Effect of modified silica on the crystallization and degradation of poly(3-hydroxybutyrate)

The crystallization and thermal degradation behaviors of poly(3-hydroxybutyrate) (PHB) filled with surface-modified silicas were analyzed by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and dynamic thermogravimetric analysis (TG). The results of FTIR and TG confirmed that the substantial amounts of methyl methacrylate (MMA) and amidoamine (AMDA) were successfully grafted onto the hydrophilic silica surfaces. From DSC and TG analyses, it was indicated that the crystallization rate, crystallinity, melting temperature (T (m)), content of the high T (m) crystals, and thermal stability of PHB were affected by the type and amount of the silicas used and changed with the grafted chemicals. The hydrophobic silica has a better effect on enhancing crystallization rate and thermal stability of PHB than the hydrophilic silica due to the better compatibility with PHB. However, the MMA and AMDA grafted onto the hydrophilic silica surfaces effectively improved the crystallization and degradation effects of the hydrophilic silica. The addition of two parts AMDA-modified silica in a hundred parts PHB has the best improvement in terms of of the crystallization, melting characteristics, and thermal stability of PHB.