Graft polymers based on PVC

This chapter has so far dealt with the major fields of use of vinyl chloride polymers, namely plasticised PVC homopolymer, unplasticised PVC, including impact-modified grades, and copolymers particular based on vinyl acetate. There are, however, five particular special forms of vinyl chloride polymer which merit separate consideration, namely crystalline PVC, after-chlorinated PVC (often known as CPVC) and certain graft copolymers and two vinyl-chloride-based copolymers. 

In a quite different but very important industrial area, free-radical polymerizations have made great inroads In the optimization of the desired commercial properties of impact-modified poly(vinyl chloride) (PVC). In a most sophisticated variation, grafted impact modifiers based on the quaterpolymerization of acrylic esters, butadiene, styrene, and acrylonitrile have been produced and almost precisely match the refractive index of PVC. The blending of the Impact modifier with PVC yields a completely clear polymer suitable for shampoo bottles and food containers. In addition to excellent clarity these polymers have extremely good impact strength combined with improved fabricability by flow molding equipment. 

Core-shell impact modifiers have also been reported as impact modifiers for engineering polymers. MBS impact modifiers with a SBR core, a polystyrene middle layer and an outer layer of MMA copolymers with glycidyl methacrylate, acrylamide or methacrylic acid functional monomers were evaluated in PC/PBT blends [104]. Optimal results were obtained with 60 wt% SBR content in the MBS and a modest amoimt of a functional monomer in the MMA copolymer shell. Core-shell impact modification of polycarbonate [105] (PMMA grafted on poly(n-butyl acrylate) and PBT[106] (SAN grafted onto a butadiene based rubber) have been reported. A comprehensive review of core-sheU impact modification of various polymers (PMMA, PVC, PC, PBT, PET, polyamides, thermoplastic blends, thermosets) has been presented by Cruz-Ramos [107]. 

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