Polyacrylic elastomer

A wide range of polymers which form thin, flexible films are used. They can be split into two categories, polymeric elastomers and rubbers. The polymers include polyurethanes, polyvinyl chloride, polyvinylidene chloride, polyethylene, polytetrafluoroethylene, silicone elastomers, polyacrylates, and chlorinated and chlorosulphonated polyethylenes. 

Data have been published dealing with successful applications of HAS in stabilization of other polymers than PO elastomers, styrenic polymers, polyamides, polycarbonates, polyacetals, polyurethanes, linear polyesters, thermoplastic polyester elastomers, polyacrylates, epoxy resins, poly(phenylene oxide) or polysulfide [12]. In spite of their basicity, HAS may also be used for stabilization of PVC. This application includes less basic derivatives of piperidine and 1,4-dihydropyridine [12,13,145,146]. 

Uses Monomer for solv.-resist. elastomers, polyacrylate rubbers, UV-curable reactive diluent, soft contact lenses, PVC impact modifier, fabric coatings, barrier coatings for polyethylene, textile coatings Properties APHA 50 color m.w. 130.15 sp.gr. 1.012 (20/20 C) flash pt. 82 C 98.5% act. 

Uses Prod, of solv.-resistant elastomers, polyacrylate rubbers UV-cur-able reactive diluent soft contact lenses PVC impact modifier fabric coatings barrier coatings for polyethylene textile coalings plasticizer softener... 

Thermoplastic elastomers Polyacrylic acid Polyvinyl alcohol Polyethylene... 

Various types of monomers have been used to introduce cure-sites into polyacrylic elastomers. Polyacrylic elastomers containing active chloride, epoxy, and carboxyl groups as active cure-sites have been developed for industrial applications. Polyacrylic elastomers which contain epoxy groups are vulcanized with ammonium salts and dithiocarbamate salts, whereas elastomers which contain active chloride are vulcanized with sulfur-metal soap, organic amines, etc. 

Other elastomers which have been used to modify polyesters include EPDM (ethylene-propylene-diene-methylene), poly(epichlorohydrin) with hydroxyl end groups (Crosbie and Phillips, 1985b Ullett and Chartoff, 1995), organic siloxane elastomers, polyacrylates (Ullett and Chartoff, 1995), and polyurethane elastomers (IQm and Chan-Park, 1994). 

Polyacrylate elastomers find limited use in hydrauhc systems and gasket apphcations because of their superior heat resistance compared to the nitrile mbbers (219,220). Ethylene—acrylate copolymers were introduced in 1975. The apphcations include transmission seals, vibration dampers, dust boots, and steering and suspension seals. Further details and performance comparisons with other elastomers are given in reference 221 (see also Elastomers, SYNTHETIC-ACRYLIC ELASTOTffiRS). 

Most elastomers can be made iato either opea-ceUed or closed-ceUed materials. Natural mbber, SBR, nitrile mbber, polychloroprene, chlorosulfonated polyethylene, ethylene—propylene terpolymers, butyl mbbers, and polyacrylates have been successfuUy used (4,111,112). 

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. 

Ozonc-rcsjstant elastomers which have no unsaturation are an exceUent choice when their physical properties suit the appHcation, for example, polyacrylates, polysulfides, siHcones, polyesters, and chlorosulfonated polyethylene (38). Such polymers are also used where high ozone concentrations are encountered. Elastomers with pendant, but not backbone, unsaturation are likewise ozone-resistant. Elastomers of this type are the ethylene—propylene—diene (EPDM) mbbers, which possess a weathering resistance that is not dependent on environmentally sensitive stabilizers. Other elastomers, such as butyl mbber (HR) with low double-bond content, are fairly resistant to ozone. As unsaturation increases, ozone resistance decreases. Chloroprene mbber (CR) is also quite ozone-resistant. 

E. Chang and E. Ma22one, "A New Non-Postcure Curative Package for Polyacrylate Elastomers", paper presented atMCA BjibberDivisions Detroit, Mich., Oct. 17—20, 1989. 

If the compound can be attacked by water, for example polyacrylate and fluoroelastomer elastomer based compounds, the preforms are air cooled. 

Mechanical Properties of Thermoplastic Elastomers Based on Acrylate Rubber-Fluorocarbon Rubber-Polyacrylate Monomer... 

Kofod, G., Kombluh, R., PeMne, R., and Sotntner-Larsen, P., Actuation response of polyacrylate dielectric elastomers, smart stmctures and materials 2001, in Electroactive polymer actuators and devices, Y. Bar-Cohen (Ed.), Proceedings ofSPIE, Vol. 4329, 0277-786X/2001. 

Various additives show considerable extraction resistance, such as impact modifiers (polyacrylates and polyblends PVC/EVA, PVC/ABS, etc.), highpolymeric processing aids (PMMA-based), elastomers as high-MW plasticisers, reactive flame retardants (e.g. tetrabromobisphenol-A, tetrabromophthalic anhydride, tetrabromophthalate diol, dibromostyrene). Direct measurement of additives by UV and IR spectroscopy of moulded films is particularly useful in analysing for additives that are difficult to extract, although in such cases the calibration of standards may present a problem and interferences from other additives are possible. 

