CRYSTAL MODULUS OF POLYHYDROXYBUTYRATE) Jintana Siripitayananon and Teerapol Wongchanapiboon, Biomedical Polymers Research Unit^*, Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai, 50200, Thailand; Timothy M. Nicholson, A. Paul Unwin, Ian M. Ward, IRC in Polymer Science and Technology, University of Leeds, Leeds, UK LS29JT

The crystal modulus of poly(hydroxybutyrate) (PHB) has been measured using changes in the X-ray diffraction pattern of oriented samples under stress. Results obtained below the b -transition temperature give a value of 9 GPa. Two molecular modelling packages, BIOSYM and CERIUS, have been used to predict the full matrix of stiffness coefficients for PHB and hence, via the aggregate model, the properties of a uniaxial fibre. The modulus along the chain direction compares well with the experimental value. Both packages predict a high transverse modulus and this is shown to be consistent with the measured modulus of the isotropic polymer on the basis of the aggregate model.

^*The Biomedical Polymers Research Unit is a network research unit of the National Metal and Materials Technology Center (MTEC).