Browsing by Author "Senevirathna, A.M.W.K."
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Item Cellulose Whiskers Extracted from Banana Pseudo-Stem as Reinforcing Filler for Natural Rubber Tyre Treads Using Latex Intercalation Method(Uva Wellassa University of Sri Lanka, 2018) Bandara, T.A.R.W.M.M.C.G.; Etampawala, T.N.B.; Kularathne, S.; Wijesinghe, H.G.I.M.; Senevirathna, A.M.W.K.Reinforcing the rubber compounds using cellulose fibre is an emerging trend in rubber industry because of unique physical properties of cellulose fibre. In this study, cellulose fibres were extracted from pseudo-stern of banana using alkali treatments and converted into cellulose whiskers (CW) with high pressure defibrillation followed by acid treatment and bleaching. The CW was characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffractometry (XRD) and Particle Size Analyzing. Both FTIR and XRD confirm the cellulose structure. XRD studies showed that the percentage crystallinity of bleached fibres is about 69%. The particle size shows a bimodal distribution where approximately 21% of the sample has average size of 110 nm and the rest has the size of 795 nm. The purified CW was intercalated in diluted natural rubber (NR) centrifuged latex in order to prepare CW/NR composites and converted into rubber sheets. Mooney viscosity and stress relaxation coefficient of CW/NR composites were measured. The lowest Mooney viscosity and the highest stress relaxation coefficient were observed in CW/NR composites ensuring higher processability. The compounds were prepared in an internal mixture according to a tyre tread formulation, keeping the sample without CW as the control. Cure characteristics were evaluated at 120 °C and physical properties were evaluated on par with the ASTM standards. The highest cure rate and better scorch time were observed in CW/NR composite. The density, hardness, resilience, cut & chip and tensile strength of the composite were superior while tear strength and abrasion volume loss were inferior to the control. In overall, we observed that cellulose whiskers have a great potential to use as a reinforcing material for natural rubber tyre tread compounds.Item A Comparative Study on Degradability of NBR and NR Latex Gloves(Uva Wellassa University of Sri Lanka, 2021) Manukularathne, W.G.P.D; Sandamali, P.K.N.N; Siriwardena, S.; Lochana, E.A.L.; Senevirathna, A.M.W.K.Natural rubber (NR) and Nitrile rubber (NBR) gloves are two main types of latex gloves used in the personal protective equipment market. In the face of an abrupt increase in the demand and usage of these gloves due to the present Covid-19 pandemic, degradation of these gloves after usage may create an environmental threat. Therefore, a study was conducted to compare the degradable behavior of these products. Both glove types were treated under thermal and hydrothermal, and UV radiation environments. Untreated samples were used as the control. Under thermal, hydrothermal and photo- oxidative treatments, an increase of the swelling index of untreated NR gloves (65.2%) increased by 38.23%, 14.69% and 7.17%, respectively while NBR gloves showed a percentage swelling index increment of 14.52%, 15.56% and 12.12% with compered to the percentage of the swelling index of the untreated sample (28.77%) in the same order of treatments. The average tensile strength of NR was decreased from 16.89 to 15.67, 11.19, and 15.63 MPa while for NBR it decreased from 28.06 to 24.35, 23.93 and 20.56 MPa after the thermal, hydrothermal and UV exposure, respectively. Hydrothermally treated NR gloves showed new peaks suspected as hydroxyl groups and carbon- carbon triple bonds. Spectra of thermally and hydrothermally treated NBR showed identical loss of the peak responsible for the cyanide group. TGA analysis showed that the initial decomposition temperature of NR has reduced from 365.42 ̊C to 364.95 ̊C, 360.63 ̊C and 365.27 ̊C, respectively after the thermal, hydrothermal and UV treatments. NBR gloves also showed the same trend except for hydrothermal treatment where an increase in initial decomposition temperature was recorded. Overall, hydrothermal treatment was the best degradation method for NR gloves among candidates while exposure to UV radiation exhibited the highest degradation potential for NBR gloves. It was also found that removal of cyanide group when NBR gloves were subjected to hydrothermal degradation. Keywords: Fourier transform infrared spectroscopy; Natural