ARTICLE pubs.acs.org/IECR
Influence of Nanoclay Concentration on the CO2 Diffusion and Physical Properties of PMMA Montmorillonite Microcellular Foams Vera Realinho, Marcelo Antunes,* Antonio B. Martínez, and Jose I. Velasco Centre Catala del Plastic, Departament de Ciencia dels Materials i Enginyeria Metallurgica, Universitat Politecnica de Catalunya, C/Colom 114, E-08222, Terrassa (Barcelona), Spain ABSTRACT: Microcellular foams of poly(methyl methacrylate) with variable concentrations of an organically modified montmorillonite, oMMT (2.510 wt %), were prepared using a supercritical CO2 dissolution physical foaming process. Particular importance was given to the analysis of the influence of the montmorillonite on the CO2 desorption behavior out of the several nanocomposites. The saturation concentration of CO2 was found to be two times higher in the nanocomposites when compared to the pure PMMA and a comparative analysis of the desorption curves showed that a higher concentration of CO2 remained in the nanocomposites for long times when compared to PMMA, except for the 10 wt % oMMT nanocomposite. Also, the incorporation of oMMT promoted the formation of submicrometric foams with much lower cell sizes and higher cell densities. With increasing the amount of oMMT, the glass transition temperature of PMMA decreased in both the solids and foams and important improvements were observed regarding the specific elastic moduli of the foams, demonstrating the mechanical reinforcement effect of oMMT.
1. INTRODUCTION Because of some of their inherent characteristics, polymer foams are used in a wide range of applications, including packaging, buoyancy, thermal insulation, acoustic attenuation, and vibration damping, among many others.1,2 Recently, polymer nanocomposite foams, i.e., foams with some sort of nanosized fillers incorporated into the polymer matrix, have received increasing interest by both the scientific and industrial communities, where the possibility of creating new multifunctional materials with improved specific properties has given rise to a great deal of interest.3,4 Particularly, the dispersion of high aspect ratio nanoclays in polymers has been used as a possible strategy to improve some properties of the base material at relatively low filler amounts (
