Browsing by Author "Premachandra, J.K."

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    Enhancement of physical properties of natural rubber vulcanizates by incorporating rice husk ash with carbon black as a filler
    (Uva Wellassa University of Sri Lanka, 2015) Gnanasubramaniam, M.; Premachandra, J.K.
    There is a higher demand for carbon black and silica as reinforcing fillers in manufacturing of various rubber products which enhance the properties such as modulus, tensile strength, resilience and hardness of vulcanized rubber. Because of their increased prices, it has become a major concern for finding new fillers replacing carbon black and silica. One of the possible candidates in this regard is rice husk ash (RHA) which is an agricultural waste causing environmental pollution (Chuayjuljit, et al., 2001). RHA mainly consists of silica and carbon. Two types of RHA, white rice husk ash (WRHA) and black rice husk ash (BRHA) can be produced by controlled burning of rice husk (Sarkawi, et al., 2003, Ramasamy, et al., 2013). In this research the use of WRHA and BRHA as fillers in enhancing the properties of natural rubber vulcanizates replacing carbon black was investigated. Methodology Two cylindrical metal baskets, one is smaller than the other, were placed coaxially and space between the cylinders was filled with dried rice husk. Ignition was done inside the small basket which contained small holes. It formed a little smolders which slowly spread into the rice husk facilitating controlled burning (Allen, 2004). The burning was continued for a day and obtained WRHA. In order to produce BRHA the dried rice husk was burnt in an open place for an hour. Both WRHA and BRHA were sieved to obtain particles with a size range from 150 μm to 300 μm. Rubber compounding formula for tire side wall was used to prepare the natural rubber (RSS 1) compounds with different amounts of fillers. A series of rubber compounds having varying amounts of carbon black (N 330) and BRHA filler. Mixing of the ingredients was carried out in an internal mixture followed by mixing on a two-roll mill for 5 minutes at 80 °C. Two rubber compounds were prepared varying the amounts of carbon black (N 330) and WRHA filler employing the same mixing process. Investigating the processing characteristics of the resulting compounds using a Rheometer, optimum curing time for each sample at 150 °C was determined. The rubber samples were prepared by curing the compounds in a hydraulic press at 150 °C for relevant curing time periods. The tensile properties of resulting vulcanizates were determined following ASTM D412 standard using Instron machine model 2713. For tear testing the same machine was used following ASTM D- 638 standard. Hardness test was performed using Elastocon machine following IRHD standard. Result and Discussion The samples were designated according to the types of fillers and the amounts of fillers in grams incorporated. In the designation the letters C, B and W represent the presence of carbon black, WRHA and BRHA, respectively. Each number following the each letter in the sample designation represents the amount filler in grams present in each sample. Variation of the tensile strength upon the filler composition in samples is shown in Figure 01. Values of tensile strength of all the rice husk ash containing samples are considerably higher than that of the reference sample which contains only carbon black. The samples C81B54, C27B108 and C67.5B67.5 show tensile strength values greater than 20 MPa. Tensile strength of C67.5B67.5 is little less than the doubled value of the tensile strength of reference sample. The improvement of tensile strength of RHA containing rubber samples can be attributed to enhanced rubber-filler interaction and good filler dispersion in the rubber matrix. This is resulted by relatively high surface area of small RHA particles enabling better wetting of the particles by the rubber matrix (Onyeagoro, 2012).
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    Investigation on the use of coconut shell powder replacing carbon black as filler in natural rubber
    (Uva Wellassa University of Sri Lanka, 2015) Tharmaratnam, T.; Premachandra, J.K.
    Natural rubber is an elastomer which mainly consists of cis-1, 4-polyisoprene. It is used in a wide range of applications, mainly in tire manufacturing. Vulcanizates of natural rubber are reinforced by incorporating fillers such as carbon black and silica. There is a demand in replacing these fillers by fillers made of natural materials such as coconut shells, since natural filler possesses environment friendly processing, with no wear of tooling and no skin irritation (Bhaskar and singh, 2013). Coconut shell powder (CSP) is a natural lignocellulosic material which has been used as reinforcing natural filler in a broad range of applications such as building materials, marine cordage, fishing nets, furniture, and other household appliances (Sapuan and Harimi, 2003). The presence of highly polarized hydroxyl groups on the surfaces of the lignocellulosic fillers makes it difficult to achieve strong interfacial bonding with non-polar polymer matrix. As a result, lignocellulosic fillers show poor mechanical properties in polymer composites. However, the interfacial bonding can be improved by employing surface treatments methods including alkaline treatment, esterification and silane treatment (Egwaikhide et al., 2007). In the current research it was expected to improve the properties of natural rubber vulcanizates by incorporating CSP and surface modified CSP replacing carbon black filler. Methodology Coconut shells were crushed into powder and it was dried in an oven at 80 ºC for 24 hours (Tengkufaisal et al., 2010). The powder having the particle size range of 150 µm to 300 µm was separated by sieving and used for this research (Koayseong chun et al., 2013). Surface modification of coconut shell powder was achieved by acid treatment. The powder was soaked in an aqueous acetic acid solution with powder to solution ratio of 1g/20 l and the mixture was stirred for 1 hour. The treated powder was separated by filtering. It was washed with distilled