Abstract: A macromolecular coupling agent, which was prepared from toluene diisocyanate (TDI) and cardanol (CNSL), was grafted on jute fibers, the obtained fiber was used as reinforcement in composites of unsaturated polyester resin (UPR). The tensile strength, elongation at break, and impact strength of pure UPR, 5 % CNSL toughening UPR, 25 % of alkalitreated jute fiber UPR composites, and 25 % grafted jute fiber UPR, 25 % grafted jute fiber and 5 % CNSL UPR composites were compared. It was found that the addition of CNSL improved the toughness of the composite, jute fibers improved the tensile strength. 25 % CNSL grafted jute UPR could improve both the tensile strength and toughness. 25 % CNSL grafted jute fiber and 5 % CNSL toughened UPR composite provided a toughness of 12.10 kJ/m^2.

Key words: jute fiber, unsaturated polyester, cardanol, interfacial performance, toughing mechanism