Dynamic mechanical behavior of natural rubber and its composites reinforced with short coir fibers has been studied. Maxima in tan d, E00
and the middle point of E0 vs. temperature curves of the gum natural rubber compound at different frequencies almost coincide with one
another. But the maxima in tan d and E00 do not coincide in the case of composites. It is observed that as frequency increases the values of tan
d and E00 decrease whereas the values of E0 increase in the case of both gum and the composites. The values of E00 and tan d increase with fiber
incorporation, which indicates lower heat dissipation in the gum. Two prominent peaks are observed in the tan d vs. temperature curve of
these composites due to the dynamic mechanical behavior of matrix and fiber. The additional small peak represents the dynamic mechanical
behavior at the interface. The effect of chemical treatment of coir fiber on damping of composites was studied and it was found that composite
with poor interfacial bonding tend to dissipate more energy than that with good interfacial bonding.