Influence of chemical structures of bisamide nucleating agents on the crystallization behavior and properties of isotactic polypropylene

• Published in: Journal of thermal analysis and calorimetry 2023-03, Vol.148 (6), p.2417-2428
• Main Authors: Xiang, Jiao, Li, Yan, Zhong, Jin-Rong, Lu, Cui-Hong, Zhang, Yue-Fei
• Format: Article
• Language: English
• Subjects: Analytical Chemistry; Calorimetry; Chemistry; Chemistry and Materials Science; Crystallization; Differential scanning calorimetry; Epitaxial growth; Epitaxy; Inorganic Chemistry; Isotacticity; Lattice matching; Measurement Science and Instrumentation; Mechanical properties; Nucleation; Physical Chemistry; Polymer Sciences; Polypropylene; Stiffness; Unit cell
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-022-11874-8

In this work, the applicability of a series of bisamide compounds (DCDC-R-n/R) with different structures as nucleating agents for isotactic polypropylene (iPP) was investigated. The effect of these nucleating agents on crystallization and melting behavior of iPP was analyzed using differential scanning calorimetry (DSC), results revealing a clear impact on the nucleus density in iPP. It is shown that the nucleation effect is better when the carbon number of the methylene chain in the intermediate structure is even rather than odd. In addition, the effect is stronger when the side substitution is a cyclic group rather than a branched group, while bisamide nucleating agents containing a cyclic intermediate group tends to form more β-crystals in iPP. The crystallization peak temperature ( T c ) of iPP can be increased by more than 10 °C when the addition amount of DCDA-Cy-4, DCDA-Cy-6 and DCDA-Cp-6 is 0.3 mass%. The analysis of the iPP mechanical properties shows that DCDA-Cy-4 and DCDA-Cy-6 greatly improve its stiffness, while DCDA-Cy-Cy and DCDA-Cy- p Ph have an excellent toughening effect on iPP as a result of β -phase. The structure-nucleation effect relationship of bisamide compounds was confirmed by further tests using wide-angle X-ray diffractometer (WAXD) and Materials Studio, showing good agreement with DSC data. Furthermore, the nucleation mechanism of these nucleating agents in iPP was investigated by using the lattice matching theory. The unit cell parameters of nucleating agents and iPP match well, indicating that these nucleating agents can induce epitaxial growth of iPP on their surface.