سنتز كوپليمر وينيل استات - اتيلن به روش پليمرشدن امولسيوني ناپيوسته : 2- بررسي اثر بافر و غلظت امولسيون كننده

Synthesis of Vinyl Acetate-ethylene Copolymer Through Batch Emulsion Polymerization, II: Effect of Buffer and Emulsifier Concentration

Emulsion copolymerization of vinyl acetate-ethylene is carried out in a pressure reactor. Control of parameters such as pressure, temperature, monomer concerntration, etc., is essential because they affect final properties of the copolymers. In emulsion polymerization of vinyl acetate-ethylene the aim is to obtain a polymer having substantial ethylene content (15-20 wt%) with high vinyl acetate conversion. Increasing emulsifier concentration based on a mix emulsifier with protective colloid increases the viscosity of emulsion medium which in turn reduces the diffusion of monomers. Consequently, vinyl acetate conversion and ethylene content were both decreased. Addition of buffer to the emulsion system maintained pH at a constant value which facilitated a constant rate of initiator decompositon dur-ing polymerization. As a result, monomer conversion and ethylene content of the copolymers were decreased. Glass transition temperature of the copolymers have been also investigated.