When liquid water touches the surface of Hydrospan it is attracted to the atomic charge of the polymer molecules. As water is absorbed the polymer matrix stretches to accommodate the in coming water. The absorbed water is so tightly held inside the Hydrospan polymer it appears almost dry to the touch when fully expanded. Even cutting or crushing the polymer will not easily release liquid water. Migrating water molecules inside the Hydrospan uniformly surround each polymer molecule, evenly stretching the internal polymer matrix in all directions. Through this process Hydrospan produces near perfect expansion of molded shapes by soaking in ordinary tap water.
Hydrospan is a safe easy to use 2 component flexible urethane. It is nonhazardous for shipping purposes and produces no odor. It has a mix ratio of 2 parts A to 1 part B component by measured by volume, working life is 10-minutes, full cure time 24 hours. Hardness of cured Hydrospan (before soaking) is 45 Shore A / hardness of expanded Hydrospan (after water soaking for 14 days @ 72 F ) is 35 Shore A. Maximum Percent increase in size is +60%.
To calculate size of fully expanded shape multiply starting dimensions by a factor of 1.6. For example an object which measures 10 inches tall, will become 16 inches tall after one full expansion (10 X 1.6 = 16). Partial expansions of less than the full +60% are possible by early removal from water soaking. Partially expanded castings may have distortions because thin wall areas will increase in size more rapidly than thick sections. Place partially expanded castings in an air tight plastic container until distortions equalize away.
Hydrospan is mixed by hand stirring or electric drill with mixer attachment. The color is transparent blue. We recommend using silicone rubber molds to avoid the use of a release agent which can slow the absorption of water and subsequent expansion process. The time required to complete the expansion process will very with the thickness of the Hydrospan casting. Thin castings will fully expand In several days. Thicker castings with a cross thickness of 2 or 3 inches will require 2 to 3 weeks of water soaking to achieve full expansion. Some temporary distortion occurs as Hydrospan begins the expansion process because thin walled elements tend to expand more rapidly. Water ports can be installed in thicker castings to reduce cross thickness and speed expansion.