Polystyrene was widely used in many fields because it bosses a lot of good properties [1, 2, 3]. But this polymer likes other synthetic polymers from mineral-oil. After finishing their functional life they have to spend many years to degrade and residues have resulted in a broad range of pollution, litter and waste disposal problems for the society [4, 5, 6]. To resolve this problem, many researches have been investigated for along time. A good choice, composite from plasticized starch (TBS) and PS is concerned as an exchangeable material [7, 8]. In this study, the properties of starch/PS-g-Benzoic acid have been investigated. The TBS as a filler for thermoplastics has been tested using three various ratios of PS/TPS-g Benzoic acid 90/10
80/20 and 70/30. To improve the compatibility of the starch with the polymer matrix, treatment of starch have also been performed by grafting Benzoic acid on the structure of starch to make it enhance hydrophobic ability. From there, starch could be dispersed into polymer matrix to make homogeneous morphology. The mechanical properties of the materials are enhanced at ratio PS/TPS-g- 5 percent Benzoic acid was 80/20.