Effect Of Ionization Of PA-66 Nucleator On The Crystalline And Thermal Properties Of Heterogeneous Nucleated PET

Due to the slow crystallization rate and low crystallinity of poly(ethylene terephthalate)(PET),its application in the engineering field of high-performance is greatly limited.Nucleation modification is a common method to improve the crystallization properties of PET.However,the current commercial nucleators are likely to cause PET molecular chain degradation or have poor nucleation effects.In this study,polyamide-66(PA-66)is used to prepare new ionene nucleators of Ca Cl₂–PA-66 and Zn Cl₂–PA-66 through solution ionization reactions with Ca Cl₂ and Zn Cl₂,respectively.Fourier transform infrared spectroscopy,inductively coupled plasma optical emission spectroscopy,and differential scanning calorimetry(DSC)are used to verify the success of the ionization reaction.Then,the ionene nucleators with different ion contents are used to modify PET,and the effects of various ionene nucleators on the crystalline and thermal properties of PET are investigated by DSC,polarized optical microscopy and X-ray diffraction.Studies have shown that the nucleation efficiency of the nucleators first rises and then reduces with the increase of its ion content.The optimal ion content of Ca Cl₂–PA-66and Zn Cl₂–PA-66 are 6.5 mol%and 2.6 mol%,respectively.The study also finds that the crystallization properties of PET/Zn Cl₂–PA-66 is stronger than that of PET/Ca Cl₂–PA-66.The reason may be that the coordination effect of Zn Cl₂ is stronger than that of Ca Cl₂,which leads to differences in the compatibility of the two systems.The crystallization temperature,degree of crystallinity and crystallization rate constant of PET/Zn Cl₂–PA-66 are improved by 30.2 ^oC,17.9%and 0.039,respectively,compared with PET,and the ionene nucleator can make PET crystals become finer and denser,but this has no obvious effect on the crystal form of the PET matrix.The thermal property analysis of the nucleated modified PET shows that the Vicat softening point temperature of PET/Zn Cl₂–PA-66 is 55.1 ^oC higher than that of pure PET,and their thermal decomposition temperature is basically the same,which verifies that Zn Cl₂–PA-66 not only improves the crystallity of PET,but also significantly enhances its heat resistance,but it has little effect on the thermal decomposition stability of the PET matrix.In summary,it is finally determined that the Zn Cl₂–PA-66 ionene nucleator with an ion content of 2.6 mol%has the best nucleation effect on PET.Finally,the crystalline mechanism of ionene heterogeneously nucleated PET has been explained.Due to the introduction of ionic groups,a strong ion–dipole interaction is generated on the two-phase interlayer,thereby enhancing the interfacial compatibility;the compatibilization makes the nucleus size of the nucleator dispersed phase smaller and the nucleus number density increase,thereby significantly improving the nucleation efficiency of the nucleator;but as the compatibility is further enhanced,it will improve the volume fraction of the amorphous interlayer and may cause ionic crosslinking,which in turn inhibits the nucleation rate of PET.Therefore,a nucleating agent with a moderate ion content is more conducive to improving the crystallization peroperties of PET.Adjusting the interfacial compatibility of the two phases by changing the ion content of the ionene nucleator seems to provide a new method for optimizing the nucleation efficiency of the nucleator.