Swelling capacity

The swelling capacity of a polymer is the amount of a liquid that can be absorbed by it. This test can done by two methods:

1. Beaker test method^[1]
2. Tea bag test method^[2]

Beaker test method

In this method

• A small amount of superabsorbent polymer material is taken (0.1g) and it is placed in the beaker.
• 100 ml of deionized water is poured into the beaker.
• After 20 min the swollen polymer was separated by using [filter paper]
• By weighing the polymer, one can find the swollen capacity of the SAP material.^[3]

Tea bag test method

• In this method, 0.1 g of SAP material is placed into a permeable bag, which is suspended over excess water in a beaker.
• Wait 20 min. and weigh the bag and then calculate the percentage of swelling through the following formula:

  (w2-w1)/(w1)  %

  w1= weight of the polymer (Before swelling)

  w2= weight of the polymer (After swelling)

• Note: Filter paper only for removing water.

Schroeder's paradox

Main article: Schroeder's paradox

Some polymers exhibit larger experimentally measured swelling capacity when immersed in pure liquid compared to testing with saturated vapor. This phenomenon is known as the Schroeder's paradox.