rubber; Nitrile Butadiene rubber; Thermo gravimetric analysis; UltravioletItem A Dual Filler System for Low Speed Tire Base Compound(Uva Wellassa University of Sri Lanka, 2019) Gunasekara, T.D.I.K.; Ranatunga, R.R.M.S.K.; Wijesinghe, H.G.I.M.; Senevirathna, A.M.W.K.The effects of the dual filler system of Carbon Black (CB) and Chopped Tire Cord (CTC) were investigated on the mechanical properties and cure characteristics of low speed tire base compound made out of Natural Rubber (NR) and Reclaim Rubber. Chopped tire cord is a cost effective filling material which is derived from the rejected pneumatic tires. To determine the composition of materials, Thermo Gravimetric Analysis (TGA) was carried out for two CTC grades as weight percentages and the grade having high amount of CB (25%) was selected and used during the study. Compounds were prepared keeping CB to CTC ratios at 65:35, 55:45, 45:55 and 35:65 in parts per hundred parts of rubber (pphr) filler loading levels. Then curing and physico-mechanical properties were investigated according to ISO standards. Mooney viscosity of the compounds was within the accepted levels of 60-85 Mooney Units. Scorch time (Ts2) and optimum cure time (T90) have increased due to the reduction of CB content when increasing the CTC content in the compounds. However, it has improved the processing safety of the newly developed base compound. Hardness was within the accepted levels of 87-92 (Shore A) and the tensile strength was greater than 6 MPa. Tear strength and rebound resilience have improved along with the increase of CTC content. In conclusion, it is highly possible to use CTC in Base compounds of low speed tires as a cost effective filler at 65 pphr level with improved properties because the cost of CTC is well below the cost of CB.Item 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.Item Effect of Fiber Size on Properties of Oil Palm Fiber Waste Filled Natural Rubber Composites(Uva Wellassa University of Sri Lanka, 2021) Madushika, T.G.K.H.; Weerasinghe, U.A.; Edirisinghe, D.G.; Lochana, E.A.L.; Senevirathna, A.M.W.K.The twenty-first century has witnessed remarkable achievements in the rubber industry regarding green technology through the development of natural fiber based rubber composites. A wide variety of natural fibers extracted from coconut, palmyra and banana has been used as fillers in the development of natural rubber (NR) based green composites, most importantly to reduce environmental pollution caused by hazardous powdered fillers and to enhance reinforcement. Oil palm fiber (OPF) is hard, tough and has the potential to reinforce the rubber matrix. Mesocarp part of OPF, which generates as a waste material of palm oil processing mills was used as a filler in this study. The objective was to investigate the effect of size of OPF on cure, physico-mechanical, water absorption and ageing properties of NR composites. A chemical treatment was conducted to reduce fiber size and to improve physico-mechanical properties. Chemical processing with sodium hydroxide, bleaching with sodium chlorate and oxalic acid were conducted to remove residual oil and reduce fiber size. A series of NR composites were prepared with 2 phr OPF by varying its size from 250 μm to below 50 μm. The NR composite prepared without OPF, but with 2 phr of carbon black was considered as the control. Although an increase in properties was expected with the reduction of fiber size, no significant increase was observed. Nevertheless, results showed the highest values for the NR composite prepared with OPF in the size range 125-175 μm in regard to modulus at 300% elongation, tensile strength, hardness, resilience and an average value for water absorption. This revealed even dispersion of OPF in the rubber matrix of the above composite and the results were in agreement with crosslink density indicated by the delta cure value. There was no decrease in tensile modulus and strength after ageing, which indicates high retention of these properties. Overall, results revealed that carbon black in NR composites could be replaced with OPF to manufacture rubber products requiring hardness ranging from 29-36 Shore A. Keywords: Oil palm fiber; Natural fillers; Natural rubber; Cure characteristics; Physico-mechanical propertiesItem Effect of Mixing Method on Properties of Natural Rubber/Acrylonitrile Butadiene Rubber Blend Composites Reinforced with Silica Extracted from Rice Husk Ash(Uva Wellassa