INVERSE GAS-CHROMATOGRAPHY FOR POLYMER SURFACE CHARACTERIZATION ABOVE AND BELOW TG

Inverse gas chromatographic experiments (IGC) with a styrene-butadiene rubber (SBR) as the stationary phase have been conducted at temperatures on either side of the polymer T(g) and at carrier gas flow rates up to 60 mL/min. Above the T(g) retention volumes decrease with rising carrier flow rate, attaining equilibrium values at high flow rates. The equilibrium values are interpreted as being due solely to surface interactions, calculations having shown that under these carrier gas flow rates dwell times of probe molecules at the polymer surface are too short to permit diffusion into the bulk. In this manner it is possible to use IGC for surface characterizations of polymers above their T(g). The chromatographic data also allow the maximum size of vapor molecules able to diffuse into the polymer bulk to be estimated.