Poly chloroprene

Poly(chloroprene) was one of the first synthetic elastomers. It came on the market in 1931, and was developed at the Du Pont factory as part of their search for elastomers for special areas of application. The industrial synthesis of the monomer became possible when Nieuwland discovered mono vinyl acetylene. Today, chloroprene is produced from monovinyl acetylene C4H4, butadiene butene C4H8, or butane C4Hio- 

Under similar conditions, the emulsion polymerization of chloroprene proceeds about 700 times faster than that of isoprene. The resulting heat of polymerization therefore must be dissipated as quickly as possible by effective external cooling or by using flow techniques. Alternatively, the reaction rate can be moderated by adding an inhibitor. Sulfur is used commercially for this purpose with chloroprene, although this inhibitor cannot be used in the polymerization of butadiene or isoprene. Coagulation of emulsion is finally brought about by the addition of acids or multivalent salts. The emulsion polymerizates possess only about 1.5% 1,2 structures. 

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C. W. Stewart, Sr., R. L. Dawson, and P. R. Johnson, Effect of Compounding Variables on the Rate of Heat and Smoke Release from Poly chloroprene Foam, Du Pont elastomer bulletin C-NL-550.871, 1974. 

F. J. Stark, Jr., Poly chloroprene as an Extender for Reycled Rjcbber, Preprints of the ACS Racbber Division Meeting, 1983, The American Chemical Society, Washington, D.C., 1989. 

Resistance to weathering. Zinc oxide and magnesium oxide stabilize poly-chloroprene against dehydrochlorination. Further, zinc oxide helps vulcanize the rubber, and magnesium oxide reacts with /-butyl phenolic resin to produce a resinate which improves heat resistance of solvent-borne polychloroprene adhesives. 

Other ingredients. Bacterial and fungal attack can be a problem in poly-chloroprene latex formulations with pH below 10. It is manifested by odour, discolouration and gas evolution 500-1500 ppm of a biocide should be added. 

Tanno, T. and Shibuya, L., Special behaviour of para tertiary phenol dialcohol in poly-chloroprene adhesives. Adhesives and Sealant Council Meeting, Spring 1967. 

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),... 

The mechanism of chloroprene polymerization is summarized in Scheme 4.11. Coleman et ai9iM have applied l3C NMR in a detailed investigation of the microstructure of poly(chloroprene) also known as neoprene. They report a substantial dependence of the microstructure on temperature and perhaps on reaction conditions (Table 4.3). The polymer prepared at -150 °C essentially has a homogeneous 1,4-tra/rv-niicrostructure. The polymerization is less specific at higher temperatures. Note that different polymerization conditions were employed as well as different temperatures and the influence of these has not been considered separately. 

FIGURE 4.8 Comparative tensile stress-strain plot of polychloroprene-ordinary zinc oxide (ZnO) and poly-chloroprene-nano-ZnO system. (From Sahoo, S., Kar, S., Ganguly, A., Maiti, M., and Bhowmick, A.K., Polym. Polym. Compos., 2007 (in press). Courtesy of Smithers Rapra Technology Ltd.)... 

The first important commercial synthetic rubber was poly(chloroprene) which was made available for sale as Neoprene by DuPont in 1931. It is still made and sold today because of its superior resistance to oils, sunlight, and oxygen (ozone). 

Anthony, Caston, and Guth obtained considerably better agreement between the experimental stress-strain curve for natural rubber similarly vulcanized and the theoretical equation over the range a = 1 to 4. KinelP found that the retractive force for vulcanized poly-chloroprene increased linearly with a — l/a up to a = 3.5. 

Poly(vinyl ethers) 1928 1936 Adhesives, plasticizers Poly(chloroprene) 1925 1932 Elastomers... 

Uses. Accelerator in the curing of poly-chloroprene (neoprene) and polyacrylate rubber intermediate in the manufacture of antioxidants, insecticides, fungicides, dyes, pharmaceuticals, and synthetic resins... 

Blend of poly chloroprene and NBR Carbon black and multifunctional acrylate 50 15,000 20 (2,900)... 

Styrene-butadiene rubber (SBR) accounts for about 40 percent of the total consumption of butadiene. SBR is the material used to make most automobile tires. Other synthetic rubbers, such as polybutadiene and poly-chloroprene (neoprene), make up another 25 percent of the butadiene market. 

