Synthesis Of 1, 3; 2, 4-Benzylidene Sorbitol And Its Application As The Nucleating Agent Of PP

This dissertation is divided into two parts. In the first part, the third generation sorbitol-typed nucleating agent 1,3-2,4- di(3,4- dimethy- benzylidene) sorbitol (DMDBS) was synthesized and this nucleating agent was charactered, whose practical applications in the PP was researched in the second part.In the study of the synthesis of the third generation sorbitol-typed nucleating agent DMDBS, we mainly examined the influence of raw materials ratio, the category and mass of catalyst, etc on the yield of DMDBS. The results of the optimized experiment,are listed as follows: under the protection of N2, the materials are put into reactor in one portion.(the ratio of aldehyde to sorbitol is 2:1 and 2% paratoluenesulfonic acid is taken as the catalyst), and then reactor was heated slowly, refluxing for 6 hours. The reaction was quenched by sodium hydroxide solution. The raw product was washed and cyclohexane was recycled by evaporation. The raw product is refined by acetone, with the average yield of DMDBS 85%. The refined DMDBS was white and odorless. The craft was reasonable and repeatable. The purity of the refined DMDBS is above 98%, which meets the demands of nucleating agent of this type at home and abroad. We studied the influence of compounded DMDBS-nucleating agent on the mechanical and crystallization characteristics of polypropylene. And the results showed that the compounded nucleating agent can improve the toughness and the transparency. The elongation at break increased from the original 55% to 79%. by adding 0.6% nucleating agent and it improves nearly half time than pure PP. The light transmittance increased by 7.45%. The properties of PP can be obviously improved when the content of the nucleator increased from 0 to 0.6%. However, there were no more changes in terms of PP mechanical properties with nucleator contents more than 0.6%.