Orientation of HDPE inclusions within solid-state drawn rubber-modified isotactic polypropylene: DSC insight

Abstract

Effect of drawing temperature on the melting behavior of oriented isotactic polypropylene (PP) modified with ethylene-propylene-diene monomer rubber with a small amount of high-density polyethylene (HDPE) is explored in this study. Injection-molded specimens both neat and 8 vol % modified PP were solid-state drawn to natural drawing ratio and characterized by X-ray diffraction, dynamic mechanical analysis (DMA), Charpy impact test and differential scanning calorimetry (DSC). A synergy of orientation and embedding rubber particles caused a significant increase of low-temperature notched impact strength of oriented blends. It was shown, that the DSC method can be used successfully for the indirect but very sensitive characterization of orientation on a nanometre scale. At the drawing temperature of 120°C, the DSC data indicated an incomplete transition of the PP crystalline structure: This is reflected by splitting and shifting of the melting peak of PP. An increase of the melting temperature of the HDPE inclusions by 3.5°C reflects the high orientation. © 2013 Wiley Periodicals, Inc.