Rheological characterization and thermal stability of triblock copolymers-modified asphalt reinforced with montmorillonite nanoparticles in physical mixing
Caracterización reológica y estabilidad térmica de asfalto modificado con copolímeros tribloque y montmorillonita en un mezclado físico
M.A. Vargas-Hernández1* and H. Vázquez-Torres2
1 Tecnológico de Estudios Superiores de Ecatepec, Av. Tecnológico S/N, Valle de Anáhuac, 55210 Ecatepec de Morelos, Estado de México. *Corresponding author. E-mail: angelesvh@yahoo.com Tel. 55-71-43-92.
]]> 2 Departamento de Física, Universidad Autónoma Metropolitana-Iztapalapa. Av. San Rafael Atlixco 186, col. Vicentina, México, D.F. CP. 09340.
Received June 7, 2014
Accepted May 22, 2015
Abstract
Effects of montmorillonite (MMT) on the rheological, thermal stability and morphological properties of triblock copolymer modified asphalts are investigated. Modified asphalts were prepared by successively mixing the clay and SBS, SIS, or SEBS with the asphalt AC-20. Results show that the MMT modified asphalt may form an intercalated or exfoliated structure. MMT increased slightly both the softening point and the viscosity of the modified asphalts at high temperatures. Furthermore, the modified asphalts exhibited a relatively higher complex modulus and, in consequence, displayed enhanced viscoelastic properties, which improve its resistance to rutting at high temperatures. The high-temperature storage property can be increased by improving the compatibility between polymer and asphalt The morphology observed by optical microscopy revealed the better compatibility between triblock asphalt/polymer/MMT, thus influencing the final rheological properties of the studied systems. Indeed, asphalt or asphalt/polymer blends gave a typical terminal relaxation behavior for polymer (G'~ w2, G"~ w1), which is modified by the addition of MMT particles. Furthermore, the activation energy of nanocomposites resulted slightly higher than that of asphalt/polymer blends without MMT.
Keywords: asphalt, montmorillonite, triblock polymers SBS, SIS, SEBS, modified asphalt, rheology, storage stability.
Resumen
]]> Se estudió el efecto de la montmorillonita (MMT) sobre las propiedades reológicas, estabilidad térmica y morfología del asfalto AC-20 modificado con copolímeros tribloque. El asfalto modificado (AM) se preparó por mezclado sucesivo de nanopartículas y polímeros SBS, SIS y SEBS. Los resultados obtenidos muestran que la arcilla puede formar distribuciones intercaladas y/o exfoliadas. La presencia de la MMT en el AM aumenta ligeramente la temperatura de ablandamiento y la viscosidad del asfalto a temperaturas altas y disminuye el grado de penetración. Adicionalmente, estos materiales muestran un aumento en los módulos elástico y viscoso, lo que indica un considerable mejoramiento en la resistencia a la deformación permanente por acanalamiento a temperaturas elevadas. La estabilidad térmica del asfalto modificado aumenta con la presencia de MMT, debido a la mejora de la compatibilidad entre el asfalto y el polímero por sus interacciones con la arcilla. En efecto, la morfología del AM observada por microscopía optica presenta una reducción en el tamaño de partícula del polímero en el sistema ternario asfalto/polímero/MMT, lo cual se ve reflejado en el mejoramiento de la compatibilidad y de sus propiedades viscoelásticas. El asfalto AC-20 y las mezclas binarias polímero/asfalto presentan una relajación terminal característica del polímero (G' ~ w2, G" ~ w1),). Por su parte, las mezclas asfalto/polímero/MMT muestran un cambio en el espectro de relajación terminal (G' y G" ~ w1), además de un ligero aumento en la energía de activación.Palabras clave: asfalto modificado, arcilla MMT, polímeros tribloque, reología, estabilidad térmica.
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