Chloroprene rubber temperatures

Park et al. [20] reported on the synthesis of poly-(chloroprene-co-isobutyl methacrylate) and its compati-bilizing effect in immiscible polychloroprene-poly(iso-butyl methacrylate) blends. A copolymer of chloroprene rubber (CR) and isobutyl methacrylate (iBMA) poly[CP-Co-(BMA)] and a graft copolymer of iBMA and poly-chloroprene [poly(CR-g-iBMA)] were prepared for comparison. Blends of CR and PiBMA are prepared by the solution casting technique using THF as the solvent. The morphology and glass-transition temperature behavior indicated that the blend is an immiscible one. It was found that both the copolymers can improve the miscibility, but the efficiency is higher in poly(CR-Co-iBMA) than in poly(CR-g-iBMA),... 

Emulsion polymerization is the most important process for production of elastic polymers based on butadiene. Copolymers of butadiene with styrene and acrylonitrile have attained particular significance. Polymerized 2-chlorobutadiene is known as chloroprene rubber. Emulsion polymerization provides the advantage of running a low viscosity during the entire time of polymerization. Hence the temperature can easily be controlled. The polymerizate is formed as a latex similar to natural rubber latex. In this way the production of mixed lattices is relieved. The temperature of polymerization is usually 50°C. Low-temperature polymerization is carried out by the help of redox systems at a temperature of 5°C. This kind of polymerization leads to a higher amount of desired trans-1,4 structures instead of cis-1,4 structures. Chloroprene rubber from poly-2-chlorbutadiene is equally formed by emulsion polymerization. Chloroprene polymerizes considerably more rapidly than butadiene and isoprene. Especially in low-temperature polymerization emulsifiers must show good solubility and... 

Terpolymers in which the acrylate monomer is the major component are useful as ethylene-acrylate elastomers (trade name Vamac) [Hagman and Crary, 1985]. A small amount of an alkenoic acid is present to introduce sites (C=C) for subsequent crosslinking via reaction with primary diamines (Sec. 9-2d). These elastomers have excellent oil resistance and stability over a wide temperature range (—50 to 200°C). They are superior to nitrile and chloroprene rubbers. Although not superior to silicone and fluorocarbon elastomers, they are less costly uses include automotive (hydraulic system seals, hoses) and wire and cable insulation. 

If a rubber-like polymer is used as the vinyl polymer, this IPN will show good damping properties at elevated temperatures. So, butyl acrylate, ethylene glycol dimethacrylate, phenolic novolac, and bisphenol A type epoxies were used as IPN components. The dynamic mechanical properties of these IPNs were examined first, because the loss tangent is very important to damping properties. Then the damping properties of IPN and commercial chloroprene rubber were measured at various temperatures. 

Judging from the results of dynamic mechanical analyses, IPNs showed more effective damping properties than commercial chloroprene rubber at elevated temperatures. In addition, filled IPNs prepared by adding platelet fillers showed even higher attenuation (logarithmic decrement). 

Chloroprene rubber (CR) is perhaps the most natural rubberlike of all synthetic plastics or elastomers, particularly with regard to its dynamic response. CRs are a family of elastomers with a property profile that approaches that of natural rubber (NR) but that has better resistance to oils, ozone, oxidation, flame, aging, and heat. CRs are about 25% heavier than NR and do not have the low temperature flexibiUty of NRs. See dynamic elongation polychloroprene rubber/elastomer rabber. 

Chloroprene rubbers also are compatible with TPU and can be used to reduce the hardness of TPU and improve low-temperature impact. 

Ta b I e 5.62 Upper and lower temperature limits for elastomeric materials (R C backbone with unsaturated units, M C backbone with only saturated units, 0 both C and 0 in the backbone, U C, N and 0 in the backbone, T C and S in the backbone, Q siloxane backbone NR natural rubber, IR isoprene rubber, BR butadiene rubber, CR chloroprene rubber, SBR styrene butadiene rubber, NBR nitrile rubber, HR butyl rubber, EPDM ethylene propylene ter-rubber, EAM ethylene vinyl acetate rubber, FKM fiuoro rubber, ACM acrylate rubber, CSM chlorosulfonated polyethylene, CM chlorinated polyethylene, ECO epichlorohydrin rubber (epichlorohydrin, ethylene oxide), AU polyurethane rubber (did), EU polyurethane rubber (diisocyanate), VMQ silicone rubber) specialties [229]... 

