Glossary of Foam & Sponge Terms

A2LA - American Association of Laboratory Accreditation- a non-profit, professional membership society committed to the success of laboratories through the administration of a broad spectrum, nationwide laboratory accreditation system and a full range of training on laboratory practices taught by experts in their field.

Abrasion Resistance - The ability of a fiber or fabric to withstand surface wear and rubbing.

Accelerated Aging - A test method to represent extended aging of material in a shorter amount of time. For cellular rubber it is the process of artificially increasing time to measure physical property changes. This usually involves exposure to air at an elevated temperature.

Acrylic Adhesive - A pressure sensitive adhesive formed by the polymerization of acrylic ester monomers. These adhesives exhibit high temperature resistance, excellent U.V. resistance, good plasticizer resistance and good aging characteristics.

Ambient - An ambiguous term referring to a stable temperature environment of approximately 70°F or “room temperature.”

Antioxidants - Chemical compounds or substances that are added to foams to improve their resistance to oxidation. An examples of oxidation in polyurethane foams is a gradual shift of color to yellow.

ASTM - Initials used as an abbreviation for the American Society for Testing and Materials, which is an organization devoted to the establishment of standard methods and procedures of testing materials.

ASTM D 1056-07 - American Society For Testing and Materials. This specification (D 1056) covers flexible cellular rubber products known as sponge rubbers and expanded rubbers. It is designed to provide certain physical property parameters and test methods for cellular rubber. The 07 stands for the revision year 2007. Previous versions include 2000, 1998, 1991, 1985, 1978, 1968, 1967 & 1965.

Ball Rebound Test - One of several test methods for comparing flexible foam for resilience (see Resiliency). Basically, a steel ball of specified mass is dropped from a fixed height onto a foam sample, and the height of the rebound of the ball is recorded. The rebound height is divided by the original height to give a percentage. The method is a relative test rather than absolute, since the density of the foam has a strong influence on the results.

Batch Number - On Rubberlite certifications this basically means ship date. An example would be A-110. The A stands for the month, 11 stands for the day and the 9 stands for the year. The result of this example would be January 11, 2000.

Blemish - An imperfection occurring in a cellular rubber product. It is usually circular in appearance and does not go completely through the material. Sometimes referred to as a dimple.

Blend Materials - Various polymers used in the manufacture of cellular rubber materials that are blended together to give a product a wide range of resistance properties.

Blowing Agent - Various chemicals used in the manufacture of cellular rubber products that cause the material to expand by giving off a gas when they are exposed to heat.

Bun - A cellular rubber product that is manufactured in a mold and is usually rectangular in appearance. Also known as a block and/or plank.

Capability (Process) Index, Cp or Cpk - A statistical measure used to describe the capability of a process to produce a product (output) within specification tolerance limits. The index is a measure that indicates high or low process variability. Note: Where k is a constant number of subgroups of a given size.

Carrier - When referring to double coated pressure sensitive adhesive, it is the thin medium to which the adhesive is anchored to on both sides. One of the most common carriers is Mylar.

Cells - Refers to the cavities or bubbles left in the foam structure after the walls have completely polymerized, which forms a skeletal structure. Cells can be closed (intact walls) or open (skeletal ribs only).

Cellular Rubber - Low to medium density rubber products containing a cellular structure. The cells may either be open and interconnecting or closed and not interconnecting; a generic term for materials containing many cells (either open or closed, or both) dispersed throughout the mass.

Chemically Blown - A term applying to a cellular material in which the cells are formed by gases generated from thermal decomposition or other chemical reaction. In other words and in most cases, a powdered chemical that is added to a rubber mixture which, when exposed to a certain temperature, turns into a gas and causes the foam to expand.

Closed Cell Rubber - A rubber product produced by a specific manufacturing process that utilizes gas forming ingredients in the rubber compound or by subjecting the compound to a high pressure gas such as nitrogen. Closed cell rubber is defined as a product whose cells are totally enclosed by its walls and hence not interconnecting with other cells. This unique physical property enables closed cell rubber to function as an excellent seal for moisture, dust, air, gas, smoke, noise, etc.

Coarse Cell Structure - A term used to describe the appearance of expanded cellular rubber when the individual cells are larger and/or spread apart further than normal. Sometimes incorrectly referred to as Open Cell.

