0 0 0 0 Cooling time, sec. 20 20 20 Dwell,sec. 0.1 0.1 0.1 Injection pressure, kg/cm2 49.2 98.4 Pack pressure, kg/cm2 21.1 21.1 Hold pressure, kg/cm2 0 0 Designation TPE-5 TPE-6 TPE-7 TPE-8 Nozzel,C 210 210 210 210 Zone #1, C 204 204 204 204 Zone #2, C 199 199 199 199 Zone #3, C 193 193 193 193 Injection time, mm/sec. 25.4 25.4 25.4 25.4 Pack time, sec. 1 1 1 1 Hold time, sec. 0 0 0 0 Cooling time, sec. 25 30 30 30 Dwell,sec. 0.1 0.1 0.1 0.1 Injection pressure, kg/cm2 49.2 49.2 22.5 Pack pressure, kg/cm2 21.1 21.1 21.1 Hold pressure, kg/cm2 0 0 0 Designation TPE-9 TPE-10 TPE-11 Nozzel,C 210 210 210 Zone #1, C 204 204 204 Zone #2, C 199 199 199 Zone #3, C 193 193 193 Injection time, mm/sec. 25.4 25.4 25.4 Pack time, sec. 1 1 Hold time, sec. 0 0 Cooling time, sec. 30 30 Dwell,sec. 0.1 0.1 Injection pressure, kg/cm2 19.7 28.1 Pack pressure, kg/cm2 21.1 21.1 Hold pressure, kg/cm2 0 0 Plaques plaques, n.pl 1. brain lesions found within the vacant areas between nerve cells. 2. deposits of cholesterol in artery walls that characterize arteriosclerosis. injection molded were re-molded using compression. This allowed the material to anneal To take the brittleness out of metal, plastic or certain carbon composites. Performed in the preparation of new products or in their restoration, annealing is accomplished via a heat treating process. at a temperature above the transition temperature. Tests used for evaluation Shrinkage Initial shrinkage of the plaques was measured in the two directions given, according to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. standard methods. The plaques were then placed in an oven for two hours above their recommended processing temperatures and then their shrinkage was measured again. The shrinkage anisotropy is calculated as follows: Shrinkage anisotropy = relative parallel shrinkage/relative perpendicular shrinkage The data obtained and the temperatures used are recorded in table 4. Table 4 - shrinkage Designation TPE-1 TPE-2 TPE-3 Measurement - parallel - mm 138.29 137.66 138.39 Measurement - perpendicular - mm 138.65 138.62 140.06 138.65 Shrinkage - parallel - mm/mm 0.0192 0.0236 0.0184 Shrinkage - perpendicular - mm/mm 0.0166 0.0168 0.0066 Shrinkage anisotropy 1.1538 1.4051 2.7957 Temperature of oven 348 348 212 Measurement - parallel - after 133.33 120.72 137.49 Measurement - perpendicular - after 135.89 134.49 139.3 Shrinkage parallel - mm/mm after 0.0543 0.1438 0.0248 Shrinkage perpendicular - mm/mm after 0.0362 0.0461 0.0120 Shrinkage anisotropy - after 1.5020 3.1185 2.0710 Mold measurement - parallel 140.99 Mold measurement - perpendicular 140.99 Designation TPE-4 TPE-5 TPE-6 Measurement - parallel - mm 137.85 137.72 Measurement - perpendicular - mm 138.49 138.37 138.65 Shrinkage - parallel - mm/mm 0.0223 0.0232 Shrinkage - perpendicular - mm/mm 0.0177 0.0186 Shrinkage anisotropy 1.2560 1.2481 Temperature of oven 196 348 Measurement - parallel - after 118.96 119.66 Measurement - perpendicular - after 133.76 134.03 Shrinkage parallel - mm/mm after 0.1563 0.1513 Shrinkage perpendicular - mm/mm after 0.0513 0.0494 Shrinkage anisotropy - after 3.0470 3.0647 Mold measurement - parallel Mold measurement - perpendicular Designation TPE-7 TPE-8 TPE-9 Measurement - parallel - mm 138.45 139.25 139.65 Measurement - perpendicular - mm 138.89 139.43 139.35 138.65 Shrinkage - parallel - mm/mm 0.0180 0.0123 0.0095 Shrinkage - perpendicular - mm/mm 0.0149 0.0111 0.0116 Shrinkage anisotropy 1.2095 1.1154 0.8171 Temperature of oven 348 348 348 Measurement - parallel - after Measurement - perpendicular - 135.92 131.97 126.36 after 137.77 134.27 132.95 Shrinkage parallel - mm/mm after Shrinkage perpendicular - mm/mm after 0.0228 0.0360 0.0640 Shrinkage anisotropy - after 1.5745 1.3423 1.8197 Mold measurement - parallel Mold measurement - perpendicular Designation TPE-10 TPE-11 Measurement - parallel - mm 138.93 138.75 Measurement - perpendicular - mm 139.5 139.13 138.65 Shrinkage - parallel - mm/mm 0.0146 0.0159 Shrinkage - perpendicular - mm/mm 0.0106 0.0132 Shrinkage anisotropy 1.3826 1.2043 Temperature of oven 348 348 Measurement - parallel - after Measurement - perpendicular - 136.54 126.86 after 137.62 135.9 Shrinkage parallel - mm/mm after 0.0316 0.1002 Shrinkage perpendicular - mm/mm after 0.0239 0.0361 Shrinkage anisotropy - after 1.3205 2.7760 Mold measurement - parallel Mold measurement - perpendicular Tensile strength tensile strength Ratio of the maximum load a material can support without fracture when being stretched to the original area of a cross section of the material. When stresses less than the tensile strength are removed, a material completely or partially returns to its Tensile strength of the samples was measured according to ASTM ASTM abbr. American Society for Testing and Materials D412 Die C. Values for ultimate tensile strength, ultimate elongation elongation, in astronomy, the angular distance between two points in the sky as measured from a third point. The elongation of a planet is usually measured as the angular distance from the sun to the planet as measured from the earth. and 100% modulus See modulo. were recorded. Table 5 provides a summary of the data obtained on injection molded, extruded and compression molded samples. Table 5 - tensile tensile, adj having a degree of elasticity; having the ability to be extended or stretched. properties Designation TPE-1 TPE-2 TPE-3 TPE-4 Tensile strength - extrusion, Mpa 6.354 7.557 15.463 10.936 Tensile anisotropy - extrusion 0.957 0.990 0.829 1.068 Elongation - extrusion, % 547 477 599 721 Elongation anisotropy - extrusion 0.998 1.037 0.824 1.163 100% modulus - extrusion, Mpa 3.128 3.018 2.972 3.090 100% modulus anisotropy - extrusion 0.902 0.892 1.007 1.031 300% modulus - extrusion, Mpa 4.400 4.950 5.648 5.072 300% modulus anisotropy - extrusion 0.927 0.929 1.218 0.900 Tensile strength - perpendicular, Mpa 6.640 7.633 18.657 10.243 Tensile strength - parallel, Mpa 6.185 6.797 19.188 7.330 Tensile anisotropy - injection 1.074 1.123 0.972 1.397 Elongation - perpendicular, % 548 460 727 620 Elongation - parallel, % 436 348 673 462 Elongation anisotropy - injection 1.257 1.322 1.080 1.342 100% modulus - perpendicular, Mpa 3.467 3.384 2.950 2.997 100% modulus - parallel, Mpa 3.777 4.312 3.035 3.386 100% modulus anisotropy - injection 0.918 0.785 0.972 0.885 300% modulus - perpendicular, Mpa 4.745 5.326 4.639 5.637 300% modulus- parallel, Mpa 5.176 6.288 5.042 5.800 300% modulus anisotropy - injection 0.917 0.847 0.920 0.972 Tensile strength - compression, Mpa 6.347 5.277 19.600 Tensile anisotropy - compression 0.956 0.691 1.914 Elongation - compression, % 473 291 527 Elongation anisotropy - compression 0.863 0.632 0.850 100% modulus - compression, Mpa 3.185 3.287 4.210 100% modulus anisotropy - compression 0.919 0.971 1.405 300% modulus - compression, Mpa 4.775 5.379 5.636 300% modulus anisotropy - compression 1.006 1.010 1.000 Designation TPE-5 TPE-6 TPE-7 TPE-8 Tensile strength - extrusion, Mpa 14.777 13.193 10.609 6.107 Tensile anisotropy - extrusion 0.823 1.139 1.017 1.174 Elongation - extrusion, % 585 * 681 550 Elongation anisotropy - extrusion 0.876 #value 0.801 1.0582 100% modulus - extrusion, Mpa 4.104 2.374 1.635 2.711 100% modulus anisotropy - extrusion 0.927 1.008 0.942 1.099 300% modulus - extrusion, Mpa 5.283 3.841 2.956 4.132 300% modulus anisotropy - extrusion 0.948 1.108 1.110 1.098 Tensile strength - perpendicular, Mpa 17.955 11.579 10.429 5.204 Tensile strength - parallel, Mpa 9.691 11.651 7.483 4.895 Tensile anisotropy - injection 1.853 0.994 1.394 1.063 Elongation - perpendicular, % 668 1032 850 520 Elongation - parallel, % 441 717 485 Elongation anisotropy - 977 injection 1.515 1.056 1.185 