Transport processes during the incubation time of ion track etching in polymers

The processes which take place in polymers before visible etch track format ion sets in after exposure to alkaline solutions, i.e, during the so-called "incubation time", are thought to consist of the penetration of the liquid into the polymer and the polymer's subsequent glassy-to-rubbery phase tran sformation. We have studied systematically the first of these steps - the p enetration process - by measuring the depth distributions of tracer ions di ssolved in the penetrant solutions in different polymers as a function of p H value, temperature, and penetration time. Determination of the free volum e of pristine and ion-irradiated polymers by positron annihilation spectros copy served as an additional important source of information. Our findings show that the solutions' penetration is often a highly complex process whic h eventually dominates the overall incubation time. (C) 1998 Published by E lsevier Science B.V. All rights reserved.