L A Wisojodharmo, R Fidyaningsih, D A Fitriani, D K Arti, Indriasari, H Susanto
Center for Material Technology, Agency for the Assessment and Application of Technology,
Building 224, Puspiptek Area, Serpong, Tangerang Selatan, Indonesia
E-mail: lieswisojo@hotmail.com

The objective of this study is to optimize the performance of the tread compound, by
mixing of specified ingredients, such as Natural Rubber (NR) and Butadiene Rubber (BR) at various compositions, and also the type of carbon black as filler. The composition of NR and BR are used as follows 100:0 ; 95:5 and 85:15. Other materials used as rubber additives are peptizer, ZnO, stearic acid, additives, processing oil, and curatives. Two types of carbon black namely N220 and N234 are used in this research. The un-vulcanized rubber from each formula was characterized of curing characteristics and Mooney viscosity. The vulcanized rubber was then characterized its mechanical and thermal properties. It is clear from the research that, the addition of BR into the NR compound increases the abrasion resistance, rebound resilience and hardness, yet the glass transition temperature of the rubber compounds decreases. On the other hand, it seems that the rubber compound reinforced N220 or N234 gives comparable results on both mechanical and thermal properties.

1. Introduction
Regarding its vast improvement in the last decades, tire industry has always won the first place considering the volume of the studies done on the properties of rubber. Many researchers, from all over the world, are trying to present new products with higher capabilities and efficiency.
From among these studies, the most has been dedicated to the tread of the tire for this is the part of the tire which has the greatest impact on the way and the type of use. The performance of tire tread was measured by combination of ìmagic triangle propertiesî. They are rolling resistance, traction and wear. The balance of those properties increases the quality of tire tread [1]. Shiva and Atashi (2010) [2] have studied the optimization of failure properties of the Passenger Tire Tread Compound made of a compound of SBR with NR and BR, by altering curing condition and modeling rubber’s behavior. Phamet al. studied the blends of two types of SBR with NR and the inherent properties of rubbers on the properties of the final compound [3]. The results showed an increase in Mooney viscosity and scorch time as the SBR increased in the compound. Kaushik et al, (2010) [4] studied the compound of NR/BR/HSR with the presence of different amounts of carbon black and found that the samples gained a very good abrasion resistance and in addition, as the size of carbon black particles decreased and became close to nano particle size, the strength of the samples increased.

2. Experimental
All mixing ingredients were used as received. Natural rubber (NR) as Ribbed Smoked Sheet (RSS1) type with the density of 0.95 was provided by local supplier in Indonesia. Butadiene rubber (BR) with the Mooney viscosity 40 and the density of 0.92 was obtained from Goodyear Chemical. Carbon black N 220 and N234 were purchased from Cabot. 2.1 Preparation and Testing of Rubber Compound A laboratory-sized kneader Moriyama DS3-10MWB-E was employed to prepare rubber compounds.
The mixing was divided into two stages. In the first stage, the mixing condition was set at the temperature of 100∞C and the velocity of 60 rpm. The mixing was started by mixing NR or NR-BR at various compositions along with plasticizers for about 5 min, and followed by adding zinc oxide, stearic acid, carbon black, other additives and a half of oil for about 6 min. The remaining oil was then added into the kneader for about 2 min. The compound was passed on the two roll mill at 70∞C for 6 times. After the master batch was stored for a night to allow the rubber compound to rest, the batch then was mixed with curatives in the kneader. The temperature was set at 70 ∞C and the velocity of 60 rpm for about 2 min. At the end of the mixing, the batch again was passed on the two-roll mill, cooled and stored for another 24 h before it can be used for further analysis

3. Results and Discussion
The processing characteristics and physical mechanical properties of rubber compounds have been presented in graph or table below.
3.1 Unvulcanized Rubber Curing Characteristic and Mooney Viscocity It can be seen from Figure 1 and Table 2 that the addition of BR into the NR compound does not have a significant effect on altering curing time, scorch time or delta torque. There is no significant difference of curing characteristics between rubber compound containing N220 and N234.
the addition of BR into the rubber compound slightly lowering the Mooney viscosity
(MV). It is because the MV of BR is lower than NR due to low molecular weight of BR compared toNR [6]. There is no significant difference of Mooney Viscosity between rubber compound reinforced N220 and rubber compound reinforced N234 since both types of carbon black has similar particle size and gave the same effect to the viscosity of compounding.

4. Conclusion
A blend of natural rubber (NR)/cis-butadiene rubber (BR) in the presence of carbon black filler showed excellent mechanical properties of a tread formulation. The mechanical properties such as abrasion resistance and rebound resilience have been improved with the presence of cis-butadiene rubber. Here the presence of carbon black N220 could give slightly better mechanical properties compared to carbon black N234 due to the better dispersion of N220 into the rubber compound. Due to good properties of these blending, it is possible to apply this formulation in tread tyre. Detail testing in order to fulfill the requirement of tread compound should be performed in advanced.

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[3] Pham T H et al 2001 Polym Testing 20 539ñ544.
[4] Kaushik P et al 2010 Mater and Design 31 1156-1164.
[5] Wang M J et al 1991 Rub. Chem. Technol. 64 559-576.
[6] Wolf S and Wang M.J 1992 Rub. Chem. Technol. 65 329-342.
[7] Bice J A E et al Rub World. 217 58-67.
[8] Choi1S et al 2004 Polym.. Adv. Technol. 15 122ñ127.
[9] Gatti L 2001 Tire Technol. Int. 1 39-45.
[10] Rattanasom N et al 2007 Polym. Test. 26 369-377.
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[12] Choi S-S 2002 Polym. Test. 21 201- 208.
[13] Rattanasom N and Chaikumpollert O 2003 J. Appl. Polym. Sci. 90 1793-1796.

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