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Glossary of Terms

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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.
AWG (American Wire Gauge)
A standardized wire gauge system used for the diameters of round, solid, nonferrous, electrically conducting wire. Lower gauge numbers indicate larger conductor size.
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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.
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The formation of three-dimensional covalent bonds between molecular chains in a polymer, thereby improving the mechanical and thermal properties.
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A measurement of the hardness or resistance to surface penetration of a polymer. Usually measured using Shore or Rockwell scales.
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European Union (EU) Directive
A legal act of the European Union which requires member states to achieve a particular result without dictating the means of achieving that result. A directive is 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)
  • EU 2000/95/EC (RoHS: Restriction of Hazardous Substances)
  • EU 2011/65/EU (RoHS 2: Improves Regulatory Conditions and Legal Clarity)
  • EU 1907/2006 (REACH: Registration, Evaluation, Authorization and Restriction of Chemicals)
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.
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.
A polymer compound containing fluorine. These compounds are typically very chemically resistant and can withstand extreme elevated temperatures.
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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.
A measurement of resistance to surface penetration that correlates well with mechanical strength and rigidity. Usually measured using Shore or Rockwell scales.
Heat Shrinkable
Tubing that is capable of being reduced in size when exposed to heat.
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Low Density PolyEthylene; Typical density range of 0.910-0.940 g/cm³.
Linear Low Density PolyEthylene; LLDPE has a very short chain branching from 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.
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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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" for more details.
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A class of polymers known as polyamides. Nylon is a tough, abrasion resistant, semi-rigid material with good high temperature properties.
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Operating Temperature
The maximum recommended temperature at which tubing may operate in continuous service.
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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.
Polypropylene (PP)
Similar to high density polyethylene, but more heat resistant (it can handle boiling water) and has high tensile strength and clarity. Common applications are plastic rope and drinking straws.
A tough, abrasion resistant polymer having excellent low temperature properties and high clarity. Chemically resistant to fuels, oils and solvents. Available in a range of hardnesses. Common uses for polyurethane tubing include fuel line and wire abrasion protection.
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.
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.
Proposition 65
Proposition 65 requires businesses to provide warnings to Californians about significant exposures to chemicals that cause cancer, birth defects or other reproductive harm.  These chemicals can be in the products that Californians purchase, in their homes or workplaces, or that are released into the environment. By requiring that this information be provided, Proposition 65 enables Californians to make informed decisions about their exposures to these chemicals.  Proposition 65 also prohibits California businesses from knowingly discharging significant amounts of listed chemicals into sources of drinking water.  Proposition 65 requires California to publish a list of chemicals known to cause cancer, birth defects or other reproductive harm. This list, which must be updated at least once a year, has grown to include approximately 900 chemicals since it was first published in 1987.  Proposition 65 became law in November 1986, when California voters approved it by a 63-37 percent margin.  The official name of Proposition 65 is the Safe Drinking Water and Toxic Enforcement Act of 1986.
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Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) is a European Union regulation dating from 18 December 2006. REACH addresses the production and use of chemical substances, and their potential impacts on both human health and the environment. Its 849 pages took seven years to pass, and it has been described as the most complex legislation in the Union's history and the most important in 20 years. It is the strictest law to date regulating chemical substances and will affect industries throughout the world. REACH entered into force on 1 June 2007, with a phased implementation over the next decade. The regulation also established the European Chemicals Agency, which manages the technical, scientific and administrative aspects of REACH.
REACH also addresses the continued use of chemical substances of very high concern (SVHC) because of their potential negative impacts on human health or the environment. From 1 June 2011, the European Chemicals Agency must be notified of the presence of SVHCs in articles if the total quantity used is more than one tonne per year and the SVHC is present at more than 0.1% of the mass of the object. Some uses of SVHCs may be subject to prior authorisation from the European Chemicals Agency, and applicants for authorisation will have to include plans to replace the use of the SVHC with a safer alternative (or, if no safer alternative exists, the applicant must work to find one) - known as substitution. As of 15 June 2015, there are 168 SVHCs on the candidate list for authorization.
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 ehat shrinkable tubing after being allowed to recover fully.
Recovery Temperature
The midpoint of the recovery versus temperature curve of heat shrinkable tubing.
RoHS stands for Restriction of Hazardous Substances. RoHS, also known as Directive 2002/95/EC, originated in the European Union and restricts the use of specific hazardous materials found in electrical and electronic products (known as EEE). All applicable products in the EU market after July 1, 2006 must pass RoHS compliance.  The substances banned under RoHS are lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (CrVI), polybrominated biphenyls (PBB), polybrominated diphenyl ethers (PBDE), and four different phthalates (DEHP, BBP, BBP, DIBP).
RoHS 2 
RoHS 2, or the Recast RoHS 2 Directive 2011/65/EU, was published in July 2011 by the European Commission. The scope of the original RoHS was expanded to cover all electrical/electronic equipment, cables, and spare parts with compliance required by July 22, 2019 or sooner depending on product category.  RoHS 2 requires additional compliance recordkeeping from everyone in the supply chain. Additional compliance recordkeeping (which must be kept for 10 years) can include a conformity assessment, CE marking, maintenance of compliance throughout production, and self reporting of non-compliance.
The proposed changes to the original RoHS Directive in RoHS2 (2011/65/EU) are relatively minor. No additional substances have been added to the six currently restricted. Inclusion of RoHS categories 8 (medical devices) and 9 (control and monitoring instruments) products in RoHS has been added as well. RoHS 2 took effect January 2, 2013.
RoHS 3
RoHS 3, or Directive 2015/863, adds four additional restricted substances; Bis(2-ethylhexyl) phthalate (DEHP), Butyl benzyl phthalate (BBP), Dibutyl phthalate (DBP), and Diisobutyl phthalate (DIBP) to the orginal list of six, as cited under REACH legislation. It also adds Category 11 products. RoHS3 takes effect 22 Jul 2019.
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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.
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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).
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 as ThermoPlastic Rubber (TPR) or ThermoPlastic Vulcanate (TPV).
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. Available in a range of hardnesses. Common uses for polyurethane tubing include fuel line and wire abrasion protection.
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WEEE is the acronym for Waste from Electrical and Electronic Equipment. WEEE, also known as Directive 2002/96/EC, mandates the treatment, recovery and recycling of electric and electronic equipment. All applicable products in the EU market after August 13, 2006 must pass WEEE compliance and carry the "Wheelie Bin" sticker. WEEE compliance aims to encourage the design of electronic products with environmentally-safe recycling and recovery in mind. RoHS compliance dovetails into WEEE by reducing the amount of hazardous chemicals used in electronics manufacture.
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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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