University of Sri Lanka, 2020) Gamlath, G.R.V.S.; Wijesinghe, H.G.I.M.; Senevirathna, A.M.W.K.; Edirisinghe, D.G.Acrylonitrile butadiene rubber (NBR) is used where rubber products require swelling resistance. Natural rubber (NR) can be blended with NBR for synergism of properties using either phase mixing or pre-blending methods. According to literature, the mixing method may have a significant effect on properties of blends and it has not investigated for NR/NBR blends filled with silica extracted from rice husk ash (RHAS). RHAS is used as the filler, an alternative to carbon black which induces high heat built-up in products. The sol-gel method was used to extract RHAS, X-ray diffractogram and Fourier Transform Infrared Spectroscopy proved the amorphous nature and the chemical compatibility of RHAS with commercial silica. Blends filled with 25 parts per hundred parts RHAS were prepared to keep NR to NBR ratio at 0:100, 20:80, 40:60, 60:40, 80:20, and 100:0 using phase mixing and pre-blending methods referring to the control, American Standard Testing Method reference formulation for oil seals. Curing, physical and swelling properties of blends were evaluated. Results revealed that there was no significant difference between mixing methods on properties. Blends with high NBR amounts showed higher crosslinking density while all blends showed acceptable scorch and cure times. Tensile and tear strength showed comparatively lesser values in all blends than the control while elongation properties were compatible with control. The compression set varied from 1-6%, control had 4.3%. Hardness ranged from 45-60 IRHD, control had 73 IRHD. Equilibrium swelling (%) of control in toluene is 82%, but all blends showed values from 80-150%. Equilibrium swelling (%) of control in hydraulic and engine oil was below 2% while high NBR content showed lower swelling. Equilibrium Swelling (%) ranged from 1-16% in hydraulic oil and 1-12% in engine oil. Overall, these blends can be used in the preparation of non-marking stationary sealing articles and there is a potential to use RHAS in NR/NBR blends for reinforcement. Keywords: Natural rubber, Acrylonitrile butadiene rubber, Pre-blending, Phase mixing, Rice husk ash silicaItem Effect of Residual Diammonium Hydrogen Phosphate Content on Properties of Natural Rubber Centrifuged Latex(Uva Wellassa University of Sri Lanka, 2021) Siriwardhana, M.W.H.N.M.; Attanayake, A.; Lochana, E.A.L.; Senevirathna, A.M.W.K.Natural rubber particle, a polyisoprene core is surrounded by a shell of non-rubber components, proteins and phospholipids. Natural PO43- are added to ammonia preserved latex due to the hydrolysis of phospholipid layer around the rubber particle. Although this process contributes to the stability of the latex this could produce a waste sludge; a precipitate of magnesium with phosphate. In centrifuged latex (CL) manufacturing process PO43- are added as diammonium hydrogen phosphate (DAHP) before centrifugation in order to remove residual Mg2+ present in field latex to the level of 80-100 ppm. In most cases, added DAHP will leave excess PO43- in latex as most manufacturers added it without estimating the remaining Mg2+ present in latex. It results in a high amount of PO43- in latex as a considerable amount of PO43- are released from the natural process of hydrolysis with storage time. This study aimed to determine the variation of residual PO43- content of CL with storage time and its ultimate effect on latex property development. A series of centrifuged latex samples were prepared by adding 0 g (control sample), 3 g, 6 g, 9 g, 12 g, and 15 g of 15% DAHP. Changes of the latex characteristics such as mechanical (MST) and chemical stability time (CST), PO43- and Mg2+ concentration, viscosity were determined with time. All the testing were carried out according to ISO procedures. High ammonia preserved CL showed a considerable amount of natural PO43- of about 300-200 ppm with storage time. The PO43- content of latex is not a stable amount and showed several fluctuations with time due to several chemical reactions within the latex sample. The excess amount of PO43- in the latex leads to a decrease in viscosity and stability of latex due to colloidal destabilization. The control sample showed the highest MST (315 seconds) and CST (97 seconds) with storage time than other samples revealing that there is no need for the addition of DAHP if the Mg2+ content of field latex is below 