Predictive power in oil resistance of fluororubber and fluorosilicone rubbers based on three-dimensional solubility parameter theory

Abstract

Equilibrium swelling test was employed to determine the swelling responses of Fluororubber (FKM) and Fluorosilicone Rubber (FVMQ) in different types of solvents, and the one-dimensional solubility parameters of FKM and FVMQ were obtained with a range of 17–25 MPa1/2 and 16–20 MPa1/2 respectively. It was attempted to calculate the three-dimensional solubility parameters (HSP) of FKM and FVMQ by using a professional computer software, and a new type of bio-fuel, represented by biodiesel, was further selected as an object in this work to investigate its swellability. Flory-Huggins interaction parameter (χHSP) between FKM, FVMQ and each solvents used in this work was calculated by HSP values, and the results turned out that the swelling ratio (q) decreased with increasing χHSP value. By mathematical fitting, two functional relationships between q and χHSP for FKM and FVMQ were achieved to predict the swelling properties of rubber in fluids. The increasing use of biodiesel with their effect on rubber materials has become an important topic of industrial research. The second components, including ethanol and ethylene glycol, were added into biodiesel with the purpose of cost reduction, which however might cause a critical increase of rubber swelling. One of the possible applications of χHSP values is the prediction or explanation of swelling behavior. Therein, χHSP values between FKM, FVMQ and biodiesel/additive blends were calculated and found that χHSP firstly decreased and then increased with increase of the additive (ethanol and ethylene glycol) content. Taking advantage of this tendency one can predict the swelling properties of rubber products in the biodiesel blends and provide an important reference for such applications in liquid medium.