Comparative evaluation of hydrocolloid dressings by means of water uptake and swelling force measurements: II

Abstract Hydrocolloid dressings are composite systems made of a hydrophobic matrix and a hydrophilic phase, which renders them capable of absorbing water. In a previous paper, water uptake and swelling force measurements, carried out in separate experiments were used to characterise and compare different hydrocolloid dressings. In particular, swelling force measurements provide information on the modifications induced by water absorption, which influence the in vivo performance of patches. In the present work, simultaneous measurements of water uptake and swelling force were carried out on some hydrocolloid dressings in order to achieve a better understanding of the relationship between the two phenomena. A computer-aided apparatus, which is a combination of the two apparatus formerly described for separate water uptake and swelling force measurements, was set up. A parameter referred to as the ‘force equivalent’, which represents the capability of the patch of transforming water uptake into swelling force, was used for characterising the various patches. This parameter is suitable to differentiate between patches characterised by similar composition but different hydration and swelling propensity. The patches examined in the present work could be divided into two groups, depending on their greater or lesser capability of transforming water uptake into swelling force. The time course of the derivative of the swelling force vs water uptake curve allowed a further differentiation between and within groups. It is envisaged that both the force equivalent value and the rate of attainment of force equivalent are related to adhesion performance.