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.
Highlights
It is well-documented that polypropylene (PP) has excellent properties, such as being non-toxic, odorless, low density and easy to process, as well as having a high chemical resistance
nucleating agent (NA)-21 provides an excellent clarity at lower molding temperatures and has a high nucleation efficiency and, as a result, is popular in industrial applications [32].The works mentioned above have provided a firm foundation for the study of the crystallization properties of the NA/PP blends, and most of the research was only about low melt index PP
We describe some extraordinary findings on the change in viscosity when adding NA-11 and NA-21 into the different molecular weights of the PP matrix
Summary
It is well-documented that polypropylene (PP) has excellent properties, such as being non-toxic, odorless, low density and easy to process, as well as having a high chemical resistance. NA-21 provides an excellent clarity at lower molding temperatures and has a high nucleation efficiency and, as a result, is popular in industrial applications [32].The works mentioned above have provided a firm foundation for the study of the crystallization properties of the NA/PP blends, and most of the research was only about low melt index PP. The effect of organic phosphate NAs on rheological behavior, change of molecular weight and crystallization properties of PP with different molecular weights were systematic studied. Our contribution to the study of NAs mixed with PP was to use rheological methods as a means of characterizing the influence of NAs on the intermolecular interactions, molecular chain motion and crystallization behavior of polymer macromolecules. All the samples were dissolved in trichlorobenzene (TCB) at 150 ◦C
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