The Application of Organic Phosphate Nucleating Agents in Polypropylene with Different Molecular Weights

Abstract

Two kinds of organic phosphate nucleating agent (NA-11 and NA-21) were used in PP with different molecular weights through the melt extrusion method. The dispersibility of the nucleating agents in PP, and the effect of the nucleating agents on the molecular weight, rheological behavior and crystallization behavior of PP were investigated. SEM and TEM analysis showed that the average radius of the dispersed particles (nucleating agents) was larger in LPP than that in HPP. The good dispersion of NA-21 also created more nucleation embryos for the adsorption of polypropylene molecules than the agglomerated NA-11. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of HPP and LPP both decreased with the addition of a nucleating agent. The rotational rheometer and capillary rheometer analysis showed that the effect of NA-21 on reducing intermolecular entanglement was more significant, whether in HPP or LPP. The addition of NA-21 had less elastic energy storage and better flow stability, and could be processed at a higher speed. Simultaneously, the relaxation time in the blends with LPP was shorter than that with HPP. It was found that the crystallinity and nucleation efficiency of HPP/nucleating agent blends increased remarkably, while there was a barely perceptible increase in LPP/nucleating agent blends.