Effect of processing additives on (bio)degradability of film-blown poly(?-caprolactone)

Abstract

Poly(ε-caprolactone)s (PCL) with slip masterbatch, Erucamide, SiO2 and Erucamide + CaCO3 as low-molecular-weight processing additives, were film-blown in a single screw extruder. The films and recycled PCL without additives were exposed to composting, anaerobic sewage sludge (37 and 55°C), pure fungal culture, and chemical hydrolysis at two pH (7 and 10.5) and at two temperatures (room temperature and 50°C). Recycling and addition of processing additives resulted in a slightly slower degradation rate compared with the degradation of pure PCL. The degradations in biotic environment were generally faster than in abiotic environment. Higher degradation rates are observed in more complex environments (composts and anerobic sewage sludge) due to synergism between high temperature and a richer fauna of microorganisms. In the biotic environments, faster reductions in number-average molecular weight (Mn) than in weight-average molecular weight (Mw) were observed. A decrease of Mn with up to 75–80% was estimated for composted pure PCL, while similar samples in anaerobic sludge at 55°C were completely degraded in 50 days. The mechanical properties of the samples subjected to composting exhibited a more rapid enbrittlement compared to the samples subjected to abiotic hydrolysis. The observed increase in crystallinity with increasing degree of degradation is explained by crystallization made possible by chain cleavage in the amorphous phase. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 61–74, 1998