A Simple Method for Water Absorption Kinetics of Swellable Polymer Matrices

Purpose of the study was to develop a novel method for water absorption kinetics of swellable polymer matrices. Numerous findings have reported methods like use of optical microscopy (e.g., polarized microscopy, photomicrography, and optical imaging), spatula method, and nuclear magnetic resonance imaging. Due to their complexity and tedious nature, seldom are attempts made to study the kinetics of water absorption. Hence, we have developed the method using plastic sheets (perforated and nonperforated) to study water absorption kinetics. The method used 2 cm² plastic sheets printed with black concentric circles of different diameters. Compacts were placed on these concentric circles on the plastic sheet and submerged in water placed in petri plate. At predefined time intervals the sheet and compact were taken out and weighed to determine weight of water absorbed (W). From W and time, the average velocity of water penetration front (U) and mass degree of swelling (Q) were calculated. It was observed that, the method gives entire water absorption kinetics up to the complete erosion of compacts without disturbing erosion front unlike other methods. The difference in the values of W, U and Q obtained from method using perforated plastic sheet non-perforated sheet were statistically insignificant at p<0.05. Initially for 1 hour, uptake of water was found to be rapid in all cases and maximum swelling attained was up to 5 hours followed by decline due to erosion of polymer chains from gelled layer of polymer compact. Because of simple set up, sensitivity, and less tedious nature, method seems to be promising.