EFFECT OF BLEND COMPOSITION ON THE STRUCTURE-PROPERTIES RELATIONSHIPS OF NANOSTRUCTURED POLYMER COMPOSITES FROM POLYCONDENSATE/POLYOLEFIN BLENDS

Abstract

Nanostructured polymer composites (NPC) are obtained by melt-blending of poly(ethylene terephtalate) (PET) and polypropylene (PP) as well as polyamide 66 (PA66) and PP in wt. ratio 70/30, 50/50 and 30/70, followed by cold drawing of the extruded bristle and compression molding of the drawn bristles in form of film. The blends are studied by X-ray diffraction, scanning electron microscopy (SEM), and static mechanical testing. SEM and X-ray reveal different blend morphologies created during the stages of NPC manufacturing: isotropic blend after extrusion, fibrillization of both components after drawing, izotropization of the PP matrix with preservation of the PET- or PA66 fibrils after hot pressing. Also observed was a strong epitaxial effect of the nanostructured microfibrils of PET or PA66 on the non-isothermal crystallization of PP during cooling after compression molding at 215°C. Thus, the cold drawn and thermally treated PET/PP and PA66/PP blends represent anisotropic transcrystalline structures. The PP crystallites in the transcrystalline layers are reoriented at aprox. 40° with respect to the drawn direction (fiber axis). This is valid for the whole amount of PP in the case of PET/PP blend and only partially for the blend PA66/PP. These morphological peculiarities affect the mechanical properties of the NPC: the Youngs modulus and the tensile strength of the compression molded films are respectively about 4–6 and about 10–15 times higher (depending of the chemical composition and proportions of the components in the blends) than those of the compression molded neat PP.