Grafting Efficiency in High-Impact Polystyrene by SEC Combined with Theoretical Predictions from a Polymerization-SEC Model

Abstract

In high-impact polystyrene (HIPS), the grafting efficiency (GE) is the mass of grafted styrene divided by the total mass of polymerized styrene. The GE along a prepolymerization was determined from the UV size exclusion chromatogram of the total polymer. The UV sensor at 254 nm "sees" only the free and grafted polystyrene (PS) chains, but not the polybutadiene (PB) chains. The data processing involves deconvoluting the UV chromatogram into the chromatograms of the free PS and grafted PS by means of polymerization-SEC model. The GE was determined after adjusting (by trial-and-3error) the predicted UV chromatogram to the measurement. A single adjustment parameter was used: the ratio between the rate of initiation to the monomer and the rate of initiation to the rubber. The method is quick and accurate, and the estimates were verified by solvent extraction-gravimetry. It is also possible to estimate the GE by deconvolution of the differential refractometer chromatogram. However, in this case a detector calibration is required, and the results are less accurate than when employing the UV sensor.