The use of roughness for evaluating the biodegradation of poly-β-(hydroxybutyrate) and poly-β-(hydroxybutyrate-co-β-valerate)

The biodegradation of poly-beta-(hydroxybutyrate) (PHB) and poly-beta-(hydroxybutyrate-co-beta-valerate) (PHB-V) was assessed by the loss of mass, tensile strength and roughness of the polymer. The melting temperature and crystallinity were also determined. Both polymers showed similar biodegradation in soil composting medium at 46 degreesC and at room temperature (24 degreesC) and in a soil simulator. PHB-V had the lowest crystallinity values and PHB had the highest. Soil composting medium at 46 degreesC favoured the biodegradation of PHB and PHB-V based on the loss of mass. After ageing in soil composting medium at 46 degreesC for 86 days, both polymers showed a decrease in the tensile strength at break (76% for PHB and 74% for PHB-V). In agreement with this, the roughness of both polymers increased faster in soil composting medium at 46 degreesC. These results suggest that roughness may be a useful parameter for evaluating the biodegradation of polymers. (C) 2003 Elsevier Ltd. All rights reserved.