1.072 100% modulus - perpendicular, Mpa 4.429 2.356 1.736 2.466 100% modulus - parallel, Mpa 4.498 2.384 1.815 2.573 100% modulus anisotropy - injection 0.985 0.988 0.956 0.958 300% modulus - perpendicular, Mpa 5.573 3.468 2.664 3.763 300% modulus- parallel, Mpa 6.385 3.686 2.825 3.890 300% modulus anisotropy - injection 0.873 0.941 0.943 0.967 Tensile strength - compression, Mpa 11.466 8.766 4.026 Tensile anisotropy - compression 0.639 0.841 0.774 Elongation - compression, % 532 651 418 Elongation anisotropy - compression 0.796 0.766 0.803 100% modulus - compression, Mpa 3.125 1.613 2.487 100% modulus anisotropy - compression 0.706 0.929 1.009 300% modulus - compression, Mpa 5.432 2.759 3.712 300% modulus anisotropy - compression 0.975 1.036 0.986 Designation TPE-9 TPE-10 TPE-11 Tensile strength - extrusion, Mpa 4.272 9.13 9.735 Tensile anisotropy - extrusion 1.031 1.143 0.924 Elongation - extrusion, % 531 757 502.03 Elongation anisotropy - extrusion 1.002 0.933 0.883 100% modulus - extrusion, Mpa 1.950 1.054 4.415 100% modulus anisotropy - extrusion 1.176 0.933 0.952 300% modulus - extrusion, Mpa 3.070 1.756 6.407 300% modulus anisotropy - extrusion 1.069 1.038 1.028 Tensile strength - perpendicular, Mpa 4.142 7.989 10.541 Tensile strength - parallel, Mpa 4.664 6.280 8.028 Tensile anisotropy - injection 0.888 1.272 1.313 Elongation - perpendicular, % 530 811 568.56 Elongation - parallel, % 574 752 376.8 Elongation anisotropy - injection 0.923 1.078 1.509 100% modulus - perpendicular, Mpa 1.658 1.130 4.639 100% modulus - parallel, Mpa 2.105 1.609 5.378 100% modulus anisotropy - injection 0.788 0.702 0.863 300% modulus - perpendicular, Mpa 2.873 1.691 6.320 300% modulus- parallel, Mpa 3.203 2.168 7.152 300% modulus anisotropy - injection 0.897 0.780 0.871 Tensile strength - compression, Mpa 3.943 7.548 Tensile anisotropy - compression 0.952 0.945 Elongation - compression, % 453 729 Elongation anisotropy - compression 0.854 0.898 100% modulus - compression, Mpa 1.946 0.983 100% modulus anisotropy - compression 1.174 0.870 300% modulus - compression, Mpa 3.101 1.609 300% modulus anisotropy - compression 1.079 0.952 Tear strength Tear strength of the samples was measured according to ASTM D624 Die C. The strength required to tear the specimen is recorded. A summary is provided in table 6. Table 6 - tear properties Designation TPE-1 TPE-2 TPE-3 Tear strength - perpendicular - KN/m 29.5 26.1 60.1 Tear strength - parallel - KN/m 28.8 30.7 58.8 Tear strength anisotropy 1.024 0.850 1.021 Tear strength - compression, Kn/m 27.3 22.4 Tear strength anisotropy - compression 1.079 1.166 Designation TPE-4 TPE-5 TPE-6 Tear strength - perpendicular - KN/m 54.7 37.9 40.2 Tear strength - parallel - KN/m 53.3 35.1 41.2 Tear strength anisotropy 1.025 1.081 0.975 Tear strength - compression, Kn/m 45.3 32.2 Tear strength anisotropy - compression 1.206 1.176 Designation TPE-7 TPE-8 TPE-9 Tear strength - perpendicular - KN/m 27.0 32.0 22.2 Tear strength - parallel - KN/m 26.6 31.6 26.2 Tear strength anisotropy 1.016 1.014 0.847 Tear strength - compression, Kn/m 23.4 25.7 25.4 Tear strength anisotropy - compression 1.155 1.245 0.876 Designation TPE-10 TPE-11 Tear strength - perpendicular - KN/m 22.7 Tear strength - parallel - KN/m 21.4 Tear strength anisotropy 1.062 Tear strength - compression, Kn/m 17.5 Tear strength anisotropy - compression 1.298 The mechanical anisotropy of the physical properties of the materials is calculated as: Mechanical anisotropy = property in parallel direction/ of a property property in perpendicular direction Test results Eleven different thermoplastic elastomers were tested for this study. These materials varied extensively in their chemical composition. All materials experienced some anisotropy in at least one property. Tensile strength anisotropy Tensile strength was accomplished on injection