Film Properties. Of course, the dependence of the penetration of the film surfaces with aqueous-born species will be visible from the contact angle (CtA) measurements (Figure ). It seems that even with a very low DS of 0.02, with only 6-acetylation, there is some modest increase in the CtA, with the samples wetting immediately. This obviously will have a predictable effect on the penetration of the papers with water-mobile degrading species and there will be an expected trade-off between the initial kinetics of degradation based on this phenomenon. For the higher DS samples, with formation of CTA, the CtA values increase significantly and take much longer (up to 1 hour) to wet completely. From analysis of the stress-strain properties, the wet strength clearly suffers for the low DS samples. This will have a major effect on the mechanical dispersibility of the materials under different conditions. One interesting feature is that the formation of CTA has a significant effect on the wet strength and extensibility of the materials, presumably due to formation of an elastic film surface on the fibrils/fibres from the topochemical conversion of complete fibrils to CTA.