Ultrasonic Monitoring of Ash Contents and MBTS Accelerator Mixed Nitrile Rubber during the Vulcanization Process

Nitrile-butadiene rubber, commonly known as nitrile rubber, is one of the most usable synthetic rubbers that exhibits excellent heat and oil resistance. Nitrile rubber has a variety of applications, such as manufacturing of gaskets, footwear, sponges, and so on, where natural rubbers cannot be used. This paper presents a unique method of monitoring the vulcanization process in real time for nitrile rubber mixed with varied ash content (china clay and whiting) and an MBTS (benzothiazyldisulfide) accelerator using ultrasonic nondestructive evaluation (NDE). An experimental setup includes a fully automated system for acquiring ultrasonic data that has been developed in-house. It has been found that ultrasonic velocity can distinguish between china clay and whiting content in rubber, along with monitoring the curing rate and completion of curing of rubber. The cross-link density of every test sample is calculated using the equilibrium swelling method, followed by its evaluation using ultrasonic responses.