Low-temperature vulcanizable chloroprene rubber-bromobutyl rubber blend for encapsulation of undersea sensors: Nonconventional cure systems and reaction kinetics

摘要

Blends of chloroprene rubber (CR) and bromobutyl rubber (BIIR) are used in making the undersea sensors watertight by a process of encapsulation. The encapsulation process is conventionally done at high temperature approximately 150 degrees C and above using high-temperature vulcanization (HTV). However, the new class of acoustic sensors like polyvinilidenefluride (PVDF) and thin film PZT are highly temperature sensitive and fragile in nature and hence they require low-temperature vulcanization (LTV) process to avoid damages and protect their full functionalities. However, conventional cure systems are not adoptable in LTV process and hence there is a need for the search of alternate cure systems. Not much work has been reported in this area. This article reports a nonconventional cure system vulcanizable with LTV and the associated reaction kinetics for a commonly used CR-BIIR blend for encapsulation of undersea sensors. Formulations have been attempted with cure systems based on red lead (Pb3O4) and zinc oxide (ZnO) for CR-BIIR blend in 80:20 weight ratio, instead of zinc oxide, magnesium oxide, and ethylene thiourea system, which are conventionally used in HTV. The cure parameters at low temperature between 70 degrees C and 120 degrees C and the activation energy for cure reactions (E (a)) were estimated using MDR 2000 rheometer. Essential prerequisites like water resistance, electrical resistivity, and physicomechanical properties for sensor application are qualitatively analyzed for the blend cured at 90 degrees C. The results reveal that the proposed nonconventional cure systems are able to bring down the cure temperature of CR-BIIR blend to 90 degrees C from 150 degrees C enabling the suitability of the materials for undersea sensor encapsulation.