Colorfastness - The ability of a dyed material to retain its color when exposed to light, atmospheric gases or washing which can destroy its color. Degree of colorfastness is tested by standardized procedures, depending on the end-use of the material.

Compression Deflection @ 25% (CD) - The measure of the hardness of a cellular rubber product. In other words, the force required to compress a material 25% of its original thickness. It can be expressed in lb/in² (pounds per square inch) or kPa.

Compression Force Deflection (CFD) - A test which consists of measuring the force necessary to produce a 50% compression over the entire top area of the foam specimen. In other words, the force required to compress a material 50% of its original thickness. Also referred to as Compression Load Deflection (CLD).

Compression Set - The residual decrease in thickness of a test specimen measured 30 minutes or 24 hours after removal from a suitable loading device in which the specimen had been subjected for a definite time to compressive deformation under specified conditions of load and temperature.

Control Limits - Limits on a control chart that are used as criteria for signaling the need for action, or for judging whether a set of data does or does not represent a “state of statistical control.”

Converter - One that is employed in changing a raw material into another form of product.

Cordura™ - A very strong, super fine yarn fabric made of air-textured, high-tenacity nylon that meets specific strength, durability and construction requirements.

Cross Section - Concerning fabrics, the shape of an individual filament when cut at right angles to its axis. Normal shapes for manufactured fibers vary.

Cross-Linking - The bonding of molecules into a structure. This gives the polymer increased strength resulting in superior properties. Crosslinking can achieved by either physical (irradiation by an electron beam) or by chemical means.

Cure - For cellular rubber, the time period and temperature in which various chemical reactions (e.g. cross-linking) occurs. This phase of a process is critical as too much time will produce an over-cured product and too little time will produce an under-cured product.

Delamination (Fabric) - The separation of the individual plies in a laminate.

Delamination (PSA) - The undesirable separation or buckling of the release liner from an adhesive layer usually in the parallel direction of the web. Most often found during high humid conditions causing the paper to grow.

Densified foam - Sometimes called felted foam, it is foam that has been permanently compressed through a precisely controlled thermal setting process.

Density - The weight in solids of a unit volume of material expressed in pounds per cubic foot (PCF) or grams per cubic centimeter (g/cm³). In other words, it is the ratio of the mass of a body to its volume.

Dielectric Strength - The maximum electric field that a foam rubber product can withstand without breaking down, usually measured in Kilovolts per centimeter. At breakdown, a considerable current passes as an arc, usually with more or less all decomposition of the material along the path of the current.

Dimensional stability - The ability of a foam material part to retain the precise shape in which it was fabricated.

Double Coated - A pressure sensitive adhesive consisting of a carrier with similar or dissimilar adhesives applied to both surfaces.

Dry Web Lamination - A lamination process using heat activated web adhesives.

Durometer - An instrument used to measure the hardness of a material. As a general rule, this method is not as accurate as compression deflection @ 25%. Types of durometers include Shore A, D and 00. The proper one to use for soft, cellular materials is Shore 00.

ECH - Epichlorohydrin. A polymer used in the manufacture of cellular rubber. Its primary characteristics are resistance to swell when exposed to fuel and high temperature resistance up to 325ºF.

Elastomer - A macromolecular material that returns rapidly to approximately the initial dimensions and shape after substantial deformation by a weak stress and the release of the stress.

Elongation - The extension between bench marks produced by a tensile force applied to a specimen. Expressed as a percentage, this test is used to measure the length of stretch in a material before it breaks.

Ensolite® - A family of continuous PVC/Nitrile material manufactured by Armacell LLC.

EPDM - Ethylene Propylene Diene. A polymer used in the manufacture of cellular rubber. It has excellent resistance to sunlight, ozone and heat, and good resistance to alkalis and acids.

EVA - Ethylene Vinyl Acetate. It is generally used as a co-polymer in polyolefin foams resulting in greater resilience and higher tensile and tear performance.

Evazote® - A closed cell gas expanded crosslinked polyethylene/EVA foam manufactured by Zotefoams. This family of material is ideal for use in recreational sporting goods applications and certain industrial applications.

