A study on the friction properties of PAAc hydrogel under low loads in air and water

The friction properties of poly(acrylic acid) (PAAc) hydrogel have been studied under low loads using a ball-on-plate friction tester. And the influences of atmospheres, load, water contents of the polymers and its surface morph have been investigated. It is found that the friction coefficient of hydrogels is obviously lower in water than in air. The friction coefficient of PAAc hydrogel decreases as the load increases, and the effect is more conspicuous under low load. The friction property of polymer hydrogels depends on the water content of it, namely, the higher the water content, the lower the friction coefficient. The dimpled surface of PAAc hydrogel can effectively lead to a low friction coefficient. There is the balance of mechanical contact and water contact with slider surface is important for hydrogel lubrication.