molded, extruded and compression molded samples. A summary of the data obtained is shown in figure 2, not for ultimate strength comparison purposes, but to examine the relative differences in anisotropy encountered between the materials. [Figure 2 ILLUSTRATION OMITTED] Injection molded The highest degree of anisotropy was experienced in the tensile strength perpendicular versus parallel for TPE-5. The graph of the data obtained is shown in figure 3. The value in the perpendicular direction was close to being two times the value in the parallel direction. TPE-5 is an MPR (MultiProtocol Router) Software from Novell that provides router capabilities for its NetWare servers. It supports IPX, IP, AppleTalk and OSI protocols as well as all the major LANs and WANs. made from ethylene/butyl acrylate/(carbon monoxide carbon monoxide, chemical compound, CO, a colorless, odorless, tasteless, extremely poisonous gas that is less dense than air under ordinary conditions. It is very slightly soluble in water and burns in air with a characteristic blue flame, producing carbon dioxide; ) and vinyl vinyl /vi·nyl/ (vi´nil) the univalent group CH2dbondCH—. vinyl chloride a vinyl group to which an atom of chlorine is attached; the monomer which polymerizes to polyvinyl chloride; it is toxic chloride/vinyl acetate/ethylene. These two polymers appear to be marginally compatible. It is claimed to be partially cross-linked material. Bulletins (ref. 13) produced by the supplier list compression and injection molded properties, both directions. This level of anisotropy is higher than that stated in the bulletin. The morphology of this material must lead to the high level of anisotropy. No reference to morphological determinations can be found. [Figure 3 ILLUSTRATION OMITTED] The other two materials that experience relatively high anisotropy are TPE-4 and TPE-7. TPE-4 is a metallocene-catalyzed produced polyoctene. The anisotropy is expected because of the orientation of the chains during the flowing of the material and its subsequent crystallization Crystallization The formation of a solid from a solution, melt, vapor, or a different solid phase. Crystallization from solution is an important industrial operation because of the large number of materials marketed as crystalline particles. . The ability of the molecules to flow has been enhanced in TPE-4 over typical PP, and therefore orientation of the molecules seems to occur more readily. TPE-7 is a TPE based upon a SEBS block copolymer. Although several of these types of materials are represented in this study, the level of their anisotropy varies significantly. TPE-9 has a reverse anisotropic effect. The gathering together of polystyrene bundles in one direction would be expected to lead to anisotropy. TPE-9 and TPE-10 are both more highly loaded materials. It is postulated pos·tu·late tr.v. pos·tu·lat·ed, pos·tu·lat·ing, pos·tu·lates 1. To make claim for; demand. 2. To assume or assert the truth, reality, or necessity of, especially as a basis of an argument. 3. that the fillers are leading to a variation in the anisotropy of the materials. The anisotropy of TPE-1, TPE-2 and TPE-11 are similar. An interesting observation is that since these materials are known to have discrete elements that are rubbery, and TPE-7 through TPE-10 are known to have discrete elements that are plastic, then why is their anisotropy not reversed? One theory for the development of anisotropy in these materials centers around the packing of the molecules, to eliminate formation of voids (inconsistencies) in one direction. This phenomenon would be the same regardless of what material formed the discrete or continuous phases. Another possible explanation would be the formation of already elongated e·lon·gate tr. & intr.v. e·lon·gat·ed, e·lon·gat·ing, e·lon·gates To make or grow longer. adj. or elongated 1. Made longer; extended. 