Evaluation of thermal migration of ester-type plasticizers in acrylonitrile-butadiene rubbers by highly sensitive automated thermal desorption gas chromatography

A new method to evaluate thermal migration of plasticizers in acrylonitrile (AN)-butadiene rubbers was developed by use of automated thermal desorption gas chromatography (GC). A small piece of rubber sample weighing ca. 0.5 mg was subjected to thermal desorption at 260 degrees C for 15 min in an automated thermal desorption GC system under a flow of nitrogen carrier gas. The desorbed plasticizer condensed in a trap was then directly stripped at 300 degrees C for 15 min into a wide-bore fused-silica capillary separation column, programmed from 50 degrees C to 280 degrees C at a rate of 7.5 degrees C min(-1). Thus rapid and precise determination became possible for various plasticizers, such as di(2-ethylhexyl)adipate, di(2-ethylhexyl)phthalate and di(2-ethylhexyl)sebacate in samples weighing less than 1 mg taken from given depths of the rubber sheet. This highly sensitive method enabled not only depth profiling of the plasticizers in rubber samples, but also rapid estimation of the diffusion coefficients for the plasticizers in Various rubber samples with different AN content at various temperatures.