In this study, the effects of NCO/OH ratio Oil Polyurethane composites prepared from propylene oxide-modified oil palm empty fruit bunch (EFB-PO) properties were studied. From the results obtained, the diffusion of solvents in the composites produced was classified as Fickian type. The molecular weight between crosslink points and degree of crosslinking were affected as the NCO/OH was increased. This phenomenon was attributed to the interaction between excess NCO and accessible OH groups from EFB-PO to form a three-dimensional network. From the mechanical testing results, it was found that the NCO/OH ratio had a significant effect on tensile and flexural test. However, no significant influence was observed on impact strength of the composites produced. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 3647-3654, 2008