Lecture 7-12 - Lecture 7 February 7 2012 2012 Homogeneous...

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L t 7 F b 7 2012 Lecture 7 : February 7, 2012
Homogeneous vs. Heterogeneous Polymerizations (Radical Polymerizations) Advantages: Bulk Continuous Batch Solution Suspension Emulsion Impurities Temperature Temperature Temperature Temperature control control ↑ ↑ control ↑ ↑ control ↑ ↑ L i it L i it Low viscosity Low viscosity Isolation Latex product Si t l Hi h MW ith Size control High MW with high R p Good for tacky polymers Disadvantages: Temperature Isolation Isolation Agitation required to Sensitive to control maintain suspension impurities difficult High viscosity Agitation Chain transfer Washing, drying May need to required to solvent remove emulsifier Conversion may Recycling Solvent Remove suspending Cost not be complete removal agents (stabilizers)
Ad t f b lk l i ti f i l Bulk Polymerization Advantages of bulk polymerization of vinyl monomers: High rates of polymerization High degree of polymerization High purity of product High molar mass polymer are produced Disadvantages of bulk polymerization: Increase in the reaction viscosity with conversion Î difficulty in removing heat. autoacceleration if the polymer formed is insoluble in the monomer (such as acrylonitrile, vinyl chloride) Î precipitating of the polymer