Thermal and dielectric properties of blends of polymethylmethacrylate and atactic poly-3-hydroxybutyrate

Polymethylmethacrylate (PMMA) was blended with variable amounts (from 9 to 46 wt%) of atactic poly-3-hydroxybutyrate (a-PHB) and films were compression molded. The blends were characterized by TGA, DSC and dielectric spectroscopy (DETA). The TG curves of a-PHB/PMMA blends show two TGA weight losses attributed to thermal degradation of a-PHB (the lower temperature one) and PMMA (at about 400 degrees C). The DSC curves of the blends after melt quenching show a composition dependent glass transition which follows Wood's equation. Over the composition range, investigated a-PHB/PMMA blends are miscible. The DETA spectrum of the blends contains a sub-Tg relaxation associated with the secondary beta relaxation of PMMA, whose temperature and apparent activation energy increase with increasing a-PHB content.