2. Having more length than width; slender. elastomeric domains. These domains would allow the material to stretch more readily in one direction, allowing additional elongation of the sample, and therefore possibly greater tensile strength. Extrusion It was hoped that even greater anisotropy would be shown in the extrusion process. Although the pressure is less in the extrusion process, it was anticipated that there would be less laminar and convoluted convoluted /con·vo·lut·ed/ (kon?vo-lldbomact´ed) rolled together or coiled. flow. The results obtained are shown in figure 4. The sample with the highest amount of injection molding anisotropy, TPE-5, showed less anisotropy with extrusion. The extrusion process must not have aligned the particles as significantly, or there was more opportunity for relaxation prior to "freezing of the morphology." The extrusion results for this material actually end up being in the middle of the parallel and perpendicular to flow injection-molded specimens. [Figure 4 ILLUSTRATION OMITTED] None of the TPE samples, TPE-1, TPE-2 and TPE-11, showed an increase in anisotropy with extrusion. Again the morphology of the samples must allow them to relax prior to being frozen in place. The majority of the SEBS compounds had their highest tensile strength values from the extruded samples. This might be due to the polypropylene used in the compounding of this material. Of course the PP would be oriented during the extrusion process, allowing for increased crystallization in the extrusion direction. This same effect is seen in TPE-4, which would he expected to show increased crystallization with the extrusion process. Compression molded Figure 5 shows the results obtained on compression molded plaques. It would be expected that these values should be less than those obtained on the oriented injection molded specimens. This is true for all cases except for TPE-4. Formation of spheres of crystallization during the annealing process must be occurring in TPE-4. Maximum crystallization of the rest of the TPE materials must have already occurred during other forming processes. TPE-4 is also the cleanest material, so the more extensive crystallization could occur without being minimized by filler interactions. [Figure 5 ILLUSTRATION OMITTED] Elongation anisotropy If the anisotropy was being caused solely by crystallization in one preferential pref·er·en·tial adj. 1. Of, relating to, or giving advantage or preference: preferential treatment. 2. direction, then an easy way to test the theory would be to study the anisotropy of the elongation. Injection molded The effect of anisotropy on elongation, figure 6, is the same as the effect already discussed for tensile strength. Formation of domains of elasticity allows the materials to stretch further. If these domains are elongated in one direction, as has been proposed, then that elongation would allow for additional stretching. Since it is postulated that most of the stretching occurs because of the rubber particles, then their orientation would be the major contributor to elongation. Of course, this would mean that for the tri-block TPEs, the continuous phase must be oriented perpendicular to flow. Since this doesn't seem possible, then we must return to the theory of less voids (inconsistencies) being formed in one direction [Figure 6 ILLUSTRATION OMITTED] Extrusion Again, the lack of significant increase in anisotropy with the elongation of extruded specimens leads to the belief that this extrusion process could not significantly improve the orientation of the molecules/particles and/or the elimination of voids. Compression molded As shown in figure 7, we finally have an interesting phenomenon with the elongation of the materials. As expected with random crystallization formation, the elongation of the material is lower