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

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 beta-crystals in iPP. The crystallization peak temperature ( Tc) of iPP can be increased by more than 10 degrees 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-pPh have an excellent toughening effect on iPP as a result of beta-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.

Automated summary

This study investigates the applicability of different structural bisamide compounds as nucleating agents for iPP. DSC analysis shows that these agents have a clear impact on nucleus density in iPP, with better nucleation effect seen with even carbon numbers and cyclic side substitution. Further tests using WAXD and Materials Studio confirm the structure-nucleation effect relationship, while lattice matching theory suggests that the nucleating agents induce epitaxial growth of iPP on their surface.