Browsing by Author "Jayalath, U."

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    Reinforcement of Natural Rubber vulcanisates Using Mixed Fillers of Carbon Black and Mica
    (Uva Wellassa University of Sri Lanka, 2016) Navaneethan, L.; Jayalath, U.; Jayasuriya, C. K.
    The current research was carried out to investigate the possible use of mixed fillers of carbon black and mica to reinforce natural rubber vulcanisates. It is expected that the use of reduced amounts of carbon black would minimize environmental effects and allow the production of more cost effective filler system. In addition, the use of mica as a filler material would make a value addition to mica which is one of the mostly available minerals in Sri Lanka. Mica was ground into powder and was kept at 80 °C for 24 hours. The powder having the particle size in the range of (63 -125) pm was separated. Seven compounds were prepared according to the tire inner layer compound formulation by varying the relative amounts of carbon black and mica. Processing characteristics of compounds were investigated by using a Rheometer. Vulcanized samples were prepared using a hydraulic press maintaining at 160 °C for 20 minutes. Tensile and tear tests were carried out using a Tensometer. Hardness was carried out by using a Durometer. Tensile and tear strengths of the samples prepared with mixed fillers have been decreased compared to the reference sample. The modulus has been increased with increasing the amount of mica. Hardness has been improved only when small amounts of silica were replaced by mica particles. Diminishing properties could be due to undesired particle size of mica incorporated and non-uniform dispersion which interferes the process of crosslinking. Possible phase separation of mica and carbon black when higher amounts of mica are used could also be another reason. Further studies on the structure determination of the two types of particles incorporated are required to confirm the causes for observed variations. Such studies will also allow determining the best conditions for achieving reinforcing effects. Keywords: Natural-rubber, Carbon-black, Mica, Reinforcement
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    The Use of Buffing Dust in Enhancing the Mechanical Properties of Vulcanized Natural Rubber in Tyre Industry
    (Uva Wellassa University of Sri Lanka, 2016) Niroshan, A.; Jayalath, U.; Premachandra, J.K.
    Before the used tyres are completely worn out, at a certain stage, some can be made to be reused by rebuilding. At the starting point of rebuilding process, the surface of the used tyres are scratched off by tyre polishing which generates a waste called buffing dust. Buffing dust contains different sizes of vulcanized rubber particles and it can be used as a filler material in various rubber products reducing the cost of raw materials. In the current research, it was expected to do value addition for buffing dust using as a filler and cost reduction in pneumatic tyre manufacturing. Buffing dust with the particle size ranges from 150 i_tm to 180 p.m was used for the study. The pneumatic tyre compound formulation is used in rubber compounding. A series of compounds containing 5, 10, 15, 20, 25 and 30 parts per hundred rubber (phr) by weight of buffing dust was prepared. A nibber compound in the absence of buffing dust was also prepared to be used as the reference for the comparison of results. Required samples for the investigation of mechanical properties were prepared by vulcanizing the rubber compounds at 160 °C for 20 minutes. Mechanical properties such as tensile strength, tear strength, hardness and abrasive resistance of the resulting vulcanizates were investigated. The use of the buffing dust as a filler with 10 phr or lower in vulcanized natural rubber compounds enhanced the mechanical properties such as modulus at 100% elongation and hardness of the rubber compound. The samples having 15 phr or more of buffing dust showed significantly low hardness. Tear strength of the samples gradually decreased with increasing the amount of buffing dust incorporated. However, there was no drastic reduction in the tear strength of buffing dust filled samples compared with the tear strength of the reference sample. The incorporation of buffing dust into vulcanized natural rubber compounds has significantly lowered their tensile strength. Keywords: Fillers, Natural rubber, Mechanical properties, Buffing dust