Methylene diphenyl diisocyanate (MDI) affects the morphology, rheological, mechanical, and relaxation properties, as well as tendency to crystallize of PET in PET/PC/(PP/EPDM) ternary blends produced by the reactive extrusion. Irrespective of the blend phase structure, the introduction of MDI increases the melt viscosity (MFI dropped), resulting from an increase in the molecular weight of the polymer chains; the PET crystallinity was also reduced. MDI favors compatibility of PET with PC in PET/PC/(PP/EPDM) blends. This is explained by intensified interphase interactions on the level of segments of macromolecules as well as monomer units. The presence of MDI causes a substantial rise in the dynamic shear modulus within the high-elastic region of PET (for temperature range between T g,PET and that of PET cold crystallization); the processes of PET cold crystallization and melt crystallization become retarded; the glass-transition temperatures for PET and PC become closer to each other. MDI affects insignificantly the blend morphology or the character of interactions between the disperse PP/EPDM blend and PET/PC as a matrix. PP/EPDM reduces the intensity of interphase interactions in a PET/PC/(PP/ EPDM), but a rise in the degree of material heterogeneity. MDI does not change the mechanism of impact breakdown in the ternary blends mentioned above. Increased impact strength of MDI-modified materials can be explained by higher cohesive strength and resistance to shear flow at impact loading.

Abstract. It has been investigated how methylene diphenyl diisocyanate (MDI) influences the morphology, rheological, mechanical and relaxation properties, as well as PET crystallizability, of PET/PC/(PP/EPDM) ternary blends produced by the reactive extrusion process. It appears that irrespective of phase structure of the blends, MDI causes a rise in melt viscosity (decreased MFI-values) of the material which is the result of an increased molecular weight of the macromolecules; PET crystallization becomes retarded. MDI improves compatibility between PET and PC in PET/PC/(PP/EPDM) ternary blends. Addition of MDI leads to higher values of the dynamic shear modulus for PET high elastic state (in the temperature range between Tg PET and cool crystallization temperature of PET); the PET cool crystallization and melt crystallization processes become retarded; the PET and PC glass transition temperatures approach one another. MDI has been shown not to influence significantly the blend morphology or the character of interaction between the PP/EPDM disperse phase and PET/PC blend matrix.

The effect of diisocyanate chain extender (CE) on the mechanical, rheological, and relaxation properties, as well as on molecular weight and crystallizability, of starting poly(ethylene terephthalate) (PET) and its composites containing carbon nanomaterials (CNM) such as carbon nanotubes (CNTs) and commercial carbon (CC) has been studied. The composites were compounded in molten PET using twin-screw extruder (screw diameter 35 mm; L/D = 40). To improve the distribution of CNM in the polymeric matrix (before introduction into the melt), they were blended with PET powder and subjected to an ultrasonic treatment in methylene chloride. The salient features of the materials structure were estimated based on DSC and relaxation spectrometry (dynamic mechanical analysis) data. It has been found that CNM additives partly suppress the PET-chain extension reactions which take place during interaction between macromolecular end groups and CE. Besides, both CNT and CC favour crystallizability of the modified PET owing to nucleation of the crystallization process. The influence of CNT appears to be more effective than that of CC. Enhancements in true mechanical strength and deformability of PET/CE/CNM composites, as against PET/CE materials, were found to be most clearly exhibited by the CNT-containing composites.