Interaction of self-nucleation and the addition of a nucleating agent on the crystallization behavior of isotactic polypropylene

The relationship between heterogeneous or homogeneous nucleation and self-n ucleation of polypropylene (PP) and PP nucleated by an organic phosphate sa lt (PPA) was studied by DSC. For pure PP, it homogeneously nucleated during cooling after melting at the selected temperature (T-s) of 170-200 degrees C for 3 min, but at the T-s of 160-168 degreesC self-nucleation occured; PP A only nucleated heterogeneously at the T-s of 168-200 degreesC, and there existed self nucleation at the T-s of 160-168 degreesC. The double melting peaks of PP and PPA at the T-s of 162 degreesC were observed. Once the self -nucleation occurred, the change of the crystallization temperature and hea t of fusion of PP is more significant than that of PPA with the change of t he T-s, depending upon the crystallization conditions. Results were explain ed by homogeneous nucleation, heterogeneous nucleation, self-nucleation, an d annealing crystallization. (C) 2001 John Wiley & Sons, Inc.