Comparative evaluation of oil resistance, dielectric properties, AC conductivity, and transport properties of nitrile rubber and chlorinated nitrile rubber

Abstract

Nitrile rubber (NBR) has been extensively used in high oil resistance application such as in automotive seals and gaskets. Due to the poor mechanical strength of NBR, the performance of these products undergoes deterioration when it is in contact with hot oils and solvents. The aim of the present work is to investigate the molecular transport of petroleum fuels and oil through chlorinated NBR (Cl-NBR) with respect to different contents of chlorine. It also focuses on the effect of chlorine content on the alternating current (AC) conductivity and dielectric properties of Cl-NBR for flexible electronic applications. The transport characteristics of petroleum fuels through the NBR and Cl-NBR membranes have been studied by a simple sorption gravimetric analysis in the temperature range 27–50°C. The diffusion results have been explained in terms of the size of liquid molecules and the diffusion mechanism was found to follow the anomalous trend. The diffusion, sorption, solvent uptake, and permeation constants were investigated and were found to decrease with increase in the level of chlorine content in NBR matrix. The activation energy for diffusion and permeation processes were increased and reached maximum value for Cl-NBR (22% Cl content). The oil resistance property of Cl-NBR was significantly higher than pure NBR. The swelling of Cl-NBR in ASTM oil was three times lower than NBR. The electrical conductivity and dielectric properties of NBR was found to be increased with the increase in chlorine content of NBR. NBR showed the AC conductivity value of 7.24 S cm−1 at 106 Hz, while the Cl-NBR with 24% chlorine showed the conductivity value of 4.69 S cm−1. The higher AC conductivity and dielectric properties, solvent, and oil resistance of Cl-NBR than that of NBR suggests that the Cl-NBR can be used as multifunctional materials for flexible nano-electronic devices and high-performance oil-resistant applications.