100 ppm in manufacturing CL. Keywords: Latex; Diammonium; Phosphate; Magnesium; Destabilization; ColloidalItem Growth Response of Rubber (Hevea brasiliensis) Seedlings to Different Dosage of Inorganic Fertilizer(Uva Wellassa University of Sri Lanka, 2020) Antony, C.G.V.; Senevirathna, A.M.W.K.; Wijesekara, C.; Herath, H.M.S.K.Rubber cultivation in Sri Lanka has been confined in the past mainly to the Wet Zone where the extent of land under rubber declined rapidly with urbanization. Therefore, to meet the demand for natural rubber, cultivation has been extended to Uva Province too in the Intermediate Zone. Ideally, high quality budded plants are required to produce within the region. However, the time taken for this process is comparatively a little longer than that in the Wet Zone. The present study was conducted in the government rubber nursery at Monaragala to examine the effectiveness of different dosages of inorganic fertilizer and compost on the growth of rubber nursery plants for two months. Fertilizer mixture: 9:11:11:4 for N:P:K:Mg, respectively, recommended by the Rubber Research Institute was used. Three levels of fertilizer mixture: 1.25 (control), 2.5, and 3.7 g per plant at fortnight interval were applied. Two levels of compost: 0 and 50 g per plant were used for the potting mixture with topsoil. Compost and fertilizer levels were considered as two factors (4 replicates and 25 plants per replicate) and a nursery was arranged as complete randomized block design. Germinated seeds were transplanted into polybags which were filled with two potting media. Growth attributes viz. stem height, stem diameter, and number of leaves were recorded at the 2nd , 3 rd, 4th, 6th, and 7th weeks; and chlorophyll content (SPAD), number of leaf whorls at the 7th week after transplanting. Data were subjected to ANOVA. There was no significant difference (p>0.05) in the growth attributes as well as in the SPAD value among the treatments tested. Therefore, use of currently recommended lowest dosage of the fertilizer mixture, i.e. 1.25 g per plant at fortnight interval without additional compost, when using topsoil is cost-effective in maintaining the rubber nurseries at pre bud grafting period in the Intermediate Zone of Uva Province. Keywords: Compost, Hevea seedlings, Inorganic fertilizer, Intermediate zoneItem Influence of Partial Replacement of Carbon Black with Areca Nut Husk Fiber on Properties of Natural Rubber Composites(Uva Wellassa University of Sri Lanka, 2019) Madushika, K.P.I.; Wijesinghe, H.G.I.M.; Senevirathna, A.M.W.K.; Edirisinghe, D.G.Development of Natural Rubber (NR) composites using natural fibers (NF) such as coconut, bamboo, banana, sisal, etc. has been increased during the recent past due to the growing need for green rubber composites. NF are low density and low cost materials having high recyclability and biodegradability. However, compatibility between NF and NR is not adequate to achieve properties required for various applications. Areca nut husk is one of the good sources of NF which is abundantly present as a waste. One series of composite was prepared with six NR composites using carbon black (N 330) and surface treated (with silane coupling agent) Areca nut husk fibre (SAF) by varying the SAF loading from 0 to 50 phr at 10 phr intervals, whilst maintaining the total filler loading at 60 phr. Another series with six NR composites was also prepared using the same formulation, but with untreated Areca nut husk fibre (UAF). UAF and SAF composites were characterized using Fourier Transform Infrared Spectroscopy (FTIR). Cure characteristics and physico-mechanical properties of these composites were tested to select the best ratio of the two filler materials in terms of properties for low cost applications. Cure rate decreased, however scorch safety improved with the increase of the amount of SAF in the composite. Hardness, tensile strength and tear strength decreased, whilst resilience, abrasion weight loss and compression set increased with the increase of SAF loading. Results indicated that two third of the carbon black in NR composites could be replaced with SAF without a significant effect to the properties.Item A Novel Process to Manufacture Low Protein Contained Centrifuged Latex(Uva Wellassa University of Sri Lanka, 2020) Hansani, P.M.G.S.; Sudusinghe, Y.C.Y.; Senevirathna, A.M.W.K.; Lochana, E.A.L.; Sandamali, P.K.N.N.Removal of protein in Natural Rubber (NR) latex has been a focus