Bottoming Out- This happens when a gel is subjected to a load and the gel is no longer evenly distributed under the load, thus no longer supporting the load.

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Closed cell- Used to describe the cell structure, or bubbles, in foams. Closed cell foam has closed cells making the foam denser and usually more impervious to the environment.

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Compression load deflection- The force required to compress a material a given distance.

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Compression set- The amount of deformation that a material retains after compressive stress is released, usually given as a percent of the original dimensions.

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Cone penetration- A method used to show the hardness of a very soft gel by pressing a cone into the material and measuring the depth of its penetration.

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Density- The mass per a unit of volume.

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Durometer- A testing method used to show the hardness of a gel, on different scales. It measures the depth of an indentation in the material created by a given force on a standardized presser foot. (see table)

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Elastomer- A polymer with the ability to return to its original shape after being deformed by a load.

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Elongation- The amount of deflection a material can withstand without failing while being stretched, usually given as a percent of the original dimensions.

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Hydrophilic- The aptitude of a material to absorb water.

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Hydrophobic- The aptitude of a material to repel water.

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Indentation force deflection- A test method to determine load bearing capacity, meaning the firmness or stiffness, of a foam at a given percentage of deflection

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Knit- When thread is looped together to form a uniform fabric, also known as stitching

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Mil- One-thousandth of an inch.

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Open cell- Used to describe the cell structure in foam, open cell foam has open cells making the foam less dense than closed cell.

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Polyester (gels, films, foams)- A polymer consisting mostly of carbon and oxygen with a great ability to resist chemicals

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Polyether (gels, films, foams)- A polymer consisting mostly of carbon and hydrogen with a great ability to resist water

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Polymer- Is a molecule comprised of repeating structural units usually comprised mainly of carbon.

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PU- Common abbreviation for polyurethane, a polymer.

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Resiliency- The ability of a material to absorb energy while being deformed, and unloading the energy, and return to its original state.

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Shore durometer scale A- Used for soft rubbers, elastomers, and plastics (see comparison chart)

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Shore durometer scale OO-Used for foams, and gels (see comparison chart)

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Shore durometer scale OOO- Used for very soft gels (see comparison chart)

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Specific gravity- The ratio of the density of a substance to the density of water. If the specific gravity is greater than 1 it is denser than water.

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Tack- The measurement of the ability of an adhesive to adhere to another surface.

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Tear strength- The force required to rip, or fail a material latitudinally.

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Tensile strength- The force required to fail a material longitudinally.

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Thermoplastic- A polymer that when heated turns to liquid, and when cooled returns to a solid. This material can then be melted repeatedly.

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Thermoset- A polymer that irreversibly cures, either by heat or by chemical reaction. 

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TPE- Abbreviation for thermoplastic elastomer.

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TPU- Abbreviation for thermoplastic polyurethane.

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UV- Stands for ultraviolet light, which could either negatively or positively, effect polymers.

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Viscoelastic- A material that has both viscous and elastic properties. Viscous materials resist shear flow and strain linearly with time. Elastic materials can return to original state once a force is removed.

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Warp- Threads of a weave that run lengthwise against the weft

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Weave- When threads are woven together in a criss-cross pattern often measured in the number of threads per inch.

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Weft- Threads of the weave that run across from side to side, supporting the warp which run lengthwise.