Wood Sawdust Fibres as a Secondary Filler in Carbon Black Filled NR Vulcanizates
Studies into the properties of polymer-wood composites (PWC) are mostly focused on thermoplastics as the matrix phase and wood flour as a reinforcing phase. This article aims to identify the optimum contents of wood sawdust fibre and silane coupling agent to be introduced into natural rubber (NR) compounded with carbon black (CB). The authors have considered a wide range of composite properties, including cure characteristics, % bound rubber, crosslink density, sorption and desorption behaviour, tensile modulus, elongation at break, tensile and tear strengths, hardness, and morphological properties. The results suggest that the overall mechanical properties of the NR composites improved with increasing CB content, but deteriorated sharply with sawdust content up to 40 phr. Addition of further sawdust was recommended as an economical benefit to industries as the properties of the NR/CB composites remained unchanged with increasing sawdust content above 40 phr sawdust fibre. Addition of N-(βaminoethyl)-γ-aminopropyl-trimethoxy silane coupling agent to the NR vulcanisates, containing 40 phr of wood sawdust fibres and 45 phr carbon black at 0.5-1.0 %wt of wood sawdust, improved the mechanical properties. The explanations for the results given in this paper are unique in that they refer to bound rubber, crosslink density and rubber-filler phase continuity in the composites, and to a change in composite rigidity.