Vulcanization kinetics of natural rubber–organoclay nanocomposites

Abstract

ABSTRACT:The effect of the incorporation of a bentonite on the vulcanization kinetics of natural rubber was investigated by means of both cure-meter testing and differential scanning calorimetry (DSC) under dynamic and isothermal conditions. The vulcanization curves showed that the modified clay behaved as an effective vulcanizing agent, accelerating the vulcanization reaction of the elastomer. A marked decrease in the induction time and optimum cure time of the elastomer were observed in the presence of the organoclay. Although the octadecylamine itself accelerated the vulcanization process, the octadecylamine-modified clay gave rise to a further noticeable increase in the vulcanization rate, which could be attributed to a synergetic effect between the filler and the amine. Moreover, in the presence of the organoclay, a dramatic increase in the torque value was obtained because of the formation of a higher number of crosslinks, which could be attributed to the confinement of the elastomer chains within the silicate galleries and, consequently, to better interactions between the filler and the rubber. However, no significant changes were observed in the unmodified clay composite. These results were in concordance with those obtained by DSC. In addition, the activation energy of the vulcanization process was also calculated by means of both techniques. A clear decrease in the activation energy was observed when the organoclay was added to the nanocomposite, which indicated that the layered silicate favored the processing of the elastomer.

Vulcanization Kinetics of Natural Rubber Based On Free Sulfur Determination

“…Some methods to analyze the rubber vulcanization have been performed, such as, Bideau et al [3] have used the short wave infra red irradiation, Jaunich et al [4] monitored the reaction of vulcanization using ultrasonic online, Salgueiro et al [5] used SANS, or Pazur et al [6] used NMR. DSC was used to analyze the vulcanization reaction as conducted by Chough et al [7], Manchado et al [8], and Ding et al [9]. Rheometer is one of the methods to analyze the vulcanization reaction and has been still very popular in rubber technology.…”

Rubber‐Clay Nanocomposites

“…Many data were reported in the literature, supporting these conclusions, in rubbers such as NR (hexadecyltrimethyl ammonium, octadecyltrimethyl ammonium, tetraoctyl phosphonium, triphenyl vinylbenzyl phosphonium, octadecylamine chloridrate were used as intercalants) [81][82][83][84][85][86], SBR (Mt/octadecyltrimethylamonium) [87], (NBR (octylamine; dodecylamine and octadecylamine chloridrates were the intercalants) [76]. A reduction of the activation energy for sulphur based NR crosslinking was found by using a bentonite modified with octadecylamine chloridrate [83,88].…”

“…A reduction of the activation energy for sulphur based NR crosslinking was found by using a bentonite modified with octadecylamine chloridrate [83,88]. OC could thus present a warning, as they could lead to premature scorching but, at the same time, they could present the chance of performing vulcanization reactions at lower temperatures.…”

Micro-structural evolution of rubber/clay nanocomposites with vulcanization process

“…Most previous studies about the vulcanization kinetic of RCNs indicted that addition of OMC would considerably increase curing rate and crosslinking density of various rubber compounds, including NR [24,25], ENR [26], BR [27,28], SBR [29], EAR [30], NBR [31], and NBR/SBR blend [32]. On the other hand, some studies [12,33] on EPDM/OMC systems shown that addition of OMC prolonged the optimum curing time and reduced the cross-linking density of the composites.…”