3.4 Cure properties
Scorch time (ts1) and optimum cure time (tc90) of the compounds are shown in Fig. 7(a) and (b), respectively. Both scorch and optimum cure times of the compounds are prolonged when ENR contents and mole% of epoxide are increased. This is might be due to the high polarities of ENR and silica which interfere with the vulcanization. Even though part of the silanol groups are assumed to have interacted with epoxide groups, the remaining free silanol groups as well as free epoxide groups can possibly form hydrogen bonds with polar accelerators, causing accelerator adsorption on the polar surface. In addition, due to the polarity difference between NR and ENR, the more polar curatives can migrate into the ENR phase, and so cause a delay of the vulcanization reaction in the NR matrix. For the silica filled-compound with TESPT, because TESPT itself can act as sulfur donor and optimized mixing conditions were employed to ensure a good silanization reaction, the compound therefore displays shorter scorch and cure times.
3.4 Cure propertiesScorch time (ts1) and optimum cure time (tc90) of the compounds are shown in Fig. 7(a) and (b), respectively. Both scorch and optimum cure times of the compounds are prolonged when ENR contents and mole% of epoxide are increased. This is might be due to the high polarities of ENR and silica which interfere with the vulcanization. Even though part of the silanol groups are assumed to have interacted with epoxide groups, the remaining free silanol groups as well as free epoxide groups can possibly form hydrogen bonds with polar accelerators, causing accelerator adsorption on the polar surface. In addition, due to the polarity difference between NR and ENR, the more polar curatives can migrate into the ENR phase, and so cause a delay of the vulcanization reaction in the NR matrix. For the silica filled-compound with TESPT, because TESPT itself can act as sulfur donor and optimized mixing conditions were employed to ensure a good silanization reaction, the compound therefore displays shorter scorch and cure times.
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