Effect of dispersants on the hydroxyapatite‐filled natural rubber biocomposites with enhanced functional properties

Abstract

The aim of this work was application of the hydroxyapatite (HAP) in various amounts by weight as a filler of natural rubber (NR) biocomposites. Innovatively, silanes, that is, (3‐aminopropyl)‐triethoxysilane (APTES) and bis[3‐(triethoxysilyl)propyl] tetrasulfide (TESPTS), surfactant, that is, cetyltrimethylammonium bromide (CTAB), and alkylimidazolium ionic liquids (ILs) with halide anions, that is, 1‐butyl‐3‐methylimidazolium chloride (BmiCl) and 1‐decyl‐3‐methylimidazolium bromide (DmiBr), were used to improve the dispersion of the HAP and curatives particles in the rubber matrix, and consequently the curing characteristics and properties of NR biocomposites. The influence of HAP and dispersants on the crosslink density, tensile properties, thermal stability, resistance to thermo‐oxidative aging, and ability to damp vibration of vulcanizates were investigated. It has been proven, that HAP can be efficiently used as a filler of NR biocomposites alternatively to commercial inactive or active fillers, for example, chalk, talc, or silica. The optimal HAP content is 30 phr. HAP did not detrimentally affect the curing characteristics of NR composites, crosslink density, and damping properties of the vulcanizates, while significantly raised their tensile strength, thermal stability, and resistance to thermo‐oxidative aging. Most importantly, CTAB and ILs considerably improved the dispersion of HAP and curatives particles in the NR matrix and consequently lowered the vulcanization temperature by approximately 25°C and enhanced by approximately 50% the crosslink density and tensile strength of the NR biocomposites.