Dispersing agent graft copolymers

Surface active agents are important components of foam formulations. They decrease the surface tension of the system and facilitate the dispersion of water in the hydrophobic resin. In addition they can aid nucleation, stabilise the foam and control cell structure. A wide range of such agents, both ionic and non-ionic, has been used at various times but the success of the one-shot process has been due in no small measure to the development of the water-soluble polyether siloxanes. These are either block or graft copolymers of a polydimethylsiloxane with a polyalkylene oxide (the latter usually an ethylene oxide-propylene oxide copolymer). Since these materials are susceptible to hydrolysis they should be used within a few days of mixing with water. 

Compatibilization along with dynamic vulcanization techniques have been used in thermoplastic elastomer blends of poly(butylene terephthalate) and ethylene propylene diene rubber by Moffett and Dekkers [28]. In situ formation of graft copolymer can be obtained by the use of suitably functionalized rubbers. By the usage of conventional vulcanizing agents for EPDM, the dynamic vulcanization of the blend can be achieved. The optimum effect of compatibilization along with dynamic vulcanization can be obtained only when the compatibilization is done before the rubber phase is dispersed. 

The "comb" dispersing agent was a graft copolymer of polymethylmethacrylate-methacrylic acid (methoxypolyethylene oxide methacrylate) supplied by ICI Paints Division (Slough) and used as received. The exact molecular weight of the polymer is not known, but it is ejqpected to be in the region of 20-30,000 (as indicated by ICI Paints Division). The of the polyethylene chains was 750. 

Critical Compatibilizer Concentration Mathos [1993] showed that the critical concentration of interfacial agents is directly related to the interfacial area of the dispersed phase, thus related to interface saturation. The chemical stmcture played an important role in the emulsification ability of copolymers. Many block or graft copolymers were selected such that their segments were identical to those of the homopolymers. Alternatively, the blocks could be chemically... 

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