ALIPHATIC COMPOUND	A polymer composed of hydrogen and carbon that does not contain aromatic rings. The carbons can be joined in chains, branched chains or nonaromatic rings. Examples are ethylene and acetylene. See Aromatic compound.
AMORPHOUS POLYMERS	Sanitary works Clauses and advice on repair PHP , Javascript Accommodation of clausesThermoplastics that have no crystallinity; for example, polysulfone or polycarbonate. Amorphous polymers have a glass transition temperature (a range at which they soften) but no defined melting point. See Semi-crystalline polymers.
AROMATIC COMPOUND	A polymer composed of carbon and hydrogen which contains benzene rings or similar rings of atoms. The bonds form a very stable molecule. See Aliphatic compound.
ASTM	American Society for Testing and Materials
BULK DENSITY	The weight of a unit of a material in powdered or granular form, including voids (air) inherent in the material.
BUMP TUBING	A bump tube (also called taper tube or draw down) has different diameters at each end; the diameter may also vary along the tube’s length. Generally, the smaller diameter end is inserted into the body and the larger diameter end attaches to the medical device.
CO-EXTRUSION	Co-extrusion is the process of combining or layering materials so that the medical tube obtains characteristics from each. For example, one material might help a very small tube retain the flexibility to reach further into the vasculature while the other material supplies the strength and kink resistance needed to push it in. Co-extrusion may change a tube’s appearance, chemical characteristics or mechanical attributes, like lubricity.
CO-POLYMER	Two monomers polymerized together to form a polymer.
CROSSHEAD	A device for changing the extrudate flow.
CRYSTALLINITY	Ordered repeated structures (crystals) encountered in polymers below a certain temperature. Most polymers are semi-crystalline, containing both crystalline and amorphous regions.
DEGRADATION	A change in the properties—tensile strength, color, shape, etc.—of a material under the influence of one or more environmental factors, such as heat, light or chemicals.
DENSITY	Density affects most end-product physical properties like stiffness, impact strength and optical properties. See Specific gravity.
DUROMETER	A test that measures the depth of an indentation in a material, created by a given force on a standardized presser foot. This depth depends on the hardness of the material, its visoelastic properties, the shape of the presser foot and the duration of the test. Depending on the testing standard used, there may be as many as 12 scales. In general, the A scale is for softer plastics and the D scale is for harder ones. A higher value indicates a harder material. See Hardness.
ELASTICITY	The plastic's ability to return to its original size and shape after being deformed. Elasticity is the opposite of plasticity, in which plastic holds the shape to which it is deformed.
ELONGATION AT BREAK	The maxium elongation a plastic can undergo. See Tensile Elongation.
ENGINEERING RESINS	Resins for high-performance applications, such as polycarbonate (PC).
EXTRUDER	Equipment for melting, pressurizing and homogenizing plastics by means of a rotating screw. Different configurations are possible; the most simple one is a single screw extruder mainly used for conversion processes like profile extrusion.
GLASS TRANSITION TEMPERATURE	The lowest temperature at which a polymer can be considered softened and possibly flowable. The temperature at which amorphous polymers undergo a second order phase transition from a rubbery, viscous amorphous solid to a brittle glassy amorphous solid.
GUIDEWIRE	Guidewires are inserted in a patient to the spot where a catheter or other tube must go. The medical tube is then inserted over the guidewire. Coatings increase lubricity, reduce the risk of infection or add other desired characteristics.
HARDNESS	Resistance of a surface to deformation. The different hardness measures for characterizing polymers include Shore hardness (two scales, A for softer and D for harder materials). See Durometer.
HDT	See heat distortion temperature.
HEAT DISTORTION TEMPERATURE	HDT is the initial softening  point of a polymer and relates closely to the glass transition temperature of the polymer. Mechanical strength deteriorates above the HDT.
HEAT RESISTANCE	The ultimate heat resistance is the temperature above which irreversible degradation occurs to the material. Up to this temperature, if the material is cooled, it will revert back to an equal or slightly stronger level. Above this temperature, strength is lost even after cooling.
IMPLANT	A device that is placed into a surgically or naturally formed cavity of the human body and is intended to remain implanted continuously for a period of 30 days or more. The FDA may use its discretion to determine that devices placed in the body for shorter periods of time are implants.
LUBRICITY	Having a slippery or smooth quality. Good lubricity goes with a low coefficient of friction.
MELTING POINT	The temperature at which the structure of a crystalline polymer is destroyed to yield a liquid. It is not scientifically correct to talk about the melting point of an amorphous polymer because it has no crystalline structure. In extrusion practice, however, the glass transition temperature plus 122°F (50°C) is often used to define an equivalent melting point for amorphous polymers.
MINIATURIZATION	The drive to miniaturize reflects the desire for minimally invasive procedures and for appropriately sized pediatric products. Tubes with micro-miniature dimensions have the potential to considerably reduce trauma and risk, particularly for pediatric patients.
