Effect of the nucleating agent 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol on the γ phase content of propylene/ethylene copolymer

The influence of the concentration of a nucleating agent (NA), namely 1,3:2,4-di(3,4-dimethylbenzylidene) sorbitol (DMDBS), on the γ phase content in a propylene/ethylene copolymer was investigated by means of Differential Scanning Calorimetry (DSC), Wide-Angle X-ray Diffraction (WAXD), Small-Angle X-ray Scatter (SAXS) and Polarized Optical Microscopy (POM). It was found that the nucleated cPP showed two endothermic peaks, corresponding to the melt behaviors of α and γ crystal; both α and γ crystal forms were present in each lamella within the same spherulite; the γ phase developed on the edges of α phase lamellae rather than on the less favorable DMDBS nucleating agent; the γ content in the crystallized samples increased initially with increasing DMDBS concentration and reached a maximum, then decreased with further increment of NA concentration under the non-isothermal condition. We interpreted these results in terms of competition and deposition between α and γ crystals.