Cardanol grafted natural rubber: A green substitute to natural rubber for enhancing silica filler dispersion

Abstract

Natural rubber (NR) usage is wide‐spread from pencil erasers to aero tyres. Carbon black and silica are the most common reinforcing fillers in the rubber industries. Carbon black enhances the mechanical properties, while silica reduces the rolling resistance and enhances the wet grip characteristics. However, the dispersion of polar silica fillers in the nonpolar hydrocarbon rubbers like natural rubber is a serious issue to be resolved. In recent years, cardanol, an agricultural by‐product of the cashew industry is already established as a multifunctional additive in the rubber. The present study focuses on dispersion of silica filler in natural rubber grafted with cardanol (CGNR) and determination of its technical properties. The optimum cure time reduces and the cure rate increases for the CGNR vulcanizates as compared to that of the NR vulcanizates at all loadings of silica varying from 30 to 60 phr. The interaction between the phenolic moiety of cardanol and the siloxane as well as silanol functional groups present on the silica surface enhances the rubber–filler interaction which leads to better reinforcement. The crosslink density and bound rubber content are found to be higher for the silica reinforced CGNR vulcanizates. The physico‐mechanical properties of the silica reinforced CGNR vulcanizates are superior to those of the NR vulcanizates. The CGNR vulcanizates show lower compression set and lower abrasion loss. The dynamic‐mechanical properties exhibit less Payne effect for silica reinforced CGNR vulcanizates as compared to the NR vulcanizates. The transmission electron photomicrographs show uniform dispersion of silica filler in the CGNR matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43057.

The effects of natural astaxanthin‐modified silica on properties of natural rubber

“…As mentioned earlier, the surface modification of silica by natural astaxanthin in solution strengthens the interface force of composites. The degree of aggregation between the silica particles is reduced, thereby weakening the filler network . Therefore, it reduces the repeat destruction and reconstruction of the network, which gives rise to a lower compression heat buildup.…”

“…Silica is well‐known as being a type of reinforcing agent to enhance the properties of rubber matrix and its consumption is next only to the carbon black in the field of rubber processing . Compared with carbon black, the tread rubber filled with silica has the advantages of low hysteresis loss, small rolling resistance and strong wet grasping force . Replacement of carbon black by silica has been growing steadily, especially in the tire industry, as the introduction of the “Green Tire Technology” by Michelin in 1992 .…”

On‐demand tuned hazard free elastomeric composites: A green approach

“…Cure characteristics were measured by using a Monsanto R‐100S oscillating disc rheometer (ODR) according to the test methods of ASTM D 2084, at a temperature of 150°C for 30 min . The optimum cure time T c90 and scorch time T s2 of the compounds were determined.…”

“…Various studies have been reported to investigate the size of aggregates and agglomerates that build impacts on the physico‐mechanical and dynamic mechanical properties of elastomer composite and tentatively correlated with silica structure . Only a few studies have been reported to determine the particle networks and cluster formation in silica reinforced elastomers . On the other hand, many morphological studies such as three‐dimensional Transmission electron microscopy (TEM), high‐resolution TEM and Scanning electron microscopy (SEM) have been done extensively to investigate the silica dispersion .…”

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

“…This was due to the in situ formed silica particles being well dispersed in the rubber matrix, while the commercial silica particles were agglomerated. Mohapatra et al . presented NR grafted cardanol for enhancing silica filler dispersion.…”