MULTI-LUMEN	Multi-lumen tubing has multiple holes (lumens) through which different tasks can be accomplished: for example, delivery and withdrawal of fluids, wires for steering a catheter, devices to grasp tissue for a biopsy and a fiber optic line to allow doctors to monitor progress during a surgical procedure.
OPERATING TEMPERATURE	It’s generally acceptable to use 9 to 18°F (-12 to -7°C) below the heat deflection temperature (HDT) as the maximum short-term operating temperature
POLYMER	A large molecule (macromolecule) composed of repeating structural units connected by covalent chemical bonds. Well-known examples of polymers include plastics, DNA and proteins.
PROFILE EXTRUSIONS	Profile extrusions are tubes that are not circular in shape and/or have lumens that are not circular. A D-shaped tube, for example, might be necessary to meet specifications such as flexibility or strength or to connect to the medical device. Sanitary works Clauses and advice on repair PHP , Javascript Accommodation of clauses
PROPERTIES	The physical and mechanical properties of a polyurethane, nylon or engineering resin depend on its chemistry, structure, chain length and bonds between chains. They can be altered by combining the material mechanically and chemically with other materials, creating a copolymer that shares some of the properties of both materials.
RADIOPAQUE	Radiopaque materials, such as barium sulfate, bismuth subcarbonate, bismuth trioxide and tungsten, are visible in x-rays. See Stripes.
SEMI-CRYSTALLINE POLYMERS	A thermoplastic with both amorphous and crystalline regions; for example, nylon. These polymers have both a glass transition temperature and a sharp melting point, but they lose a significant amount of their mechanical properties when heated above the glass transition temperature. See Amorphous polymers.
SHORE HARDNESS	See Hardness.
SPECIFIC GRAVITY	The ratio of the density of a given substance to the density of water when both are at the same temperature, making it a dimensionless quantity. Substances with a specific gravity greater than 0.036 lb/in3 (1 g/cc) are denser than water and will sink in it. Specific gravity is a special case of, or in some usages synonymous with, relative density. See Density.
STRIPES	In striped tubing, a clear tube might have co-extruded stripes to help identify the tube or orient it in the body, while still allowing the contents of the tube to be seen. An irrigation device, for example, might have two long tubes, one to deliver liquid and one to flush it. When each tube is striped with a different color, they are easy to identify and separate no matter how long they are or how deep they go. Yet the striping also leaves a clear "window" in the tube, allowing medical personnel to track the tube’s contents. Stripes can also carry radiopaque materials (barium sulfate, bismuth subcarbonate, bismuth trioxide and tungsten) that are visible in x-rays. As an example, the radiopaque stripe on a urology stent indicates whether the curled end is in the correct position before the guidewire is extracted. Radiopaque stripes must be concentric to keep them visible to the x-rays from every angle in the body.
TENSILE ELONGATION	The amount that length increases in response to a tensile load, expressed as a percent of the original length. Elongation at break is the maximum elongation the plastic can undergo.
TENSILE STRENGTH	The amount of stress a material will endure before failing. In general, tensile strength increases with polymer chain length. Tensile properties are the most important indication of the strength and stiffness of the material.
THERMOPLASTICS	Polymers that can be melted by heating and solidified by cooling, and may be re-melted repeatedly. (Themosets, by contrast, flow before molding but harden after; if more heat is added, the polymer degrades rather than melting.) Thermoplastics are elastic and flexible above each resin’s specific glass transition temperature. Depending on the temperature, most thermoplastics have a crystalline region (giving it strength and rigidity) and an amorphous region (giving it elasticity). Thermoplastics that do not crystallize are called “amorphous” plastics and are most often used in applications where clarity is important. Examples of thermoplastics are polyethylene, polycarbonate and nylon. See thermosets.
THERMOSETS	Plastics that flow before molding but undergo chemical change during processing, which cures or hardens them. If more heat is applied, the polymer degrades rather than melting. (Thermoplastics, by contract, soften when heated and harden when cooled.) Example of thermosetting plastics are polyurethane and neoprene. See thermoplastics.
VICAT SOFTENING POINT	The temperature at which a flat-ended needle of 1 mm2 circular cross-section will penetrate a thermoplastic specimen to a depth of 1 mm under a specified load using a selected uniform rate of temperature rise. It's the softening point for materials (such as polyethylene) that have no definite melting point. Also known as Vicat hardness.
VISCOSITY	The resistance to flow of a fluid, defined as the ratio of shear stress to shear rate. The viscosity of a polymer decreases as the shear rate increases.
WATER IMMERSION	The percent increase in weight of a specimen (dried for 24 hours) before and after immersion in 23°C water for various times. This property affects dimensional stability and some mechanical properties.