In¯uence of benzoic acid on thermal, crystallization and mechanical properties of isotactic polypropylene under irradiation Shamshad Ahmed, A.A. Basfar * Institute of Atomic Energy Research, King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442, Saudi Arabia Abstract Degree of super-cooling is denoted by the temperature dierence 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 aected the transparency of blends slightly. Thermogravimetric analysis of (is)-PP-BA blends showed that there is no adverse eect on thermal stability of the polypropylene. Also, the irradiation of (is)-PP-BA blends did not bring about any signi®cant changes in their thermal stability. (is)-PP-BA blends demonstrated, in general, improved tensile strength when compared to pure (is)-PP. Moreover, no signi®cant detrimental in¯uence of irradiation was observed on the tensile strength of (is)-PP-BA blends. Ó 1999 Elsevier Science B.V. All rights reserved. Keywords: c-Irradiation; (is)-Polypropylene; Benzoic acid; Thermo-mechanical; Crystallization 1. Introduction The addition of nucleating agents changes polymerÕs crystallization temperature, spherulite size, density, clarity and tensile properties [1,2]. The in¯uence of addition of the nucleating agent (NA), t-(butyl) benzoic aluminium on crystalliza- tion parameters of a polypropylene (random) co- polymer containing 6% ethylene (PP-ran-Ethylene) was investigated by Shamshad and Ruimin [3]. Degree of super-cooling was found to decrease progressively with corresponding increase in the amount of the NA. Dongyuan et al. [4] reported that PP-benzoic acid composites have lower ulti- mate deformation, when compared with unirradi- ated samples. Kadir and coworkers [5] investigated the in¯uence of t-(butyl) benzoic aluminium on the radiation stability of polypropylene having dier- ent molecular weights, and reported that the polypropylenes with the nucleating agent are less stable during radiation than polypropylene with- out nucleating agent, especially low molecular weight ones. In this work, the in¯uence of adding Nuclear Instruments and Methods in Physics Research B 151 (1999) 169±173 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +4883555; fax: +4388756. 0168-583X/99/$ ± see front matter Ó 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 0 8 1 - 6