SUPERCRITICAL TRANSITIOMETRY OF POLYMERS

Employing supercritical fluids (SCFs) during polymers processing allow s the unusual properties of SCFs to be exploited for making polymer pr oducts that cannot be obtained by other means. A new supercritical tra nsitiometer has been constructed to permit study of the interactions o f SCFs with polymers during processing under well-defined conditions o f temperature and pressure. The supercritical transitiometer allows pr essure to be exerted by either a supercritical fluid or a neutral medi um and enables simultaneous determination of four basic parameters of a transition, i.e., p, T, Delta(tr)H and Delta(tr)V. This permits dete rmination of the SCF effect on modification of the polymer structure a t a given pressure and temperature and defines conditions to allow rep roducible preparation of new polymer structures, Study of a semicrysta lline polyethylene by this method has defined conditions for preparati on of new microfoamed phases with good mechanical properties. The low densities and microporous structures of the new materials may make the m useful for applications in medicine, pharmacy, or the food industry, for example.