How do polymer crystals absorb water

As I kept thinking about the water crystal pearls, I realized that I am ready to the next step — to try and understand how these superabsorbent polymers work.

My first stop for information was an article in Wikipedia thanks to the people who wrote it! Here is what I found there:. Superabsorbent polymers SAP also called slush powder are polymers that can absorb and retain extremely large amounts of a liquid relative to their own mass. Water absorbing polymers, which are classified as hydro gels when cross-linked, [2] absorb aqueous solutions through hydrogen bonding with water molecules.

In deionized and distilled water, a SAP may absorb times its weight from 30—60 times its own volume , but when put into a 0. The presence of valence cations in the solution will impede the polymers ability to bond with the water molecule.

The total absorbency and swelling capacity are controlled by the type and degree of cross-linkers used to make the gel. Low density cross-linked SAP generally have a higher absorbent capacity and swell to a larger degree.

These types of SAPs also have a softer and more sticky gel formation. How to Make Polymer Crystals. How to Dissolve Polyethylene.

Science and Sponge Activities. Science Projects for 7 Year Olds. How to Make Crystals Out of Salt. How to Make Bouncy Putty. Citric Acid Experiments. Homemade Clear Liquid Plastic. How to Grow Mineral Crystals. How to Rubberize an Egg.

How to Make Sugar Water for Bees. Substances That Are Impermeable to Water. How to Shrink Rubber Bands. The crystals can be dried in the sun. The sunlight will shrink them to a smaller size.

An extension of this experiment involves taking a baby diaper apart to determine which part of the diaper "keeps baby dry". Addition of salts of sodium or calcium reverses the swelling process. Water is no longer needed inside the polymer to balance the salt concentration, so the structure collapses or deflates. Polyacrylate is non-toxic.

It is, however, irritating to the eye and nasal membranes. Always wear chemical splash goggles when using this material. The gelled material can be disposed of in the trash. Do not put it in the sink, as it may clog the drain! Super-Absorbing Polymer Powder Sodium polyacrylate is an example of a super-absorbing polymer. Continue adding water to both cups until absorption seems to stop.