Natural-fiber-reinforced polymers can exhibit very different mechanical performances and environmental aging resistance depending on their interphase properties. A lack of good interfacial adhesion and poor resistance to moisture absorption make oil palm fibers less attractive as reinforcing agents. To improve the interfacial properties, oil palm fibers were grafted with different percentages of allyl methacrylate (AMA) in methanol. Darocur 2959 was added as a photoinitiator and initiated photochemical polymerization. The fiber surfaces were pretreated by an alkali, KMnO4, and dewaxed; this was followed by grafting with AMA to determine the effect of various surface treatments on the physicomechanical properties of grafted fibers. The alkali treatment increased the surface roughness with better impregnation of the polymer, which increased the tensile properties by about 20%. A minute amount of an additive (urea) and a coupling agent (silane) were added to the optimum formulations. These increased the physical properties of the grafted oil palm fibers because of increased crosslinking. The treated and untreated fiber samples were also subjected to various weather conditions, such as simulated weather, soil, and water aging, to determine the degradation properties, and lower losses were observed for the treated samples than the untreated fibers. (C) 2007 Wiley Periodicals, Inc.