mass transfer during the pre-usage dehydration of polyvinyl alcohol hydrogel wound dressings

nowadays, hydrogels are widely used as wound dressings in biomedical applications. similar to other types of the moist (wet) wound dressings, it is necessary to have sufficient information about their dehydration kinetics during the pre-usage period (e.g. storage duration) and also the wound healing process. in this work, hydrogel wound dressings based on polyvinyl alcohol were prepared by cyclic freezing-thawing method and their dehydration process investigated by experimental and mathematical methods. the dehydration tests were performed at atmospheric pressure at 37 °c, using hydrogels containing initial water content of 70, 80 and 90 wt% and thickness of 1, 3 and 4 mm. the dehydration kinetics of each hydrogel was determined by plotting the relative water loss (ratio of water loss to initial water content) versus time. the obtained results showed that the dehydration rate has inverse dependency to the thickness of wound dressing. on the other hand, the initial water content of the wound dressing has not significant effect on its dehydration rate. to compare the obtained results with theoretical data, the mathematical modeling on the basis of diffusion mechanism was developed to predict the dehydration process of the wound dressings. the results obtained from the mathematical modeling were in agreement with the experimental results showing that the main phenomenon governing the dehydration of the wound dressings is the diffusion.