High Performance Elastomers

FORREST M j, HOLDING s R and HOWELLS D, The usc of two-dimcnsional GC-MS for the identification and quantification of low molecular weight compounds from high performance elastomers . High Performance and Speciality Elastomers, Geneva, Rapra Technology Ltd, 2005. 

Uses. Vinyhdene fluoride is used for the manufacture of PVDF and for copolymerization with many fluorinated monomers. One commercially significant use is the manufacture of high performance fluoroelastomers that include copolymers of VDF with hexafluoropropylene (HFP) (62) or chlorotrifluoroethylene (CTFE) (63) and terpolymers with HEP and tetrafluoroethylene (TEE) (64) (see Elastomers, synthetic-fluorocarbon elastomers). There is intense commercial interest in thermoplastic copolymers of VDE with HEP (65,66), CTEE (67), or TEE (68). Less common are copolymers with trifluoroethene (69), 3,3,3-trifluoro-2-trifluoromethylpropene (70), or hexafluoroacetone (71). Thermoplastic terpolymers of VDE, HEP, and TEE are also of interest as coatings and film. A thermoplastic elastomer that has an elastomeric VDE copolymer chain as backbone and a grafted PVDE side chain has been developed (72). 

Amine Cross-Linking. Two commercially important, high performance elastomers which are not normally sulfur-cured are the fluoroelastomers (FKM) and the polyacrylates (ACM). Polyacrylates typically contain a small percent of a reactive monomer designed to react with amine curatives such as hexamethylene-diamine carbamate (Diak 1). Because the type and level of reactive monomer varies with ACM type, it is important to match the curative type to the particular ACM ia questioa. Sulfur and sulfur-beating materials can be used as cure retarders they also serve as age resistors (22). Fluoroelastomer cure systems typically utilize amines as the primary cross-linking agent and metal oxides as acid acceptors. 

Polymeric isocyanates or PMDI ate cmde products that vary in exact composition. The main constituents are 40—60% 4,4 -MDI the remainder is the other isomers of MDI, trimeric species, and higher molecular weight oligomers. Important product variables are functionaHty and acidity. Rigid polyurethane foams are mainly manufactured from PMDI. The so-called pure MDI is a low melting soHd that is used for high performance polyurethane elastomers and spandex fibers. Liquid MDI products are used in RIM polyurethane elastomers. 

Vaidyanathan, R., and EI-Halwagi, M. M. (1994). Computer-aided design of high performance polymers. J. of Elastomers and Plastics, 26, 277-293. 

Polyesters are one of the most versatile classes of polymers ever produced, covering a wide range of properties and applications. Polyesters are present in fibers, engineering thermoplastics, and high-performance polymers as well as in thermosetting resins and elastomers. Table 2.1 lists the chemical structure, abbreviations, and uses of some commercially important thermoplastic polyesters. 

Better physical properties due to molecular regularity (esp. dynamic properties, high-performance elastomers)... 

The full-prepolymer, quasi-prepolymer, and one-shot techniques may appear to be quite similar, but they each have important bearing on equipment requirements and physical properties. The full-prepolymer method, for example, is die process of choice for making high-performance cast elastomers with superb dynamic properties, such as industrial bumpers and bushings. Quasi-prepolymers are used in less demanding applications like shoe soles, adhesives, and spray elastomers. One-shots make up the rest, including most foams and elastomers. 

Table summarizes the material properties of structural proteins, high performance synthetic materials and synthetic elastomers... 

Uritani, P. Kishita, H. In HPE 2002, International Conference Focusing on High Performance Elastomers 2nd, Cologne, Germany, November 13-14, 2002 Rapra Technology Ltd Shrewsbury, UK, 2002, pp 139-150. 

Some copolymers (Nuj and Nu2 substituants) are already manufactured on an industrial scale as high performance elastomers... 

Swogger, K.W., Carnahan, E.M., Hoenig, W.D., and Frencham, A.R., The Development of a New Generation of Novel High Performance Olefin Elastomers Erom Molecular Design to Market Development, SPEANTEC Tech. Papers, 52, 1008 (2006)... 

Hiltner, A., Wang, H., Khariwala, D., Cheung, W., Chum, S., and Baer, E., Solid State Structure and Properties of Novel High Performance Olefin Elastomers, SPE ANTEC Tech. Papers, 52, 1000 (2006)... 

Kevlar fibers are available in four forms Kevlar, Kevlar 29, Kevlar 49 and the recently developed Kevlar 149. Kevlar is designed specifically for reinforcements of elastomers (e.g. tires and belts), while Kevlar 29 is used primarily for tensile members sueh as ropes, cables, webbings and ballistic cloth. Kevlar 49 and 149 are designed for reinforcement of high performance PMCs. Kevlar 149 offers a 40%... 

Nonsulfur Vulcanizing Agents. Many high performance specialty elastomers do not contain diene moieties in their molecular structure and therefore cannot be sulfur-cured. These elastomers require cross-linking agents capable of reacting with the specific functional group(s) contained by the specific elastomer. Some common nonsulfur curatives include peroxides, difunctional resins, and metal oxides. 

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