THERMOMECHANICAL STABILITY OF POLYMER-CERAMIC COMPOSITE MEMBRANES

The mechanical stability of thin-film polymer-ceramic composite membra nes has been evaluated in a variety of processing steps with temperatu res ranging from 25 to 350 degrees C. Although not measured in this wo rk, references for similar materials indicate that the coefficients of thermal expansion for the two layers of the membrane are considerably different. Upon heating, this difference led to the development of th ermally-induced stresses. These stress could be relieved if the membra ne were heated in an unrestrained manner; however, they were sufficien t to cause membrane failure if not relaxed. Heating to temperatures ab ove the glass transition of the polymer resulted in defect formation i n that layer due to flow into the ceramic support. These results indic ate that, if properly handled, the membranes are sufficiently stable t o be used over a wide range of temperatures. However, serious consider ation must be given to these issues in the design of larger-scale devi ces.