Expanded Rubber - A term reserved for closed-cell compounds that are made by incorporating gas-forming ingredients in the rubber compound or by subjecting the compound to high-pressure gas, such as nitrogen. These materials are manufactured in sheet, roll, strip, molded, and special shapes by molding or extrusion.

Extrusion - Material that is formed by being forced through a shaping orifice as a continuous body.

Fabric Lamination - The process by two or more substrates are fused together under a combination of heat, pressure and adhesives (typically fabric to fabric or fabric to foam).

Fabricator - One that constructs a finished product by combining, assembling or processing a raw material.

Filament - A fiber of an indefinite or extreme length such as found naturally in silk. Manufactured fibers are extruded into filaments that are converted in filament yarn.

Filler - A non-fibrous material added to a fabric to increase its weight or to modify its appearance. Examples are insoluble clays or gypsum, starches or gums.

Flame Retardant - Resistant to catching fire. Usually, additives included in the manufacturing ingredients to prevent the material from catching fire, although some polymers are naturally resistant.

Flammability - The characteristics of a material that pertain to its relative ease and relative ability to sustain combustion.

Fleece fabric - Typically a brushed, knitted, polyester fabric with relatively high pile.

Fluid Immersion Test - The submersion of a piece of cellular rubber in Fuel B (similar to Jet Fuel). The foam is weighed before and after and the test measures the amount of fuel absorbed by the material. The lower the % of mass gain, the better the resistance to petroleum based fuels.

Foam - A product, either flexible or rigid, that has been produced by the internal generation of a gas in a fluid medium that is polymerizing while expanding in volume. The final result is either an open or closed-cell product.

Foam to Foam Lamination - A method of fusing together two or more different foam substrates. Sometimes used for dual density applications.

Hardness - The resistance to indentation, as measured under specific conditions.

Hole (void) - An unintentional cavity occurring in a cellular rubber product. It is usually circular in appearance, medium to large in size and goes completely through the material.

Hydrophilic - A foam that has an affinity for water or easily absorbs water. A sponge would be an example.

Hydrophobic - A foam that is resistant to water or won’t easily absorb water.

HyPUR-cel® - A family of medium to high density, open cell polyurethane foams manufactured by Rubberlite, Inc. that exhibit excellent resistance to compression set, they are breathable and can be cut to a custom thickness.

I

Indentation Force Deflection (IFD) - A hardness test which consists of measuring the force necessary to produce designated indentations in a foam material. For example, a 25 and 65% compression. Also referred to as Indention Load Deflection (ILD).

Instron - A company who supplies instrumentation, support services and expertise for testing materials, products and structures.

K Factor - A measure of the thermal conductivity of heat insulation expressed as BTUs/sq. ft. Lower values indicate better insulating materials.

Laboratory Accreditation - Accreditation is defined as: the granting of approval to an institution of learning by an official review board after having met specific requirements. This applies to laboratories based on test methods, documentation and traceability.

Lamination - The process of adhering flexible foam, PSA, vinyl and fabrics in a variety of different combinations. Two common processes are fabric lamination and PSA lamination.

Leveling - The process of taking raw material rubber products and skiving thin cuts of material from it until the rubber is uniform in thickness.

Lot Number - A term used to describe the code on a material that is used for traceability.

Machine Direction - The long direction within the plane of a material, in other words, the direction in which the material is being produced by the machine.

Manufacture Date - The quarter of the year that any given material is processed into its final form.

MIL-C-3133C - A military specification for molded or fabricated parts of cellular elastomeric materials. It primarily covers fabricated parts, sampling, marking and packing procedures. It is used in conjunction with Mil-STD-670-B which covers grade numbers and test requirements.

MIL-R-6130C - A military specification which establishes physical property requirements for chemically blown cellular rubber. Some of these requirements ranges are for Compression Deflection @ 25%, Density, Water Absorption, Low Temperature Resistance, Flame Resistance, etc.

MIL-STD-670-B - See MIL-C-3133C

Modulus - Defined as the force required to elongate material.

MVSS-302 - Motor Vehicle Safety Standard. This specification (302) describes test procedures used to determine the burn rate of parts, portions of parts, and composites used as interior trim parts in passenger cars, multipurpose passenger vehicles, trucks and buses.

