Degradation in Sweet Water and Marine Environment

From these data an erosion rate of about 0.4-1.7 pm/week can be estimated for PHB and 11 pm/week for PHBV. 

Beside the work on natural PHA - polyesters, degradation experiments in sea water with synthetic polymers snch as poly(e-caprocalcone) (PCL) and modified polyethylene are reported in the literature, too. 

Rutkowska and co-workers reported a complete defragmentation of PCL samples in sea water (Baltic sea) at temperatures between 9 C and 21 °C [7] within 8 weeks. Temperature was stated to be a major influence factor for the degradation. For PCL, chemical hydrolysis and enzymic surface erosion are responsible in parallel for the polymer degradation. The same research group found for poly(ester urethanes) a significant weight loss in sea water (Baltic sea) within 12 months, while a poly(ether urethane) was not biologically attacked under the same experimental conditions [8]. 

However, no significant changes in material properties nor any reliable weight loss of different modified polyethylenes and polypropylenes could be observed by Gonsalves and co-workers [9, 10] at sea water exposure (1-9 m depth, temperatures 13-30 °C) for 5 to 12 weeks. The primary (chemical) degradation depends on the exposure temperature and at the quite low temperatures in sea water, the reaction rate is probably too slow to observe any changes in the materials within the period of time investigated. 

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