Rubber vulcanisation method for FBG sensors integration

Abstract

This paper presents the experimental analysis of the vulcanisation process of nitrile rubbers for the manufacture of diaphragms used in pressure sensors based on fibre Bragg gratings (FBGs). To investigate the chemical degradation of the vulcanisation process, diaphragms were created utilising various vulcanisation parameters such as temperature, curing time, and rubber thickness. Subsequently, the diaphragm surfaces were analysed by digital macrography, quantifying the degraded area and loading tests to verify the rigidity of vulcanised diaphragms. Also, FBG sensors were incorporated into the diaphragms using different thickness parameters to analyse the sensitivity through pressure tests. Diaphragms vulcanised at 125 °C showed smaller areas of average degradation, 17.5%, 14.5% and 11.0% for diaphragms with rubber thicknesses of 0.5 mm, 1.0 mm and 1.5 mm, respectively. The stiffness of diaphragms vulcanised at 150 °C was higher than that of diaphragms vulcanised at 125 °C, corresponding to 36.69N/mm, 45.25N/mm and 78.29N/mm for rubber thicknesses of 0.5 mm, 1.0 mm and 1.5 mm, concluding that diaphragms with the greater degraded area have less elasticity. Pressure tests with FBGs built into the diaphragms showed high wavelength sensitivity in diaphragms vulcanised at 125 °C and with thicknesses of 0.5 mm, corresponding to 39.08 pm/kPa. Finally, it is possible to have the impact of variables in the vulcanisation processes. In addition, it is possible to align the sensitivity of pressure sensors with FBGs with the vulcanisation parameters, allowing for a more accurate choice of process variables with better responses.