DYNAMIC-MECHANICAL PROPERTIES AND MORPHOLOGY OF POLYPROPYLENE MALEATED POLYPROPYLENE BLENDS/

The dynamic mechanical properties of both homopolypropylene (PPVC)/Mal eated Poly propylene (PP-g-MA) and ethylene-propylene block copolymer (PPSC)/Maleated Polypropylene (PP-g-MA) blends have been studied by us ing a dynamic mechanical thermal analyzer (PL-DMTA MKII) over a wide t emperature range, covering a frequency zone from 0.3 to 30 Hz. With in creasing content of PP-g-MA, alpha relaxation of both blends gradually shift to a lower temperature and the apparent activation energy Delta E(alpha) increases. In PPVC/PP-g-MA blends, beta relaxation shifts to a higher temperature as the content of PP-g-MA increases from 0 to 20 wt % and then change unobviously for further varying content of PP-g- MA from 20 to 35 wt %. On the contrary, in the PPSC/PP-g-MA blends bet a(1) relaxation, the apparent activation energy Delta E(beta 1) and be ta(2) relaxation are almost unchanged with blend composition, while De lta E(beta 2) increases with an increase of PP-g-MA content. In the co mposition range studied, storage modulus E' of both blends increases b efore alpha relaxation as content of PP-g-MA increases; however, the i ncrement of E' value for PPSC/PP-g-MA blends decreases progressively b etween beta(2) and alpha relaxation with increasing temperature, but i n the region the increment for PPVC/PP-g-MA blends is independent of t emperature. The flexural properties of PPVC/PP-g-MA blend show more ob vious improvement on PP than one of PPSC/PP-g-MA blends. Scanning elec tron micrographs of fracture surfaces of the blends clearly demonstrat e two-phase morphology, viz. the discrete particles homogeneously disp erse in the continuous phase, the main difference in the morphology be tween both blends is that the interaction between the particles and th e continuous phase is stronger for PPVC/PP-g-MA than for PPSC/PP-g-MA blend. By the correlation of the morphology with dynamic and mechanica l properties of the blends, the variation of the relaxation behavior a nd mechanical properties with the component structure, blend compositi on, vibration frequency, and as well as the features observed in these variation are reasonably interpreted. (C) 1996 John Wiley & Sons, Inc .