Blends of thermoplastic polyurethane and polypropylene. I. Mechanical and phase behavior

Abstract

Pure thermoplastic polyurethane (TPU), polypropylene (PP), and TPU/PP blends with different weight ratios prepared in a twin-screw extruder were investigated by dynamic mechanical analysis (DMA), the universal tester for mechanical investigation, and by wide-angle X-ray diffraction (WAXD). The addition of PP above 20 wt % to the TPU stepwise changed the ductility and Young's modulus, i.e., apparently a kind of ductile ? brittle transition occurred between TPU/PP 80/20 and TPU/PP 60/40 blends. This fact and the result of analysis of WAXD curves indicated matrix ? dispersed phase inversion in this concentration region. TPU melt enabled easier migration of the PP chains and prolonged crystallization of PP matrix during solidification process affecting thus crystallite size, orientation, and crystallinity. In accordance to this fact, DMA results indicated partial miscibility of PP with polyurethane in the TPU/PP blends due to the lack of interfacial interaction and adhesion between the nonpolar crystalline PP and polar TPU phases.

Blends of thermoplastic polyurethane and polypropylene. II. Thermal and morphological behavior

“…The completion of the investigation of the structureproperty relationships of TPU/PP blends through examinations of their thermal and morphological behaviors confirmed some conclusions presented in a previous article 11 and emphasized new conclusions:…”

“…Obviously, the completion of the cocontinuous phase morphology could be expected between the 60/40 TPU/PP and 80/20 TPU/PP blends. These results, as well as the stepwise change in the ductility and Young's modulus, 11 locate the PP matrix to TPU matrix inversion in the concentration region between the 60/40 and 80/20 TPU/PP blends. This is in accordance with some morphological models predicting the occurrence of a cocontinuous (bicontinuous) phase morphology on the basis of the viscosity ratio of the components (the empirical Jordhamo law).…”

“…The mixing of the PP and TPU chains in the soft, amorphous phases reduced the mobility of macromolecular chains, and this led to the stiffer TPU/PP blends when PP was the matrix phase. 11 This explanation may reconcile the structural changes of both the TPU and PP amorphous phases and the TPU T g during crystallization by partial miscibility on the one hand and by immiscibility on the supermolecular or macrophase level deduced from the two-phase morphology revealed by SEM and optical microscopy on the other hand. The values of d sph , calculated with eq.…”

The Effects of Thermoplastic Polyurethane on the Structure and Mechanical Properties of Modified Polypropylene Blends

“…These results can be attributed to the immiscibility and incompatibility between PP and TPU, which led to an inhomogeneous phase with poor interaction [8]. Qu et al examined the mechanical properties of TPU/PP blends with various contents of TPU (10-90 wt%) and found that a U-shaped mechanical property curve formed when TPU content increased.…”

“…Our results indicated that the tensile properties of PP/TPU blends decreased as more TPU was added. Some problems resulted from the larger intrinsic structure of TPU and from interphase interaction and transformations [8], so the proportion of TPU was set at 10 wt%. In the meantime, the pure PP and pure MPP were used as control groups, and the effects of using TPU on the blending morphology, melting behavior, crystalline behavior, and mechanical properties of polymer blends were investigated.…”