Instrumented falling weight impact of coinjection-molded multipolypropylene sandwich plaques containing beta-phase polypropylene core

The instrumented falling weight perforation impact behavior of coinjection-molded multipolypropylene sandwich plaques of various compositions having a beta-phase isotactic polypropylene (PP) homopolymer core was studied at room temperature and T = -40degreesC, respectively. The results were compared with those achieved on injection-molded monomaterial plaques of alpha- and beta-polymorphs. It was found that the coinjection strategy is beneficial only if the skin-forming alpha-phase PP has a markedly lower molecular weight than the beta-nucleated core PP. Sandwich plaques with PP copolymer skins exhibited an outstanding per-foration impact resistance. The coinjection strategy for extrusion grade PPs yielded no improvement. Perforation impact at T = -40degreesC showed a prominent toughness reduction of the multi polypropylene plaques which became comparable with that of the monolayer plaques.