Non-polluting aqueous polyurethane-based dispersions were synthesized in the presence and absence of montmorillonite hydrophilic clay (WPUs and CWPUs, respectively). The permeability of carbon dioxide (CO2) through dense membranes obtained from the dispersions was evaluated. The reagents used in the synthesis of the materials were: poly(propylene glycol) (PPG), block copolymer of poly(ethylene glycol) and poly(propylene glycol) (EG-b-PG), dimethylolpropionic acid (DMPA), isophorone diisocyanate (IPDI) and ethylene diamine (EDA) as chain extender, leading to the formation of urea linkages. The proportion of poly(ethylene glycol) (PEG) segments and clay content (0.5 and 1%) was varied in the formulations. The dispersions were evaluated in terms of solids content and apparent viscosity. The membranes were characterized by infrared spectrometry (FTIR) and permeability to carbon dioxide (CO2). The influence on the gas barrier properties, imparted by different contents of PEG segments in polyurethane chains, and by the clay in the formulations was verified. The permeability of CO2 increased with increasing amounts of PEG segments and decreased with the insertion of clay, since the latter is impermeable to gas and forms, in the polymeric matrix, tortuous pathways that retard gas diffusion.
Polyurethane; aqueous dispersions; clay; montmorillonite; membranes; gas permeability; barrier properties
