Study on Characteristics of Paper laminated with Biodegradable Plastics (3): Elemental and Morphological Analyses of Polylactide Deterioration

Elemental and morphologocal analysis were applied to investigate the degradation behavior of commercial polylactide(PLA) film, poly (L-lactide)(PLLA) and poly (DL-lactide)(PDLLA) by X-ray photoelection spectroscopy (XPS) and atomic force microscopy (AFM), ewspectively. The PLA and PDLLA samples consisted og three types of carbon:C-C(C-H), C-O and O=C-O, which correspond to their theoretical composition. However, the XPS analysis revealed that the surfaces of the PLA filmhighly resistant to acid hydrolysis were overspread with unknown constitutions consisting of nitrogen and unoxidized carbon, not being announced offically. The AFM analysis offered a clear distinction in the surface deterioration of the PLA samples; and the alkaline treatment excavated numerous holes on the PLA surfaces. These results indicated that thecommercial plastics are chemically modified on their surfaces to improve the phisical propeties for practical use, resulting in being deprived of biodegradability and eco-compatibility. It was also suggested that the enlargement in the specific surface area, which may occur at the early stage on PLA degradation, possibly accelerated the PLA decomposition rate. A new conception in the material design for paper-based compositites was proposed; a local alkaline circumstance expected by alkaline fillers, e.g., CaO available in papermaking processes would effectively promote the PLA decomposition.