CHARACTERIZATION OF MICROSTRUCTURE AND FRACTURE-BEHAVIOR OF POLYPROPYLENE ELASTOMER BLENDS CONTAINING SMALL CRYSTAL IN ELASTOMERIC PHASE

Fracture behavior of polypropylene (PP)/ethylene-propylene-rubber (EPR ) blends containing small crystal in elastomeric phase was investigate d. Various ethylene-alpha-olefin copolymers (ECP) were used as crystal components and put into the elastomer phase of the blends. The crysta llite size was controlled by changing the composition of the ECP. From thermal analysis and electron microscopic analysis, it was found that the ECP having a smaller crystal had better affinity to EPR and thus the crystal was finely dispersed in the elastomeric phase. The ECP wit h large crystallite size had poorer affinity to EPR and tended to segr egate in the elastomeric phase. Scratch resistance and tensile elongat ion of blends were measured and it was found that the small crystal dr astically improved the above properties while the large crystal deteri orated them. The dispersed small crystal was thought to act as a cross linking point in the elastomeric phase. The reinforcement of the elast omeric phase by such quasi-crosslinking structure was the possible rea son for the improvement of the mechanical properties of the blends. (C ) 1995 John Wiley and Sons, Inc.