The density of the resin when it is dried is called the true density. The weight of the wet resin per unit volume (including voids between particles) is called the apparent density. The density of the resin is related to its degree of crosslinking and the nature of the exchange groups. Generally, resins with a high degree of cross-linking have a higher density, strongly acidic or strongly basic resins have higher densities than weaker acids or weakly basic ones, and macroporous resins have a lower density. For example, the true density of styrenic gel-type strong acid cation resin is 1.26g/ml and the apparent density is 0.85g/ml; while the true density of acrylic gel-type weak acid cation resin is 1.19g/ml and the apparent density is 0.75 g/ml.
Solubility of resin
The ion exchange resin should be insoluble. However, substances with a low degree of polymerization included in the synthesis of the resin, and substances generated by the decomposition of the resin will be dissolved during the operation. Resins with a low degree of crosslinking and many active groups have a greater tendency to dissolve.