“…For example, polyethylene has a chemical structure of -(CH 2 -CH 2 ) n -, its molecular weight will determine the degradability and degradation rate whether degradable or non-degradable. Furthermore, the purity of the materials in product forms is an unavoidable issue and critically important information, but many investigators used commercially available products rather than pure resin to cast or mold their specimens for research investigation without acknowledging the fact that products contain a range of chemicals, including plasticizer, filler and colorant etc in addition to the backbone polymers (Gu, 2003;Gu et al, 1993;1996a, b). In this context, processing of polymers into products requires the addition of plasticizer, filler and molding chemicals so that the expected products can be made successfully.…”