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Plastic Piping Definitions and Terms

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 ABRASION RESISTANCE:

Ability to withstand the effects of repeated wearing, rubbing, scraping, etc.

ACCEPTANCE TEST:

An investigation performed on an individual lot of a previously qualified product, by, or under the observation of, the purchaser to establish conformity with a purchase agreement.

ACRYLIC RESINS:

A class of thermoplastic resins produced by polymerization of acrylic acid derivatives.

ACRYLONITRILE - BUTADIENE STYRENE (ABS):

Plastics containing polymers and/or blends of polymers, in which the minimum butadiene content is 6 percent, the minimum styrene and/ or substituted styrene content is 15 percent, and the maximum content of all other monomers is not more than 5 percent, and lubricants, stabilizers and colorants.

ADHESIVE:

A substance capable of holding materials together by surface attachment.

AGING:

The effect of time on materials.

ALKYD RESINS:

A class of thermosetting resins produced by condensation of a polybased acid or anhydride and a polyhydric alcohol.

ANNEAL:

To prevent the formation of or remove stresses in plastic parts by controlled cooling from a suitable elevated temperature.

BELL END:

The enlarged portion of a pipe that resembles the socket portion of a fitting and that is intended to be used to make a joint by inserting a piece of pipe into it. Joining may be accomplished by solvent cements, adhesives, or mechanical techniques.

LISTER:

Undesirable rounded elevation of the surface of a plastic, whose boundaries may be either more or less sharply defined, somewhat resembling in shape a blister on the human skin. A blister may burst and become flattened.

BOND:

To attach by means of an adhesive.

BURNED:

Showing evidence of thermal decomposition through some discoloration, distortion, or destruction of the surface of the plastic.

BURST STRENGTH:

The internal pressure required to break a pipe or fitting. This pressure will vary with the rate of build-up of the pressure and the time during which the pressure is held.

BUTYLENE PLASTICS:

Plastics based on resins made by the polymerization of butane or copolymerization of butene with one or more unsaturated compounds, the butene being in greatest amount of weight.

CELLULOSE:

Chemically a carbohydrate, which is the chief component of the solid structure of plants, wood, cotton, linen, etc. The source of the cellulosic family of plastics.

CELLULOSE ACETATE BUTYRATE:

A class of resins made from a cellulose base. Either cotton tinters or purified wood pulp, by the action of acetic anhydride, acetic acid, and butyric acid.

CEMENT:

A dispersion of solutions of a plastic in a volatile solvent. This meaning is peculiar to the plastics and rubber industries and may or may not be an adhesive composition.

CHEMICAL RESISTANCE:

(1) The effect of specific chemicals on the properties of plastic piping with respect to concentration, temperature, and time of exposure. (2) The ability of a specific plastic pipe to render service for a useful period in the transport of a specific chemical at a specified concentration and temperature.

COALESCENCE:

The union or fusing together of fluid globules or particles to form larger drops or a continuous mass.

COLD FLOW:

Change in dimensions or shape of some materials when subjected to external weight or pressure at room temperature.

COMPOUND:

A combination of ingredients before being processed or made into a finished product. Sometimes used as a synonym for material formulation.

COMPRESSIVE STRENGTH:

The crushing load at failure applied to a specimen per unit area of the resistance surface of the specimen.

CONDENSATION:

A chemical reaction in which two or more molecules combine with the separation of water. Also, the collection of water droplets from vapor onto a cold surface.

COPOLYMER:

The product of simultaneous polymerization of two or more polymerizeable chemicals known as monomers.

CRAZING:

Fine cracks at or under the surface of a plastic.

CREEP:

The unit elongation of a particular dimension under load for a specific time following the initial elastic elongation caused by load application. It is expressed usually in inches per inch per unit of time.

CURE:

To change the properties of a polymeric system into a final, more stable, usable condition by the use of heat, radiation or reaction with chemical additives.

DEFLECTION TEMPERATURE:

The temperature at which a specimen will deflect a given distance at a given load under prescribed conditions of test. See ASTM D648. Formerly called heat distortion.

DEGRADATION:

A deleterious change in the physical properties of a plastic evidenced by impairment of these properties.

DIELECTRIC CONSTANT:

A value that serves as an index of the ability of a substance to resist the transmission of an electrostatic force from one charged body to another, as in a condenser. The lower the value, the greater the resistance. The standard apparatus utilizes a vacuum, whose dielectric constant is 1; in reference to the various materials interposed between the charged terminals have the following values at 20 C : air, 1.00058; glass, 3; benzene, 2.3; acetic aced, 6.2; ammonia, 15.5; ethyl alcohol, 25: glycerol, 56; and counts for its unique behavior as a solvent and in electrolytic solutions. Most hydrocarbons have high resistance (low conductivity). Dielectric constant values decrease as the temperature rises.

DIFFUSION:

The migration or wandering of the particles or molecules of a body of fluid matter away from the main body through a medium or into another medium.

DIMENSION RATIO:

The diameter of a pipe divided by the wall thickness. Each pipe can have two dimension ratios depending upon whether the outside or inside diameter is used. In practice, the outside diameter is used if the standards requirement and manufacturing control are based on this diameter. The inside diameter is used when this measurement is the controlling one.

DRY-BLEND:

A free-flowing compound prepared without fluxing or addition of solvent.