The crystallization process is temperature dependent and has its maximum rate at -5°C to -10°C. This effect is responsible for the hardening and the reduction in elasticity of chloroprene rubber (CR) polymer compounds and vulcanizates during storage at low temperatures. Crystallization is completely reversible by heat or dynamic stress. In general, the raw polymers crystallize 10 times faster than vulcanized, plasticizer-free compounds (ISO 2475, ASTM D 3190-90). 

Chloroprene rubber is typically supplied in chip form and is normally coated with talc to prevent blocking during shipping and storage. These chips can be processed on open mills or internal mixers using conventional or upside-down techniques. Crystallized chips cause no problems in processing because the crystallites melt at temperatures above 40°C-60°C. 

The monomer, 2-chlorobuta-1,3-diene, better known as chloroprene, is polymerised by free-radical emulsion methods to give a polymer which is predominantly (-85%) fr<2 s-l, 4-polychloroprene but which also contains about 10% cii-1,4- 1.5%, 1,2- and 1% of 3,4-structures (Figure 11.17). The commercial polymers have a Tg of about -A3°C and a of about 45°C so that at usual ambient temperatures the rubber exhibits a measure of crystallinity. 

Over 5.5 billion pounds of synthetic rubber is produced annually in the United States. The principle elastomer is the copolymer of butadiene (75%) and styrene (25) (SBR) produced at an annual rate of over 1 million tons by the emulsion polymerization of butadiene and styrene. The copolymer of butadiene and acrylonitrile (Buna-H, NBR) is also produced by the emulsion process at an annual rate of about 200 million pounds. Likewise, neoprene is produced by the emulsion polymerization of chloroprene at an annual rate of over 125,000 t. Butyl rubber is produced by the low-temperature cationic copolymerization of isobutylene (90%) and isoprene (10%) at an annual rate of about 150,000 t. Polybutadiene, polyisoprene, and EPDM are produced by the anionic polymerization of about 600,000, 100,000, and 350,000 t, respectively. Many other elastomers are also produced. 

Fig. 19. Polymerization of chloroprene by natural rubber mastication. Effect of time, monomer concentration and temperature on monomer conversion. / 24.2% chloroprene, 15° C 2 24.2% chloroprene, 25°C 3 39.0% chloroprene, 15°C 4 49.0% chloroprene, 15° C (69)...

Another large use of normal butenes in the petrochemical industry is in the production of 1,3-butadiene (CH2 = CH = CH = CH2). In the process, a mixture of n-butenes, air, and steam is passed over a catalyst at a temperature of 500°C to 600°C. Butadiene is used extensively to produce synthetic rubbers (see Isoprene) in polymerization reactions. The greatest use of butadiene is for styrene-butadiene rubber, which contains about a 3 1 ratio of butadiene to styrene. Butadiene is also used as a chemical intermediate to produce other synthetic organics such as chloroprene, for adhesives, resins, and a variety of polymers. 

Polymerization in emulsion under normal pressure and in the temperature range from —20 C to 60°C uses a fine emulsion of oil-soluble monomers in water and initiates the reaction with a system of water-soluble catalysts. This method is probably the most important of all, because it is used in very large scale in die copolyiuerization of butadiene and styrene and in the polymerization of many other monomers, such as chloroprene and vinyl chloride, to produce latices of the various synthetic rubbers. 

Chloroprene is of high industrial importance for manufacture of synthetic rubbers. For a long time the synthesis was based on acetylene. More recent processes are based on butadiene as a feedstock, which is substantially cheaper [29]. The initial step is a gas-phase free-radical chlorination at 250 °C and temperature control is ensured by use of excess butadiene (molar ratio of Cl2 to butadiene 1 5 to 1 50) [44]. To limit side reactions, short contact time reactors operating at higher temperatures and residence times below one second are also known [45], Good mix-... 

Solid-state 13C NMR has been used to identify elastomers in binary blends of chloroprene (CR) and NR, CR and CSM, NR and CSM, and SBR and acrylonitrile-butadiene rubber (NBR). The type of NBR can be determined by identifying the sequences of acrylonitrile and butadiene. The tertiary blend of NR/SBR/BR was also studied [49]. High-temperature 13C solid-state NMR identified ethylene-propylene diene terpolymer (EPDM) and fluoro and nitrile rubbers [50]. 

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