of great importance as some users face serious allergy issues when they exposure to NR latex-based products. Therefore, in this study, an attempt was taken to develop a commercially viable and environmentally friendly hybrid route by combining fractionation and creaming processes, to manufacture quality centrifuged latex with reduced protein level. Firstly, preserved NR field latex was fractionated at four different Dry Rubber Content (DRC) levels: 15%, 18%, 21%, and 24%. Subsequently, all fractionated and diluted field latex samples at 10% DRC were creamed up to 30% DRC using sodium alginate at 20 phr concentration. Creamed latex obtained were then subjected to the centrifugation process. Fractionated Creamed Centrifuged Latex (FCCL) samples were compounded according to the basic formula and cured in a drying oven at 120 ℃ for 20 minutes. Latex properties and their film properties were studied according to the standard test procedures and compared with Single Centrifuged Latex (SCL) and Double Centrifuged Latex (DCL). The FCCL sample fractionated at 15% DRC (15% FCCL) showed the lowest nitrogen content than other centrifuged samples while other samples follow the order of 18% FCCL< 21% FCCL < 24% FCCLItem Phosphorus Behaviour in Boralu Series Soil of Rubber (Hevea brasiliensis) Plantations(Uva Wellassa University of Sri Lanka, 2020) Samaranayaka, K.T.T.; Herath, H.M.S.K.; Senevirathna, A.M.W.K.; Hettiarachchi, R.P.; Silva, E.D.; Edirimanna, V.Monoculture cropping system adopted for more than a hundred years in rubber (Hevea brasiliensis) plantation with same agro-management practices has resulted in nutrient imbalance due to either depletion or accumulation of nutrients in soils. Phosphorus (P) is an essential macronutrient for rubber plantations. The main objective of this study was to determine P behaviour in Boralu series soil in relation to soil pH, organic carbon, available P, moisture content, cation exchange capacity, and bulk density. Forty-eight soil samples representing Boralu series soil were evaluated for available P by NH4F/HCl and organic carbon by the Walkley Black method. Descriptive statistical data were derived and a regression analysis was also carried out to find a relationship between soil parameters. Available P varied from 30.77mg kg-1 in manure circle and 23.20mg kg-1 outside the manure circle. Organic carbon content in both areas, in and out of the manure circle, varied from 1.16 to 1.16%. Significant (p=0.03) differences were observed between the inside and outside the manure circle for organic carbon content. Whereas no significant differences between the inside and outside of manure circle were observed for the moisture content (p=0.31), available P (p=0.37), and cation exchange capacity(p=0.13). There was a positive correlation between organic carbon and available phosphorus with R2=0.27 by the action of phosphorus solubilizing microbes. There was a negative correlation between the organic carbon content and soil pH with R2=0.27as well as available P and bulk density with R2=0.25. Results show that available P content increase with organic matter. Keywords: Available phosphorus, Boralu series, Bulk density, Organic carbon, pHItem Potential of Using Rice Husk Ash Silica as Filler in Acrylonitrile Butadiene Rubber Compounds(Uva Wellassa University of Sri Lanka, 2020) Wadugodapitiya, R.R.W.M.U.G.K.; Wijesinghe, H.G.I.M.; Edirisinghe, D.G.; Senevirathna, A.M.W.K.Rice husk is a most available and reliable natural source which contains more than 90% of silica (SiO2) in its ash. Silica in its amorphous or crystalline forms can easily be derived from rice husk ash (RHA). Replacement of environmentally harmful carbon black (CB) using such a natural source is important. Therefore, this study was conducted to investigate the potential of using RHA silica (RHAS) as filler for Acrylonitrile butadiene rubber (NBR) compounds as partial replacement of CB. Commercial grade silica (CS) was used for the comparison of the performance of RHAS during the study. RHAS was derived by sol-gel technique and X-ray diffractogram proved the amorphous nature of RHAS and Fourier Transform Infrared Spectrophotometric analysis underlined that the chemical nature of RHAS is almost similar to that of CS. NBR compounds (Series 1) were prepared by keeping CB: RHAS ratio as 55:5, 50:10, 45:15, 40:20, and 35:25 parts per hundred parts of rubber by weight (phr). The compounds (Series 2) which contain CB and CS