Isothermal crystallization behavior and melting characteristics of injection sample of nucleated polypropylene

Abstract

The isothermal crystallization behavior and melting characteristics of pure polypropylene (PP) and PPs nucleated with a phosphate nucleating agent (A) and a sorbitol derivative (D) have been studied by differential scanning calorimetry (DSC). Compared with pure PP, nucleated PPs show a shorter half-times of crystallization. Dependence of crystallization rate of nucleated PP on the crystallization temperature is stronger than that of pure PP at the higher crystallization temperature, whereas the opposite results are obtained at the lower crystallization temperature. Addition of nucleating agent shifts the temperature at the deviation from the baseline of DSC melting curve, T m o , and the temperature at the completion of melting, T m f , to higher temperatures, indicating that nucleated PPs exhibit a higher perfection of PP crystals. A shoulder peak in the high temperature range of melting peak of nucleated PP and a wider low temperature region in the melting peak of pure PP are observed. Obviously, PP and nucleated PPs form different distribution of crystal perfection in the isothermal crystallization process. According to the half-time of crystallization, nucleating agent A is more effective than D.

Analysis of the isothermal crystallization of isotactic polypropylene nucleated with sorbitol derivatives

“…There is little kinetic data available in the case of sorbitol derivatives, and as shown as an example in Figure 6(b) our results for the behavior of the global rate constant as a function of the crystallization rate were compared with some values described in the literature 9,23 for three different sorbitol derivatives at concentrations of 0.1 and 0.3 wt%. The results described by Kim et al 24 in the nucleation of iPP with p-Cl-p-methyldibenzylidine sorbitol (EC4) and bis(pethylbenzylidine sorbitol) (NC4) showed saturation effects in the nucleating activity at concentrations of 0.2-0.3% due to the fact that the number of effective nuclei was reduced at higher concentrations because of particle agglomeration.…”

Influence of nucleating agent on the crystallization kinetics and morphology of polypropylene

“…They are also used to accelerate polypropylene crystallization kinetics, reducing injection molding cycle times and, by consequence, reducing production costs. The nucleating agent efficiency depends on its particle size, morphology, chemical structure and behavior when incorporated into the polymer [2] . In order to maximize the nucleation efficiency and reach the best cost benefit ratio, nucleating agents evolved and there are various types in the market, from different chemical families.…”

Comparative investigation on crystallization conditions dependence of polymorphs composition for β‐nucleated propylene/ethylene copolymer and propylene homopolymer

“…In principle, the overall crystallization rate is nucleation-controlled at high temperatures and growth controlled at low temperatures. 49,50 In other words, within certain temperature range, the effect of the present nucleating is more obvious under higher crystallization temperatures where the self nucleation of PP is difficult and the nucleating agents could offer large amounts of heterogeneous nuclei. In b nucleated PPR system, the comonomer defects which favors the formation of c form largely suppressed the nucleation ability of b nucleating agent that induces the formation of the b form.…”