Method and Model for the Analysis of Gel-Blocking Effects during the Swelling of Polymeric Hydrogels

Abstract

This paper focuses on a method to determine the swelling pressure of polymeric hydrogels. The method is based on determining the swelling pressure at a defined volume of swelling that is smaller than the volume the gel can attain by free swelling to equlibrium. Data for one type of polymer particles made from weakly cross-linked and partly neutralized poly(acrylic acid) are presented for swelling in deionized water. For polymer volume fractions (φ P ) in the range of 0.05-0.30, swelling pressures in the range of 0.25-4.31 MPa were obtained. The kinetic data are discussed with a combined diffusion-relaxation model for low and medium polymer volume fractions. A novel model is presented for higher polymer volume fractions. The mechanism of the gel-blocking effect that is evident in this φ P range is explained and considered in the novel model, in the form of a blocking factor. The results obtained may be used for the design of improved sealing concepts that are based on "super absorbing polymers".

Oxidation and sulfonation of cellulosics

“…However, as the total acid group value of the nanosamples increased, the water retention values decreased and a gel-like material was obtained after sulfonation. Studies by Ulbrich and Parsons of polymeric hydrogels have reported that gel-like properties reduce water retention values (Wack and Ulbricht 2007;Waring and Parsons 2001).…”

Preparation and properties of swellable thermoplastic elastomer alloys based on elastomeric powder, polypropylene, and superabsorbent polymer

“…Inside the material, the liquid might be transported by diffusion through the material matrix as well as along the interfaces between SAP and the matrix. In interaction with already existing swelling models23 these qualitative results can contribute to clarify the material transport processes taking place. This is the subject of current studies.…”

How much weighs the swelling pressure

“…If, however, the porous part of the confinement is too low, the scale readout is also low (case 1 of Figure 2). This behavior can be explained with gel blocking [16,17,22] which describes the reduction of water inflow with increasing swelling of the gel layer in direct contact with water due to the confined geometry. Of all the investigated confinements, case 4 leads to the highest increase of the apparent mass (highest swelling pressure) due to the lowest µ 1sg (cf.…”

“…The latter method has the advantage that composition dependence of the swelling pressure is obtained in just a single experiment [9]. Progressing miniaturization of devices for pressure measurements stimulated during the last decade the development of small sensors utilizing the swelling pressure of gels [12][13][14][15][16][17]. In biology and medicine the swelling pressure plays a major role in the function of connective tissues and hence, methods have been developed to study for example the isometric compressive stress of cartilage in a sophisticated apparatus with feedback control to ensure strict volume constancy [18].…”