An investigation on the reinforcing potential of red earth as filler for natural rubber compounds

Abstract

Locally sourced red earth (RE) was air-dried, pulverized, and screened with a sieve of mesh size 75 nm. It was characterized in terms of its moisture content, loss on ignition, silica content, iodine adsorption number, oil absorption, pH, and metal oxide compositions. Natural rubber, standard Nigerian rubber used for this work was first characterized in terms of its dirt, ash and nitrogen contents, volatile matter, plasticity retention index, and Mooney viscosity. The RE was applied as filler wholly and in blends with standard carbon black, CB (N330) filler in the natural rubber compounding using efficient vulcanization system. The cure and the physicomechanical properties of the compounds and vulcanizates were, respectively, measured as function of filler loading. The results were compared with those of the standard carbon black (N330)-filled natural rubber. It was found, that the RE-filled natural rubber showed substantial reinforcement of the rubber, though inferior to carbon black (N330) filled vulcanizates, the tensile strength of the carbon black-filled vulcanizates is about one half times that of the RE-filled vulcanizates. The tensile properties of the RE-filled vulcanizates improved markedly by blending the RE-filler with the carbon black (N330).

<i>Calamus deerratus</i> fibre reinforced natural rubber vulcanizates

“…The results also showed that the loss on ignition at 1000 0 C was higher for CB(N330) thus suggesting that CB(N330) has higher content of carbon and other combustible materials than CDF. It has been postulated that fillers with high content of carbon exhibit high reinforcing effect Egboh, 2007a and2007b). The results further showed that CB(N330) has higher iodine adsorption number and hence larger surface area (which implies smaller particle size) than the CDF filler.…”

“…The results further showed that CB(N330) has higher iodine adsorption number and hence larger surface area (which implies smaller particle size) than the CDF filler. It has been documented that the most important factor that determines the reinforcing ability of a filler is its particle size (or surface area); a reinforcing filler must have very small particle size (large surface area) in order to maintain a strong surface contact with the polymer matrix (Boonstra, 1984;Osabohien and Egboh, 2007b;Yamashita and Tanaka, 2014). Both fillers are acidic as shown by the pH of their aqueous slurries, but the CDF is more acidic.…”

“…These surface active groups can contribute to the surface reactivity of a filler which can influence its reinforcing potential. It has been shown that they could have a catalytic effect on the rate of cure, modulus, electrical and thermal conductivity of vulcanizates (Blow and Hepbum, 1982;Osabohien and Egboh, 2007b;Osabohien, 2010).…”

“…The CDF-filled SNR 10 vulcanizates had higher scorch times and cure times and lower maximum torque than CB(N330)-filled SNR 10 vulcanizates probably due to the larger particle size, smaller surface area, higher moisture, metals or non-metal contents, presence of lignin and other impurities of the CDF compared to the CB(N330). The metals or their oxides present in the CDF filler could have a retarding effect on the accelerator activity which in turn can slow down the sulphur vulcanization process leading to increase in cure time and scorch time (Osabohien and Egboh, 2007b). The increase in the torque values suggests that there is a good interaction between the filler surface and rubber matrix which results in some reinforcement in the vulcanizates.…”

Tensile Stress Relaxation Studies of TiO2 and Nanosilica Filled Natural Rubber Composites

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16] A variety of nonblack fillers are used in the rubber industry to improve and modify the physical properties of elastomeric materials. The addition of filler usually leads to the increase in modulus and to significant improvements in abrasion and tear resistance.…”