Partition of Tert-Dodecyl Mercaptan in Systems Containing Styrene, Polystyrene and Polybutadiene.

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

e-Polymer

Año: 2007 p. 1 - 18

1618-7229

Abstract: 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 PS-rich and PB-rich 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 [1]; and then, to combine it with a polymerization model extended from that of 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.