Cross-linking of carboxyl-terminated nitrile rubber with polyhedral oligomeric silsesquioxane

Glycidyl polyhedral oligomeric silsesquioxane (POSS) was used as a cross-linking agent to prepare a new organic-inorganic hybrid material from carboxyl-terminated poly(acrylonitrile-co-butadiene) (CTBN). The structure of the reacted material was characterized by Fourier transform infrared spectroscopy. Differential scanning calorimetry (DSC) at different heating rates in the presence and absence of catalyst, triphenyl phosphine (TPP), was conducted to investigate the curing kinetics. The reaction is catalyzed by the addition of TPP, and rate is maximum at higher catalyst concentrations. Different kinetic models were used to analyze the kinetic parameters. The effect of catalyst on curing process was determined by calculating the activation energy (E (a)) using Kissinger method. Dependency of E (a) with extent of conversion was monitored by different isoconversional methods. The curing mechanism of POSS-CTBN system followed autocatalytic model. Moreover, the predicted curves from the kinetic models fit well with the non-isothermal DSC curve. The E (a) of gelation obtained from rheological studies matched with that from DSC study, in league with the Flory's theory of cross-linking.