Effect of zinc borate and wood flour on thermal degradation and fire retardancy of Polyvinyl chloride (PVC) composites

The thermal decomposition, fire retardancy and mechanical properties of wood-flour-polyvinyl chloride composites (WF-PVC) were investigated. Thermogravimetric analysis (TGA) tests showed that the addition of wood flour (WF) and zinc borate (ZB) significantly influenced the thermal degradation behavior of PVC and WF-PVC composite. WF reduced the initiation temperature (T-initial) for thermal degradation of PVC, while ZB scarcely affected the initial temperature of WF-PVC. WF retarded the thermal decomposition of PVC in the early stage while ZB increased the rapidest decomposition temperature and reduced the decomposition rate of WF-PVC. The mechanism of thermal decomposition of the composite was analyzed by Fourier transform infrared (FTIR) spectroscopy using the attenuated total reflectance (ATR) method. The decrease of C-H bonds and increase of C=C bonds indicated WF and ZB promote the crosslinking and charring reactions of PVC. According to the cone calorimetry (CONE) tests, WF had a positive effect on fire performance of PVC but had little effect on smoke suppression. In contrast, the incorporation of ZB had little effect on flame retardancy of WF-PVC but it was an effective smoke suppressant, decreasing the total smoke produced (TSP) by more than 50%. Mechanical results indicated that ZB had some negative effects on the strength properties of WF-PVC, however the modulus increased compared with the untreated composite. (C) 2013 Elsevier B.V. All rights reserved.