in non-uniformity of the composite and hence changes its properties. This non-uniformity could be overcome by incorporating a suitable adhesion promoter and/or a coupling agent. Although titanate coupling agents are used in this study was aimed at incorporating a CA to natural rubber (NR) and low-density polyethylene (LDPE) blend through calcium carbonate (CaCO 3 effect of CA loading on properties of the composites. In this hundred parts of polymer). CaCO 3 loading was kept constant at 20 pphp. Brabender plasticorder was used to prepare o of 60 rpm. Physico-mechanical properties were evaluated according to ISO standards. Degree of swelling and gel content and dynamic properties of the composites were investigated. composites increased with the addition of CA and showed the best properties at a CA loading of 0.7 pphp. Hardness of tensile properties and water resistance were also shown at 0.7 pphp showed better compatibility and the best properties. coupling agent.

Polymer blends are prepared by melt mixing, solution or latex blending. Thermoplastic vulcanizates (TPVs) are generally produced by melt mixing. TPVs can be co-injected or co-extruded to produce complex articles built from very soft/hard components. Dynamic vulcanization would give rise to a uniform and fine distribution of rubber and thermoplastic phases. The aim of this study was to identify a suitable dynamic vulcanization system to produce natural rubber (NR)/low-density polyethylene (LDPE) blends with improved chemical, ageing and morphological properties. Three 50:50 NR/LDPE blends were prepared by varying the vulcanizing agent as sulphur, dicumyl peroxide (DCP) and 50:50 sulphur: DCP. A control was prepared without any vulcanizing agent. All these blends were prepared by melt mixing. The blends were characterized using FTIR spectroscopy and SEM analysis of tensile fracture surfaces. Water absorption, swelling and ageing behaviour of the blends were investigated. Water absorption percentage of blends prepared with DCP and the mixed curing system was zero. Analysis of gel content indicated a higher crosslink density for the blend prepared with the mixed curing system compared to the other blends. Also, the former blend showed the highest retention of strength properties and elongation at break compared to the other two blends prepared with vulcanizing agents. SEM analysis showed a fine and smooth textured morphology for this blend. Results in overall indicated that the 50:50 NR/LDPE blend prepared with the mixed curing system would be suitable to manufacture heat and solvent resistant products.

Modified graphite has attracted considerable interest over recent years due to its surface functionality and better dispersibility with polymeric materials. Incorporation of a small quantity of modified graphite filler into polymer can create novel composites with improved properties. In this study, polyethylene glycol (PEG) was grafted onto the graphite surface in the presence of maleic anhydride (MAH). The PEG-grafted graphite (PEG-g-Graphite) was characterized via Fourier Transform infrared spectroscopy (FTIR), X-ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), and the analysis proved that PEG was successfully grafted onto the graphite surface. Subsequently, natural rubber (NR) composites were prepared by varying the PEG-g-Graphite loading from 0 phr (parts per hundred rubber) to 10 phr at 2 phr intervals. The 10 phr PEG-g-Graphite filled NR composite showed an increment in scorch time and cure time in comparison to the NR composite prepared without PEG-g-Graphite (control). Further, heat resistance of the PEG-g-Graphite/NR composites prepared with 8 and 10 phr loadings of PEG-g-Graphite was at a high level. Due to sheet resistance, values of the 10 phr loading of PEG-g-Graphite and the control composites were 2 × 10 5 and 3.9 × 10 7 ohms/square, respectively. The NR composite prepared with 10 phr loading of PEG-g-Graphite could be suitable for high electrical conductive polymeric applications.

No abstract

A wide variety of natural fibres such as coconut fibre (coir), bagasse, banana fibre, sisal, etc. can be used to reinforce polymers. Natural fibre reinforced, biodegradable composites are eco-friendly. However, the interfacial adhesion between natural fibre and most of the biodegradable polymers is not adequate. The objective of this study was to modify readily available coir by coating with natural rubber (NR) as well as synthetic rubber latices with the aim of improving adhesion between coir and rubber in order to develop a coir filled NR based composite suitable in manufacture of tyre treads. Coir was coated with different compounded latices namely, neoprene, nitrile and NR and with uncompounded NR latex. Thereafter, composites were produced by mixing 15 phr of the latex coated coir fibres with virgin NR according to a tyre tread formulation and properties of the composites were evaluated and compared. Results revealed that processing safety of the compounded NR latex coated coir filled rubber composite is higher than that of the other three composites, whereas uncompounded NR latex coated coir filled rubber composite showed a similar processing safety to that of the two synthetic latex coated coir filled rubber composites. However, the two NR latex coated coir filled rubber composites were faster curing than the synthetic latex coated coir filled rubber composites. Minimum torque results indicated that compounded NR latex coated coir filled rubber composite has a higher processability when compared to the other composites. However, the latter composites indicated a higher state of cure and cross-link density in comparison to the former composite. Tensile strength, elongation at break, resilience and abrasion volume loss of the compounded NR latex coated coir filled rubber vulcanisate are superior to those of the other three vulcanisates. In overall cure characteristics and mechanical properties, especially abrasion resistance of the composite based on compounded NR latex coated coir indicates that it could be used in manufacture of tyre treads.