FUNCTIONALIZED POLYPROPYLENE PREPARED BY MELT FREE-RADICAL GRAFTING OF LOW VOLATILE OXAZOLINE AND ITS POTENTIAL IN COMPATIBILIZATION OF PP PBT BLENDS/

This article concerns the functionalization of polypropylene (PP) with oxazoline functionality by melt free radical grafting along with a lo w degree of degradation of PP in a batch mixer. A low volatile oxazoli ne, ricinoloxazoline maleinate (OXA), was used as the monomer. The gra fting yield of OXA ranged from about 0.5 phr up to 1.5 phr (grams per 100 grams of PP) when its initial concentration and that of the peroxi de ranged from 1.5 to 6.0 phr and 0.1 to 0.7 phr, respectively. The co rresponding conversion of OXA to grafted OXA ranged from about 15 to 5 0%. Addition of styrene (St) as the comonomer did not enhance the graf ting yield of OXA but markedly reduced the PP degradation. Also, littl e homo- and/or copolymers of OXA and/or St were found in the grafting system. This agrees with our finding that OXA and St did not copolymer ize easily. The potential of using an OXA modified PP (PP-g-OXA) as th e compatibilizer precursor in PP/PBT blends was examined as well. The presence of PP-g-OXA reduced the particle size of the dispersed phase (PBT) along with improved cohesion between the PP and PET phases. This is consistent with a model kinetic study, which showed that the react ion between oxazoline and carboxylic functionalities was very fast. (C ) 1996 John Wiley & Sons, Inc.