Crystallization kinetics of ATPU grafted polypropylene

A melt-grafting approach was employed to prepare a novel functional PP (FPP)-amino-terminated polyurethane grafted polypropylene (PP-g-ATPU). The isothermal crystallization kinetics were characterized using spectral depolariscope. The results showed that at a low dosage (< 2.0 wt.%) ATPU acted as a heterogeneous nucleation agent during the crystallization of PP/FPP blends. However, when the content of ATPU reached 2.0 wt.% or higher, ATPU deteriorated the crystallization of PP or PP/FPP blends. The Avrami exponent n between PP and PP/FPP suggested that the isothermal crystallization kinetics of PP/FPP blends followed a three-dimensional growth via heterogeneous nucleation. Moreover, the non-isothermal crystallization kinetics of PP and PP/FPP were investigated by differential scanning calorimetry (DSC) with various cooling rate. The Avrami analysis modified by Mandelkern, Ozawa method and a method combined with Avrami and Ozawa equations were employed to describe the non-isothermal crystallization kinetics of samples. The difference of kinetics indicated that non-isothermal crystallization corresponded to tridimensional growth with heterogeneous nucleation. The values of t1/2, Zc, Zt, F(T) and K(T) showed that the crystallization rate of PP/FPP blends were faster than that of pure PP at a given cooling rate.