Napping - A finishing process that raises the surface fibers of a fabric by means of passage over rapidly revolving cylinders covered with metal points. Produces a downy appearance and is used for certain knit goods, blankets and other fabrics with a raised surface.

Natural Rubber - Derived from botanical sources, primarily from the Heavea brasiliensis tree.

Neoprene (CR) (NEO) - Polychloroprene. A synthetic rubber discovered by the Du Pont Company in 1931. It is a polymer composed of carbon, hydrogen and chlorine. Its features include resistance to petroleum based fluids and flame resistance.

Nitrile Rubber (NBR) - Emulsion copolymers of Butadiene and Acrylonitrile in varying proportions. This chemical is used in the manufacture of expanded rubber primarily for its resistance to swelling in oils and solvents.

Nylon fabric - Man-made fiber in which the forming substance is a synthetic polyamide. These fibers generally exhibit excellent strength, flexibility, elasticity and abrasion resistance.

Nylon/Spandex - A trico fabric specially designed for Rubberlite utilizing bright yarns to produce a slick, high stretch fabric with bright sheen. This fashion forward fabric is used in many higher end consumer products.

Oozing - Concerning PSA, referring to the condition where the sides of a roll become sticky or tacky due to the flowing out of adhesive between the layer of tape.

Open Cell Rubber Material - A rubber product produced by a specific manufacturing process that utilizes a chemical blowing agent that expands the mass during the vulcanization process. Open cell rubber is defined as materials whose cells are not totally enclosed by its walls and open to the surface, either directly or by interconnecting with other cells. The primary characteristics are that water, air or gas can pass through, much like the way water is absorbed by a dish sponge. This type of material is also excellent for padding and cushioning applications where low compression set is required.

Over-Cure - For cellular rubber, the time period or temperature in which various chemical reactions which occur (e.g. cross-linking) last too long. The result is blisters, too tight of a cell structure, voids along the edges, etc. This problem is most apparent on the edges of a material.

Ozone Resistance - The ability of a material to resist degradation in sunlight and/or outdoor exposure.

Physical Properties - Of or pertaining to the matter and energy of a material or the characteristics as applied to physics. For cellular rubber, this pertains to compression deflection, density, water absorption, tensile strength, elongation, etc.

Pin Hole - An unintentional cavity occurring in a cellular rubber product. It is usually circular in appearance, very small and goes completely through the material.

Plastazote® - A closed cell chemically crosslinked polyethylene foam manufactured by Zotefoams. This family of material is ideal for use in cushion and packaging applications.

Plastic - One of many high polymeric substances, including both natural and synthetic products, but excluding rubber. At some stage in its manufacture, every plastic is capable of flowing, under heat and pressure, if necessary, into the desired final shape.

Plasticizer - A substance added to materials during the manufacturing process to improve flexibility, workability, etc.

Plasticizer Migration - Loss of plasticizer from an elastomeric compound. It often migrates to the surface of the material where it is absorbed by another product or evaporates. This process causes the material to lose its flexibility and can contaminate other products.

Plush Nylon fabric - A short pile plush fabric for those customers requiring a soft comfortable fabric next to the end user’s skin.

Polyester fabric - A manufactured fiber in which the fiberforming substance is any long chain synthetic polymer composed of at least 85% by weight of an ester of dihydric alcohol and terephtalic acid (FTC). Polyester fibers are high strength and are resistant to shrinking, stretching and wrinkling.

Polyester Foam - Urethane foams made by reacting isocynate with polyester.

Polyether Foam - Urethane foams made by reacting isocynate with polyether.

Polyethylene - A thermoplastic composed of polymers of ethylene.

Polymer - In dealing with sponge rubber, this is a large molecular chain made up of two or more monomers. These monomers are polymerized or chemically reacted to form a material that is significantly different than either of the two base monomers from which it was made.

Polypropylene - Any of various thermoplastic resins that are polymers of propylene. Propylene is a flammable gas derived from petroleum hydrocarbon cracking and used in organic synthesis.

Polyurethane - Any of various thermoplastic or thermosetting resins, widely varying in flexibility, used in tough chemical-resistant coatings and in adhesives, foams, and electrical insulation.

