Polychloroprene

Abstract

The active center of the chain transfer agent reacts with the growing chain to stop further chain propagation. A new free radical, A, is formed from the Vol. 0 POLYCHLOROPRENE POLYCHLOROPRENE Vol. 0Chloroprene-Sulfur Copolymerization. The high reactivities of chloroprene and dichlorobutadiene permit copolymerization with sulfur to yield toluene-insoluble and partially gelled copolymers of high molecular weight. Gelled polymers are highly crosslinked polymers that are insoluble in toluene.In solution or aqueous emulsion polymerization, a growing polychloroprene radical reacts with rhombic (nonpolymeric) sulfur (24) or suitable sulfur donors such as 1,2,3,4-tetrasulfocyclohexane (25) or polysulfides (26) to yield a copolymer. Reaction with elemental sulfur involves cleavage of the eight-membered sulfurGraft Polymerization. Graft polymerization is related to block copolymerization. A block copolymer contains long sequences of two monomers (ie, AAA monomer blocks followed by BBB monomer blocks) along the copolymer chain. Graft copolymers consist of long chains of one monomer with occasional branches consisting of long chains of a second (grafted) comonomer. The branched points are normally formed by allylic atom (typically hydrogen) abstraction by free-radical initiators (eg, peroxides) to yield a resonance-stabilized free radical. The free radical initiates the addition polymerization of a second monomer beginning at the locus of the free radical. Generally grafting is performed to significantly modify polymer properties. In the production of emulsion-polymerized acrylonitrilebutadiene-styrene tripolymer, styrene and acrylonitrile are grafted onto rubbery polybutadiene to improve compatibility between the thermoplastic and rubber matrix used in impact modification (12). Methyl acrylate, acrylonitrile, alkyl methacrylates (eg, methyl, octyl, lauryl), fumaronitrile, methacrylic acid, and dichlorobutadiene have been employed in solution and emulsion graft polymerization with polychloroprene. Generally, solvent resistance, heat resistance, and Vol. 0 POLYCHLOROPRENE 7 POLYCHLOROPRENE Vol. 0 POLYCHLOROPRENE Vol. 0 POLYCHLOROPRENE Vol. 0 9.5. Latex Applications. A good way to remember the applications for latex is to follow the first six letters of the alphabet. A ¼ adhesives, B ¼ binders, C ¼ coatings, D ¼ dipped Goods, E ¼ elasticizers, and F ¼ foam. Vol. 0 POLYCHLOROPRENE 25