Mechanical properties and chemical structures of biodegradable poly(butylene-succinate) for material reprocessing

Poly(butylene-succinate) (PBS) was examined as a promising biodegradable and reprocessable material used for material recycling. The mechanical properties of PBS after immersed in water were investigated and it was found that the bending strength of PBS decreased as the immersion time and the immersion temperature increased due to the chemical degradation of PBS caused by hydrolysis. The chemically-degraded PBS was then reprocessed and re-examined to investigate the mechanical properties. An unusual increase both in the bending strength and in the molecular weight of PBS was observed. The increase was highly due to the autocatalytic action of PBS molecules during the reprocessing by esterification: dicarboxylic acids were produced through the low molecular PBS during the chemical degradation, which ended up in dehydration re-synthesis of PBS with higher molecular weight. The characteristic of the recovering behavior in the molecular weight of PBS after reprocessing could not be observed in poly(lactic acid) (PLA), one of the most-used biodegradable plastics.