The incompatibility between the natural fiber and the polymeric matrix composite due to hydrophilic and hydrophobic characteristic of the respective materials results in lower mechanical properties of the composite. Epoxy resin (EP) compatibilizer was added into the polypropylene (PP)/ recycled acrylonitrile butadiene rubber (NBRr)/ kenaf composites and the effect to the tensile strength has been investigated. The composites were prepared by mix melt PP and NBRr with Kenaf filler by using heated two roll mill at temperature of 180 ºC with speed of 15 rpm for 9 min. The ratio of PP/NBRr was varied from 100:0 up to 40:60 phr while kenaf filler and EP remain constant at 15 phr and 4 phr respectively. The samples were molded to form 1 mm sheet by using a hot press at 180 ºC temperature before cut in-to dumbbell shape. The tensile testing was conducted according to ASTM D638 (2003) Standard Test Method by using Instron Universal Testing Machine 3366 with crosshead speed of 5 mm/min. The Fourier Transform infra-red (FTIR) analysis and swelling test were also performed. The results of tensile test show that the tensile strength and modulus of elasticity were decreased with the increasing of NBRr ratio but increased the elongation at break (Eb). The composite with EP showed a better performance in both tensile strength and modulus of elasticity with increment 4–28% and 29 to 50% respectively, along the varies ratio. But, the Eb had reduced about 0.9 to 1.65%. FTIR results showed the spectra of C ≡ N at peak 2237.87 cm-1 was lost due to the esterification of PP/EP compatibilizer with kenaf or PP/EP compatibilizer with NBRr. The swelling test indicated higher water uptake for non-compatibilized composites as compared to compatibilized with EP compatibilizer.
