Acrylic rubbers curing systems

Elastomers are generally crosslinked in a random manner and therefore it is difficult to obtain the quantitative, independent information (molecular weight M, between crosslinks, functionality (p of the network) required to test the molecular theories. However, some systems such as natural rubber cured by dicumyl peroxide >, irradiated polymers " or even chemically randomly crosslinked polydimethyl-siloxane and poly(ethyl acrylate) have been investigated. Mark has exploit ... 

Nitrile and Acrylic Rubber. Nitrile rubbers are made by the emulsion copolymerization of acrylonitrile (9-50%) and butadiene (21) and are abbreviated NBR (eq. 11). The ratio of acrylonitrile (ACN) to butadiene has a direct effect on the properties and the nature of the pol5nners. As the ACN content increases, the oil resistance of the poljnner increases (14). As the butadiene content increases, the low temperature properties of the polymer are improved. Nitrile rubber is much like SBR in its physical properties. It can be compoimded for physical strength and abrasion resistance using traditional fillers such as carbon black, silica, and reinforcing clays. The primary benefit of the polymer is its oil and solvent resistance. At a medium ACN content of 34% the volume swell in IRM 903 oil at 70°C is typically 25-30%. Nitrile rubber can be processed on conventional rubber equipment and can be compression, transfer, or injection molded. It can also be extruded easily. Nitrile rubber compoimds have good abrasion and water resistance. They can have compression set properties as low as 25% with the selection of a proper cure system. The temperature range for the elastomers is from -30 to 125°C. The compounds are also plasticized nsing polar ester plasticizers. 

Self-curing acrylic rubbers have been announced which apparently function by the inclusion of acrylic cure sites. In one system two copolymers are blended together. One copolymer is made by copolymerizing ethyl acrylate, with possibly some alkoxyethyl acrylate to improve low temperature properties, with methylol acrylamide. The other copolymer is made from ethyl acrylate and acrylamide (or possibly an alkoxy methyl acrylamide). On heating cross-linking occurs between amine and methylol groups. The rate of cure may be accelerated by the use of an acidic material such as phthalic anhydride ... 

Although the earliest acrylic rubbers did not have any special cure site incorporated and had to be cured by such materials as amines, peroxides and metasilicates, the use of special cure-site monomers has been well established for many years and most curing systems have been based upon them. Until the late 1960s these cure systems were based on amines, ammonium salts and related materials. The discovery (Holly et u/., 1965) that very useful and versatile systems could be based on a soap-sulphur combination has drastically altered technological practice. Although some of the early acrylic rubbers are not suitable for this type of cure, rubbers announced since the discovery of this method have been designed to use it. 

Kobe, 23rd-27th Oct.1995, p.531-4. 012 ACRYLIC RUBBERS AND THEIR CURING SYSTEMS... 

We have been investigating the effects of multifunctional monomers, rubber modification and light intensity upon both the rate and final degree of cure in acrylated epoxy systems. 

Relevant systems are mbber-toughened epoxy resins, high-impact acrylic (PMMA particles in mbber matrix, obtained by radical polymerization of 80/20 MMA/EVAc mixture), polyimide/silica hybrid materials (obtained using the sol-gel method), and a very high strength ( 60 MPa) mbbers (obtained by peroxide cure of a hydrogenated nitrile rubber/ zinc dimethacrylate system) [Inoue, 1995]. 

One of the newer developments in adhesives is the growing use of ultraviolet light or electron beam radiation to cure adhesives. Adhesives designed for UV- or E-beam curing are usually pressure sensitive or hot-melt systems based on acrylates, functional rubbers, or epoxidized rubbers, and use special UV or EB lamps to provide the cure. These systems can provide greatiy improved heat resistance compared to hot melts, and avoid the soivent emission problems of some of the solvent-based systems with which they compete. 

Uses Monomer for creating and modifying polymers, acrylic resins, urethane methacryiates marine antifouling paint resin comonomer reactive comonomer for acryiic and S/B resins rubber modifier binder for textiies/paper adhesives, nonwoven fabrics, enamels, adhesives grafting of textiie fibers scaie inhibitors adhesion promoter for polymers hydrophilic polymers It.-curing polymer systems reactive thinner for radiation curing food-pkg. adhesives, polymers Manuf./Distrib. Acros Org. Aldrich Allchem Ind. Ashland BP Amoco Electron Microscopy Sciences Fluka ICN Biomed. Research Prods. Kessler Lancaster Synthesis Laporte Perf. Chems. Monomer-Polymer Dajac Labs Pfaltz Bauer Rohm Haas Rohm Tech San Esters Scientific Polymer Prods. Sigma TCI Am. Ubichem pic Whyte Chems. Ltd... 

Triforine cure accelerator Dipentaerythrityl acrylate cure activator, oxidation butyl rubber Benzothiazyl disulfide cure inhibitor, RTV systems Dimethicone, vinyidimethyl-terminated cure moderator, RTV systems Dimethicone, vinyidimethyl-terminated cure promoter, polyesters Benzene phosphinic acid cure promoter amine-cured epoxies Furfuryl alcohol curing agent... 

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