Effect of latex coated coconut fibre on cure characteristics and physico mechanical properties of natural rubber-coir composites

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.