Thermogravimetry (TG) is a special measure of thermal degradation, where weight losses are calculated with the increases of temperature and time. Sometimes, TG is used to examine the kinetics of the physicochemical change involved in thermal reaction. Figures 10.4 and 10.5 and Table 10.5 show the TG & DTG for comparison among untreated OBF, 9 wt% OBF-PFR, 19 wt% OBF-PFR, 29 wt% OBF-PFR, 38 wt% OBF-PFR composites and 100 % PFR. It is seen that initial decomposition temperature (7]) and final decomposition temperature (Tf) are found highest for PFR and lowest in case of OBF. Here, TG curve of composite samples shows two steps degradation: first is related to fibre degradation and the second is related to PFR degradation. Among the composite samples, 38 wt% OBF-PFR composite has the

lowest onset and decomposition temperature. It shows that 38 wt% OBF-PFR composites degrade in higher percentage than other composites, maybe due to moisture loss and more volatile content in fibre. The residual char or ash content at 600 °C temperature is higher in the case of OBF, and it decreases with the increases of PFR content in composites and the lowest value is found for pure PFR sample.

The first derivative of the sample weight with respect to time at constant tem­perature is termed as DTG. The DTG curves in Fig. 10.5 show rate of weight loss with temperature. The PFR gives single degradation peaks. On the other hand, fibre and composite samples show multiple degradation peaks due to weight loss in different stages of moisture and various constituents of fibre.