Síntese de poliuretano termoplástico modificado com POSS via extrusão reativa

Abstract

In this work, thermoplastic polyurethanes (TPU) were synthesized in solution process and reactive extrusion in twin-screw extruder. The TPUs were obtained with the use of pre-polymer based on 4,4´-Methylenediphenyl diisocyanate (MDI) and a polyester functionalized polyol, the bis-2-(hidroxyethyl)ether hidroquinone and the n-phenylaminopropyl-POSS as a second chain extender. The reagents and products were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and also capillary rheometry (only for those products). The DSC analysis presence influenced the melting enthalpy (ΔHm) of the TPU synthesized by solution. The samples synthesized through reactive extrusion at 80 ºC presented a higher Tm compared to the 90 ºC TPUs, with a higher ΔHm, suggesting that the temperature favors the formation of a greater number of crystals with a lower medium size. Exothermic phenomena were observed during the heating of samples synthesized in reactive extrusion, probably due to the availability of free isocyanate groups, which were detected by FTIR in the ~2253 cm-1 region. The thermal stability of the TPUs was enhanced by the addition of POSS, while the polymers obtained through reactive extrusion presented higher onset degradation temperatures. The TGA analysis in isothermal conditions showed progressively lower mass loss values in samples obtained by reactive extrusion, demonstrating that the amount of POSS, as well the synthesis temperature, had influence in the final properties of the TPU. The thermal resistance of samples polymerized in reactive extrusion. In capillary rheometry tests, the insertion of POSS in the polymer led to a progressively higher value of intrinsic viscosity of the TPUs, indicating an increase in the mean molar mass of the TPUs obtained through solution synthesis. The same method was applied to the samples obtained through reactive extrusion, which showed similar apparent viscosities, yet the analysis was probably influenced by the degradation of the TPU inside the loading cell, leading to no measurable tendency in the viscosity of the polymer.