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 composite
s
with different
fiber
particle size
s
.
Composites with s
maller particles cured at higher temperature
s
and the maximum tan
δ
values of the composites were lower. As the temperature
was
raise
d
, the mobility of the
thermoset resin molecules increased.
However,
the incorporation of rigid fib
er
particles
in the composite system adversely restricted the movement of resin molecules
and
increased the viscosity.