Study On Synthesis Process Of Dibenzylidene Sorbitol And Its Application As The Nucleating Agent Of Polypropylene

Synthesis technology and the effects of the nucleating agents, dibenzylidene sorbitol (DBS) and its derivatives on the properties of transparent polypropylene were investigated in this thesis. The research works were focused on the influence factors of the feed compositions and the reaction conditions, such as temperature, time and stirring velocity.The nucleating agents were synthesized from the condensation reaction of sorbitol and benzaldehyde by the catalysis of an acid. During the experiments, the optimum reaction conditions were that the molecular ratio of sorbitol and benzaldehyde was 1: 2 and the reaction temperature was 75℃and the reaction time was 4 hours. Under the above conditions, the yield of the sorbitol was 98.3%, and its purity was 99.5%.The structural analysis and the melting point measurement showed that the quality and purity of the produced DBS by Lanzhou Petrochemical Institute could compete with the product of the corresponding Japan corporations. This indicates the production level of DBS in the former catch up with the international ones.To investigate the effects of DBS on the properties of polyolefin product, the transparent polypropylene was made by the doping of DBS. The testing results showed that the cloud point was 12.8% and the transparency of the polypropylene could achieve 80% when 0.15-0.25% of DBS was doped. It was also found that the doping of DBS effectively increased the heat-proof temperature and the rigidity by 10 oC and 12%, respectively.