The effect of deformation temperature on microstructure and properties of die-drawn iPP/HDPE blends

Abstract

It is urgent to recycle non-degradable waste plastics. Conventional mechanical recycling requires sorting different types of polymer materials which is quite expensive or even not practical. Hence it is crucial to develop a processing method for incompatible polymer blends. In this work, we successfully processed isotactic polypropylene (iPP) and high-density polyethylene (HDPE) blends via a die-drawing process at different temperatures. It turned out that changing the deformation temperature could influence the microstructure and properties of the die-drawn samples. For samples deformed at temperatures below the melting point of HDPE, the molecular chain orientation and long period increased markedly after die-drawing, while this increase was less significant for samples deformed at temperatures above the melting point of HDPE. Subsequently, the former samples exhibited better thermal stability and mechanical properties than both the latter samples and the undeformed samples. The Young's modulus is more than two times and the fracture stress is more than five times the values determined for the undeformed sample. As for the samples deformed at temperatures above the melting point of HDPE, their fracture stress doubled comparing to the one of undeformed sample, despite voids with dimensions of several hundreds of nanometers which were observed in these samples.