Influence of the β-Nucleator on the Thermal and Sagging Behaviours of Polypropylene

According to the crystallization conditions, polypropylene (PP) can be crystallizedinto three forms: α-monoclinic, β-hexagonal, and γ-form. The major problem withthermoforming of PP is its narrow processing window. Due to broadening the meltingregion, β-crystal form has a significant effect on the thermoformability of PP. In this studyγ- quinacridone (Q-dye) was used as a β-nucleator agent. Three different concentrationsof Q- dye (5, 10, and 50 ppm) were mixed separately with PP by a laboratory twin screwextruder. X-ray graphs confirmed the β-nucleating effect of Q-dye obviously. Differentialscanning calorimetry (DSC) was used For evaluating of the crystallization behaviour. Bothmelting points of α - and β- crystals were seen in the samples containing Q-dye. Crystallization temperature and the rate and degree of crystallinity increase with β-nucleator concentration. Sagging tests were carried out at 170°C and it was observed that sag distance and sagging rate decreased with increasing Q-dye content.