A series of segmented poly(urethane-urea) polymers have been synthesized varying the hard segments content, based on the combination of polycaprolactone diol and aliphatic diisocyanate (Bis(4-isocyanatocyclohexyl) methane), using diamine (1,4-Butylenediamine) as the chain extender. The microstructure and properties of the material highly depend on the hard segments content (from 14 to 40%). These PUUs with hard segment content above 23% have elastomeric behaviors that allow high recoverable deformation. The chemical structure and hydrogen bonding interactions were studied using FTIR and atomic force microscopy, which revealed phase separation that was also confirmed by DSC, dynamic-mechanical, and dielectric spectroscopy.
Polypropylene composites reinforced with continuous and unidirectional polyester fibers were prepared by the powder method. Three different polyester fibers with different mechanical properties were used. The composite mechanical properties showed a clear influence from the synergistic combination of the fiber properties and the material’s unidirectionality. The impregnation process based on a polypropylene powder cloud was studied, and a method to prepare composites was designed. In general, the powder method showed high compatibility leading to high-quality unidirectional composites.
ResumenLa estabilidad hidrolítica de una serie de polímeros de Poliuretanourea segmentado (PUUs) fue estudiada bajo degradación in vitro en buffer de fosfato salino (PBS) con pH de 7.4 y 37 °C durante 20 semanas. La degradación y las propiedades mecánicas de los productos finales fueron controladas por el contenido de segmentos rígidos y el tratamiento cercano a la temperatura de fusión del glicol utilizado. La asociación de los segmentos rígidos se incrementó usando diisocianato y dioles lineales. Las interacciones moleculares promovieron diversas respuestas viscoelásticas, que a su vez, fueron influenciadas por el envejecimiento térmico promovido en las cercanías del glicol. Los estudios de degradación se realizaron en películas delgadas obtenidas por evaporación lenta del solvente. Los PUUs fueron caracterizados mediante técnicas de espectroscopia de IR, calorimetría, análisis dinámico-mecánico y difracción de rayos X. Descriptores: Poliuretanourea, separación de fase, segmentos rígidos, degradación hidrolítica, microdominios.
AbstractThe hydrolytic stability of a series of segmented polyurethaneurea polymers (PUUs) was studied under in vitro degradation in phosphate buffer saline (PBS) at pH 7.4 and 37 °C for 20 weeks. Degradation and the mechanical properties of the final products were monitored by the content of rigid segments and the treatment near the melting temperature of the glycol used. The association of the hard segments was increased using diisocyanate and linear diols, which causes various viscoelastic responses when it is influenced by heat aging near the glycol used. Degradation studies were performed on thin films obtained by slow evaporation of solvent. The PUUs were characterized by techniques of infrared spectroscopy, differential scanning calorimetry, dynamic mechanical analysis and X-ray diffraction.
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