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 low degree of degradation of PP in a batch mixer. A low volatile oxazoline, ricinoloxazoline maleinate (OXA), was used as the monomer. The grafting 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 peroxide ranged from 1.5 to 6.0 phr and 0.1 to 0.7 phr, respectively. The corresponding conversion of OXA to grafted OXA ranged from about 15 to 50%. Addition of styrene (St) as the comonomer did not enhance the grafting yield of OXA but markedly reduced the PP degradation. Also, little 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 copolymerize easily. The potential of using an OXA modified PP (PP-g-OXA) as the 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 PBT phases. This is consistent with a model kinetic study, which showed that the reaction between oxazoline and carboxylic functionalities was very fast. © 1996 John Wiley & Sons, Inc.