than it is with non-random crystallization formation. This starts to show that the crystallization of the materials in the TPE substrate The base layer of a structure such as a chip, multichip module (MCM), printed circuit board or disk platter. Silicon is the most widely used substrate for chips. Fiberglass (FR4) is mostly used for printed circuit boards, and ceramic is used for MCMs. is not as critical a factor as the orientation of the pockets of crystallization and the orientation of the molecules in the continuous phase. [Figure 7 ILLUSTRATION OMITTED] 100% modulus anisotropy Many people feel that the 100% modulus of a material is significant when describing the elastic properties of a material (ref. 7), mainly because very few materials operate near the ultimate elongation. For most applications, the materials operate at or below 100% elongation. Plots were made of 100% modulus anisotropy for injection molded, extruded and compression molded specimens. Most of the samples showed very little anisotropy in their 100% modulus values, regardless of how they were prepared. The effect of increased crystallization on TPE-4 was visible in the compression molded samples. Tear strength anisotropy The lack of effect of anisotropy on tear strength as shown in figures 8 and 9 gives insight into the formation of tears. If the tears were originating in the continuous phase, then it would be expected that the anisotropic effect would be high because the chain orientation would make it harder to tear in the parallel direction. Also, if the tears were originating in the crystalline portion of the materials, more of an anisotropic effect could be postulated. The data suggests that the tearing tear·ing n. Epiphora. action must be originating in the interfaces between the two phases. If we agree that tensile strength anisotropy is caused by voids, then it would appear that these voids are not origins of tears. [Figures 8-9 ILLUSTRATION OMITTED] Shrinkage anisotropy It is recognized that the optimum temperature for studying the shrinkage factors of these materials was not always reached during this study. The ideal would have been to obtain DSC graphs for all of the materials in question and then pick a point right at the transition. For those materials with two transitions, a measurement could be taken after relaxation right above the first transition and after relaxation right above the second transition. However, several interesting facts were discovered during this process. The majority of the materials had very little difference in their shrinkage values when measured just as they came out of the mold. Figure 10 shows the shrinkage anisotropy of the TPE materials. The material that seemed to be affected the most was TPE-3, a material that had very little anisotropic effect in the physical property area. [Figure 10 ILLUSTRATION OMITTED] Figure 11 shows quite a significant story about shrinkage. All the materials exhibited some shrinkage in both directions, with most materials exhibiting significant shrinkage in the parallel to flow direction. TPE-2, TPE-4, TPE-5 and TPE-11 all exhibited very significant changes in dimensions. The explanation for this is not clear, since not all of these materials exhibited significant anisotropy in the strength measurements. Work done previously on PE (ref. 5) showed a direct correlation Noun 1. direct correlation - a correlation in which large values of one variable are associated with large values of the other and small with small; the correlation coefficient is between 0 and +1 positive correlation with the measured shrinkage and the crack growth in extruded samples. A linear regression Linear regression A statistical technique for fitting a straight line to a set of data points. analysis was accomplished using the tensile strength anisotropy and the shrinkage anisotropy. The data