A New Approach to Recycling PET Bottles by Blending Polyethylene- Terephthalate and HDPE Using Chemical Reactions in One Step Process

Abstract

The overall goal of this study is to propose a new approach to simplify the recycling process for producing high quality material from the waste of beverage bottles and other sources at a lower cost by using mechanical recycling and chemical reactions inside injection molding machines in a one-step process. The water and soft drink bottles are made of PET material, while the caps are made mainly of HDPE. The blends of PET and HDPE are incompatible. The resulted material has poor mechanical properties due to the immiscibility of polymer blend components, phase separation, and lack of interfacial adhesion. (HDPE-g-MA) was found to be an excellent reactive compatibilizer for the PET/HDPE blend. For the purpose of investigating the mechanical and morphological properties in this study, blends of rPET and virgin HDPE in weight compositions of 80/20, and 60/40 were modified with concentrations of 2 and 5 wt percent of (HDPE-g-MA). The addition of 4,4-Methylenebis (phenyl isocyanate) and compatibilizer increased the viscosity and molecular weight of the blends while also improving miscibility and interaction bonds between molecules, resulting in a significant reduction in interfacial tension and improved phase dispersion and adhesion via interpenetration and entanglements at the interface. The rPET segments have been grafted onto HDPE backbone chains. Since the crystallinity of HDPE is low, the crystallinity and crystallization temperature of rPET in the blends were reduced. The mechanical characteristics were improved by achieving uniform phase morphology. The main finding of this study is that the immiscible rPET/HDPE materials can be treated and processed in a single step inside the injection molding process. The one-step process is sufficient because it shows high improvement in the mechanical characteristics, while the two-step process, namely the extrusion followed by injection molding, improves fewer mechanical characteristics and is more expensive.