Particle size and related physical property of ion exchange resin has big influence to its operation and performance in softening water equipment.
Particle Size
Normally ion exchange resins are made into beads-like small particles, its size is very important. Smaller particles with its faster reaction speed, but higher resistance to liquid, hence it would need higher working pressure; especially liquid like priming, the influence is obvious. We suggest select proper size of ion exchange resin. With the size of ion exchange resin less than 0.2 mm (approx. 70 mesh), it would apparently increase liquid resistance, decrease flow rate and production capacity.
Wet screening is often used to measure resin size, screen it after ion exchange resin absorb water and swell, accumulating its retention on screen mesh with 20, 30, 40, 50……mesh, the 90% particles which can pass through respective screen meshes we call it as Effective Particles. The effective particles of most ion exchange resin products are between 0.4-0.6mm.
Density
The density of dry ion exchange resin is referred to as true density, the weight of wet resin ÿ single λ volume with its spaces between particles are referred to as apparent density. The density of ion exchange resin has something to do with its degree of crosslinking and exchange group character. Normally, higher crosslinking degree, higher density, the density of strong acid and base resin are higher than weak ones, and macro-porous resin is with low density.
E.G.:
The true density of styrene gel strong acid cationic resin is 1.26g/ml, apparent density 0.85g/ml;
The true density of acrylic gel type weak acid cationic resin is 1.19g/ml, apparent density 0.75g/ml.
Solubility
Ion exchange resin should be a substance without solubility. But some polymerization-lowered matters generated in synthetizing process, and some matters generated in resin decomposition, would dissolve out in operation. The resin with low crosslinking degree, and including more active group, is with large dissolution tendency.
Degree of Swelling
Ion exchange resin contain lots of hydrophilic group, swelling as touching with water. While ions in resin are exchanging, as cationic ion resin changes from H+ to Na+, negative ion resin change from CI- to OH-, it would swell because its diameter increase. Normally resin with low crosslinking degree is with large swelling degree. Degree of swelling has to be considered to fit volume change in operation when ion exchange equipment is designed.
Durability
Resin particles change such as transfer, friction, expansion and contraction during operation, some few wear and tear after long-term use, hence the resin should be with high mechanical strength and abrasive resistance. Normally, the resin with low crosslinking degree is easy to break, but its durability is mainly subject to uniformity coefficient and strength of crosslinking structure. E.g.: macro-porous resin, has higher crosslinking degree, stable structure, and be able to regenerate repeatedly.
