URETHANE INDUSTRY GLOSSARY - I

A shortened form of Indentation Load Deflection value, formerly known as RMA value. A series of readings would be used to make an IFD curve, a single specified reading such as the 25% IFD value would be used for direct comparisons. The Test Method is described in ASTM D 1564-63T.

A ratio of the 65% compression value divided by the 25% value. This ratio or index indicates, to some extent, a more or less linear relationship between readings taken to form a resilience (IFD) curve. Index readings above 2.00 are usually considered good for urethane foam; while index readings below 1.75 are considered poor, and the foam can be described as 'boardy'.

A term used to describe the power driven mixing blade or rotor that is used to mix urethane components in a mixing head.

The shell surrounding the impeller and forming the outer limits of what is commonly called the mixing chamber. This is often readily removable for cleaning purposes. It may be smooth, grooved, or baffled.

See IFD Value.

A measure of the stoichiometric balance or the relationship between the equivalent weights of the combining substances. In the case of urethane foam, this is the relationship between the equivalent weights of the isocyanate materials on the one side and the water and polyol equivalent weights on the other side. An Index of 100 indicates that both equivalents are equal or 'balanced'. An Index of 95 indicates that there is a 5%shortage of isocyanate while an Index of 105 indicates a 5% surplus of isocyanate. A slight theoretical excess of isocyanate, usually 3-5%, is common practice, particularly with flexible foams. Other levels may be specified with special formulations.

The ability to control the rate of flow of one or more of the components to any amount desired. This is very ambiguous, since maximum and minimum limits must usually be specified to obtain the desired tolerances of Accuracy. Some degree of infinite control can be achieved with pressure pot metering, pneumatic drive motors, hydraulic drive motors, variable pitch sheaves, variable contact cones, etc. With some of these a wider range of control is achieved by the sacrifice of stability at a specified setting.

A substance that slows down chemical reaction. Inhibitors are sometimes used in certain types of monomers and resins to prolong storage life.

A spot of off-quality foam located at the point where the first amount of liquid mixture was deposited. This can be due to improper pressure balance, unbalanced discharge velocities, extreme differences in viscosity, oversized mixing chamber, etc.

A synonym for cream time. In frothing it usually refers to the delay time between the initial expansion and the beginning of the secondary or final expansion.

A molding procedure whereby a heat-softened plastic material is forced from a cylinder into a relatively cool cavity which gives the article the desired shape.

Cutting machines that have been installed directly in a continuous slab foam production line so that handling of the foam is minimized. Some manufacturers trim only the top, bottom, and side skins at this point; others go all the way and make all the cuts in-line.

Heat exchangers that have been installed in the flow circuit so that the pump must be operating for the exchanger to be effective. This serves to differentiate between this type and the blanket type units that are wrapped around machine tanks.

A special mixer that has been added to one of the flow circuits in order to premix one or more of the minor ingredients into one of the major component streams. A common use is to premix the silicone and air into the polyol stream at a point just prior to the final mixing zone.

A word used to describe the entire foam producing mechanism after it has been placed into its operating environment and provided with all the services required.

An instrument utilized to determine the tensile, compressive properties and other mechanical properties of foams.

A molded urethane foam product having a dense, tough outer foam skin and a relatively lower density core. The product is achieved in a single pour through a combination of chemical and mechanical aids.

The practice of using a single power source to drive two or more fluid metering system. Each fluid metering systems would be independently variable in output to provide for setting an exact ratio between components , but changing the speed of the master drive motor would change the total flow rate without disturbing the ratio. This is also called a 'master-slave' system.

The practice of mixing the various components inside a mixing chamber or housing and then discharging the mixture through one or more discharge ports. This is usually a more efficient mixing device than an external mixer but generally requires some solvent cleaning at intervals, dependent on the formulation, relative on time, duration of off times, etc. See external mix.

A technique of pouring individual Blocks of slab foam in boxes of a definite length in order to make a wider and higher Block than would ordinarily be possible with the maximum flow rate of the machine available. This is possible because the box ends Block lateral foam movement, forcing the foam upward. On continuous slab the upstream side is always open, resulting in a required increase in conveyor speed to prevent the foam from falling over.

The foaming and swelling of a plastic when exposed to high surface temperatures or flames. It has particular reference to ablative urethanes used on rocket nose cones, and to intumescent coatings. It is extremely useful for fire resistance.

Coatings which when exposed to flame or intense heat decompose and bubble into a foam which protects the substrate and prevents the flame from spreading. Such coatings are used, for example, on reinforced plastic building panels.

A term used to describe foam that has a mixture of widely varying cell sizes and presents a very irregular appearance. This effect is sometimes caused by excessive air introduced to the mixing head and sometimes by certain chemicals added to the formulation.

The family name for those chemical compounds having one or more reactive NCO radicals or groups attached to the main molecule. Tolyene diisocyanate is the most commonly used member of this group.

A regulator installed in a fluid metering circuit in such a manner that variations in downstream pressure do not affect metering accuracy. These are used in R-12 metering and catalyst pressure developing.

Any one of two or more chemical compounds having the same number of the same kind of atoms in their structure, but arranged in a different way. This change in structure sometimes affects the reactivity rate of the compound. In the case of tolylene diisocyanate a definite mixture of isomers is provided to the customer. The most commonly used mixture is an 80/20 blend. See isomer ratio.

Is the ratio between the 2.4 isomer and the 2.6 isomer in commercial TDP. The 50/20 ratio of 2.4/2.6 isomer is the most common blend although the 65/35 2.4/2.6 isomer blend is also available.

Foam characterized by having the same strength proper- ties in all directions. To achieve this the rigid foam, in particular, would have to have 100% spherical shaped cell structure. In actuality the foam bubbles normally achieve a regular dodecahedron shape rather than Spherical. See Anisotropic for additional information.