The use of natural fibers as filler or reinforcement in composite has increased recently due to low cost and the demand to environmentally friendly materials. However, lack of good interfacial adhesion between natural fiber filler and polymer matrix encourage many researches to explore ways to overcome this limitation. In this research, kenaf is used as natural fiber reinforcement with polymeric composites to produce new ideal of green composites. The surface modification using sodium hydroxide (NaOH) was carried out to modify the fiber properties. In this study, kenaf were treated by using NaOH of 6% concentration immersed for 24 h. The composites were prepared by using heated two roll mill at temperature 180 °C with speed of 15 rpm for 11 min. The ratio of kenaf filler loading in the composite was varied from 0 up to 25 phr while PP/NBRr matrix was remain constant at 70/30 respectively. Then the mixture compound was molded by using hot press at temperature 180 °C to form 1 mm sheet samples before cut into dumbbell shape. The mechanical properties and morphology of untreated and treated PP/NBRr/kenaf composites at various filler loading were obtained by using tensile testing and Scanning Electron Microscopic (SEM) respectively. The results showed that as the filler loading increased up to 25 phr, the tensile strength and elongation at break were decreased while the Young’s modulus was increased. The composites with NaOH treatment of kenaf showed a better performance in tensile strength, elongation at break and Young’s Modulus as compared to composite with untreated kenaf with increment by 32–88%, 0.5–2.8% and 8–32% respectively. It was proved by morphological properties that the composite with NaOH treatment kenaf have a good attachment with the PP/NBR matrices.