PMA is a tough leathery resin with a low Tg and a solubility parameter of 10.5 H. In polymers of alkyl acrylates the solubility parameter decreases as the size of the alkyl group increases. The flexibility also increases with the size of the pendant groups but because of side chain crystallization this tendency is reversed when the alkyl group has more than ten carbon atoms. Polyalkyi acrylates are readily hydrolyzed by alkalis to produce salts of polyacrylic acid. The copolymer of ethyl acrylate (95%) and chloroethyl vinyl ether (5%) is a commercial oil-resistant elastomer. 

HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HMX HNS NTO NTO/HMX NTO/HMX NTO/HMX PETN PETN PETN PETN PETN PETN PETN PETN PETN PETN RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX RDX TATB/HMX Cariflex (thermoplastic elastomer) Hydroxy-terminated polybutadiene (polyurethane) Hydroxy-terminated polyester Kraton (block copolymer of styrene and ethylene-butylene) Nylon (polyamide) Polyester resin-styrene Polyethylene Polyurethane Poly(vinyl) alcohol Poly(vinyl) butyral resin Teflon (polytetrafluoroethylene) Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Cariflex (block copolymer of butadiene-styrene) Cariflex (block copolymer of butadiene-styrene) Estane (polyester polyurethane copolymer) Hytemp (thermoplastic elastomer) Butyl rubber with acetyl tributylcitrate Epoxy resin-diethylenetriamine Kraton (block copolymer of styrene and ethylene-butylene) Latex with bis-(2-ethylhexyl adipate) Nylon (polyamide) Polyester and styrene copolymer Poly(ethyl acrylate) with dibutyl phthalate Silicone rubber Viton (fluoroelastomer) Teflon (polytetrafluoroethylene) Epoxy ether Exon (polychlorotrifluoroethylene/vinylidine chloride) Hydroxy-terminated polybutadiene (polyurethane) Kel-F (polychlorotrifluoroethylene) Nylon (polyamide) Nylon and aluminium Nitro-fluoroalkyl epoxides Polyacrylate and paraffin Polyamide resin Polyisobutylene/Teflon (polytetrafluoroethylene) Polyester Polystyrene Teflon (polytetrafluoroethylene) Kraton (block copolymer of styrene and ethylene-butylene)... 

Diacyl peroxides are used in a broad spectmm of applications, including curing of unsaturated polyester resin compositions, cross-linking of elastomers, production of poly(vinyl chloride), polystyrene, and polyacrylates, and in many nonpolymeric addition reactions. 

Ethvlenethiourea (2-mercaptoimidazolinej imidazolidine-2-thione imidazoline-2-thiol, VIII) is a water-soluble white crystalline solid used extensively in curing elastomers (rubbers, e.g., polychloroprenes, polyacrylates, etc.) It is also present as an impurity in the ethylene bisdithiocarbamates widely used as fungicides. When the fungicides are present as a contaminant in heated foods, they may be converted to the ethylenethiourea (ref. 

Surface treatments consist of washing with solvent, abrading, or, in the most demanding applications, cyclizing with acid. The most common elastomers to be bonded in this way include nitrile, neoprene, urethane, natural rubber, SBR, and butyl rubber. It is more difficult to achieve good bonds with silicones, fluorocarbons, chlorosulfonated polyethylene, and polyacrylate. 

Grafted copolymers obtained by VCM polymerisation and polyacrylic elastomer grafting, give high bulk density resins for products with high impact strength suitable for outdoor applications. The separate addition of acrylate impact modifiers to the PVC formulation is covered in Section 4.5.2. 

The high mechanical strength of natural and organic rubbers as used in tires is due to the incorporation of pyrogenic carbon blacks as active fillers. Elastomers of a more polar polymer backbone, such as polyacrylates, polyurethanes or polysulphides, require fillers of higher polarity. In particular the performance of polydimethylsiloxane elastomers (silicone rubber) is basically related to the addition of fumed silica. 

FIGURE 9.17 Dependence of productivity and separation factor /3p C6H5CH3/H2O of membranes based on various rubbery polymers on the glass transition temperature of the polymer (pervaporation separation of saturated toluene/water mixture, T = 308 K) (1) polydimethyl siloxane (2) polybutadiene (3) polyoctylmethyl siloxane (4) nitrile butadiene rubber with 18% mol of nitrile groups (5) the same, 28% mol of nitrile groups (6) the same, 38% mol of nitrile groups (7) ethylene/propylene copolymer (8) polyepichlorohydrin (9) polychloroprene (10) pol3furethane (11) polyacrylate rubber (12) fluorocarbon elastomer. (From analysis of data presented in Semenova, S.I., J. Membr. Sci., 231, 189, 2004. With permission.)... 

A recent approach to ocular inserts was presented by Chetoni et in a study of cylindrical devices for oxytetracycline, made from mixtures of silicone elastomer and grafted on the surface of the inserts with an interpenetrating mueoadhesive polymeric network of polyacrylic acid or polymethacrylic acid. The inserts were tested for drug release and retention at rabbit eyes. It was shown that some of the inserts are able to maintain prolonged oxytetracycline concentrations in the lacrimal fluid for 36 h. 

Diak [Du Pont]. TM for a series of rubber accelerators used to vulcanize Viton fluoroelas-tomer and polyacrylate elastomers. 

Gahlmer, F. H. and Nleske, F. W., "Hydrolytic Stability of Urethane and Polyacrylate Elastomers in Humid Environments," Urethanes In Elastomers and Coatings (articles from the Journal of Elastoplastlcs), pp. 6-20, Technomlc Publ. Co., Inc., Westport (1973). 

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