Browsing by Author "Karunarathna, A.K.S."

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    Development of Natural Rubber (NR) and Ethylene-Propylene-Diene-Monomer (EPDM) Rubber Blend for Tie Down Strap Compound
    (Uva Wellassa University of Sri Lanka, 2013) Karunarathna, A.K.S.; Withanage, N.S.; Withanachchi, A.J.M.
    Tarpaulins or tarps are basically heavy duty waterproof covers that are used to secure loads in pickup trucks, tractors, dump trucks, etc. preventing from any untoward incidences happening during transportation. The tarps for trucks come with hooks or tie down straps to attach them securely to the vehicle body. These tie down straps are mainly used to hold tarps securely in place by providing high tensile strength and constant tension. Tie down strap is made out of natural rubber (NR), ethylene propylene diene monomer rubber (EPDM) or a combination of the both NR & EPDM by using cross-blending of two master batches method. Both NR and EPDM rubber have unique properties inherent to each material. Strap material selection is based on the climate they are used in. Natural rubber is ideal for cooler climates, as it will not crack and split in colder conditions. EPDM rubber was designed for warmer climates as it stands up better to extended sun exposure and hot UV rays (Anonymous, 2013).When concern the properties, NR will stretch further than EPDM rubber and will return to its normal non-stretched state quicker than EPDM rubber. To obtain the desired properties of both NR and EPDM, blends of the NR & EPDM are being used. The development of blends of NR and EPDM will deliver superior physical properties with the combination of excellent resistance to weathering of EPDM, in particular to attack by ozone (Rattanasupa, 2007). The addition of compatibilizer improves the compatibility of the NR/EPDM blends. It has been reported that graft copolymers widely used as compatibilizing agents, usually to enhance interfacial interaction in polymer blends, thus improving their mechanical properties (Arayapranee and Rempel, 2007). Based on above literature, a study was conducted to identify the most promising NR/EPDM blend ratio depend on cure characteristics and physical properties and to identify the effect of Methyl- methacrylate-butadiene-styrene (MBS) as a compatibilizer on NR/EPDM blend for tie down strap compound. Methodology The research study was carried out in a laboratory of Samson Compounds (Pvt) Ltd, Bataduwa, Galle. Complete randomized design (CRD) was used as the experiment design and the experiment was divided into two sub experiments as experiment 01 and experiment 02 aligning with the objectives. Total mixing time and the ingredients were different for each experiment but the blending procedure for both experiments was remained same. In experiment 01, the different blend ratios of NR/EPDM (N90, N80, N70, N60, N50, N40, N30, N20, N10) were prepared by mechanical blending and blend ratios were tested for cure characteristics, physical properties and thermal aging characteristics aged at 70°C for 22 h in respect of product specifications (Samson rubber products, 2012) of tie down strap. Replicates of hardness and tearing were three and replicates of tensile strength, elongation at break and tension set were arranged as four.
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    Development of Natural Rubber (NR) and Ethylene-Propylene-Diene-Monomer (EPDM) Rubber Blend for Tie Down Strap Compound
    (Uva Wellassa University of Sri Lanka, 2013) Karunarathna, A.K.S.
    The tie down strap is mainly used to hold tarpaulins securely in heavy duty vehicles by providing high tensile strength and constant tension during transportation. Tie down strap is made out of pure natural rubber (NR) or pure ethylene-propylene-diene monomer (EPDM) rubber depending on the climate they are being used. NR tie down straps have high tensile strength but easily crack and split due to deterioration of NR in warmer climates. EPDM rubber tie down straps are designed for wanner climates but, it has low tensile strength. Therefore, development of a tie down strap by blending NR and EPDM together to obtain both desired properties of NR and EPDM rubber is worthwhile. This research study was conducted to develop a suitable tie down strap compound having the best NR/EPDM blend ratio. Then the effect of a compatibilizer on NR/EPDM blends was also tested. Nine different blend ratios (N90:E10, N80:E20...N10:E90) were prepared by mechanical blending and they were tested for cure characteristics and physical properties (tensile strength, elongation at break, tear strength, tension set and hardness) with respect to the product specifications (Samson rubber products, 2012) of tie down strap. The same series of blends were further evaluated by adding a compatibilizer (methacrylate-butadiene-styrene or MBS) and similar properties were measured. The results revealed that, NR: EPDM blend ratios of 90:10, 50:50, 30:70 and 10:90 have achieved acceptable cure characteristics according to the given product specifications. When physical properties were concerned, only N90:E10 blend has achieved almost all the physical properties of the product specification except tension. Cure characteristics and physical properties have not significantly changed after adding the compatibilizer. Therefore, it can be concluded that NR/EPDM blend ratio of 90:10 is more suitable for tie down strap compounding and the added compatibilizer has not significantly affected on cure characteristics and physical property improvement of NR/EPDM blends. Key words: Tie down Strap, NR/EPDM Blend, Compatibilizer, Cure characteristics, Physical properties