Browsing by Author "Attanayake, A.P."

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    Effect of Ethephon Stimulation on Physico-Mechanical Properties of Carbon Black Filled Natural Rubber Vuleanizates
    (Uva Wellassa University of Sri Lanka, 2018) Nanayakkara, E.N.N.; Attanayake, A.P.; Wijesinghe, H.G.I.M.; Senevirathna, A.M.W.K.
    Low intensity harvesting systems (LIH) with ethephon stimulation were introduced to rubber plantations due to the shortage of skilled latex harvesters. The objective of this research study was to identify the effect of ethephon stimulation on physicomechanical properties of the carbon black filled natural rubber vulcanizates. The study was conducted with the RRIC 121 clone using half spiral, once in three-day harvesting system. Experiments were laid out in Randomized Complete Block Design using three blocks with six ethephon treatments (0, 1, 2, 3, 4, 5 %). Each block was composed of 150 trees and each treatment was applied in 25 trees while the non- stimulated (0%) trees were considered as the control. Latex was separately collected from each treatment and processed into unfractioned, unbleached crepe rubber (UFUBCR) and carbon black filled natural rubber vulcanizates were produced according to the general compounding formulation. The vulcanization was carried out at 150 °C for 10 minutes. Initial Plasticity and Mooney Viscosity of UFUBCR reduced with the increase of ethephon concentration, while Plasticity Retention Index showed marked reduction at 4% and 5% ethephon concentrations. Rebound resilience, tensile strength and elongation at break have reduced with high ethephon concentrations. However, hardness, compression set and tear strength has increased with high concentrations of ethephon. Results revealed that elastic properties have reduced and filler reinforcement has increased with high ethephon concentrations. LIH systems with ethephon stimulation does not have any adverse effect on physico-mechanical properties up to 3% ethephon concentrations. However, such properties were negatively affected with the application of higher ethephon concentrations beyond 3%, therefore the application of ethephon up to 3% could be recommended.
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    Reduction of Enzymatic Discolouration of Natural Rubber Latex by Using Antioxidant and Moringa oleifera Leaf Extract
    (Uva Wellassa University of Sri Lanka, 2019-02) Arachchi, N.N.M.; Attanayake, A.P.; Senevirathna, A.M.W.K.; Wijesinghe, H.G.I.M.
    Natural rubber latex tends to discolour due to enzymatic activity. This should be avoided to maintain the quality of natural rubber latex. Natural rubber latex of RRISL 203 clone shows higher degree of enzymatic discolouration due to the presence of phenolic substances. The objective of this study was to find a solution to reduce the enzymatic discolouration of latex of the above clone using natural and commercial antioxidants. Leaf extract of Moringa oleifera has been evaluated for its antioxidant activity as it contains higher amount of powerful antioxidant quercertin. Three treatments: M. oleifera leaf extract, Vitamin C (a solution made by dissolving vitamin C tablets) and ‘antioxidant G’ (is a natural antioxidant) were used to perform antioxidant activity in latex obtained from RRISL 203 clone. Three replicates were done for latex samples obtained from three tapping blocks. Each solution of antioxidant was added separately prior to add formic acid to latex. Samples were prepared as unfractioned-unbleached crepe rubber with a control. Samples were analyzed for Mooney viscosity, Plasticity Retention Index, Volatile Matter Content and Ash Content. Further, colour index test was done for the colour comparison which determine the enzymatic discolouration. There was no significant difference (P>0.05) in raw rubber properties among the treatments whereas significant difference (P<0.05) among treatments for the colour index was observed. Lowest colour index values (1, 1.5 and 2.0) were resulted by the ‘antioxidant G’ in three blocks as compared to the other treatments. Crepe samples prepared by treating Vitamin C and leaf extract of M. oleifera were inferior in colour as compared to the ‘antioxidant G’ treated samples. It can be concluded that ‘antioxidant G’ can be used effectively to reduce the discolouration of natural rubber latex while maintaining its properties satisfactorily.