Transport behavior of R134a refrigerant through rubber composites

Abstract

The transport behavior of commercial R134a (1, 1,1,2-tetrafuoroethane) refrigerant including its permeability, adsorption, and diffusion through rubber composites were investigated. Butadiene-acrylonitrile rubber (NBR), brominated butyl rubber (BIIR), and epichlorohydrin rubber (ECO) were used as a matrix, while silica, carbon black, mica sheet, and graphite were used as fillers in the present study. The effects of rubber structure and geometry, surface polarity, as well as loading of filler on transport behavior were studied to correlate transport parameters with the rubber structure and filler nature. The R134a permeation in rubber composites was largely dominated by diffusion rather than solubility. The polarities of rubber and filler played dominant roles in determining the solubility, whereas the structure of rubber and the shape and loading of filler exerted a stronger effect on diffusion than solubility. Nonpolar and layered graphite-filled BIIR rubber composites showed the lowest permeability to R134a. Additionally, shell-like free volume theory was applied to reasonably explain R134a transport behavior.