5. Conclusion

and the torque exerted on the rotor drops. The lowest torque value is called moment lowest (ML), which can be used to study the stiffness of the uncured rubber compound at a given temperature, noted as "Min" in Table 5. After the curing process begins, the torque rises. When the torque increases 2 dNm unit above ML value, the time is recorded as Ts2. It tells about the moment the curing process actually starts. With the curing progressing, the torque

98 Advanced Surface Engineering Research

Figure 4. SEM plots of compounded rubber sheets at 25 K magnification, illustrating rubber-filler bonding system [11].

(a) SEM plot of Run 20 filled rubber sheet. (b) SEM plot of N660 filled rubber sheet.

Coconut shell, as a high-volume problematic waste material, has the potential to be successfully converted into a high-quality carbon black-like char filler, and high heat value, renewable energy materials (mainly oil and some gases) at relatively small scale. Thus, global fossil fuelderived emissions can be reduced by the help of the ability of biochar to sequester the carbon contained in the coconut shell by conversion into a stable and nonavailable form. This type of process has been regarded as popular sector with growth potential in the global carbon market with a controllable, clean, and simple manufacturing process.

High external surface area values (315.89 m2 /g), along with high levels of purity (99.95%) and suitable surface pH (9.70), can be achieved by the coconut shell char filler. The char filler produced was comparable on a physicochemical basis with the commercial semireinforcing carbon black N772. Since most of the performance testing of the rubber products was highly comparable, the semireinforcing carbon black can be partially replaced by the coconut char filler. If the level of filler-polymer interaction can be enhanced, while the current level of filler-filler interactions maintained, the char filler would have very interesting properties with regard to low energy losses, such as tire rolling resistance. Further surface modification for the char filler has been identified as a part of post-production process for further optimization, such as filler-rubber interaction. At the same time, since coconut shell char is a new type of rubber filler, the vulcanization and mixing process needs to be to be investigated for further improvement for short cure time and good tensile strength.

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