Pilot System Utilizing Electrical Properties to Monitor Rubber Vulcanization

Abstract

An in situ rubber cure monitoring system (RCMS) has been developed based on the measurement of electrical properties to monitor the vulcanization progress. The sensors are connected to an LCR meter and measured the changes in the capacitance and conductance of rubber during vulcanization in the compression mold. The parameters are investigated in this study including, the effect of frequency, vulcanization temperatures, vulcanization systems and carbon black contents. The scorch time, optimum cure time, degree of cure, and the cure rate from a moving die rheometer (MDR) and RCMS methods were compared. The results show that capacitance during curing correlated with the time profile of torque from MDR, which the frequency at 5 kHz is suitable for monitoring the progress of natural rubber vulcanization. Moreover, the decrease in the minimum torque, maximum torque, delta torque, scorch time, and optimum cure time was observed with increasing vulcanization temperature. Torque and capacitance showed a close correlation at all cure temperatures. A linear correlation of optimum cure time obtained from RCMS and MDR with different vulcanization temperatures was achieved. The vulcanization system and type of curing agent have affected the changes of the torque and the capacitance during the vulcanization process.The RCMS can be used to indicates the scorch time and optimum cure time for both sulfur and peroxide vulcanization systems. In the case of using carbon black no more than 30 phr, RCMS can monitor the rubber vulcanization. Which supports the potential of RCMS for real-time determination of the optimum cure time during the vulcanization of natural rubber by compression molding, which is a challenge in the rubber industry.