Glossary

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 and/or loss of strength during extrusion processing.

AWG (American Wire Gauge): A method of specifying conductor size. Lower gauge numbers indicate larger conductor size.

Braid: A woven fiber layer applied over wire or cable to act as a protective barrier.

Colorant: Pigment additives used to introduce color to tubing. Both natural colored PVC and clear PVC can be colored.

Compound: A chemical mixture of base resin and desired additives, which can be extruded into tubing.

Concentricity: A comparison of the thinnest wall thickness to the thickest wall thickness.

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.

Elastic Memory: The ability of a polymer to be deformed to a predetermined shape, hold that shape for a period of time, and then return 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 that tubing can be stretched in length before it breaks.

European Union Directive: Several European countries (European Union ¨C EU) require that by a specified date, certain hazardous materials be eliminated from all components of automobiles and electronic equipment sold within the counties. The primary concerns are lead, hexavalent chromium, mercury, cadmium, polybrominated biphenyls (PBB) and polybrominated diphenyl ethers (PBDE).

Expansion: A thermal and mechanical process used to create heat shrinkable tubing in which extruded tubing is enlarged in diameter while being reduced in wall thickness.

Expanded ID: The minimum internal diameter of heat shrinkable tubing as supplied to the customer, i.e., 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, and cooling and vacuum tanks to form tubing.

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

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

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

Lead Free Tubing: see European Union Directive.

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

Longitudinal Shrinkage: The change in length of heat shrinkable tubing during the recovery process initiated upon application of heat.

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 temperature at which tubing may operate in continuous service.

Plasticizer: A chemical additive that is included in PVC compounds in significant amounts to provide flexibility or improve processing.

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 (can handle boiling water) and with high tensile strength and clarity. Common applications are plastic rope, drinking straws, and cigarette package wrapping.

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.

Polyvinyl Chloride (PVC): A resin that can be easily mixed with many different additives to change the resultant properties of the mixture. Common flexible PVC applications are tubing and telephone cords. Common rigid or semi-rigid PVC applications are drainpipe and house siding.

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

Polyolefin: A generic term for cross-linkable thermoset polymers. Polyolefin heat shrink tubing is usually made from polyethylene and its copolymers.

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

Resin: The base material in a plastic compound.

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 reduction of the stress or strain on an object that is obtained through the use of an outer covering of tubing to provide additional stiffness.

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 each cycle. Common examples are polyvinyl chloride and polyethylene.

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

Ultraviolet Degradation: The degradation 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.

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