Mechanical properties of a hydrophilic acrylic polymer.

Acrylic polymers with hydrophilic groups (i.e., ethyl hydroxyl) may be prepared that convert to a soft elastic gel by absorbing water. Such a polymer has been applied t o dentistry for use as an elastic lining material for dentures. A commercial product, Hydron, was used in this study. The linear expansion of this material after 520 hr of water immersion was found to be 20.4%. Hardness was found to decrease from 15.7 K H N for the dry polymer to 1.5 KHN a t 19% absorbed water content. The swelling pressure was measured and found to reach a maximum value of 157 psi after 204 hr of water immersion. The Young’s modulus was found to decrease from a value of 295,300 psi to 290 psi with 19% absorbed water content. Values were determined on intermediate water contents for the properties studied.