Foam Glossary

Air Flow – Amount of air expressed in cubic feet per minute, that can be drawn through a 2″ x 2″ x 1″ FPF sample at .5-inch water pressure differential.

ASTM – American Society for Testing and Materials. An organization devoted to the establishment of standard methods and procedures for testing materials.

Auxiliary Blowing Agent (ABA) – An additive used in the production of FPF which supplements the primary blowing agent (water) and can be used to make FPF softer or lighter. Compounds used to produce gases to expand, or blow, FPF during production. Auxiliary blowing agents are low temperature boiling solvents, such as super-critical liquid carbon dioxide (recovered from the atmosphere), acetone, and isopenthane. Chlorofluorocarbons and methylene chloride are not used in the US in the manufacture of FPF.

Ball Rebound – A test procedure (ASTM D3574) used to measure the surface resilience of FPF. The test involves dropping a standard steel ball on known mass from a predetermined height onto a FPF sample and measuring the percent of rebound.

Board Foot – A unit of FPF measurement equal to a square foot of material one inch in thickness.

Boardy – FPF with a stiff or rigid feel, generally indicated by high 25% IFD values and low compression modulus.

Bonded FPF – FPF particles or shredded FPF (often manufacturing scrap) that has been glued to form a useful product. The resultant FPF block is peeled into the desired thickness. Largest use is for carpet cushion.

Bonding – The combination of two or more components into a multiple-layer composite. In furniture applications, FPF is often adhered to other FPF grades or to polyester fiber.

Boston Chair Test – Boston Fire Department test method to measure performance of FPF padding materials when exposed to a fairly severe flaming ignition source. This test is a full scale composite test. Test method is now similar to California TB 133 with additions.

Bottom Out – Lack of support under full weight load.

Bun – A segment of FPF cut off from continuously produced slabstock type of FPF.

California Technical Bulletin 117 FPF – FPF that will meet the component combustibility requirements of this standard.

Cell – The cavity remaining in the structure of FPF surrounded by polymer membranes or the polymer skeleton after blowing is complete.

Cell Opening – In FPF materials, the breaking of membranes within the cell structure, permitting flow of air through the material.

Closed Cells – FPF cells having intact cell membranes thereby reducing or eliminating passageways for airflow.

CFC-Free FPF – FPFs that have been made without the use of chlorofluorocarbons as auxiliary blowing agents.

Combustion Modified FPF – FPFs manufactured by using additives based on chlorine, bromine, or phosphorus chemistry to reduce ease of ignition. Hydrated alumina or melamine are also used.

Comfort – The ability of the cushioning structure to deflect at the surface and to conform to body shape, preventing a concentration of pressure on the body.

Compression Modulus – Ratio of an FPF’s ability to support force at different indentation (or compression) levels. It is determined by taking the ratio of the FPF’s IFD at 25% indentation and 65% indentation (65% IFD/25% IFD). The compression modulus is typically a function of FPF chemical formulation and the manufacturing process. In most cases, the higher the density the greater the compression modulus. Other terms that are used interchangeably are: support factor, and modulus.

Compression Set – A permanent loss of initial height of an FPF sample after compression due to a bending or a collapse of the cell framework within the FPF sample. It is most commonly expressed as a percent of original height.

Conventional FPF – Polyether type FPFs made by the basic manufacturing process.

Convoluted – An FPF product resulting from a fabrication process involving the use of special cutting equipment to produce an FPF sheet with peaks and valleys.

Cradling – The ability of the cushion system to distribute body weight uniformly over the seating area.

Crushing – A conditioning process using a mechanical or vacuum-assisted procedure to open the closed cells of a high resilience slabstock or molded FPF.

Density – A measurement of the mass per unit volume. It is measured and expressed in pounds per cubic foot (pcf) or kilograms per cubic meter.

Durability – How well an FPF retains its comfort, support and shape with use.

Dynamic Fatigue – A durability test performed in the laboratory using roller-shear or pounding type mechanisms.

Flex Fatigue – The loss of FPF firmness after flexing the FPF a predetermined number of cycles.

FPF – The new acronym used to describe flexible polyurethane foam.

Hand – The feel of the FPF as the hand is rubbed lightly over the surface. In home furnishings, FPF with a good hand has a springy, velvet feel.

High Comfort (HC) FPF – Low density (1.8 – 2.2 pcf) high resilience FPF

High Resilience (HR) FPF – High Resilience FPF have a high support factor and greater surface resilience hat conventional FPFs and are defined in ASTM D3770. High resilience FPF has a less uniform (more random) cell structure, different from conventional products. The different cell structure helps add support, comfort, and resilience or bounce.

Hysteresis – The ability of FPF to maintain original characteristics after flexing. Lower hysteresis values, or less IFD loss are desirable.