were prepared using the same ratios. Compound with 60 phr of CB was considered as the control. Both series of compounds have shown desirable highest torque, Delta cure, and lowest torque with better-crosslinking density and processability at all loading levels compared to control. Scorch time and Cure time showed extended times. Hardness, compression set, and tensile strength of both series showed acceptable values even though elongation at break and tear strength showed somewhat inferior properties. Swelling resistance is very high in both series with no significant between the series and to the control. Overall, there is a potential to use RHAS as a partial replacement of CB in NBR compounds and can be used to replace CS. Keywords: Acrylonitrile butadiene rubber, Carbon black, Commercial silica, Rice husk ash silicaItem Preparation and Characterization of Deproteinized Crepe Rubber using a Serin Type Proteolytic Enzyme(Uva Wellassa University of Sri Lanka, 2020) Chandramali, T.H.D.S.; Sudusingha, Y.C.Y.; Siriwardena, S.; Lochana, E.A.L.; Senevirathna, A.M.W.K.A serin type Proteolytic Enzyme (PE) was used as a substitute for traditionally used papain which has no reliable supply at present in the local market, for the manufacture of Deproteinized Crepe Rubber (DPCR). Field latex was coagulated by different PE dosages varying from 1 to 4 ml with 1 ml intervals per litre of the diluted field latex at 10% DRC and matured for 72 hours. The control sample was coagulated within 24 hours using 1% formic acid and all coagula were converted into pale crepe form. The impact of the maturation period (24-72 hours) on raw rubber properties was also studied using the selected sample which meets the lowest Nitrogen Content (NC) among all the candidate samples. Raw rubber properties, curing characteristics, and physicomechanical properties of all the vulcanizates were studied. All enzyme-treated samples showed lower NC (0.10- 0.14%w/w) than the control (0.31%w/w). It was noticed that the increase of PE volume and maturation period reduced the NC in the samples. Raw rubber properties of the enzyme-treated samples with a 72-hour maturation period have complied with the required specifications of DPCR except for the Plastic Retention Index (PRI). It was found a reduction of PRI and ash content while increasing in Po values with the increment of PE dosage and maturation period. However, the enzyme treatment (4ml/liter) with a 24-hour maturation period was able to achieve the slightly higher PRI value (63.3%) than the recommended value (60%) for both control and DPNR. It was found that curing time (T90) of the control sample was higher than the enzyme-treated samples and the control sample showed better tensile strength than the enzyme-treated samples due to the protein reinforcement effect and higher crosslink density. Overall, it could be concluded that the selected enzyme has the potential to use it for manufacturing DPCR. Keywords: Deproteinized crepe rubber, Nitrogen Content, Maturation period, Raw rubber propertiesItem 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.Item Silica Extracted from Rice Husk Ash as an Effective Reinforcing Filler for Natural Rubber Composites(Uva Wellassa University of Sri Lanka, 2018) Samaraweera, K.C.; Wijesinghe, H.G.I.M.; Etampawala, T.N.B.; Edirisinghe, D.G.; Senevirathna, A.M.W.K.Rice husk is abundantly available in Sri Lanka, which is generated in larger volumes as rice husk ash (RHA) due to combustion. In general, RHA dumped at landfills as a waste. However, RHA is a promising source of silica as it contains more than 90% by weight. This silica can effectively be extracted by Sol-Gel method. In this research such silica was extracted and characterized using Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffractometry (XRD). Both FTIR and XRD analysis confirmed the chemical and amorphous nature of the extracted silica. Natural rubber composites were prepared incorporating silica from 0-10 parts per hundred Rubber (phr) at 2.5 phr intervals using two-roll mill. The effect of silica on curing characteristics and the mechanical properties of vulcanizates were studied. The curing characteristics of the compounds revealed an increase in cure rate and thus considerable decrease in cure time and scorch. Tensile strength, modulus at 100% elongation and tear strength has increased significantly compared to control sample. The effect is prominent with increasing the silica loading. The