Pressure Sensitive Adhesive (PSA) - A term used to designate a distinct category of adhesive tapes which in dry (solvent free) form are aggressive and permanently tacky at room temperature and adhere to a variety of surfaces without the need of more than finger or hand pressure. They require no activation by water, solvent or heat and have sufficient cohesive strength so they can be handled with the fingers.

PUR Adhesive - A reactive hot-melt polyurethane used for bonding fabric to fabric or fabric to foam.

PVC - Polyvinyl chloride. A polymer used in the manufacture of expanded rubber. This compound is inherently fire retardant because of its high chlorine content.

RE - Terminology derived from the ASTM-D-1056-65 specification. The R stands for cellular rubbers made from natural rubber, synthetic rubber or rubber-like materials, alone or in combinations where specific resistance to the action of petroleum based oils is not required. The E is a designation for closed-cell material.

Resiliency - A test to determine the shock absorption properties of a foam. On this test, a material is placed flat on an instrument and a weight is dropped onto it from a specified height. The amount of bounce is then taken from a scale to get the final value. The lower the value, the higher the shock absorption properties of the foam.

RO - Terminology derived from the ASTM-D-1056-65 specification. The R stands for cellular rubbers made from natural rubber, synthetic rubber or rubber-like materials, alone or in combinations where specific resistance to the action of petroleum based oils is not required. The O is a designation for open-cell material.

Rubber - A material that is capable of recovering from large deformations quickly and forcibly, and can be, or already is, modified to a state in which it is essentially insoluable (but can swell) in boiling solvent.

Rubber Based Adhesives - An adhesive made from one or more synthetic or natural elastomers and tackifiers to produce a pressure-sensitive adhesive. These adhesives are characterized by having higher quick tack and adhesion than acrylics, however, they lack aging and weather resistance.

SAE-J-18 - A test method which covers flexible cellular products known as sponge rubbers and expanded rubbers. It is essentially the same as ASTM-D-1056. The SAE stands for Society of Automotive Engineers.

SBE - Terminology derived from the ASTM-D-1056-65 specification. The SB Designation stands for cellular rubbers made from synthetic rubber or rubber-like materials having oil resistance with low swell. The E is a designation for closed-cell material.

SBR - Styrene-butadiene rubber. A polymer used in the manufacture of expanded rubber. It is very economical and possesses no unique chemical resistance properties.

SCE - Terminology derived from the ASTM-D-1056-65 specification. The SC Designation stands for cellular rubbers made from synthetic rubber or rubber-like materials having oil resistance with medium swell. The E is a designation for closed-cell material.

Scrim (Tissue) - A thin layer of fabric type material that open-cell sponge rubber is extruded and cured upon. It primarily improves the bonding characteristics to PSA and other types of adhesives.

Self-Extinguishing - A somewhat loosely used term describing the ability of a material to cease burning once the source of flame has been removed.

Shelf Life - The period of time that a product can be stored under specific conditions and still remain suitable for use.

Shore - A company that manufacturers testing and other related types of equipment. “00” is a type of durometer used to test the hardness of cellular rubber. “A” is a type of durometer used to test the hardness of solid rubber.

Shrinkage - An inadvertent dimensional decrease of cellular structure without an actual breakdown or collapse of the cell. This characteristic is relatively common in all cellular rubber and plastic products. The primary cause is the equalization of pressure from the manufacturing process to normal atmospheric pressures.

Silicone - A rubber made from silicone elastomers and noted for its retention of flexibility, resilience, tensile strength and wide temperature range.

Skin - A relatively dense layer at the surface of a cellular rubber material. This layer is the result of exposure to heat and/or contact with a mold during the manufacturing process.

Skive - To shave or cut off the surface of a rubber material in a horizontal manner. Sometimes referred to as splitting which means to divide sharply or cleanly into layers.

Slitting - The action of cutting material to width.

Specification - A document that spells out the requirements for a particular material or group of materials. It normally details the physical properties, performance requirements, general composition, sampling procedure and packaging characteristics.

Sponge Rubber - A cellular rubber consisting predominantly of open cells made from a solid rubber compound. These products are manufactured in sheet, roll, strip, and molded or special shapes. Sometimes referred to as foam rubber.

Sportloop - An unbroken loop fabric meeting your need for a low cost, economical and moderate cycle life hook compatible fabric.

