The results obtained from dynamic mechanical analysis (Fig s. 1 and 2) showed that both the content and particle size of rice husk fiber affected the gelation temperature of the composite system. However, the effect of particle size was more significant. The same gelation temperature was selected for composites with the same rice husk fiber size to simplify
the processing procedure. The temperatures corresponding to the maximum values of tan δ were 140°C for MF-PP/RH
composites with 20-60 mesh rice husk powder, 150°C for MF-PP/RH composites with 60-90 mesh rice husk powder, and 165°C for MF-PP/RH composites with 120-200 mesh rice husk powder. The curing times of composites with different particle sizes and blend ratios were measured by the isothermal DMA method. The isothermal curing temperature was set at the temperature where the gelation point was measured. The results fothe curing times are listed in Table 2.
igure 2 shows the loss factor of composites with different fiber particle sizes. Composites with smaller particles cured at higher temperatures and the maximum tan δvalues of the composites were lower. As the temperature was raised, the mobility of the thermoset resin molecules increased. However, the incorporation of rigid fiber particles
in the composite system adversely restricted the movement of resin molecules and increased the viscosity.