Influence of benzoic acid on thermal, crystallization and mechanical properties of isotactic polypropylene under irradiation

Degree of super-cooling is denoted by the temperature difference between the melting temperature of the polymer T-m, and peak crystallization temperature T-p. Upon addition of progressively increasing amounts of benzoic acid (BA) to isotactic polypropylene {(is)-PP}, the degree of super-cooling was found to decrease, which leads to considerable reduction in moulding cycle time and savings in production cost. Haze % was found to progressively decrease with the corresponding increase in the amount of benzoic acid in (is)-PP, resulting in much improved transparency of the (is)-PP-benzoic acid blends. Irradiation to an absorbed dose of 25 kGy affected the transparency of blends slightly. Thermogravimetric analysis of (is)-PP-BA blends showed that there is no adverse effect on thermal stability of the polypropylene. Also, the irradiation of (is)-PP-BA blends did not bring about any significant changes in their thermal stability. (is)-PP-BA blends demonstrated, in general, improved tensile strength when compared to pure (is)-PP. Moreover, no significant detrimental influence of irradiation was observed on the tensile strength of (is)-PP-BA blends. (C) 1999 Elsevier Science B.V. All rights reserved.