Mechanical properties of highly aligned short pineapple leaf fiber reinforced - Nitrile rubber composite: Effect of fiber content and Bonding Agent

Highly aligned short fiber reinforced rubber composite was developed from locally sourced and renewable material and nitrile rubber (NBR). Short and fine pineapple leaf fiber (PALF) was used as the reinforcement. Highly aligned PALF-NBR composites containing 10, 20 and 30 parts (by weight) per hundred of rubber (phr) of PALF were prepared and tested for their mechanical properties both in the direction parallel and perpendicular to the fiber axis. In addition, systems containing a fixed amount of an adhesion promoter, so called bonding agent, composed of hexamethoxy methyl melamine, resorcinol and hydrated silica were also studied and compared. It was found that the stress-strain curves of the composites were greatly modified. In the longitudinal direction, the stress rose sharply with strain and the slope of the curve increased with increasing PALF content. In the transverse direction, the effect was much less. The stress ratio anisotropy, defined as the ratio of stress measured in the longitudinal direction to that measured in the transverse direction, reached a peak value of 8.9 at 6.3% strain for 30 phr PALF. Bonding agent improved all properties mentioned above. Observation of the fractured surface with SEM suggested that there was improved interfacial adhesion between the rubber matrix and PALF.