Effect of blend composition on the structure.Properties relationships of nanostructured polymer composites from polycondensate/polyolefin blends

摘要

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 micro fibrils 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 tran-scrystalline 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 respectvely about 4-6 and about 10-15 times higher(depending of the chemical lcomposition and proportions of the components in the blends)than those of the compression molded neat PP.