Partition of tert-dodecyl mercaptan in systems containing styrene, polystyrene, and polybutadiene. Its effect on the macromolecular characteristics of high-impact polystyrene

N. CASIS; C. LUCIANI; D. ESTENOZ; M. MARTINELLI; M. STRUMIA; G. MEIRA

E-POLYMERS

EUROPEAN POLYMER FEDERATION

Año: 2007 vol. 85 p. 1 - 18

1618-7229

This work investigates the distribution between phases of tert-dodecyl mercaptan (t-ddm) in systems containing styrene (St), polystyrene (PS), and polybutadiene (PB) with the aim of studying its effect on the molecular macrostructure of High-Impact Polystyrene (HIPS) produced via the bulk process. Experimental work involved the study of several St/PS/PB/t-ddm blends, and of 2 polymerizations of St in presence of PB (with and without t-ddm). Blends were prepared with increasing PS/St ratios to emulate monomer conversions of 7, 9, 11, 13, and 15%, employing 2 base PSs of different molar masses, and several total concentrations of t-ddm. Measurements by Proton Nuclear Magnetic Resonance (1H NMR) indicate that t-ddm is almost evenly distributed between the phases at room temperature. In addition, for samples taken along the 2 investigated polymerizations, monomer conversion, grafting efficiency, and free PS molecular weights were measured. Theoretical work involved first to model the species partitions through the Flory-Huggins theory [1]; and then, to combine such partition model with a polymerization model extended from that by Casís et al. [2]. Theoretical estimations were in good agreement with experimental determinations. Simulations suggest that t-ddm partition coefficients exhibit a weak dependence with temperature, but a strong dependence with its total concentration. Also, the combined partition/polymerization model indicates that the free PS contained in the occlusions region exhibits lower molecular weights than that in the continuous matrix.