Comparison of Nucleation Effects of Organic Phosphorous and Sorbitol Derivative Nucleating Agents in Isotactic Polypropylene

Organic phosphorous and sorbitol derivatives are two types of very effective nucleating agents for isotactic polypropylene (iPP). The effects of two kinds of organic phosphorous nucleating agents, Irgastab NA-11 and ADK NA-21, and two kinds of sorbitol derivatives, Irgaclear DM and Millad 3988, on mechanical properties and crystallization behaviors of iPP are compared in this paper. The organic phosphorous nucleating agents had better effects on mechanical properties of iPP than sorbitol derivatives, whereas the latter had better effects on transparency of iPP than the former. At the same time, the organic phosphorous nucleating agents and sorbitol derivatives had similar effects on the crystallization peak temperature (Tc) of iPP. When the concentration of nucleating agents was 0.2 wt%, compared to those of virgin iPP, the tensile strength and flexural modulus of iPP nucleated with Irgastab NA-11 and ADK NA-21 were increased by 19.35% and 17.67%, and 29.48% and 24.84%, and the haze value was decreased by 43.58% and 44.01%, respectively. On the other hand, the tensile strength and flexural modulus of iPP nucleated with Irgaclear DM and Millad 3988 were increased by 7.03% and 7.46%, and 7.20% and 11.96%, and the haze value was decreased by 51.03% and 52.23%, respectively. When the cooling rate was 10°C /min, the Tc of iPP nucleated with these four nucleating agents was increased from 118.74°C of virgin iPP to about 130°C. Meanwhile, the morphology study showed that addition of both organic phosphorous and sorbitol derivative type nucleating agents could decrease the spherulite size of iPP significantly and that sorbitol derivatives have greater effects.