1 RESEARCH IN RUBBER COMPOSITION FOR IMPROVING TIRE SIDEWALL PROPERTIES Huynh Tan Phat a , Tran Le Hai a , Nguyen Thi Hue Trang b , Nguyen Vinh Tri a a Faculty of Applied Science, Ton Duc Thang University of Technology, Ho Chi Minh city, Vietnam b Rubber Research Institute of Vietnam ABSTRACT Rubber composition was comprised of 40 parts by weight of carbon black, and 10 parts by weight of silica over 100 parts by weight of rubber blend (phr) which was a compound of 30 percent of butadiene rubber (BR) and 70 percent of natural rubber (NR) mixture, contributed to high flexibility of tire sidewall. This composition significantly improved crack resistance (0.148 mm/1000 periods), ply adhesion (159.4 N/cm), and decreased heat built-up (60 o C). In which, silica played an important role in rubber formula because it strongly influenced in sidewall rubber properties above. INTRODUCTION Up to 20 percent of weight in tire, sidewall component was an important part in whole tire. Based on tire structure and its practical use, sidewall properties should be relevant to Vietnam condition with following requirements (according to CASUMINA company): flexible, high crack resistance (crack growth < 0.5 mm/1000 periods), low heat built-up ( 65 o C), high ply adhesion (> 150 N/cm), good aging resistance and glossy surface. Recently, many patents of tire sidewall were announced to looking for an optimal rubber formula, focused on high cis-BR and large size carbon black to produce the flexibility for rubber compound and reduce heat built-up. In the other hand, its mechanical properties and adhesion was consolidated by combination of NR and silica. This paper was focused on not only investigating the impact of each factor on properties of rubber compound, but also calculating linear optimization the parallel effect of three factors (NR/BR ratio, carbon black, and silica). EXPERIMENTAL Materials Natural rubber SVR3L (Vietnam) and butadiene rubber KBR 01 (KUMHO, Korea) was used as rubber background, reinforced with carbon black N660 (KUMHO, Korea) and precipitated silica. Other commercial additives also added in the processing stage. Sample Preparation