The properties of recycled PVC bottle compounds. 2: Reprocessing stability

Following a study of the mechanical properties of recycled PVC recovered from post-consumer bottles, this study focuses on the effects of recycled material on processing. In particular, the effects of multiple recycling were studied to investigate any problems that may arise due to the repeated incorporation of recycled material into the processing stream. Batches of recycled flake and powder as well, as pure but processed bottle flake material were subjected to simulated multiple recycling using a Torque Rheometer. Ten minutes at 170 degrees C followed by granulation represented one recycle. Molecular weight and Infrared analyses were performed to assess the degree of degradation occurring during reprocessing. The results indicated a rapid degradation of the two recycled grades when compared with the purer bottle flake PVC. Further multiple recycling was then performed on bottle flake mixed with 0.2% polyethylene, which showed that the PE impurities accelerate the degradation process. Finally, the effects of restabilizing by adding new bottle flake material at each step were investigated. It was shown that surprisingly small levels of new material (30%) prevented degradation, even after 15 recycle steps.