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The crystallization behavior of the blends of isotactic polypropylene (iPP) and poly(ethylene-co-octene) (PEOc) under quiescent condition and shear flow were studied by differential scanning calorimetry (DSC) and rheology, respectively. The DSC curves of the iPP phase in the blends showed similar crystallization exothermic peaks to that of pure iPP itself, indicating that the addition of PEOc up to a percentage of 30 in weight almost had no influence on the crystallization behavior of iPP at quiescent condition. The rheological results of isothermal flow-induced crystallization (FIC) of iPP in the blends showed that the crystallization kinetics of iPP was enhanced with the increase of shear rate, similar to that of pure iPP, but the presence of PEOc enhanced the effect of shear on the crystallization kinetics of iPP significantly in the cases of shear rates larger than 0.2 s(-1) which was due to that PEOc played an important role to promote the nucleation of iPP. The rheological results also implied that the characteristic relaxation times of blends were longer than that of pure iPP during the FIC process, indicating a different relaxation mechanism which might be related to the occurrence of interface relaxation and chain relaxation of the PEOc phase in the blends. (c) 2007 Elsevier Ltd. All rights reserved.

Glycidyl methacrylate (GMA) was grafted onto chlorinated polypropylene (CPP) in the molten state using benzoyl peroxide (BPO) in the presence of styrene (St) as a comonomer. The differential scanning calorimetry (DSC) results indicated that the thermodynamic curve of unpurified grafted CPP was different from the purified, and showed a new broad endothermic peak at 100 degrees C, which may be attributed to the glass transition temperature (T-g) of remained copolymer of GMA and St. Furthermore, transmission electron microscope (TEM) showed that there were two-phase structures in the grafted CPP. Because the grafted CPP was to be used as a hot melt adhesive, so the influence of initiator concentration, monomer concentration, and reaction temperature on peel strength was investigated. The experiment results showed that a higher degree of grafting was obtained by using two kinds of monomers, such as GMA and St. Increasing the monomer concentration led to an initial rapid increase in the peel strength. (c) 2007 Wiley Periodicals, Inc.

The non-isothermal crystallization behaviors of long chain branched isotactic polypropylene (LCB PP), dynamically vulcanized LCB PP/ethylene-propylene-diene monomer (EPDM) blends at various weight ratios were investigated by DSC, rheology and optical microscopy. LCB PP/EPDM blends were found to show a different crystallization behavior in comparison with linear PP/EPDM blends, showing a minimum in the peak temperature of crystallization with increasing the content of EPDM while the latter showing a maximum. The nucleation and the crystallization kinetics of PP were induced and accelerated by long chain branches and EPDM. The acceleration of crystallization kinetics of LCB PP induced by LCB structures was attributed to the grafted efficient nucleation agent. The influence of EDPM on the crystallization combines the effects of enhancement and retardation, depending on its content in the blends. Based on the thermodynamics theory of crystallization, a modified crystallization model was developed to reveal the crystallization mechanism of LCB PP/EPDM blends.

A series of halogen-free intumescent flame retardants (IFR) based on home-made melamine phosphate and pentaerythritol system (MPPER) including polyamid 12, basic nickel carbonate (NiCO3·2Ni(OH)2·4H2O), lanthanum oxide (La2O3), and expandable graphite compounding with MPPER, were adopted for flame retarding olefin block copolymers (OBC). Flame-retardant effects and thermal stabilities of OBC-IFR composites were investigated by limiting oxygen index, vertical burning test (UL-94), and thermogravimetry analysis along with the analysis of morphological structures of the char residue by scanning electron microscopy. The mechanical properties and the flame-retardant mechanism of the final composited materials have been also discussed. The loading of suitable amount of IFR can improve effectively the flame retardancy of the OBC with tolerable decrease in mechanical properties. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40066.