A thermal degradation mechanism of polyvinyl alcohol/silica nanocomposites

The thermal degradation mechanism of a novel polyvinyl alcohol/silica (PVA/SiO2) nanocomposite prepared with self-assembly and solution-compounding techniques is presented. Due to the presence of SiO2 nanoparticles, the thermal degradation of the nanocomposite, compared to that of pure PVA, occurs at higher temperatures, requires more reaction activation energy (E), and possesses higher reaction order (n). The PVA/SiO2 nanocomposite, similar to the pure PVA, thermally degrades as a two-step-degradation in the temperature ranges of 300-450 °C and 450-550 °C, respectively. However, the introduction of SiO2 nanoparticles leads to a remarkable change in the degradation mechanism. The degradation products identified by Fourier transform infrared/thermogravimetric analysis (FTIR/TGA) and pyrolysis-gas chromatography/mass spectrometric analysis (Py-GC/MS) suggests that the first degradation step of the nanocomposite mainly involves the elimination reactions of H2O and residual acetate groups as well as quite a few chain-scission reactions. The second degradation step is dominated by chain-scission reactions and cyclization reactions, and continual elimination of residual acetate groups is also found in this step.