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CWI Medical

How Do Disposable Diapers Absorb

by Noah Lam, Chief Operating Officer of CWI Medical


Just recently, Lisa Nowak, the NASA astronaut, drove 900 miles wearing a diaper designed for space travel. Have you ever wondered how it really works?

The design for this astronaut incontinence product is similar to what you see on the supermarket shelf. The astronaut design resembles a pair of bike pants. In this day and age, retail consumers have a choice of Diapers with tabs, Pull Ups, Undergarments and Liners.

If you cut open a diaper, you will notice a crystal like substance called sodium polyacrylate that is usually called super absorbent polymer or SAP. These crystals have a similar feel to fine sand. This polymer was created by the scientists from the Dow Chemical Company.

When these crystals are exposed to water, the water is drawn inside the sodium polyacrylate molecule through osmosis. The polymer will continue to absorb water until the water inside the molecule is equivalent to the water outside the molecule. This mixture of water and crystals turn into a gel like substance. In fact, a pound of crystals can absorb about 50 gallons of water.

Since urine contains water and salts, these salts impede the performance of the original sodium polyacrylate. Scientists have modified the polymer to counteract the effects of the salts in urine.

The chaise of a diaper is usually made of plastic or a special designed cloth-like paper that contains wetness and give the diaper it's shape. The next layer wicks the wetness away from the skin. Some of these layers have special one way funnels where the wetness moves in one direction and does not resurface back to the skin. Finally the wetness is drawn into the absorbent inner core and locked in. This inner core is a combination of paper cellulose fluff and the sodium polyacrylate crystals.

Thanks to these new technologies, diapers are more comfortable and absorbent than ever. Can you imagine using animal skins or leaves to contain any incontinence as they did in ancient times??


Noah Lam has over 15 years of experience of providing high quality medical supplies and healthcare products from Acute Care Facilities to parents and children. His company, CWI Medical is a leading provider of clinical diabetic nutrition to healthcare facilities, dialysis centers, and for home use. In addition, CWI Medical is an ACHC Accredited organization maintaining standards of excellence in the Healthcare Field. For more information, please visit


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