Study On The Melt Crystallization Thermodynamics And Non-isothermal Crystallization Kinetics Of CHDM

1,4-Cyclohexanedimethanol(CHDM) is an important raw material for the manufacture of polyester in industry, which is widely used for modifying the physical properties of poly(ethylene terephthalate)(PET). The modification of poly(ethylene terephthalate) with CHDM has excellent chemical resistance and environmental performance. CHDM has two structure isomers,namely, trans-CHDM and cis-CHDM. The industry product of CHDM is the isomers mixture. Crystalline PCT that modified with trans-CHDM has a higher melting point than cis-CHDM, thus we hope the CHDM product which used for composing polyester has a larger percentage of trans-CHDM. As the cis-trans isomers has similar structure and the close boiling point, it is difficult to seperate CHDM through general distillation. In this paper, the melt crystallization process of CHDM was systematically studied, which can provide the basic data and theoretical instruction for the engineering design.First, we adopt analysis methods such as Gas chromatography(GC), Fourier infrared spectrometer(FT-IR), X-ray powder diffraction(PXRD) to characterize and analyze the CHDM products. We obtained the trans-CHDM characteristic peaks in spectra and the spectral band to identify CHDM cis-trans isomers.Then, we measured thermodynamic phase diagram of CHDM system by DSC and studied the solid-liquid-equilibrium by the basic equations of thermodynamics and activity coefficient method. The results show that the CHDM is a eutectic point system, and the measured results are roughly in line with the trend of the simulation of the phase diagram under the condition range.Finally, we researched the non-isothermal crystallization of trans-CHDM. By introducing different theoretical models(for example Jeziorny method, Ozawa equation, modified Ozawa model) to deal with and simulate the experimental data, we got some kinetic parameters of the non-isothermalcrystallization process of CHDM, such as Avrami index n, Ozawa exponent m.Results revealed that the crystallization of CHDM process was divided into two stages, and both the content of trans-CHDM in CHDM and the cooling rates had certain influence on crystal nucleation and growth; Jeziorny method and the modified Ozawa model not only could well describe CHDM crystallization process, but also has a certain guiding significance on the understanding of CHDM content of melt crystallization process and industrialization.