Polydimethylsiloxane Membranes Containing Multi-walled Carbon Nanotubes for Gas Separation

<div><p>Polydimethylsiloxane (PDMS) membranes with different concentrations of multi-walled carbon nanotubes were prepared in order to evaluate their gas separation performances. Mixed matrix membranes were characterized by scanning electron microscopy, thermogravimetric analysis, Fourier transformed infrared, positron annihilation lifetime and Raman spectroscopies and X-ray diffraction. The permeabilities to CO2, CH4, N2 and O2 were determined. No phase separation was noticed. For carbon nanotubes content of 1 wt%, it was shown a decrease in membrane permeability with slight increase in ideal selectivity, compared to pure PDMS. However, the increase in the filler load up to 6.7 wt% increased the free volume average size of the membranes, improving the contribution of the diffusion to the transport and decreasing ideal selectivities of CO2/CH4, CO2/N2 and O2/N2.</p></div

Nanocompósitos de poliuretana termoplástica e nanotubos de carbono de paredes múltiplas para dissipação eletrostática Thermoplastic polyurethane and multi-walled carbon nanotubes nanocomposites for electrostatic dissipation

<abstract language="eng">Polyurethane/multi-walled carbon nanotube (MWCNT) nanocomposites have been prepared with nanotube concentrations between 0.01 wt% and 1 wt%. MWCNT as-synthesized samples with ~74 nm diameter and ~7 &#956;m length were introduced by solution processing in the polyurethane matrix. Scanning electron microscopy (SEM) images demonstrated good dispersion and adhesion of the CNTs to the polymeric matrix. The C=O stretching band showed evidence of perturbation of the hydrogen interaction between urethanic moieties in the nanocomposites as compared to pure TPU. Differential scanning calorimetry and positron anihilation lifetime spectroscopy measurements allowed the detection of glass transition displacement with carbon nanotube addition. Furthermore, the electrical conductivity of the nanocomposites was significantly increased with the addition of CNT

Hydrophobic channels produced by micelle-structured CTAB inside MCM-41 mesopores: A unique trap for the hazardous hormone ethinyl estradiol

In this work, mesoporous hydrophobic cavities produced by a micelle structured CTAB (cetyl trimethylammonium bromide) trapped inside MCM-41 pores were used for the efficient removal of the hazardous hormone contaminant ethinyl estradiol (EE) present in water. The MCM-41 structure was prepared using different CTAB/Si molar ratios, i.e. 0.07, 0.12, 0.17, and 0.27. TG, SEM, TEM, BET, IR, elemental analysis, contact angle and positron annihilation spectroscopy showed that the MCM-41 silica structure is completely filled with trapped CTAB molecules (47-58wt%) which results in no porosity and very low surface areas of 1-5m2g-1. These materials showed high efficiency to remove EE from aqueous solution whereas pure MCM-41 (without CTAB) with high porosity and a surface area of 1333m2g-1 showed no adsorption. These results are discussed in terms of EE sorption into the hydrophobic environment created by the CTAB trapped molecules inside the mesoporous cavities of MCM-41.Fil: Ribeiro Santos, Tatiana A.. Universidade Federal de Minas Gerais; BrasilFil: Henriques, Fernando Fulgêncio. Universidade Federal de Minas Gerais; BrasilFil: Villarroel Rocha, Jhonny. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: de Castro, Mateus Carvalho Monteiro. Universidade Federal de Minas Gerais; BrasilFil: Magalhães, Welington Ferreira. Universidade Federal de Minas Gerais; BrasilFil: Windmöller, Dario. Universidade Federal de Minas Gerais; BrasilFil: Sapag, Manuel Karim. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Luis. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich". Universidad Nacional de San Luis. Facultad de Ciencias Físico Matemáticas y Naturales. Instituto de Física Aplicada "Dr. Jorge Andrés Zgrablich"; ArgentinaFil: Lago, Rochel Montero. Universidade Federal de Minas Gerais; BrasilFil: Araujo, Maria Helena. Universidade Federal de Minas Gerais; Brasi