Thermoset elastomers

As with all thermoplastic elastomers, the copolyesterethers can be processed as thermoplastics. They are linear polymers and contain no chemical cross-links, thus the vulcanisation step needed for thermosetting elastomers is eliminated and scrap elastomer can be re-used in the same process as virgin material (176—180). 

Although rubber originally meant a natural thermoset material obtained from a rubber tree, with the development of plastics it identifies a thermoset elastomer (TSE) or thermoplastic elastomer (TPE) material. Different properties identify the elastomers such as strength and stiffness, abrasion resistance, solvent resistance, shock and... 

Description of samples tested, specific test methods used, exposure medium notes, solubility parameters, and other important details are provided. Emphasis is on providing all relevant information so the most informed conclusions and decisions can be made by the user. Over 60,000 individual entries (specific tests) are covered in the database. Classes of materials covered include thermosets, thermosetting elastomers, thermoplastics, and thermoplastic elastomers. Approximately 700 different trade name and grade combinations representing over 130 families of materials are included. Over 3300 exposure environments are represented. 

International plastics selector , 9th edition, Int. Plastics Selector, San Diego, CA (1987). Thermoplastics, thermosets, elastomers, and key property areas critical to plastics are extensively specification defined. 

Volume 3 covers the performance of polymers, thermosets, elastomers, and composites. 

Important are behaviors associated and interrelated with plastic materials (thermoplastics, thermosets, elastomers, reinforced plastics, etc.) and fabricating processes (extrusion, injection molding, blow molding, forming, foaming, reaction injection molding, etc.). They are presented so that the technical or non-technical reader can readily understand the interrelationships. 

The PGS obtained by Wang and coworkers was a kind of thermoset elastomer with the Young s modulus of 0.282 0.025 MPa, a tensile strain of at least 267 zE 59.4%, and a tensUe strength was at least 0.5 MPa. The mechanical properties of PGS were well consisted with that of some common soft tissues. Although PGS is a thermoset polymer, its prepolymer can be processed into various shapes by solving it in common organic solvents such as 1,3-dioxolane, tetrahydrofuran, isopropanol, ethanol, and iV,M-dimethylformamide. Porous scaffolds can be fabricated by salt leaching. 

This book focuses on the relationships between the chemical structure and the related physical characteristics of plastics, which determine appropriate material selection, design, and processing of plastic parts. The book also contains an in-depth presentation of the structure-property relationships of a wide range of plastics, including thermoplastics, thermosets, elastomers, and blends. 

J.E. Mark, Thermoset elastomers. In C.D. Craver and C.E. Carraher, Jr. (Eds.), Applied Polymer Science-list Century, American Chemical Society, Washington, 2000, p. 209. 

Thermosensitive hydrogels, 13 743 THERMOSET Thermoset recycling pyramid, 13 780-781 Thermoset elastomers, 20 71 Thermoset epoxy resins, curing of, 10 421 Thermoset flexible polyurethane foams properties of, 25 461 Thermoset matrix composites, 21 456 Thermo set molding properties of diallyl isophthalate, 2 262t Thermoset polymers, 25 455 cured, 10 425... 

Poly(hexamethylene adipamide) Poly(vinylidene chloride) 1934 1838 1938 1939 Fibers, thermoplastics Thermoplastics (packing films) Unsaturated polyesters 1930 Poly(isobutylene) Stvrene-butadiene 1926 1936 1937 1937 Thermosets Elastomers Elastomers (letter Bunas)... 

Because PIB is fully saturated, it is cured as a thermoset elastomer through inclusion of about l%-2% isoprene that supplies the needed double bonds used in the curing process. Other materials including brominated paramethyl styrene are replacing isoprene for this use. PIB is also used in sealing applications and medical closures and sealants. 

SRs contain sulfur and carbon linkages that are thermoset elastomers (TSEs). They have outstanding resistance to oils, greases, and solvents but have an unpleasant odor. Their resiliency is poor and their heat resistance is only fair. The abrasion resistance of polysulfidcs is half that of NR and its tensile strength runs only from 8.3 to 9.7 MPa (1,200 to 1,400 psi). However these values are still retained even after extended immersion in oil. Their increased sulfur content improves their solvent and oil resistance but reduces their permeability to gases. 

The most significant difference between these two modes of achieving crosslinking is that the first generates a traditional thermoset elastomer, while the second gives rise to a thermoplastic elastomer (TPE) [85]. 

The concept of traditional thermoset elastomers was pioneered by Goodyear s discovery in 1839 that heating natural rubber with some sulfur converted the material from one that was tacky when warm and brittle when cold into a vulcanized rubber that was conveniently useful over a wide temperature range. Crosslinking of the macromolecules of rubber with sulfur bonds endowed the naturally occurring material with some elastic memory and caused it to behave as we have come to expect elastomers to behave. Excessive sulfur crosslinking converts the stretchable, compressible, bouncy rubber into hard rubber such as the material found in the heads of mallets used in machine shops to pound sheet metal into desired shapes. A small dose of crosslinking prevents the macromolecules of natural rubber to crystallize at low temperatures and turn into a brittle solid and to become a tacky, sticky semifluid at elevated temperatures. 

The average of 8 pounds per car of urethane elastomer was composed of 1.3 pounds of TPU, 4.8 pounds of RIM thermoset elastomer and 1.9 pounds of cast thermoset urethane. 

The use of urethane elastomers will grow as the use of soft bumpers and fascia increase. Most of this growth will be RIM thermoset elastomers. The use of A.8 pounds per car should grow to 15.3 pounds per car by 1985. 

The major increase will be the increased use of RIM urethane thermoset elastomer for flexible fascia and bumpers and reinforced RIM urethane materials for fenders and other body parts. 

Elastomers constitute a third class of polymers. Similarly to thermosets, elastomers have a network structure formed by crosslinking between the polymer chains. However, the number of links is less than in the case of thermosets which gives these materials elastic properties. Elastomers can be deformed by the application of external forces. When these forces are suppressed, the polymer recovers its original form. From a commercial point... 

Flame Retardation of Polymeric Materials. The suitability of a particular flame-retarding method is often determined by the nature of the polymer type (e.g., thermoplastic or thermoset). A brief and general discussion regarding the flame retardation of thermoplastics, thermosets, elastomers, and fibers follows. 

Sachtolith . [Sachtleben Chemie GmbH Ore Chem.] Zinc sulfide white pigment for thermoplastics, thermosets, elastomers, textile fibers, paper, sealants, lubricants. 

Versamag . [Mtxton Int l.] Magnesium hydroxide filler, fire retardant smoke suppressant for plastics, thermosets, elastomers. 

The thermoset elastomers most frequently used for cables are ethylene propylene rubber and cross-linked polyethylene. 

Starting with the silicone elastomer hydrocephalus shunt in 1955, silicone elastomer has become widely used as a soft, flexible, elastomeric material of construction for artificial organs and implants for the human body. When prepared with controls to assure its duplication and freedom from contamination, specific formulations have excellent biocompatibility, biodurability, and a long history of clinical safety. Properties can be varied to meet the needs in many different implant applications. Silicone elastomer can be fabricated in a wide variety of forms and shapes by most all of the techniques used to fabricate thermosetting elastomers. Radiopacity can be increased by fillers such as barium sulfate or powdered metals. It can be sterilized by ethylene oxide, steam autoclave, dry heat, or radiation. Shelf-life at ambient conditions is indefinite. When implanted the host reaction is typically limited to encapsulation of... 

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