Effects of spatial confinement and selective distribution of CB particles on the crystallization behavior of polypropylene

The effects of selective distribution of carbon black (CB) particles and spatial confinement on the crystallization behavior of isotactic polypropylene (iPP)/Polystyrene (PS)/CB composite were studied. The crystallization behaviors and the morphologies of the composite were studied by differential scanning calorimetry (DSC), polarized light microscope (PLM), and scanning electron microscopy (SEM). The results indicated the typical cocontinuous structure appeared in PP/PS/CB (55/45/1) composite, and CB particles are distributed in PS phase, which follows the theory of interfacial tension. Compared with PP/CB composite, the nucleation effect of CB particles on the crystallization process of PP in PP/PS/CB was greatly weakened by selective distribution. Moreover, the morphologies of cocontinuous structure, which means that the crystallization process of PP had to take place in the micron-scale spatial confinement formed by continuous PS phase, greatly influenced the crystallization behavior of PP in PP/PS/CB composite. The spherulite radial growth rate of PP in spatial confinement was lower than that of neat PP during isothermal crystallization processes, and the results of the total crystallization activation energy (Delta E) and the nucleation parameter (K-t) implied that in comparison to neat PP, the activation energy of PP chain segments arranged into crystal was higher in composite with cocontinuous structure. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3652-3661, 2012