Poly emulsion produced polymer

Finally, addition polymerization of suitably substituted furans allows incorporation of the furan nucleus into heterocyclic polymers (77MH1102). 2-Vinylfuran apparently exhibits free radical polymerizability comparable with that of styrene, although rates, yields and degrees of polymerization are low under all conditions except for emulsion polymerization. Cationic polymerization is quite facile and leads not only to the poly(vinylfuran) structure (59), as found in free radically produced polymers, but also to structures such as (60) and (61) in which the furan nucleus has become involved. Furfuryl acrylate and methacrylate undergo free radical polymerization in the manner characteristic of other acrylic esters. 

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. 

Emulsion Polymerization. Poly(vinyl acetate)-based emulsion polymers are produced by the polymerization of an emulsified monomer through free-radicals generated by an initiator system. Descriptions of the technology may be found in several references (35—39). 

Growth in PVAc consumption is illustrated in Eigure 3. The emulsions continue to dominate the adhesives and paint markets. It also shows the distribution of PVAc and copolymer usage by market. The companies Hsted in Table 10 are among the principal suppHers of poly(vinyl acetate)s and vinyl acetate copolymers, but there are numerous other suppHers. Many other companies produce these polymers and consume them internally in the formulation of products. 

Polymers of vinyl acetate are produced commercially in large volumes. Emulsions of poly(vinyl acetate) are used as paint bases, coatings, and adhesives. Overall, the polymerization processes involving vinyl acetate are quite straightforward. 

Other latexes which have been produced by this method include poly(butyl methacrylate), poly(butyl acrylate) and poly(styrene/DVB) [161]. Additionally, polymer blends were produced by mixing, under high shear, HIPEs of partially polymerised monomer, followed by completion of polymerisation. The conversion prior to blending had to be less than 5%, to allow efficient mixing of the highly viscous emulsions. The materials thus produced resembled agglomerates of latex particles, due to copolymerisation at the points of contact of partially polymerised droplets. 

Core-shell polymers were commercially introduced as impact modifiers for poly(vinyl chloride) PVC, in the 1960s. They are produced by a two-stage latex emulsion polymerization technique (Cruz-Ramos, 2000). The core is a graftable elastomeric material, usually crosslinked, that is insoluble in the thermoset precursors. Typical elastomers used for these purposes are crosslinked poly(butadiene), random copolymers of styrene and butadiene,... 

The latexes upon which this industry developed were natural rubber and polychloroprene for solvent resistance. However, technology is advancing to permit penetration of carboxylated nitrile latex for optimized solvent resistance and tougher abrasion resistance. Among the competition to latexes in this field are poly(vinyl chloride) plastisols. As technology develops in producing small particle size latexes from polymers whose synthesis is loo water-sensitive for emulsion polymerization, the dipped goods industry will quickly convert to their utilization from the solvent-based cements of these polymers now employed Prime candidates include butyl rubber, EPDM, hypalon, and vlton. 

The polymer is commonly obtained from vinyl chloride with a peroxide initiator such as peroxydicarbonates, fert-butylperpivalate, benzoyl or lauroyl peroxide, acetyl cyclohexylsulfonyl peroxide, or azobis(2,4-dimethylvaleronitrile). The polymerization can be done by suspension, emulsion or solution techniques. Low polymerization temperatures are used when high MW material is required. Suspension polymerization employs water suspension agents, such as poly(vinyl alcohol) or methylcellulose. The resulting polymer Is a partially syndiotactic material but with low crystallinity. The macromolecules typically have head to tail linkages (H-T) and a small proportion (less than 1.5%) of branching. Ziegler-Natta catalysts are not used to produce PVC. 

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