Thesis (M.Sc.)--Chulalongkorn University, 2001

In this research compatibilization of polymer blends of high impact polystyrene (HIPS) and high-density polyethylene (HDPE) by a triblock polymer of styrene/ethylene-butylene/styrene (SEBS) was elucidated. The polymer blends from many ratios of HIPS and HDPE with various concentrations of SEBS was prepared. Upon the mechanical property studies, Izod impact strength and elongation at break of the blends increased with increases in SEBS contents. They increased markedly when the HDPE contents were higher than 50 wt%. Tensile strength of blends increased when the SEBS concentrations were not higher than 5 pphr. Whenever the SEBS loading were higher than 5 pphr, tensile strength decreased and the greater increment of decrease were found in blends where in the HDPE concentrations were more than 50 wt%. The log additivity rule model was applied to these blends. The blends containing the HIPS-rich phase showed the higher compatibility at the higher shear rates. Unlikewise, the blends containing the HDPE-rich phase yielded the greater compatibility at the lower shear rates. Morphology observations of the blends indicated the better compatibility of the blends with increasing SEBS concentrations. Glass transition temperature and melting temperature of the blends showed some miscibility at the HDPE contents between 90 to 50 wt% especially in the presence of high loading of SEBS. The relaxation time (T2) values from the pulsed NMR measurements revealed that both polymer blends become more compatible when the SEBS concentrations were increased. When integrating all the investigations of compatibility in comparison with the mechanical properties, it is possible to conclude that SEBS promotes a certain level of compatibilization for several ratios of HIPS/HDPE blends