MONITORING DEGRADATION OF POLY(HYDROXYBUTYRATE) BY FRACTURE-TOUGHNESSMEASUREMENTS

The fracture behavior of poly(hydroxybutyrate) is described in terms o f ''classical'' fracture mechanics. The fracture toughness (measured b y G(c), the strain energy release rate, and K-c, the stress intensity factor) was monitored during physical aging and during chemical degrad ation with methylamine. A change in the measured K-c value was found a fter degradation by methylamine which does not seem to be due solely t o the measured thickness changes. The work lays the foundation for stu dies monitoring changes in fracture behavior during environmental degr adation.