A study of crystallization behavior of PHB homopolymer and copolymer blends as a function of aging conditions

PHA homopolymer and copolymer are known to undergo secondary crystallization on storage which may lead to brittleness. One of the reasons for brittleness is physical aging of the amorphous regions in the polymer. This is attributed to an increase in crystalline content in the polymer. The effect of temperature on crystallinity with increasing aging period was studied. The aging period was divided into long term (0-n days) and short term (0-24 hours) aging. The crystallinity was studied using differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) and their effect on mechanical properties was studies using tensile testing. It was found that P[3HB] homopolymer had intrinsicly high crystallinity through DSC measurements and later confirmed by XRD studies. The effect of aging at different conditions and their influence on the crystallinity was quantified. Even though specimens contains different concentrations of the PHB copolymer, the crystalline form of the P[3HB] (homopolymer) lattice was observed for all specimens which was demonstrated by XRD.