An increasing environmental awareness provides environmental technology with ever more growth opportunities through the development and deployment of innovative technologies. Just one of many examples is the polymer membrane, used to separate materials and for microfiltration. Depending on its structure, it allows gas or water to permeate on one side, or only allows certain microparticles or organic materials to get through. Fields of application include the processing of biogas through CO2 separation or energy-saving seawater desalination. The polymer membrane has attracted much attention as a central component of the fuel cell, where it is not only responsible for gas separation, but as an electrolyte, also conducts the protons. Many university institutes and industrial research institutions worldwide are devoted to the task of producing these components more cheaply, while at the same time improving the essential properties in terms of resistance to temperature, gas permeability and selectivity for specific gases. One of them is the Nanoscience Institute of Aragón of the University of Zaragoza, gathering renowned experts in the fields of Nanobiomedicine, Nanostructured Materials and Physics of Nanosystems from around the world.
One research project of INA dealt with the development of a composite membrane with polysulfone, a plastic resistant to high temperatures, as a polymer matrix as well as spherical ordered silica (SiO2) particles as a filler. The morphology and homogeneity of the particle distribution in the membrane was examined at different strengths, as well as the properties at different weight proportions of the spherical silica particles. The actual size proportions are far from the illustrative graphic above, portraying a fuel cell. The thickness of the membrane ranges from 75 to 100 µm and the silica particles are about 3-4 µm in diameter. A vacuum is required twice for the various experiments. On the one hand, the polysulfone must be dried in the vacuum for four hours at 100 °C before it is combined with the filler, on the other the membrane films which have been dried at room temperature are degassed at 10 mbar and 100 °C for one day in the vacuum drying oven to remove the solvent remaining from the polymer production.
Production of membranes was followed by numerous investigations with scanning electron microscope, thermogravimetry, infrared spectroscopy as well as X-rays, mechanical load tests and measurements of the permeability. It was seen here that with the selected material combination of polysulfone and silica, the proportion of filler can be kept low, although gas permeability and selectivity could be improved. The full publication is available from ACS Publications. Our special thanks go to Prof. Joaquín Coronas and Dr. Carlos Téllez from the University of Zaragoza for their support in writing this application report.
