Tubing Glossary

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Adhesive Lined Tubing: Dual-wall tubing with an inner layer that melts and flows when heated, filling voids in the areas being covered, and forming a mechanical bond to the substrate.

Antifungal: Additive used to retard fungal growth in tubing, especially for applications in which tubing is exposed to damp environments.

Antioxidant: Additive used to prevent yellowing of tubing or loss of strength when exposed to oxygen in the atmosphere.

AWG (American Wire Gauge): A method of specifying conductor size. Lower gauge numbers indicate larger conductor size. Click here for a chart of Grayline AWG Tubing Sizes

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Braided Sleeving: A fiber woven sleeve that can be coated or heat treated and that serves to insulate and protect electrical components. Grayline Braided & Expandable Sleeving

Brittleness Temperature: The temperature below which a flexible material exhibits brittle failure when subjected to a specified impact during testing.

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Colorant: Pigment additives used to introduce color to tubing. Both natural colored opaque polymers and clear polymers can be colored. Addition of colorant to clear polymers results in a tinted transparent polymer.

Compound: A chemical blend of base resin and desired additives, which becomes the raw material from which tubing is extruded.

Concentricity: Used to describe the uniformity of the wall thickness of tubing, it is a measure of the offset of the center of the inside diameter from the center of the outside diameter.

Core: The inner wall of dual wall, heat shrinkable tubing.

Cross-linking: The formation of three-dimensional covalent bonds between molecular chains in a polymer, thereby improving the mechanical and thermal properties.

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Durometer: A measurement of the hardness or resistance to surface penetration of a polymer. Usually measured using Shore or Rockwell scales. Higher numbers represent harder materials.

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Elastic Memory: The ability of a polymer to be temporarily shaped to a different geometry before returning to its original shape upon the application of heat. This is the basic principle by which heat shrink tubing has been developed.

Elongation: The maximum amount, expressed as a percentage, that tubing can be stretched in length before it breaks.

European Union (EU) Directive: One of several European requirements that must be met to allow product use in Europe. Current EU Directives include:

• EU 2000/53/EC (ELV: End of Life Vehicles) See Explanation of Common Specifications for details
• EU 2000/95/EC (RoHS: Restriction of Hazardous Substances) See Explanation of Common Specifications for details
• EU 1907/2006 (REACH: Registration, Evaluation, Authorization and Restriction of Chemicals) See Explanation of Common Specifications for details

Expansion: A process used to create heat shrinkable tubing in which polymer tubing is enlarged in diameter (and the wall thickness is reduced) under closely controlled thermal conditions, resulting in a product that will revert to the original diameter upon application of heat.

Expandable Sleeving: A loosely-woven monofilament protective sleeve that can readily expand or contract in diameter to accommodate larger diameter areas of the component being covered.

Expanded ID: The minimum internal diameter of heat shrinkable tubing as supplied to the customer, before heat is applied for recovery.

Extrusion: The thermal and mechanical process by which a polymer compound is conveyed through a heating chamber, forming dies, cooling tanks and vacuum tanks to form tubing.

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Flame Retardant: An additive that is included in tubing compounds to improve resistance to burning.

Fluoropolymer: A polymer compound containing fluorine. These compounds are typically very chemically resistant and can withstand extreme elevated temperatures.Grayline Fluoropolymer (PTFE, FEP, PFA) Tubing

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Halogen Free: A compound that does not contain Fluorine, Chlorine, Bromine, Iodine or Astatine. Halogenated compounds are often used to improve flame resistance of tubing, but when burned these compounds emit smoke which is toxic to humans and corrosive to electronic equipment. Grayline Halogen Free Tubing

Hardness: A measurement of resistance to surface penetration that correlates well with mechanical strength and rigidity. Usually measured using Shore or Rockwell scales.

Heat Forming: A secondary process in which thermoplastic tubing is permanently reformed to a new three-dimensional shape while under elevated temperature conditions.

Heat Shrinkable: Tubing that is capable of being reduced in size when exposed to heat. Grayline Heat Shrink Tubing

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Jacket: The outer wall of dual wall, heat shrinkable tubing.

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LDPE: Low Density PolyEthylene, typical density range of 0.910-0.940 g/cm3

LLDPE: Linear L ow Density PolyEthylene. LLDPE has very short chain branching form the polymer backbone compared to LLPE which has long chain branching. LLDPE typically has higher tensile and elongation.

Lead Free Tubing: see European Union Directive, RoHS.

Liner: The inner wall of dual wall, heat shrinkable tubing.

Longitudinal Shrinkage: The change in length, as opposed to the change in diameter, of heat shrinkable tubing during the recovery process initiated by the application of heat.

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MDPE: Medium Density PolyEthylene, typical density range of 0.926-0.940 g/cm3

MIL Spec: Military Specification. These are standards published by the U.S. Department of Defense. There are several Mil specs that apply to flexible tubing. These include MIL-I631, MIL-I-7444 (replaced by SAE-AMS-I-7444) and MIL-DTL-23053 (replaced by SAE-AMS-DTL-23053). Please see Learn About Tubing - Common Electrical Tubing Specifications for more details.

Monomer: A small molecule that bonds chemically with other monomers to form a longer chain polymer molecule.

