URETHANE INDUSTRY GLOSSARY - W

A term used with rigid foam to describe the percent by weight of water pickup on submergence of a specified sample under a specified depth of water.

Foam in which the gas for expansion was generated by the reaction between water and an isocyanate bearing material. See CO, blown foams and blowing agent for further clarification.

(WVP)The rate of transfer of water vapor through a film of the polymer. This is normally determined by an indirect test method on cast films of the solid polymer rather than on the foam itself. This is sometimes called water vapor transmission (WVT).

An instrument which is utilized to subject articles to accelerated weathering conditions, e.g., rich UV source and water spray.

A term sometimes used to describe scattered large bubbles that occasionally appear in large Blocks of slab foam that are otherwise uniform in cell structure.

Cell membranes or walls in flexible foam that are unbroken or ruptured but intact, which interfere with free air movement through the foam structure. Generally a high proportion of windows, as indicated by the shiny or glittering reflection of light from a cut surface, indicates a foam tending towards closed cells and consequently possibly rather poor in some physical properties. Usually a reduction in the organotin catalyst level in relation to the Amine catalyst level will reduce the incidence of windows. There are other processing factors which can also affect their presence.

See rat holes.