Kinetics of sulfur vulcanization of NR, BR, SBR, and their blends using a rheometer and DSC

Abstract

SYNOPSISThe relationship between vulcanization reactivity and chemical structure was studied using a rheometer and DSC for natural rubber (SMR 5CV), butadiene rubber (BR Ol), styrenebutadiene rubber (SBR 1501), and their blends. The overall rate of the vulcanization was SBR > BR > NR. This was the same trend as the number of allylic hydrogens in the statistical repeat unit of the rubber used. Because the corresponding rate constant for an allylic hydrogen was very similar regardless of the rubbers, it was found that the vulcanization condition for a compounded rubber could be predicted by comparing the number of allylic hydrogens. The activation energy of the vulcanization was calculated for each rubber also.

Use of TBzTD as Noncarcinogenic Accelerator for ENR/SiO2 Nanocomposites: Cured Characteristics, Mechanical Properties, Thermal Behaviors, and Oil Resistance

“…The sulfur vulcanization with unsaturated rubbers generally occurred through a free radical reaction initiated by accelerator. The resulting sulfur radicals further attack reactive allylic hydrogens in rubber chains to form sulfur crosslinks, and so the vulcanization depends upon the number of the allylic hydrogens [28]. s2 is the time required for the torque value to increase two units from L , which corresponds to the premature vulcanization of rubber compound, while t 90 is the vulcanization time for optimum cure torque [1,3].…”

“…As can be seen, NR exhibited shorter s2 and t 90 than ENR 40 after being cured under the same condition. This is because NR possessed a higher level of unsaturation and reactive sites than ENR 40, and so the crosslinks started and reached the optimum cure torque in a shorter time [1,18,28]. Moreover, the high content of benzylthiuram substituents in the TBzTD accelerator may provide a steric hindrance to the limited crosslink sites of the ENR 40.…”

Efeito do Óleo de Linhaça e do Óleo de Amendoim sobre a Vulcanização da Borracha Natural (Nr). Parte I: Modelo Generalizado

“…Assumindo que os valores de torque estão diretamente relacionados à densidade de ligações cruzadas e que a cinética é de primeira ordem, uma expressão pode ser escrita em termos de torque [13,14] :…”

“…A combinação da equação de Arrhenius com Equação 1 gera uma conveniente expressão para o cálculo da energia de ativação aparente para o processo de vulcanização. Utilizando-se dados do reômetro a partir de corridas isotérmicas, a diferentes temperaturas, tem-se [13] : Quando se analisa a estrutura dos ácidos graxos envolvidos nesta investigação, a explicação para as diferenças nos valores de k podem ser avaliados. As cadeias de ácidos graxos saturados podem adotar várias conformações que tendem a ser totalmente estendidas, pois isto minimiza as repulsões estéricas entre os grupos metilenos vizinhos.…”

The Effect of Rubber Mixing Process on the Curing Characteristics of Natural Rubber

“…For example, Bideau et al [1] employed a short-wave infrared irradiation, Jaunich et al [2] monitored the vulcanization reaction by using online ultrasonic, Salgueiro et al [3] used SANS and Pazur et al [4] used NMR. Even some utilized DSC to observe the vulcanization reaction including Chough et al [5], Manchado et al [6], and Ding et al [7]. Although a number of methods have been applied to observe the vulcanization reaction, rheometer is still used in industries and research centers, even in Universities as carried out by Cotten [8], Gerspacher et al [9], Mahalling et al [10], Choi [11], Choi et al [12], and Wang et al [13].…”