Impact testing of polypropylene blends and comosites

Polypropylene (PP) composites containing 0.30 vol% of talc filler, in addtion to blends modified with an ethylene‐propylene copolymer (EPR) elastomer were prepared and their fracture resistance was determined by the standard Ixod impact test and by a fracture mechanics technique. Effects of composition, type of modification, specimen size, and temperature were studied. The validity of linear elastic freacture mechanics (LEFM) conditions were checked: It was shown that under the conditions applied they can be satisfied even twith specimens of reasonable size (4 × 10 × 80 mm) prepared by conventional processing techniques. Calculations of minimum specimen thickness must be carried out, with material properties obtained under the conditions of impact. For heterogeneous blends and composites yield stress should be corrected for the effect of decreasing load‐bearing cross section. Linearity of the fracture energy (U) vs. BDϕ or U vs. B(D ‐ a) plots is not a proof for either elastic of plastic fracture. The composition dependence of fracture properties proved to be practicaly independent of specimen size, temperature, or measurement technique.