URETHANE INDUSTRY GLOSSARY - U

The overall coefficient of heat transfer. This value incorporates all the factors involved in the transfer of heat from one area to another, including boundary layer transfer and any or all 'IC' factors. 'U' values are generally used in calculating heat transfer of a structure in a particular environment; whereas 'IC' factors are generally used for single components of a structure.

Any chemical compound which, when admixed with a resin, selectively absorbs UV rays. ultraviolet-zone of invisible radiations beyond the violet end of the spectrum of visible radiations. Since UV wavelengths are shorter than the visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.

A term used in foam slab work, particularly flexible foam, to describe the appearance of the foam front when the angle of rise is so great that the streamers have disappeared underneath the rising foam. This can result in flow lines, side and/or top cracking and the entrapment of large bubbles in the center of the foam slab.

A term used in pour-in-place work to describe the condition of not having completely filled the void or mold with foam. Either not enough chemicals were used, or the foam failed to expand the expected amount.

A term used by some companies in place of 'crude' or 'polymeric' isocyanate.

A term for years used as the common name for a chemical more properly called ethyl carbamate (a biological poison); the term is now used to refer to the product of a reaction between a chemical containing reactive isocyanate groups on its molecule and a chemical containing reactive hydroxyl groups on its molecule. These compounds are, for the most part, biologically inert. The compounds are called polyurethanes. Since the name refers to the molecular joint between the monomer, many different chemicals can be used as the building Blocks or 'monomers' with the final product still being known as a urethane compound or polymer.