Abstract:

The β⁃form crystallization⁃modified polypropylene （PP） was prepared through melt blending with homopolymerization⁃type PP⁃700+ as a matrix resin and 2，6⁃benzenedicarboxamide （TMB⁃5） as a β⁃form nucleating agent. The effects of TMB⁃5 on the application performance and crystallization behavior of the modified PP were analyzed by using polarizing microscope， differential scanning calorimeter， universal testing machine， digital impact testing machine， and heat deflection temperature tester. The results indicated that the α⁃form crystal of PP⁃700+ were gradually transformed to the β⁃form ones through induction by the TMB⁃5 nucleating agent. With an increase in the addition amount of TMB⁃5， the content of the β⁃form crystals， crystallization temperature and crystallization rate of the modified PP gradually increased. When 0.2 wt.% TMB⁃5 was incorporated into the PP⁃700+ matrix， the content of the β⁃form crystals in the modified PP increased to 84.9 %. As a result， its tensile strength， flexural modulus， and flexural strength were increased by 4.5 %， 14.6 %， and 13 %， respectively. However， there was no change in the impact strength. The modified PP obtained an increase in the impact strength by 9.8 % for the cantilever beam mode and by 5.9 % for the Charpy beam mode， and its heat deflection temperature was increased by 42.13 ℃. These results ensure PP⁃700+ obtain a wider application range. The modified PP developed in this work is especially suitable for the products that need to be used or sterilized at high temperature， such as plastic hot drink cups， microwave cookers， baby bottles， and disposable lunch boxes.

Key words: polypropylene, nucleating agent, mechanical property, crystallization behavior, heat deflection temperature