abrasion volume loss has significantly decreased with the increase of silica loading. The lowest abrasion volume loss and the highest tear strength have reached at 7.5 phr of silica loading level. Whilst the resilience has decreased when increase the silica loading. However, silica loading does not show an impact on hardness. In conclusion, preferred curing characteristics and improved mechanical properties have been achieved. Moreover, it is important to emphasize that in this study the effect of extracted silica on mechanical properties of NR composites has not been compared with the commercially available silica and further studies are suggested.Item Socio-Economic Influence on Growth Performance of Smallholder Rubber Cultivation in Uva Province(Uva Wellassa University of Sri Lanka, 2020) Madushanka, B.G.G.T.; Jeewanthi, P.W.; Senevirathna, A.M.W.K.Rubber cultivation in Sri Lanka has been extended to Uva Province (Intermediate Zone) to meet the demand for natural rubber. This study was conducted to find the growth performance of smallholdings in Uva Province and associated socio-economic factors. Using a stratified sampling technique, a hundred farmers were selected from four and six Rubber Development Officers’ divisions in Badulla and Moneragala districts, respectively. A questionnaire-based survey including information on the family profile, income, expenditure, rubber land & its management, the government supports, yield & products, and marketing facilities was carried out. Also, stem girth, bark consumption rate, the quality of harvesting, and land management were evaluated by randomly selecting twenty rubber trees in each smallholding. Descriptive statistics and multiple regression analyses were performed. According to the results of age distribution, the majority of smallholders (45%) are in the 51-60 age group. Also, more than 50% have only primary and O/L education. According to the results, 93% farmer’s cultivation area is less than 2 acres and most have cultivated RRIC 121 rubber clone. The majority (85%) had participated in training/extension programs conducted by the Rubber Research Institute of Sri Lanka and Rubber Development Department. When considering fertilizer usage, 52% of farmers use fertilizers; of them, 68% apply fertilizer yearly. Results of regression analysis revealed that rubber stem girth positively correlated with management practices, fertilizer usage, farming experience, and age of plants. Keywords: Growth performance, Rubber smallholder, Socio-economic statusItem Study of Mechanical and Physical Properties of Nitrile Butadiene Rubber Glove with Sulfur, Accelerator and Particle Size of the Dispersion(Uva Wellassa University of Sri Lanka, 2020) Mendis, E.D.M.; Hemachandra, K.A.S.K.; Senevirathna, A.M.W.K.; Wijesinghe, H.G.I.M.Sludge formation in the latex dipping tanks is the most destructive matter in the glove industry. This problem can cause quality defects of the glove and hence, high cost of production. This study was carried out to reduce the sludge quantity while the physical properties of the nitrile butadiene rubber glove by reducing the particle size of the dispersion. The particle size of the dispersion was reduced by increasing milling cycles in the pearl mill. Two milling cycles were considered in this study. Particle sizes of two samples were 2.5µm and 1µm according to the Dynamic Light Scattering test. Those dispersion samples were used to prepare compounds to measure the sludge quantity and gloves were prepared to investigate the physical properties. Particle size with the milling cycles was studied as a preliminary study. Further improvements of the physical properties of the glove were investigated using different sulfur/accelerator ratios within three sulfur vulcanizing systems. Two levels of sulfur/accelerator ratios in each system were used to determine the best ratio with better properties. Dispersion with 1 µm particle size was given at least sludge quantity than the dispersion with 2.5µm particle size while improving the properties. Standard property levels in nitrile butadiene glove were considered as the control in this study. 