Surface treated natural rubber latex sludge as a potential filler for natural rubber compounds

Abstract

Natural rubber (NR) latex sludge, a byproduct generated from centrifuged latex manufacturing industry, contains a large portion of inorganic materials and presently treated as a waste material. In this study, the sludge was converted to a powdery material through drying and grinding processes followed by a surface modification with a long chain fatty acid with a view improving its compatibility with rubber composites. Composition and structure analysis of the latex sludge powder showed that it is mainly a crystalline material of phosphate mineral with approximately 8% of trapped rubber particles within the sludge material. Processed NR latex sludge powder was surface treated with a long chain fatty acid to offer organophilic character to the sludge. FTIR analysis confirmed that latex sludge was successfully modified with the long chain fatty acid. A series of NR compounds were prepared with different loading levels of the surface treated sludge using a laboratory scale internal mixer to study the effect of the surface modified sludge on curing and mechanical properties in comparison to unmodified latex sludge filled NR compounds. Curing characteristics measured under low shear strain rate have shown that surface modification improves the processing safety without a significant impact on other curing characteristics. Mechanical properties of surface treated sludge filled NR vulcnizates have shown an improvement in tensile properties, especially strength and elongation at break, in comparison to untreated counterparts. However, on the other hand, stiffness as measured with hardness was reduced at higher loadings of surface treated sludge filled NR vulcanizates. Both surface treatment and the increase of filler loading increased the compression strength and abrasion weight loss of the compounds.