The effects of alkali dehydroabietate on the crystallization process of polypropylene

The crystallization process of polypropylene (PP) with addition of a new kind of nucleating agent, alkali dehydroabietate, was studied. Two nucleated PP samples, PP–Nu–K and PP–Nu–Na, were used as matrices to monitor kinetics of crystallization process from the melt by differential scanning calorimeter and scanning electron microscope. Alkali dehydroabietate shortens crystallization half time t1/2, and at 129°C, t1/2 was 410, 174, and 29 s for pure PP, PP–Nu–K, and PP–Nu–Na, respectively. At the same time, the fold surface energy σe of the developing crystals, however, increased and σe was 0.172 J/m2 for pure PP, 0.183 J/m2 for PP–Nu–K, and 0.202 J/m2 for PP–Nu–Na. The increase in σe suggests nucleated PP having a smaller rate of crystal growth. SEM photographs show a much larger number of crystallization nuclei in PP–Nu–Na than in pure PP. The average volume of spherulites in pure PP is far greater than that in PP–Nu–Na. This indicates that alkali dehydroabietate can greatly increase the rate of crystallization of nucleated PP.