FOR many parents, disposable diapers are a must-have item. Have you ever wondered how a small item like a diaper is able to hold so much liquid? Diapers are usually made of plastic, paper and something called sodium polyacrylate. If you cut open a diaper, you will notice a crystal like substance – that is sodium polyacrylate, which is usually called a super absorbent polymer or SAP. These crystals have a similar feel as fine sand.