Crystallization Behavior of Compatibilized Blends

For PET/HDPE blends compatibilized by addition of functionalized polyolefins, the crystallization temperature of PET was found to be shifted to temperatures lower than those observed for plain PET and the non-compatibilized blends [99]. Moreover, the crystallinity degree of the polymers depended on the type and concentration of compatibifizer (Fig. 10.25). The crystallinity of both PET and HDPE phases was markedly depressed upon addition of HDPE-g-MA or E-GMA due to the effect of the chemical reactions of functional groups with PET and of the miscibility of the functionalized polyolefins with the HDPE phase. In fact, the crystallization of PET molecules near the interface is affected by the occurrence of interchain grafting reactions, which result in a reduced mobility of the chains and thus depression of crystallization temperature. With decreasing the size of dispersed particles the effect of compatibifizer on the crystallization of PET becomes more pronounced. 

These effects, supported by a marked increase of melt viscosity, were related to the occurrence of chemical interactions between the polyamides and functionalized polyolefins at the interface. DSC analysis showed that incompatible Ny6/PP and Ny6/LDPE blends exhibit at all compositions separated crystallization peaks of the two components, whereas the compatibilized blends displayed fractionated and/or coincident crystallization phenomena. For Ny6/PP-AA blends where Ny6 is the matrix, the crystallization of the polyamide phase takes place in a narrow range, close to 190 C, as observed for pure Ny6 (Hg. 10.26a). When Ny6 is the dispersed phase. 

The weight fraction /(t ) of dispersed Ny6 crystallizing heterogeneously in the blends (at the usual undercooling conditions) was related to the volume of Ny6 particles by the relation  

Melting thermograms of Ny6/PP-AA blends with polyamide as dispersed phase, isothermally crystallized from the melt, revealed also the presence of melting peaks of Ny6 at temperatures lower than the usual melting temperature of a form (221 °C), indicating the existence of a considerable amount of y form crystals (215 C). No melting peak of /phase was observed for Ny6/iPP blends at any Ny6 content. 

From the deconvolution analysis of WAXS spectra of the various blends, it was found that in the functionalized 

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