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

Abstract

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°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°C and 120°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°C. The results reveal that the proposed nonconventional cure systems are able to bring down the cure temperature of CR–BIIR blend to 90°C from 150°C enabling the suitability of the materials for undersea sensor encapsulation.

Low Temperature Vulcanisation Technique for CR BIIR Blend for Encapsulation of Oceanic Sensors

“…The composition of the CR-BIIR blend in the ratio 80:20, without the curing system used is the same as used in the previous study by the same authors 18…”

Accelerated aging behavior and life prediction of low-temperature vulcanizable CR–BIIR blend based encapsulant material for undersea sensors

“…The detailed composition of the basic blend of CR and BIIR in the 80:20 ratio used for the study is given elsewhere. 6 The details of the cure systems used are given in Table 1. The cure system not only controls the processing safety and cure parameters but also decides their end properties.…”

“…4,5 Hence, the CR–BIIR blend can be used for the encapsulation of underwater sensors. 6 However, these are susceptible to aging due to external environments such as heat, oxygen, ozone, light, and mechanical stresses, etc. in addition to the seawater proximity.…”