Tenacificação do poliéster insaturado pela incorporação de uretano.

Abstract

There is a strong industrial interest on the development of polymer blends as this is a low cost and efficient method to modify polymer properties. The appropriate choice of components allows the adjustment of the properties of the blend to specific needs. Nowadays the use of biomass derivatives by the chemical industries is growing steadily as these vegetable products and byproducts come from renewable sources and are substituting petroleum based products. In the present work, unsaturated polyester/polyurethane blends (UP/PU blends) were developed with the aim to produce tougher polyester based products. Blends of a single commercial unsaturated polyester and three different polyurethanes were investigated. The polyurethanes employed in this work come from natural sources and were obtained by reacting poliols, derived from castor oil, having distinct hydroxyl content, with an isocyanate capped pre-polymer also derived from castor oil. The mechanical properties (tensile and impact) of the blends were investigated as a function of polyurethane kind and content as well as of post-curing for one hour at two different temperatures (80 and 150°C). The blends were visually inspected and characterized by fourier transform infra-red spectroscopy (FTIR) and their fracture surfaces analyzed by scanning electron microscopy (SEM). The results obtained indicate that tougher polyester based products can be obtained by blending with polyurethane and that, in general, for the systems under investigation: 1) both the tensile and the impact strengths of the blends which were not post-cured, tended to increase with the reactivity (hydroxyl content) of the polyol employed in the synthesis of the polyurethane employed; 2) the modulus and the elongation at break were not dependent on the kind of PU used; 3) there was strong phase segregation at higher (15%) PU contents; 4) the properties of all systems investigated tended to decrease with post-curing at high (150°C) temperatures; 5) better overall mechanical properties were obtained for the systems post-cured for 1h at 80°C and 6) optimized impact properties were achieved for the blends with 10% PU content.