Crystallization behavior of high-density polyethylene in an oriented blend with polypropylene

Crystallization behavior of high-density polyethylene blended with polypropylene was investigated in the oriented system, using wide-angle and small-angle x-ray diffractometries and electron microscopy. When polypropylene/polyethylene (PP/PE) drawn blends were heat treated in the temperature range above the melting point of PE, a new orientation texture of PE was produced during melt-recrystallization in the PP matrix. The majority of PE crystallites are aligned with their (110) planes perpendicular to the draw direction of the film specimen. Furthermore, well-developed lamellar structure is formed in the PE phase, along the crystallite b axes oriented preferentially at angles of 30-40° to the draw direction. The reason that such a distinctive orientation texture of PE develops in the blend with PP is discussed in some detail. As a possible explanation, it is suggested that thermal shrinking stress greatly affects the crystallization behavior of PE.