Microstructure Studies of In Situ Composites Based on Polyethylene/Polyamide 12 Blends

This paper reports on the structure development at nanometer and micrometer scale during the preparation of microfibrilar composites (MFC) based on oriented blends of polyamide 12 (PA12) and high-density polyethylene (HOPE). The composites were prepared in situ by means of conventional processing techniques: extrusion blending, cold drawing and compression molding. The evolution of morphology in the unidirectionally aligned reinforcing fibrils (e.g., their visible diameters, lengths and aspect ratios) was followed during the various processing stages as a function of the blend composition by means of electron microscopy and synchrotron X-ray scattering techniques. It was demonstrated that the reinforcing fibrils comprise a PA12 core covered by a transcrystalline layer (TCL) of oriented polyethylene. A method was proposed for estimation of the thickness of that TCL. The influence of the compatibilizer content on the TCL thickness and structure as well as on the other morphological characteristics of the composites was assessed.