Browsing by Author "Edirisinghe, D.G."
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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 Evaluation of Suitability of Disulfide based Natural Product as a Reclaiming Agent for Ground Rubber Tyre(Uva Wellassa University of Sri Lanka, 2013) Rathnawardhana, M.K.N.N.; Gunathilaka, R.P.D.; Edirisinghe, D.G.Reclaimed ground rubber tyre is a solution for the shortage of raw rubber and the rise in the cost of virgin rubbers. Also, it reduces the rubber waste and hence the pollution caused by that waste. Therefore, there is a continual development of reclaiming technologies over the last few years. Ground rubber tyre (GRT) is already a vulcanized material. In the vulcanization process of rubber compounds crosslinks occur between polymer chains. Many researchers have shown that bonds between GRT and the rubber matrix are very weak because of the crosslink structure of GRT and lack of reactive sites on the GRT surface, resulting in a decrease of the mechanical properties of GRT and virgin rubber blend vulcanizates. A possible way to overcome this problem is to break the sulfur crosslinks in GRT before blending with other polymers. Therefore, work has been carried out in the past to modify GRT to enhance interfacial adhesion between the two phases. This process is called reclaiming or devulcanization. Zhang, et al., (2009) compared rubber blends containing raw GRT and rubber blends containing devulcanized GRT and have concluded that the rubber blends containing devulcanized GRT were easier to mix and exhibited much better mechanical properties than natural rubber/GRT vulcanizates. There are several physical and chemical devulcanization techniques. Physical and chemical processes normally are energy demanding or require hazardous chemicals. Tetramethylthiuram disulfide (TMTD) has been used as one of the disulphide reclaiming agents for GRT. TMTD is a synthetic and hazardous chemical. Therefore finding a natural reclaiming agent is a potentially attractive recycling and utilizing way of GRT. In this study disulfide based natural product (NP) was used as the reclaiming agent for ground rubber tyre (GRT) with the aim of replacing the hazardous reclaiming agent TMTD to formulate the tyre tread compounds. Methodology The current study was carried out at the Rubber Research Institute of Sri Lanka (RRISL), Ratmalana. Laboratory analysis was done at RRISL. In this study as step one, a series of samples of reclaimed GRT was produced by adding different amounts of the selected natural product and one sample was produced by adding TMTD. In the second step, rubber compounds were produced by blending the reclaimed rubber prepared using different amounts of NP and TMTD with virgin natural rubber (NR).In the third step, rubber vulcanizates were produced using the compounds prepared in step 2. Cure characteristics, physico-mechanical properties and anti-oxidant property of both rubber compounds and vulcanizates were evaluated and compared with those of the control; blend compound containing virgin NR and reclaimed rubber prepared with TMTD. Treatments adopted were 5phr (parts per hundred parts rubber) of TMTD [Control (1)], 1 phr of NP(2),3 phr of NP(3),5 phr of NP(4),7 phr of NP(5),9 phr of NP(6). The data were analyzed adopting the analysis of variance (ANOVA) using Minitab 16 software programme. Significant means of treatments were separated using the Least Significant Difference p<0.05.Item Evaluation of Suitability of Palmyra Fibre as a Replacement for Coconut Fibre in Carbon Black Filled Natural Rubber Composites(Uva Wellassa University of Sri Lanka, 2013) Thilanga, G.P.D.L.S.; Herath, H.M.S.K.; Edirisinghe, D.G.; Sampath, W.D.M.Natural rubber (NR) consists of cis 1,4 polyisoprene. It is an example of elastomeric type polymer, where the polymer has the ability to return to its original shape after being stretched or deformed. Fillers are materials that are particulate in nature, which are added to rubber mixes to modify the physical and, to a very smaller extent, the chemical properties, also to improve the processing characteristics and reduce cost (Briggs et al., 2000). Natural fibres are generally lignocellulose in nature, consisting of helically wound cellulose microfibrils in a matrix of lignin and hemicellulose. Palmyra fibre is an inexpensive fibre among the various natural fibres available in the world. It is abundantly available in Sri Lanka, India, like tropical countries and it’s density is least among all known fibres including coconut fibre. Therefore, the main objective of this study was to replace coconut fibre with palmyra fibre in carbon black filled natural rubber composites Methodology The current study was carried out at the Rubber Technology and Development Department, Rubber Research Institute of Sri Lanka (RRISL), Telawala Road, Rathmalana. Compound preparation and laboratory analysis were done at RRISL laboratory. The effect of different amounts of palmyra fibre on physico-mechanical properties of natural rubber compounds was investigated and the properties were compared with those of coconut fibre filled natural rubber compounds. Test pieces were prepared with the rubber compounds to carry out physico- mechanical testing. The cure characteristics and physico-mechanical properties of the rubber composites prepared with different loadings of palmyra fibre were investigated. For comparison purposes, a series of rubber compounds was prepared using coconut fibre, similar to the quantity of palmyra fibre. Two factor factorial Complete Randomized Design (factorial CRD) was conducted and data obtained from cure characteristics and physico-mechanical properties tests were analysed with analysis of variance (ANOVA) with General Linear Model (GLM) procedure of Minitab 16. Significant means of treatments were separated using the Least Significant Difference (LSD) (P< 0.05) test.Item 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 Investigation on Suitability of Banana Fiber as a Filler Material in Natural Rubber Latex-Based Household Gloves(Uva Wellassa University of Sri Lanka, 2016) Kirushanthi, T.; Edirisinghe, D.G.; Jayasuriya, C.K.With increasing demand for polymer based household items, waste disposal has become an environmental issue. Thus, researchers are concerned on producing cost effective products, which are also biodegradable. The objective of this study is to investigate the possible use of banana fiber as a filler material in making natural rubber based household gloves with improved biodegradability and cost effectiveness while retaining the desired properties. In this study, long banana fibers were extracted mechanically and ground using a blender. Then, they were sieved and size less than 400 p.m particles were selected. These were chemically treated using 4% sodium hydroxide and 2% of sodium sulfite. Natural rubber latex compounds were prepared changing banana fiber content. The films were made using casting method. The physico-mechanical properties of films, including tensile, tear and accelerated aging properties were analyzed and compared with the control sample in which no banana fiber was added. Tensile and tear strength have decreased with increasing fiber percentage compared to the control sample. This may be due to the poor interaction between rubber matrix and banana fiber. Banana fiber added natural rubber latex films exhibited, in comparison, a higher Young's modulus at 100% elongation than the control sample. Results also showed that the elongation at break has decreased steadily with the increasing of the fiber loading. Increase in the modulus and the decrease in percentage elongation may be attributed to the restriction of molecular chain movements resulting from the presence of fiber in the rubber matrix. Significant increase in retention value can be seen when higher amounts of fiber was incorporated suggesting enhanced durability in the condition of heat, oxygen and ozone. Use of nano-sized fiber particles, better coupling agent and an alternative fiber dispersing method may improve the mechanical properties. Keywords: Biodegradable, Natural rubber, Latex glovesItem 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 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.