Influence of different crystallization modification methods on crystallization properties of PET
Three types of modified polyethylene terephthalate(PET)were prepared by copolymerization modification using pu-rified terephthalic acid and ethylene glycol as raw materials separately incorporated with flexible monomer polytetrahydrofuran(PTMEG),organic nucleating agent sodium oleate and inorganic nucleating agent silica.The crystallization properties of the three modified PET prepared were studied by differential scanning calorimetry.And the non isothermal crystallization kinetics of the modified PET were analyzed by Jeziorny method.The results showed that compared with unmodified PET,the cold crystalli-zation peak of the three modified PET shifted towards low temperatures,and the melt crystallization peak shifted towards high temperatures;all three modification methods could improve the crystallization properties of PET and accelerate the crystallization process;the Avrami index(n)and crystallization rate constant(Zc)of the three modified PET both increased,and the cold crystallization rate also increased during the cold crystallization process;the n and Zc of the three modified PET increased,and the half crystallization time(t1/2)decreased during the melt crystallization process,the n of inorganic nucleating agent modified PET was above 4,which was higher than those of PTMEG modified PET and organic nucleating agent modified PET,and t1/2 was shorter than half of the t1/2 of unmodified PET.
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