Silane grafted natural rubber and its compatibilization effect on silica-reinforced rubber tire compounds

Abstract

Abstract. Natural Rubber (NR) grafted with 3-octanoylthio-1-propyltriethoxysilane (NXT) was prepared by melt mixing using 1,1′-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane as initiator at 140°C with NXT contents of 10 and 20 parts per hundred rubber [phr] and initiator 0.1 phr. The silane grafted on NR molecules was confirmed by Fourier transform infrared (FTIR), proton nuclear magnetic resonance ( 1 H-NMR) and scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM-EDX). Based on 1 H-NMR, the use of 10 and 20 phr (parts per hundred resin) of silane resulted in grafted NXT onto NR of 0.66 and 1.32 mol%, respectively, or a grafting efficiency of approx.38%. The use of NXT-grafted NR as compatibilizer in silica-filled NR compounds, to give a total amount of NXT in both grafted and non-grafted forms in the range of 0.8-6.1 wt% relative to the silica, decreases the Mooney viscosity and Payne effect of the compounds, improves filler-rubber interaction, and significantly increases the tensile properties of the silica-filled NR-compounds compared to the non-compatibilized one. At the same silane-content, the use of silane-grafted NR gives slightly better properties than the straight use of the same silane. With sulfur compensation, the use of NXT-grafted-NR with about 6 wt% NXT relative to the silica gives technical properties that reach the levels obtained for straight use of bis-(3-triethoxysilyl-propyl)tetrasulfide (TESPT) at 8.6 wt% relative to the silica.

Natural rubber‐graft‐poly(2‐hydroxyethyl acrylate) on cure characteristics and mechanical properties of silica‐filled natural rubber composites

“…The compound viscosity was strongly influenced by the rubber-filler and fillerfiller interactions, also influencing the final properties of the rubber composites. 22 The Mooney viscosity of the compounds slightly increased with the grafting level in NR-g-PHEA, indicating more rubber-filler interactions via hydrogen bonding of the silanol groups on the silica surfaces with hydroxyl as well as carboxyl groups in NR-g-PHEA. In addition, T s2 and T c90 , time to initiate curing and time required for 90% completed curing, tended to decrease with grafting level of NR-g-PHEA from 0 to 10.5%.…”

“…Mooney viscosity and cure characteristics, in terms of scorch time ( t s2 ), optimum cure time ( t c90 ), and delta torque ( M H ‐M L ), extrapolated from cure curves of NR‐g‐PHEA silica‐filled NR composites in Figure are shown in Table . The compound viscosity was strongly influenced by the rubber–filler and filler–filler interactions, also influencing the final properties of the rubber composites . The Mooney viscosity of the compounds slightly increased with the grafting level in NR‐g‐PHEA, indicating more rubber–filler interactions via hydrogen bonding of the silanol groups on the silica surfaces with hydroxyl as well as carboxyl groups in NR‐g‐PHEA.…”

“…At 14.5% NR‐g‐PHEA in the NR/silica composite, the 100% modulus, 300% modulus, and tensile strength were increased by 26, 63, and 25%, respectively. The unchanged elongation at break, despite increased modulus and tensile strength, reflect elasticity of the NR matrix . The reinforcement index was calculated by dividing the modulus at 300% elongation by the modulus at 100% elongation.…”

“…The unchanged elongation at break, despite increased modulus and tensile strength, reflect elasticity of the NR matrix. 22 The reinforcement index was calculated by dividing the modulus at 300% elongation by the modulus at 100% elongation. It is used to assess rubber-filler interactions.…”

Free‐radical emulsion copolymerization of styrene with butadiene and vinyl triethoxysilane with a cumene hydroperoxide redox initiator

“…9 To balance the processability and reinforcing efficiency of rubber-silica systems, two kinds of enols (propenol and 1-undecylenyl alcohol) and a saturated alcohol (1-undecylic alcohol) were used to modify the surface of silica. Sengloyluan et al 22 reported that a silane-grafted NR in the compound improved the filler-rubber interactions and significantly increased the tensile properties of the silica-filled NR compounds. 11 In addition, many other experimental efforts have also been made to investigate the influence of silane coupling agents on silica-filled rubber.…”