聚-4-乙基苯酚抗氧剂对聚丙烯结晶行为的影响

通过差示扫描量热仪(DSC)和X射线粉末衍射仪(XRD)研究了聚-4-乙基苯酚抗氧剂对聚丙烯结晶行为的影响。分别用Jeziorny法和Mo法处理非等温结晶动力学。同时用Friedman法和Kissinger法计算其结晶活化能。最后由结晶活化能与结晶温度的变化曲线求得Hoffman-Lauritzen参数成核速率常数(Kg)和迁移活化能(U*)值,进而求得折叠链端表面自由能(σe)和分子链段折叠功(q)。结果表明,抗氧剂的加入,使聚丙烯的结晶峰温度向低温区移动,结晶半峰宽变大,半结晶时间(t1/2)增大,Jeziorny法所得的结晶速率常数(Z)降低,Mo法所得反映结晶速率快慢的参数F(T)提高,在相同结晶转化率下,结晶活化能负值变小。Hoffman-Lauritzen参数Kg、U*、σe和q值均增大。所有变化均表明聚-4-乙基苯酚抗氧剂对PP的结晶有抑制作用。

Effect of Poly(4-ethylphenol) Antioxidant on Non-isothermal Crystallization Behavior of Polypropylene

The effect of poly(4-ethylphenol) antioxidant on the non-isothermal crystallization behavior of polypropylene(PP) was studied by differential scanning calorimetry(DSC) and X-ray powder diffractometry(XRD), respectively. The non-isothermal crystallization kinetics was studied by the Jeziorny method and the Mo method, and the activation energy was calculated by the Friedman method and the Kissinger method at the same time. The Hoffman-Lauritzen parameters of nucleation rate constant(K_g) and molecular diffusion activation energy(U^*) are obtained from the relation of crystallization activity energy and average crystallization temperatures for PP and PP with (4-ethylphenol) antioxidant(PP-A) samples, and the fold surface free energy(σ_e) and the work of chain folding per molecule(q) are then calculated. The results show that the crystallization peak of PP-A moves to a lower temperature with the addition of antioxidant, and the crystallization half-peak width becomes broader, the semi-crystallization(t_1/2) and the parameter F(T) reflecting the value of cooling rate chosen at unit crystallization time obtained by Mo method increase while the crystallization rate(Z) decreases. The negative crystallization activity energy becomes smaller at the same crystallization conversion rate, and the Hoffman-Lauritzen parameters of K_g, U^*, σ_e and q increase. All the results indicate that poly(4-ethylphenol) antioxidant inhibits the crystallization of PP.