Biodegradation studies of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

To investigate the biodegradability of novel thermoplastics poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx), films made of PHBHHx were subjected to degradation in activated sludge and compared with poly(3-hydroxybutyrate) (PHB) and Ecoflex, a biodegradable product of BASF. After 18 days degradation, 40% of P(HB-co-12%-HHx) and 20% of PHB were degraded, while Ecoflex only lost 5% of its weight. Scanning electron microscopy (SEM) revealed that the surface of Ecoflex was much smoother than that of P(HB-co-12%-HHx) and PHB. At the same time, PHBHHx degradation in a simplified system containing 0.1g/L lipase in phosphate buffer saline was found to be affected by its HHx content. It was found that P(HB-co-12%-HHx) was degraded faster compared with PHB, P(HB-co-5%-HHx) and P(HB-co-20%-HHx). SEM results revealed that P(HB-co-12%-HHx) films had the most porous surface after degradation. All these indicate that surface morphology played an important role in degradation of PHBHHx. P(HB-co-12%-HHx) combining the advantage of low crystallinity and rough surface was degraded the fastest.