STRAY FIELD MAGNETIC-RESONANCE-IMAGING OF THE DIFFUSION OF ACETONE INTO POLY(VINYL CHLORIDE)

Stray field nuclear magnetic resonance imaging has been used to study the diffusion of acetone vapour into poly(vinyl chloride) (PVC). For the first time in a n.m.r. imaging experiment the penetrant, the swollen polymer and the rigid polymer have been simultaneously visualized. Results are presented for a range of acetone vapour activities and sample preparation temperatures, and also for a sample prepared with deuterated acetone. The profiles show that the diffusion is of Case II type. A sloping profile is observed behind the penetrant front and is interpreted in terms of a softening of the swollen polymer, which occurs over a period of hours after penetration by the acetone. The softening rate has been measured as a function of temperature.