Properties and recyclability of used high density polyethylene crates for soft drink bottle transportation

The aim of this research is to study the possibility in recycling plastic wastes of high density polyethylene (HDPE) crates used for soft-drink bottle transportation. The raw materials are HDPE crates produced under the same condition, which has been used for bottle transportation for 8, 3 and 0 years, respectively. The properties of plastic crates including the mechanical and physical properties, the processability and the degradation of polymer were studied systematically. It was found that the melt flow index, %elongation at break, flexural strength at yield and impact resistance were decreased with increasing utilization time. This could be a result from the photo-oxidative degradation occurred, leading to changes in the structure of polymer molecules. The poor properties of post-used HDPE crates can be improved by blending with two types of modifying agents, stabilizer "Recyclossorb 550" (R550) and ethylene vinyl acetate copolymer (EVA). The addition of EVA (5% and 15% by weight) in post-used HDPE crates has stronger property improvement than that of R550 (0.2% and 0.4% by weight) in post-used HDPE crates. The blends of post-used HDPE crates with EVA showed a remarkable increase in %elongation at break and impact resistance. Furthermore, the blends of post-used HDPE crates with modifying agents had been recycled to produce caps for beer keg by injection process. These products were inspected and shown to satisfy the customer requirement standard.