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Nylon: A class of polymers know as polyamides. Nylon is a tough, abrasion resistant, semi-rigid material with good high temperature properties.Grayline Nylon Tubing

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OFT (Optional Flame Test): Former CSA test for measuring the flame retardance of tubing. This test is now obsolete and has been replaced with the VW-1 test.

Operating Temperature: The maximum recommended temperature at which tubing may operate in continuous service.

Oxygen Index: The minimum oxygen concentration, expressed as a % of the total ambient gases that will support candle-like combustion of a polymer.

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Phthalate: Esters of phthalic acid that are commonly used as plasticizers to soften and increase the flexibility of PVC compounds. DOP/DEHP and DINP are two commonly used phthalate plasticizers.

Phthalate Free: A compound that contains no intentionally added phthalates. Trace amounts of phthalates may still be present. Grayline's Phthalate-Free Tubing

Plasticizer: A chemical additive that is included in polymer compounds to provide flexibility. Plasticizers serve to fill and increase the spacing between polymer chains, allowing them to slip past each other more readily. Types of plasticizers include phthalates; trimellitates; adipates; epoxidized vegetable oils, and polymerics.

Polyethylene (PE): A tough, flexible low cost plastic. Common applications are bags, film, and squeeze bottles. Low-density polyethylene (LDPE) is the most flexible. Linear low-density polyethylene (LLDPE) is the toughest and cheapest. High-density polyethylene (HDPE) is less transparent, but stiffer and more heat resistant.Grayline's Polyethylene Tubing

Polypropylene (PP): Similar to high-density polyethylene, but more heat resistant (it can handle boiling water) and having high tensile strength and clarity. Common applications are plastic rope and drinking straws.Grayline's Polypropylene Tubing

Polyurethane: A tough, abrasion resistant polymer having excellent low temperature properties and high clarity. Chemically resistant to fuels, oils and solvents, and available in a range of hardnesses, common uses for polyurethane tubing include fuel line and wire abrasion protection. Grayline Polyurethane (TPU) Tubing

Polyvinyl Chloride (PVC): A resin that can be easily blended with many different additives to change the resultant mechanical, electrical and thermal properties of the compound. Common flexible PVC applications are tubing and shower curtains. Common rigid or semi-rigid PVC applications are drainpipe and house siding.Grayline's Polyvinyl Chloride (PVC) Tubing

Polymer: A compound consisting of long molecular chains formed from monomers occurring as repetitive "building blocks".

Polyolefin: A generic term for a group of polymers produced from olefin (or alkene) monomers. Olefins are hydrocarbon substances having a single carbon-to-carbon double bond. Polyolefin heat shrink tubing is typically made from polyethylene and is usually cross-linked.Grayline's Polyolefin Tubing

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Recovery (Heat Shrinkable Tubing): Heat activation of the elastic memory effect to cause expanded heat shrinkable tubing to return to its originally extruded size.

Recovered ID: The internal diameter of heat shrinkable tubing after being allowed to recover fully.

Recovery Temperature: The midpoint of the recovery versus temperature curve of heat shrinkable tubing.

Resin: The base material in a polymer compound.

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Shore Hardness: A series of scales used to indicate hardness. The Shore A scale is most commonly used to measure the hardness of plastic tubing. Within a given scale, a higher number indicates a harder material.

Shrink Ratio: The nominal ratio of expanded diameter to recovered diameter of heat shrinkable tubing.

Specific Gravity: The ratio of the density (mass per unit volume) of a material to the density of water.

Strain Relief: The use of a length of tubing to reduce the stress or strain on a wire or cable being flexed.

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Tensile Strength: The ratio of the amount of axially applied force required to break or rupture a piece of tubing to the cross-sectional area of the tubing. It is expressed in units of force/area, such as pounds per square inch (psi).

Thermoplastic: A polymer that can be repeatedly melted and solidified with only minimal degradation of the properties following each cycle. Common examples are polyvinyl chloride and polyethylene.

Thermoset: A polymer, such as polyolefin, in which irreversible chemical "curing" or "set" takes place as the molecule chains are cross-linked in three dimensions through covalent bonding. Once set, the polymer cannot be melted.

TPE: Thermo-Plastic-Elastomer: A class of copolymers or a mixture of polymers which have both thermoplastic and elastomeric properties. These materials can be melted, can be stretched and then return to their original shape, and have very low creep. TPE's are also referred to ThermoPlastic Rubber (TPR) or ThermoPlastic Vulcanate (TPV) Grayline Rubber Tubing

TPU: Thermo-Plastic-Urethane: also called polyurethane. A tough, abrasion resistant polymer having excellent low temperature properties and high clarity. Chemically resistant to fuels, oils and solvents, and available in a range of hardnesses, common uses for polyurethane tubing include fuel line and wire abrasion protection. Grayline Polyurethane (TPU) Tubing

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Ultraviolet Degradation: The loss of strength or discoloration caused by long-term exposure of tubing to sunlight or other ultraviolet rays.

Ultraviolet (UV) Stabilizer: An additive to tubing compounds that protects against loss of strength or discoloration when it is exposed to the outdoors.

Urethane: See Polyurethane.

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VW 1: A flammability test conducted by UL or CSA. Tubing with a VW-1 rating is highly flame-retardant.

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