MALZE starch was graft copolymerized with methyl methacrylate (MMA) using potassium persulphate (K2S2O8) as free radical initiator, The effect of persulphate concentration, methyl methacrylate concentration, polymerzation temperature, and starch/water ratio on the graft yield and homopolymer were investigated. Based on the results of these studies, it was concluded that: (a) grafting and homopolymerization reaction occur immediately and even before adding the initiator grovided that the pylymerization temperature is 60O or above, (b) the grafting reaction exhibits an initial fast rate resulting in maximum grafting at a persulphate concentration of 70mmole/L, followed by lower grafting at 100 mmole/L persulphate, (c) during the latter stages of reaction, on the other handm higher persulphate concentration is accompanied by lower grafting reflecting the adverse effect of higher rate of termination and the involvement of persulphate in oxidation of starch when used at higher persulphate concentration, (d) the homopolymer formation increases as the persulphate increases within the studied range (10-100 mmole/L.) (e) the homopolymerization reaction is characterized by a very fast in the initial stages, slows down with time then leves off, (f) increasing the methyl methacrylate concentration enhances the graft yield, (f) raising the temperature from 40O to 70O exerts a significant enhancement in the rate of polymerization (grafting and homopolymerization), and (h) unlike grafting which proceeds without induction period, the homopolymerization reaction shows an induction period of about 40 min at 40O and 50O . In addition the effect of starch/water ratio on the polymerization reaction was studied in two ways; the first involves polymerization using constant weight to persulphate and starch in different amount of water whereas the second entails polymerization at constant amount of starch and different amounts of water and persulphate, i.e., constant concentration of the
By: A. Hebeish, S. Farag, S. Shaarawy and A. Bayazeed
Texitl Research Department, National Research C
Submit Date: 12/31/1999 20:00