B. Assume that the GPC curve of Polymer A is that of a polydisperse linear poly-chloroprene with Mark-Houwink-Sakurada constants in THF at 30°C of K = 4.18 x 10 5 dl/g and a - 0.83. Calculate the weight and number molecular weight averages, the polydispersity and the intrinsic viscosity of this polychloroprene. 

Emulsion polymerization is the basis of many industrial processes, and the production volume of latex technologies is continually expanding—a consequence of the many environmental, economic, health, and safety benefits the process has over solvent-based processes. A wide range of products are synthesized by emulsion polymerization, including commodity polymers, such as polystyrene, poly(acrylates), poly (methyl methacrylate), neoprene or poly(chloroprene), poly(tetrafluoroethylene), and styrene-butadiene rubber (SBR). The applications include manufacture of coatings, paints, adhesives, synthetic leather, paper coatings, wet suits, natural rubber substitutes, supports for latex-based antibody diagnostic kits, etc. ... 

Fast extrusion furnace black with a particle size of 360 A, was used to verify different theoretical concepts of percolation which by definition predicts a rapid change in conductance when volume fraction of conductive particles attains a critical value. Figure 15.38 shows the effect of a carbon black addition to polychloroprene. Up to 30 phr carbon black, the conductivity of poly chloroprene is almost constant and then it increases linearly as concentration of carbon black increases. The following equation applies o = o (P - P Jwhere c is constant, P is concentration of conducting particles, Pc is percolation threshold, and P is exponent which accounts for cluster size."" When data from the Figure 15.38 are replotted as in Figure 15.39 it is evident that the percolation law is valid. 

The close structural similarities between poly chloroprene and the natural rubber molecule will be noted. However, whilst the methyl group activates the double bond in the polyisoprene molecule the chlorine atom has the opposite effect in polychloroprene. Thus the polymer is less liable to oxygen and ozone attack. At the same time the a-methylene groups are also deactivated so that accelerated sulphur vulcanisation is not a feasible proposition and alternative curing systems, often involving the pendant vinyl groups arising from 1,2-polymerisation modes, are necessary. 

Neoprene. [DiiPont DuPont UK] Poly-chloroprene versatile synthetic rubber fw wire/cable industrial hose and belting automotive gaskets, seals, hose tire sidewalls molded and extruded goods cellular prods. adhesives, sealants, and protective coatings for shoe, home crafts, sporting goods. 

Property Fluorinated ydrocarbon T etrafluoro-ethylene/ propylene copolymer Fluorosillcone Perfiuoro- elastomer Polyurethane Poly- chloroprene Chloro- sulfonated polyethylene Ethylene/ propylene copolymer... 

As previously noted, the primary use for this elastomer has been as solvent-based adhesives and sealants. Solvent-based products are losing market share to water-based poly-chloroprenes, to other polymer types such as acrylics and polyurethanes, and to hot melt adhesives. However, where the processing facility is able to contain the vapor emissions, a solvent-based adhesive or sealant is preferred because of better wetting of surfaces, faster drying, and higher performance of the cured or dried product. Many rubber bonding... 

Poly(vinyl chloride), chlorine (bromine)-butylrubber resins, poly(chloroprene) ... 

The effect of polymerization temperature upon the microstmcture of poly-chloroprenes produced by emulsion polymerization is illustrated by the results, reported by I ynard and Mochel [25], shown in Table 15.6. The chloroprene units are present mainly as trans- A structures, irrespective of the polymerization temperature. However, the distribution of the microstructures does depend somewhat upon polymerization temperature. The ratio cw-l,4/tra 5-l,4 units decreases as the polymerization temperature is reduced, but the overall content of 1,4 units increases. The balance comprises 1,2 and 3,4 units in approximately equal proportions, except for polymers produced at very low temperatures, where the 1,2 units predominate over the 3,4 units. A consequence of the overall content of 1,4 units increasing with decreasing polymerization temperature is that the sum of the contents of 1,2 and 3,4 units decreases. As will be seen in Section 15.4.4, although 1,2 units are present in relatively low concentration, their presence is very important for the technology of polychloroprene rubbers. 

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