3.5/1 sulfur/accelerator ratio was given better properties than the 2.5/0.5, 0.4/0.5, 0.8/3, 1/1, 1.5/1.5 ratios. This is because vulcanizate with a high proportion of polysulfidic bonds obtained high mechanical strength. Therefore, it is effective to use dispersions made from 1µm particle size with 3.5/1 sulfur/ accelerator ratio in the production of a nitrile glove. Keywords: Particle size, Physical properties, Sludge, Sulfur/accelerator ratioItem Study on Effectiveness of Ascorbic Acid, DRC+3 and Sodium Nitroprusside (SNP) on Recovery of Tapping Panel Dryness (TPD) of Rubber Trees(Uva Wellassa University of Sri Lanka, 2016) Watawala, W.K.S.W.; Senevirathna, A.M.W.K.; Arachchi, M.P.M.; Gunadasa, H.K.S.G.; Nayanakantha, N.M.C.; Samarasekara, R.K.Tapping panel dryness (TPD) of rubber is known as a physiological disorder (oxidative stress), which occurs in all rubber clones growing everywhere in the world resulting in severe loss of yield. At present, TPD affected trees are rested for about six months period to reduce stress to the trees in order to minimize TPD. There is no any effective treatment has been found to prevent or cure TPD. Therefore, rubber growers face serious problems due to high economic losses caused by TPD. This experiment was conducted to find the effectiveness of some chemical treatments for trees affected with TPD. Ninety TPD affected trees and 30 healthy trees of clone RRIC 121 that were planted in 1996 were selected. All the trees were being tapped at half spiral, every other day (S/2 d2), downward (J.) tapping system in the first renewed panel (C=BI- 1 panel). A commercial chemical named, DRC+3, Ascorbic acid (AA) and Sodium Nitroprusside (SNP) as a NO (nitric oxide) donor were used for the experiment, which are said to having antioxidant properties. DRC+3 (1g per tree with 6 days intervals), Ascorbic acid (1mM & 0.5mM with 6 days intervals) and Sodium Nitroprusside (100pM & 50 p..M with 2 weeks intervals) were applied on affected TPD trees with an untreated control. In another experiment, DRC+3(ig per tree with 10 days intervals) was applied for healthy trees with untreated control. Although data were not statically significant, there is a trend in increasing the yield per tree per tapping (g/t/t/) in TPD affected trees treated with DRC+3 and, Ascorbic acid, more prominently with 1 mM AA. Higher concentrations of Sodium Nitroprusside might be preferred as there was a positive effect on increasing yield of TPD affected trees with 100 11M SNP compared to 501.IM concentration, though the yield increase was not statistically significant. When compared to the pretreatment data and yield increase during the short period of the experiment, further continuation of this experiment is needed to arrive at firm conclusions. Key words: Ascorbic acid, DRC+3, Physiological disorder, Sodium Nitroprusside, Tapping panel drynessItem Use of Host Volatile, Pentanol as the Pheromone Synergist for Management of Red Palm Weevil(Uva Wellassa University of Sri Lanka, 2019-02) Pramudika, U.V.A.; Kumara, A.D.N.T.; Weerawansha, A.N.R.; Senevirathna, A.M.W.K.Red palm weevil (RPW) Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae) is a devastating pest of coconut and other palms species in Sri Lanka and other countries. Being the conceal habitat of the pest inside the palm trunk, management of the pest is difficult and prevention of the pest damage is more important. Pheromone trap is one strategy popularizing among farmers as green pest management method. Increasing the efficiency of aggregation pheromone is a challenge. Use of responsive host volatiles for pest management is a recent trend in the field of pest management. Both electrophysiological and behavioral studies were carried out to select and formulate synergistic semiochemical formulation from six host volatiles and RPW aggregation pheromone. Electroantennogramme (EAG) test results indicated, the highest EAG response (-7.476 ± 0.713, -8.310 ± 0.332 mV) to pentanol from both female and male respectively. It is always higher than RPW aggregation pheromone (-5.402 ± 0.562, - 4.310 ± 0.599 mV) and other tested five host volatiles. Behavioral studies indicated that, pentanol is an attractive volatile and 82 ± 3.74% attracts towards the pentanol applied coconut fronds than hexane applied fronds. Further, dose response of EAG, EAG and behavior studies indicated that, pentanol: pheromone at 1:1 mixture gave the highest response and attraction for both female and male (-6.49 ± 2.134, -10.376 ± 5.35 mV) among the tested mixtures of 1:1, 1:2, 1:3, 1:4, 1:5, pheromone alone and pentanol alone. Therefore, pentanol: pheromone at 1:1 formulation can be recommended for use as a semiochemical lure for RPW mass trapping after conducting mass trapping experiments in the field.