Pioneering method advances polymer industry
The method measures diffusion in films by synchronizing two processes: the gravimetric determination of mass transfer from a supercritical fluid phase to a solid phase within a high-pressure autoclave and the optical assessment of visual changes such as particle morphology and crystallinity. In order to calculate the swelling or volume change, isotherms for different pressures were obtained. The device used for measuring the spontaneous intermingling of the particles involves a magnetic suspension microbalance (MSB) connected to a view cell (VC). The view cell enables the determination of volume change of the solid sample by using a chemical composition distribution (CCD) camera. Solubility and swelling measures of CO2 in polymer films can be performed at temperatures up to 80 degrees Celsius and pressures up to 300bar. Sorption and swelling figures were achieved concurrently at the same temperature and pressure. Besides using one fluid, it is also possible to use a combination of two fluids and the microbalance cell can also be connected to a gas chromatograph. In this light, it is possible to measure the change of the mixture composition using a chromatograph during the desorption period. In addition the method developed can also be applied to solubility measurements of other supercritical fluids such as ethylene, propylene, etc. that are of interest to the European Polymer Industry. The adaptability of this new technology may very well decrease the use of traditional solvents that have elicited worldwide environmental unease and steer the polymer industry in a new direction.