water and dried in an oven at 80 ºC for 24 hours. Two sets of natural rubber (RSS 1) compounds were prepared according to the tire inner layer compound formulation by milling the ingredients. A series of compounds were prepared by varying the relative amounts of carbon black (N330) and untreated CSP. Another series of compounds were prepared by varying the relative amounts of carbon black and treated CSP. The reference compound was prepared by adding carbon black. Processing characteristics of prepared compounds were investigated by using a Rheometer. Vulcanized samples were prepared using a hydraulic press maintaining the temperature at 150 C for the relevant cure time determined from rheographs. Tensile properties of the samples were determined following ASTM D412 using Intron machine model 2713. Abrasion test was performed on the samples following DIN 53516 using Hampden machine model APH-40 and the hardness test was performed following IRHD using Elastocon machine. Result and Discussion The effect of filler composition on tensile strength of the samples of natural rubber vulcanizates is shown in Figure 01. In the sample designation, the letters C, U and T stand for the type of filler, carbon black, untreated CSP and treated CSP, respectively. In addition, the amount of each type of filler in phr is given by the number following each letter of designation. The sample with only carbon black filler shows the highest tensile strength. As the relative amount of untreated and treated CSP filler is increased the tensile strength decreases. This is due to the weak interfacial adhesion, low wettability, and poor dispersion between hydrophilic CSP and hydrophobic rubber matrix with compared to carbon black. The samples having treated CSP show a higher tensile strength than those having untreated CSP except the sample C90U60. This behaviour attributed to the improved interfacial adhesion and better dispersion between treated CSP and Rubber.
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    Preparation and Characterization of Geopolymer Composites Containing Fly Ash, Bottom Ash and Rice Husk Ash
    (Uva Wellassa University of Sri Lanka, 2016) Kajanthan, K.; Premachandra, J.K.; Cooray, J.T.
    Geopolymers being the synthetic analogues of natural zeolitic materials possess excellent properties, including fire and acid resistance, and mechanical properties. As a result, geopolymers have become an alternative construction material in place of Portland cement. They find structural applications such as sculpture, building repairing and building restoration. In producing geopolymers, the raw materials containing mainly silica and alumina are converted through chemical reactions into aluminosilicate structures in alkali medium. These aluminosilicate structures are composed of a network of randomly arranged silicate and aluminate tetrahedra in conjunction with charge-balancing alkali metal cations. The compressive strength of this resulting inorganic polymer depends on both the ratio of Si/Al and the types of the raw materials utilized. This research focused on the use of fly ash (FA), bottom ash (BA) and Rice husk ash (RHA) as a value addition in the preparation of geopolymer composites and the characterization of composites prepared. The effects of relative amounts of raw materials and the curing time of geopolymers on their compressive strength and water absorptivity were investigated. In sample preparation, a series of samples was prepared by hand mixing of selected amounts of cement, fine FA, BA, fine RHA, prewashed and dried sand, water and NaOH. The other series of samples was prepared by hand mixing of selected amounts of the same raw materials with Ca(OH)2. Further, the cylindrical samples for characterization were prepared by molding using a hydraulic press and demolded samples were kept at 80 °C for 4 hrs. Compressive strength of both series of samples was measured after curing them for 7 days and 14 days. The results showed that the compressive strength of the samples increases with increasing the curing time. At high relative amounts of cement and low amounts of the mixture containing FA and RHA, the compressive strength increases with decreasing the amount of cement and increasing the amounts of the mixture containing FA and RHA with compared to that of the samples in the absence of FA and RHA, regardless of the curing time. The incorporation of Ca(OH)2, has resulted in increase of compressive strength of samples with high relative amounts of cement and low amounts of the mixture containing FA and RHA. Keywords: Geopolymers, Fly ash, Bottom ash, Cement, Compressive strength
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    Study the Effect on Physical Properties of Rice Husk Ash and Carbon Black Filled Natural Rubber Vulcanizates
    (Uva Wellassa University of Sri Lanka, 2016) Gnanasubramaniam, M.; Premachandra, J.K.
    Rice husk ash is mainly composed of silica and carbon black remaining from incomplete combustion. Both silica and carbon black have long been recognized as the main reinforcing fillers used in the rubber industry to enhance certain properties of rubber vulcanizates, such as Hardness, Resilience and tensile strength. In this study, two grades of rice husk ash (low- and high-carbon contents) were used as filler in natural rubber. Comparison was made of the reinforcing effect between rice husk ashes and carbon black. The effect of these fillers on cure characteristics and mechanical properties of natural rubber materials at various loadings, ranging from 0 to 45 pphr, was investigated. The incorporation of RHA into natural rubber improved curing properties, tensile strength and hardness of rubber compound. But decreased tear strength, abrasion resistance, and Young's modulus of the compound. However, RI-IA gave a better resilience property, and Elongation than that of carbon black. Altogether the rice husk ash filled rubber product gave cost reduction and comparable mechanical properties like carbon black fillers. Keywords: Resilience, Abrasion, Young's Modulus
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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