چكيده لاتين :
The non-isothermal crystallization kinetics of pure polypropylene (PP) and AB3
hyper-branched polymer (HBP)/PP blends (with 5% HBP content) were investigated
with various cooling rates by differential scanning calorimetry (DSC)
method. The Avrami analysis modified by Mandelkern and a method combined with
Avrami and Ozawa equations were employed to describe the non-isothermal crystallization
kinetics of the samples. The conclusion showed that at the same cooling rate,
hyper-branched polymer could accelerate crystallization effectively. Furthermore, in the
blends, the crystallization rate decreased when the higher molecular weight of HBP
was added. An increase in the Avrami exponent showed that the addition of HBP influenced
the mechanism of nucleation and the growth of PP crystallites. The possible reason
and explanation could be attributed to the fractal structure of hyper-branched polymer
which has an influence on the diffusion mode of crystallizable segments towards
the growing nuclei. The polarized micrographs showed that the number of effective
nuclei increased obviously in the HBP/PP blends where, HBP acts as a heterogeneous
nucleation agent during the crystallization of the blends. In addition, the activation energy
of crystallization was also obtained according to the Kissinger method and the
results showed that the crystallization activation energy decreased remarkably in
HBP/PP blends.
