Browsing by Author "Siriwardena, S."

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    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; Ultraviolet
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    The Effect of Bis-(3-triethoxysilylpropyl)-Tetrasulfane and Polyethylene Glycol on the Properties of Natural Rubber/ Mica Composites
    (Uva Wellassa University of Sri Lanka, 2021) Edirisinghe, E.D.S.; Somarathna, Y.R.; Withanage, N.S.; Dhanukamalee, H.M.H.; Samarasinghe, I.H.K.; Siriwardena, S.
    The bis-(3-triethoxysilylpropyl)-tetrasulfane (Si69) is widely applied as a coupling agent to rubber- filler interactions in silica filled rubber composites. In this study, the effect of bis-(3- triethoxysilylpropyl)-tetrasulfane (Si69) and polyethylene glycol (PEG) on the properties of natural rubber (NR)/mica composites has been studied. The mica loading and the total weigh of Si69/PEG were kept constant at 30 phr and 2 phr, respectively. A composite free from Si69/PEG (SP00) was used as the control, while ratios of the above chemicals (Si69: PEG) were varied as 1:0, 0:1 and 1:1 in the other composites. These three systems were denoted SP10, SP01 and SP11, respectively. Curing characteristics, physico-mechanical properties and thermal degradation of NR/mica composites were investigated. The maximum cure time (Tc90) and scorch time (TS2) were exhibited in the SP10 compound. However, introduction of PEG into the system with Si69 in SP11 composite yield a reduction in Tc90 and TS2, which were comparable with the control (SP00). Maximum tensile strength and elongation at break were observed in Si69 treated NR/mica composite (SP10). This could be attributed to the improved rubber-filler interactions caused by incorporation of higher amounts of Si69 (2 phr). Further, the composite treated with both Si69 and PEG (SP11) with 1 phr each, has shown the second highest tensile strength among candidate composites. However, the enhanced moduli values at 100%, 300% and 500% elongation indicated better rubber-filler interactions in SP11 composite than SP10. The same reason may have resulted the highest hardness and resilience values in SP11 composite. The thermogravimetric analysis indicated that the application of Si69 and/or PEG have no significant impact on the thermal degradability of NR/mica composites. It was also found that SP01 exhibited the highest swelling ratio among all samples. Therefore, overall results indicated that PEG/Si69 treated system (SP11) could be employed more effectively than individual use of Si69 and PEG to optimize the cure characteristics, while improving the physico-mechancial properties of NR/mica composites. Keywords: Mica; Natural rubber composites; Polyethylene glycol; Coupling agent; Rubber-filler interactions
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    The Performance of Raw Rubber Dried Using Different Drying Systems
    (Uva Wellassa University of Sri Lanka, 2011) Hewapathirana, I.B.; Siriwardena, S.; Wranajith, A.K.D.; Rangith, S.L.
    Note: See the PDF Version Drying and smoking are two operations carried out simultaneously during the manufacture of smoked sheet rubber. Smoke acts as the carrier medium for heat and the chemical substances presence in the smoke. Heat removes the moisture presence in the sheets which is approximately amounts to 30% (wb). Some of the chemical substances with antioxidant and antimicrobial properties available in the smoke deposit on the sheet rubber and enhance their resistance to oxidation and mould growth. Ribbed smoked sheets which are the major Contributor for local rubber production, are conventionally dried for 4-5 days at 48 -54 C in a smoke house with intermittent interruptions of drying for the purpose loading unloading of sheets. Recently introduced single day smoke drying system (SS drying system) dries Wet sheets continuously at a rather higher temperature of 55 — 65 C. In this system, wet sheets are exposed to hot smoke at a higher drying temperature, however, for a shorter period. Sheets are also dried in open sun without control and in a stream of warm air (34 °C) for about 6-8 days to produce smoke free sheet rubber. Therefore, according to drying system used, sheet rubbers may be categorized as; Conventionally Smoke Dried sheets(CSD), Sun Dried Sheets(SDS), Air Dried Sheets (ADS) and Single day Smoke driedsheets (SS). Different drying systems may vary the quantity of smoke adsorbed to the Surface of the sheets and duration and temperature to which sheets are exposed to. Consequently, the sheets dried using different drying systems may have different degree of resistance to the oxidation and fungal attack affecting the raw rubber and rubber vulcanizate properties. This study therefore, attempts to study the raw rubber and rubber vulcanizate properties of the sheet rubber dried using, selected four drying systems.
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    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 properties