Abstract:

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.

Key words: polypropylene, antioxidant, non-isothermal crystallization