Morphologies, crystallinity and dynamic mechanical characterizations of polypropylene/polystyrene blends compatibilized with PP-g-PS copolymer: Effect of the side chain length

PP-g-PS copolymers were synthesized with the same polypropylene (PP) backbones and various side chain lengths of PS sequences via reactive comonomer p-allyltoluene (p-AT) by Ziegler–Natta copolymerization and the subsequent living anionic graft-polymerization. ¹H NMR characterized that the PP-g-PS copolymer had grafted 3.15 side chains per 1000 carbons in the PP backbones and the length of PS sequences varied in the range of 25.8–309.9 units. PP/PS blends with the PP-g-PS copolymer as compatibilizer (wt. 75/25/5) were prepared and characterized by SEM, WAXD and DMA to investigate the morphologies, crystallinity and glass transition temperatures of the PP/PS blends. All the results pointed out that the average side chain length (GL) of the graft copolymer (GL is from 25.8 to 309.9) made great effects of the PP/PS blends, such as the PS dispersed phase, the crystallinity of the PP component and the two glass transition temperatures of the blends, which showed the same trend with the increase of the GL. Overall, only with a suitable average side chain length, the PP-g-PS copolymer could achieve optimal compatibilizing efficiency of the PP/PS blends.