URETHANE INDUSTRY GLOSSARY - A

Initials used as an abbreviation for the American Society for Testing and Materials. An organization devoted to the establishment of standard methods and procedures of testing materials. Copies of the approved test methods for urethane foam may be secured by supplying the identifying code number of the test plus the fee.

Normally used in the chemical sense of being a substance used to increase the rate of a chemical reaction, often used synonymously with the term catalyst, amine catalyst, or tin catalyst.

In normal foam industry practice, it is required that the chemicals used be weighed, pumped and dispensed within plus or minus 0.5% of the correct amount. Capability of operation within these narrow limits is available from most machine suppliers. See also 'metering accuracy' and 'shot accuracy';.

The value given to trace residues of acids in the finished polyol. It is of interest because acids can react directly with NCO groups (TDI) and thus must be allowed for in formulation calculations (see index). The normal value for most polyether polyols is less than .05 parts per hundred. Most polyester polyols normally have an acid number between 0.1 and 0.5.

See accelerator

Small mechanical parts that assist the joining of 2 dissimilar pieces, normally used to join pipes of different sizes or to assist in joining pipe to hose threads. Pipe threads are normally tapered while hose threads are straight.

A general term used to describe anything that may be added to the foam chemical mixture, not required in order to produce foam. It generally covers chemical classes such as plasticizers, colorants, reodorants, anti oxidants, fillers.

See lamination.

A term used by liquid spreading device (reciprocator, traverser, spreader) manufacturers to describe the ability of machines to vary the height of the mixer discharge nozzle above the conveyor (or mold) by raising or lowering the crossbar or rails on which the mixer is riding. The adjustability may range from manually loosening bolts and lifting the crossbar into position up to automatic push button operation. Hand powered cranks turning built-in lifting screws are used for an intermediate type.

A term used by machinery manufacturers to describe the ability of their pumps and mixers to be driven at different rates of speed. The minimum type covered by this somewhat all-inclusive term is a set screw adjusted split sheave (pulley). Other types range in complexity from manually rotated cranks or hand wheels up to automatic push button adjustment. Not all adjustable speeds are positive; thus some are not able to hold a setting after adjustment and others are not able to reset at the same markings in order to repeat the desired speed of rotation.

See fixed throughput and variable flow rate.

(See pre-cure and post-cure) a term used to refer to the period of time after all accelerated curing attempts have ceased during which maximum final physical properties are attained. Temperatures are usually maintained at 70-75° F during this period. Example: a molded flexible cushion may be pre-cured for 10 minutes at 250° F to develop enough properties to permit removal from the mold, then post-cured for 1/2 to 3 hours to reach 85% to 95% of the final properties, and then packaged and shipped during which time 'after-cure' continues until 100% of the properties are achieved. After-cure generally is not longer than 3 to 6 days with most formulations.

A term which describes material dripped from the discharge orifice of a self-cleaning mixing head after the continuous flow of liquid has ceased. It is usually objectionable and is influenced by mixer design, mixer wear, mixer cleanliness, material viscosity and flow characteristics, and leakage from the liquid delivery passages (metering ports). agitators-a term which usually refers to the mechanisms that mix and recirculate the various liquids within their tanks. These may be propellers, paddles, turbines, etc. Occasionally the term is used to describe the rotor or impeller that mixes the liquids together in the final mixing chamber, just prior to foaming.

A term which refers to the practice of injecting very small amounts of compressed air (or other gas) into the mixing chamber or into the polyol stream prior to the mixing chamber in order to decrease the average cell diameter in the foam. A high degree of control over cell diameter can be achieved with a precision regulated air bleed system. See also 'catalyst air bleed adapter.'

A term which refers usually to a precision air bleed regulating system. Generally it includes regulators, filters, flowmeters, needle valves, check valves and also inline mixers.

Method of atomizing a liquid stream for spray application purposes without using compressed air at the spray nozzle. Overspray and surface rebound are minimized.

(See also Aromatic) one of the main divisions of organic compounds (those containing carbon) and particularly indicates those compounds having ab open chain molecular structure.

