Thespesia populnea Reinforced Cashew Nut Husk Tannin-Based Polyurethane Composites

Polyurethane composites were prepared by reinforcing raw and silane treated Thespesia populnea fibers in random orientations at different fiber length and loadings with polyurethane. The matrix phase is bio- polyurethane (PU1 and PU2), prepared from tannin extracted from Cashewnut husk with Hexamethylene diisocyanate in the absence and presence of extender. Surface modification was carried out with vinyltriethyl silane as coupling agent. Tensile, compression and moisture absorption properties of the composites were evaluated and fiber properties analysed. Results showed that composites had better mechanical properties compared to the non reinforced matrix. Composites from PU1 had better mechanical properties compared to that of PU2. Tensile and compression strength decreased with increase in fiber content in the matrix. PU1 based composites had less moisture absorption than PU2 based composites and the amount of absorption increased with increase in fiber length. The paper suggests that Thespesia populnea fibers have immense scope as reinforcement in the composite industry.