Indentation Force Deflection (IFD) – A measure of the load bearing capacity of flexible polyurethane foam. IFD is generally measured as the force (in pounds) required to compress a 50 square inch circular indentor foot into a four inch thick sample, typically 15 inches square or larger, to a stated percentage of the sample’s initial height. Common IFD values are generated at 25 and 65 percent of initial height. (Reference Test Method ASTM D3574. ) Note: Previously called “ILD (Indentation Load Deflection)”.

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

Isocyanate – A shorthand name for the family of diisocyanates which are one of the two major ingredients in the chemical process by which polyurethane foam is made.

Laminating – The bonding of layers of foam and/or other materials together into a single composite. This may be accomplished through adhesives or through heat processes like flame lamination.

Latex – A product manufactured partially or totally from rubber tree sap which is not related to polyurethane foam.

Laydown Device – See “Mixing Head”

Loop Slitter – A mechanical slitter which allows continuous slitting of long buns of foam.

Mixing Head – The device that mixes two or more component streams before dispensing the foam-producing mixture to the foam production surface or mold.

Mold Packing – The practice of purposely adding more material to the mold than is actually required to just fill it. The extra material serves to accommodate slight changes in material temperatures, mold temperatures, and pour patterns. It is also a way to improve load-bearing properties without changing the foam formulation.

Molded Foam – A cellular foam product having the shape of the mold cavity in which it was produced.

Open Cell Structure – A permeable structure in flexible foam in which there is minimal barrier between cells, and gases or liquids can pass freely through the foam.

Peeling – The process whereby thin sheets of foam are cut from a cylinder of foam. Similar to plywood peeling.

Pieced – Flexible polyurethane foam that has been glued together from two or more smaller pieces. Commonly seen in cushioning to create special shapes or properties, or to make use of small pieces produced during fabrication.

Percolation – Staple fiber migration though cover material.

Polymer Density – The density of the material made up strictly by the FPF chemistry without the filters or reinforcements included.

Preflex – The practice of compressing an FPF sample up to six times to a predetermined thickness before determining IFD.

Recovery – The amount of return to original dimension and properties of an FPF sample after a deforming force is removed.

Resilience – An indicator of the surface elasticity or “springiness” of FPF. It is measured by dropping a standard steel ball onto the FPF cushion from a given height and measuring what percentage the ball rebounds.

Slab Stock – FPF made by the continuous pouring of mixed liquids onto a conveyor, creating a continuous run of FPF.

Static Fatigue – The loss in load-bearing properties of an FPF sample after being under constant compression.

“Supersoft” FPF – FPFs that have an IFD measurement with the 7 to 10 pound range with a softness comparable to the feel of fiber.

Support Factor (see Compression Modulus) – Support Factor is a ratio os 65% IFD.25% IFD. When the support factor is known, it can be used in conjunction with a known 25% IFD value to determine the 65% IFD value. Seating FPFs with low support factors are more likely to bottom out.

Surface Firmness – The number of pounds of force necessary to indent an FPF sample by 25% of its original height.

Surfactants A term to describe substances that provide resiliency and stability to thin films and that markedly lower the surface tension of liquids, thus permitting easier bubble formation. An integral part of the foam manufacturing chemistry.

TDI An abbreviation for toluene diioscyanate.

Tear Strength A measure of the force required to continue a tear in a foam after a split or break has been started and expressed in pounds per inch (lbs/in.). This property is important in determining suitability of foam in applications where the material is sewed, stapled, or otherwise anchored to a solid substrate. Also important in demoldability. (ASTM D3574).

Tensile Strength The pounds per square inch of force required to stretch a material to the breaking point. (Reference ASTM D3574).

Tight Foam Flexible polyurethane foam with many closed cells, resulting in low air flow measurements.

Total Vertical Motion (TVM) The deflection of a seating system during sitting.

Urethane Actually a misnomer as applied to polyurethane foam. A colorless, crystalline substance used primarily in medicines, pesticides, and fungicides. Urethane is not used in the production of urethane polymers or foams. The urethanes of the plastics industry are so named because the repeating units of their structures resemble the chemical urethane.

Virgin Foam Unfilled flexible slabstock foam that has not been processed in any manner other than cutting to shape.

Voids The undesirable formation of large cavities or pockets in a foam structure. Voids are usually caused by poor moldability or incorrect mold filling. In the case of foam buns, voids occur when then blowing and polymerization reactions are out of balance.

Water Blown Foam Flexible polyurethane foam in which the gas for expansion is carbon dioxide generated by the reaction between water and an isocyanate material. All flexible polyurethane foam is water blown, although auxiliary blowing agents are often used to obtain special physical properties.

Windows The thin membranes formed between cell struts.Windows may be present (a closed-cell foam) or absent (an open-cell foam) depending on the particular foam chemistry used.


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