obtained are shown in table 7. Correlation was not established with these materials. Even by only looking at the similar materials in the study, no correlation was found. [Figure 11 ILLUSTRATION OMITTED] Table 7 - anisotropy regression analysis Designation Tensile anisotropy Shrinkage anisotropy TPE-5 1.853 3.0647 TPE-4 1.397 3.047 TPE-7 1.394 1.5745 TPE-11 1.313 2.776 TPE-10 1.272 1.3205 TPE-2 1.123 3.1185 TPE-1 1.073 1.502 TPE-8 1.063 1.3423 TPE-3 0.972 2.071 TPE-9 0.888 1.8197 Summary output - regression statistics Multiple R 0.477447037 R Square 0.227955673 Adjusted R square 0.131450132 Standard error 0.706775162 Observations 10 Summary In summary, TPEs exhibit significant anisotropy in their tensile, elongation and shrinkage properties. No simple explanation can be advanced for this phenomenon on these complex mixtures. The inclusion of fillers seems to diminish the effect of anisotropy but does not eliminate this phenomenon. There does not appear to he any correlation between strength anisotropy and shrinkage anisotropy. Future studies will involve a refinement of the shrinkage study accomplished here through the use of DSC. Also SEM/TEM pictures will be obtained on the materials studied here to try and identify warpage Warp´age n. 1. The act of warping; also, a charge per ton made on shipping in some harbors. of discrete domains or the direction preferential existence of voids. References [1.] Concise concise, n.pr the brand name for diacrylate resin adhesives used in composite restorations and for bonding orthodontic appliances to the enamel. Dictionary of Chemical Terms, Van Nostrand, 1990. [2.] W.A. Gurney and V.E. Gough, Rubber Chem. Technol., 20, 863 (1947). [3.] A.I. Isayev, in Injection and Compression Molding Fund-amentals, Ch. 6, A.I. Isayev, ed., Marcel Dekker Marcel Dekker is a well-known encyclopedia publishing company with editorial boards found in New York, New York. They are part of the Taylor and Francis publishing group. Initially a textbook publisher, they went to encyclopedia publishing in the late 1990's. , Inc., New York New York, state, United States New York, Middle Atlantic state of the United States. It is bordered by Vermont, Massachusetts, Connecticut, and the Atlantic Ocean (E), New Jersey and Pennsylvania (S), Lakes Erie and Ontario and the Canadian province of (1987). [4.] A.N. Gent, B.L. Gregory and J. Jeong, Polymer Engin-eering Science, Vol. 27, 1675 (1987). [5.] X. Lu, Z. Zhou and N. Brown, Polymer Engineering and Science, Vol. 34, No. 2, 109-115 (1994). [6.] H. Lavebratt and B. Stenberg, Polymer Engineering and Science, Vol. 34, No. 11, 905-912 (1994). [7.] H. Lavebratt and B. Stenberg, Polymer Engineering and Science, Vol. 34, No. 11, 913-920 (1994). [8.] E.N. Kresge, Rubber World, Vol. 208, No. 2, May 1993, 31-34. [9.] A.A. Handlios and D.G. Baird, Polymer Engineering and Science, Vol. 36, No. 3, 378-386 (1996). [10.] G. Holden Holden, town (1990 pop. 14,628), Worcester co., central Mass., a residential suburb of Worcester; settled 1723, set off and inc. 1741. Manufactures include electrical and metal products, plastics, and machinery. , Rubber World, Vol. 208, No 2, May 1993, 25-30. [11.] Thorn thorn, in botany thorn, sharp-pointed projection on some plants, usually protective in function. Botanically, thorns are distinguished as modified stems (as in the honey locust and hawthorn) from spines, which are modified leaves (as in the barberry), and , A.D., Thermoplastic Elastomers - a review of current information. RAPRA RAPRA Rubber and Plastics Research Association (UK) , 1980. [12.] D. Li and R. Faust, Macromolecules Macromolecules A large molecule composed of thousands of atoms. Mentioned in: Gene Therapy macromolecules , Vol. 28, No. 14. July 3, 1995, 4893-4898. [13.] DuPont Product Bullentin ALR-6370. |
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