Stripping - A product and/or process of producing a long, narrow piece of material that is uniform in width. Sometimes referred to as slitting.

Substrate - The surface to which a pressure-sensitive tape, fabric, foam, etc. is applied.

Supazote® - A closed cell chemically crosslinked polyethylene foam manufactured by Zotefoams. It is formulated to provide an extremely soft feel and is very elastic. This family of material is ideal for use in healthcare applications.

Tear Resistance - The force required to tear completely across a specifically nicked rubber test specimen or right angle test specimen, by elongating at a specific rate.

Temperature Range - The minimum and maximum temperature that a material can be exposed to before the physical properties and/or appearance begins to move out of their specification range.

Tensile Strength - The maximum pounds per square inch (psi) that a material can be stretched lengthwise without tearing, expressed as a percentage of the original length.

Terry Nylon fabric - A rib knit terry nylon construction for applications that require a heavier fabric with abrasion resistance and durability.

Thermal formable - To change the shape and/or structure of a material using heat and a suitable mild structure.

Thermoplastic - A material which is capable of softening or melting at elevated temperatures without degradation so that cooling of the material restores it to its original condition.

Thermoset - A material that is cured or transformed by elevated temperatures into a solid condition from which it does not change, upon reheating, until it reaches the decomposition point. Most urethane materials are thermosetting materials (e.g. flexible and rigid foams).

Tight Cell Structure - A term used to describe the appearance of an expanded cellular rubber material when the individual cells are smaller and/or tighter than normal.

Tolerance - The permissible deviation from a specified value of a dimension.

Transfer Tape - An unsupported pressure-sensitive adhesive on a release liner that has been release coated on both sides.

UBL fabric - An unbroken loop material that engages hook fasteners.In addition to our premium grade loop fastener fabric, we also offer intermediate and economy grades.

UL 94 HF1 - Underwriters Laboratory. The 94 is a specification for testing the flammability of plastic materials used for parts in devices and appliances. The HF-1 test is intended to be performed on foamed plastic materials. Other tests include 94 HBF, 94 V-O and 94 5-V

Under cure - For cellular rubber, when the time period in which various chemical reactions occurring (e.g. cross-linking) does not last long enough. The result is a loose cell structure, a mushy appearance, etc. This problem is most apparent in the center of a material and this area will often collapse after skiving.

UV Stabilizer - Any chemical compound which, when mixed with a resin, selectively absorbs UV rays. Since UV wavelengths are shorter than the visible, their photons have more energy, enough to initiate some chemical reactions and to degrade most plastics.

Vinyl - A chemical derived from ethylene and used as a basic material for plastics that are typically tough, flexible, shiny and often used for coverings and clothing.

Visco-cel - A family of medium to high density, viscoelastic polyurethane foams manufactured by Rubberlite, Inc. These foams exhibit excellent memory retention (return to its initial form after compression) and can be cut to a custom thickness.

Viscoelastic - A term describing a urethane foam where the material will return to its initial form or state after deformation or compression.

Void (hole) - An unintentional cavity occurring in a cellular rubber product. It is usually circular in appearance, medium to large in size and goes completely through the material.

Volara® - A cross-linked polyethylene foam manufactured by Voltek. It is extruded to thickness in continuous roll form.

Volextra® - A product manufactured by Voltek. It combines the properties of Volara with the added benefit of a wide range of extrusion coated surfaces on one side, two sides or in between the foam. Volextra® provides enhanced performance, processing and decorative features to meet new surface and structural requirements with a lightweight foam material.

Vulcanization - An irreversible process during which a rubber compound, through a change in its chemical structure, e.g. cross-linking, becomes less plastic and more resistant to swelling by organic liquids. The result is that elastic properties are improved or extended over a wide range of temperatures. Vulcanization can be carried out under numerous conditions but it usually involves heat.

Water Absorption Test - The process of submerging a piece of cellular rubber in distilled water and exposing it to increased atmospheric pressure. The foam is weighed beforehand and afterwards. The test measures the amount of water absorbed by the material. The lower the %, the less water the material absorbs.

Z Suffix - A suffix within ASTM-D-1056 used for special requirements. The test methods and values are to be arranged between the manufacturer and the purchaser