The nucleation effect of self-dispersed β-nucleating agent in ethylene-propylene block copolymerized polypropylene

The problem of agglomeration and poor dispersion results in the low nucleation efficiency of β-nucleating agent (β-NA) in polypropylene. In this paper, a self-dispersed β-NA (Adi-Zn) was prepared in situ (IS) by adding adipic acid and zinc oxide at equimolar ratio in PPB powder during extrusion. The results showed that the nucleation efficiency of Adi-Zn (IS) was better than the direct addition of Adi-Zn. The impact strength of PPB nucleated with 0.05 wt% Adi-Zn (IS) was 25% higher than that with the same additive amount of Adi-Zn. Also, the β-crystal content (kβ value) almost reached 1. Crystallization temperature of PPB nucleated with Adi-Zn (IS) was slightly increased compared with that of Adi-Zn. The reaction mechanism of Adi-Zn (IS) was explored by Fourier transform infrared spectroscopy (FTIR). The results showed that adipic acid and zinc oxide generated zinc adipate, and zinc adipate acted as β-NA during the crystallization of PPB. By means of energy dispersive X-ray (EDX) analysis and transmission electron microscopy (TEM), the reason for the good dispersion of in situ synthetic method was confirmed, which further leads to good nucleation efficiency of Adi-Zn (IS).