An ambiguous term usually coupled with temperature and refers to the normal temperature of the particular room or environment in which the foam producing equipment or process is installed. It is often used to indicate U.S.A. house or factory temperatures of approximately 70° F.

A term which refers to a class of catalyst compounds used in the urethane foam reaction, These are characterized by having N or NH groups in the molecule and generally accelerate the 'blowing reaction' in preference to the 'gelling reaction'. The amines used as foam catalysts usually (but not necessarily) have a distinctive odor, and are miscible with water.

See amine.

An analysis value determined for isocyanate materials to express their reactive strength, used in some methods for calculating 'stoichiometric balance' of a formula . The value secured has an inverse relationship to the strength of the chemical as the larger the value, the weaker is the reactive strength of the isocyanate per unit of weight. For example, the amine equivalent value for pure TDI is approximately 87 while that of the less reactive crude 'polymeric isocyanates' may be over 130. The method of analysis may be obtained by request to one of the major chemical companies supplying the isocyanate.

A term which refers to the angle formed between the rising foam front and the moving surface from which it is rising on a continuous slab process. This is usually critical for a given formula with an excessively large angle tending to cause cracking of the foam block, while too low an angle tends to cause excessive settling and splits. Adjustments to conveyor speed, chemical flow rate or conveyor angle are usually helpful. Under extreme conditions, the catalyst balance' of the formulation or the processing temperature may have to be modified.

Is used to describe foam having different properties when tested along axes in different directions, e. g. parallel to foam rise as opposed to perpendicular to the foam rise. This difference occurs under conditions causing the individual bubbles to elongate in the direction of foam rise, creating a strong columnar structure parallel to foam rise and a weaker cylindrical structure perpendicular to the foam rise.

Materials which when added to a foam formulation improve the resistance of the foam to oxidative type reactions. Some of these materials retard the yellowing of flexible foam; some improve the aging characteristics of the final foam product under both dry and humid high heat conditions.

Chemicals which impart a slight to moderate degree of electrical conductivity to plastic compounds, thus preventing the accumulation of electrostatic charges on finished articles. They may be incorporated in the materials before molding or applied to their surfaces after molding. They function either by being inherently conductive or by absorbing moisture from the air. Examples of antistatic additives are long-chain aliphatic amines and amides, phosphate esters, quaternary ammonium salts, polyethylene glycols, polyethylene glycol esters, and ethoxylated long-chain aliphatic amines.

A term sometimes used as a noun in describing the practical use of a particular formulation or piece of equipment. The use of urethane foam is often described in a manner such as 'an insulating application' or a 'spray-in-place application'.

A term used to describe an individual or company specializing in the application of foam to a surface or structure. It is often used to describe those who apply foam by spraying and thus are called 'spray applicators'.

A term which refers to a class of organic chemical compounds characterized by having a benzene ring type molecular structure. Tolylene diisocyanate is an example of this type chemical but other isocyanates may or may not be. See also aliphatic.

The accelerated testing of plastics to determine their changes in properties such as dimensional stability, water resistance, resistance to chemical and solvents, light stability, and fatigue resistance.

A term used to describe a control system on a metering unit in which a pressure surge or over-pressurization in the fluid circuit is sensed, actuating a relay which turns off the pump drive motor. This is an excellent safety-feature and does not affect the positive metering value of the system.

A term used to describe a solvent cleaning system for a urethane foam mixing and dispensing head. The usual system is activated by a push button which begins a cycle consisting of a timed amount of solvent, dispensed by a pressure pot or pump, injected into the solvent flush hose and then followed by a timed dispensing of compressed air blowing the solvent from the hose line into the mixing chamber and from there to the waste container. Both solvent and air timers can usually be adjusted to obtain optimum cleaning with maximum economy. A newer system termed 'fully automatic solvent flush' includes an additional timer which initiates the solvent cycle automatically if pouring has not occurred during a preset time period.

A term which usually describes a 'low temperature boiling solvent' type blowing agent added to a formulation deriving at least 80% of the gas required for foam expansion from the water-TDI reaction.