DUROMETER:

The Durometer determines the hardness of rubber or plastics by measuring the depth of penetration (without puncturing) of a blunt needle compressed on the surface for a short period of time.

ELASTICITY:

That property of plastics materials by virtue of which they tend to recover their original size and like properties.

ELONGATION:

The capacity to take deformation before failure in tension. Expressed as a percentage of the original length.

EMULSION:

A dispersion of one liquid in another, possible only when they are mutually insoluble.

ENVIRONMENTAL STRESS CRACKING:

Cracks that develop when the material is subjected to stress in the presence of specific chemicals.

ESTER:

A compound formed by the reaction between an alcohol and an acid. Many esters are liquids. They are frequently used as plasticizers in rubber and plastic compounds.

EXTRUSION:

Method of processing plastic in a continuous or extended form by forcing heat-softened plastic through an opening shaped like the cross-section of the finished product. This is the method used to produce thermoplastic (PVC) pipe.

FABRICATE:

Method of forming a plastic into a finished article by machining drawing, cementing, and similar operations.

FIBER STRESS:

The unit stress, usually in pounds per square inch (psi) in a piece of material that is subjected to an external load.

FILLER:

A relatively inert material added to a plastic to modify its strength, permanence, working properties or other qualities or to lower costs.

FLAMMABILITY:

The time a specimen will support a flame after having been exposed to a flame for a given period.

FLEXURAL STRENGTH:

The pressure in pounds necessary to break a given sample when applied to the center of the sample which has been supported at its end.

FORMULATION:

A combination of ingredients before being processed or made into a finished product. Sometimes used as a synonym for material or compound.

FORMING:

A process in which the shape of plastic pieces such as sheets, rods, or tubes is changed to a desired configuration.

FUSE:

To join two plastic parts by softening the material through heat or solvents.

GENERIC:

Common names for types of plastic material. They may be either chemical terms or coined names. They contrast with trademarks which are the property of one company.

GRAVES TEAR STRENGTH:

The force required to rupture a specimen by pulling a prepared notched sample.

HARDNESS:

A comparative gauge of resistance to indentation.

HEAT DISTORTION:

The temperature at which a specimen will deflect a given distance at a given load.

HEAT JOINING:

Making a piper joint by heating the edges of the parts to be joined so that they fuse and become essentially one piece with or without the addition of additional material.

HEAT RESISTANCE:

The ability to withstand the effects of exposure to high temperature. Care must be exercised in defining precisely what is meant when this term is used. Descriptions pertaining to heat resistance properties include boilable, washable, cigarette-proof, sterilizable, etc.

HOOP STRESS:

The tensile stress, usually in pounds per square inch (psi) in the circumferential orientation in the wall of the pipe when the pipe contains a gas or liquid under pressure.

HYDROSTATIC DESIGN STRESS:

The estimated maximum tensile stress in the wall of the pipe in the circumferential orientation due to internal hydrostatic pressure that can be applied continuously with a high degree of certainty that failure of the pipe will not occur.

HYDROSTATIC STRENGTH (quick):

The hoop stress calculated by means of the ISO equation at which the pipe breaks due to an internal pressure build-up, usually within 60 to 90 seconds.

IMPACT STRENGTH:

Resistance or mechanical energy absorbed by a plastic part to such shocks as dropping and hard blows.

INJECTION MOLDING:

Method of forming a plastic to the desired shape by forcing heat-softened plastic into a relatively cool cavity where it rapidly solidifies (freezes).

JOINT:

The location at which two pieces of pipe or a pipe and a fitting are connected together. The joint may be made by an adhesive, a solvent cement, or a mechanical device such as threads or a ring seal.

KETONES:

Compounds containing the carbonyl group (CO) to which is attached two alkyl groups. Ketones, such as methyl ethyl ketone, are commonly used as solvents for resins and plastics.

LIGHT STABILITY:

Ability of a plastic to retain its original color and physical properties upon exposure to sun or artificial light.

LONGITUDINAL STRESS:

The stress imposed on the long axis of any shape. It can be either a compressive or tensile stress.

LONG-TERM HYDROSTATIC STRENGTH:

The estimated tensile stress in the wall of the pipe in the circumferential orientation (hoop stress) that when applied continuously will cause failure of the pipe at 100,000 hours (11.43 years). These strengths are usually obtained by extrapolation of log-log regression equations or plots.

LUBRICANTS:

A substance used to decrease the friction between solid faces sometimes used to improve processing characteristics of plastic compositions.

OLDING, COMPRESSION:

A method of forming objects from plastics by placing the material in a confining mold cavity and applying pressure and usually heat.

MONOMER:

The simplest repeating structural unit of a polymer. For additional polymers this presents the original unpolymerized compound.

OLEFIN PLASTICS:

Plastics based on resins made by the polymerization of olefins or copolymerization of olefins with other unsaturated compounds, the olefins being in greatest amount by weight. Polyethylene, polypropylene, and polybutylene are the most common olefin plastics encountered in pipe.

ORANGE PEEL:

Uneven surface somewhat resembling an orange peel.

ORGANIC CHEMICAL:

Originally applied to chemicals derived from living organisms, as distinguished from inorganic chemicals found in minerals and inanimate substances; modern chemists define organic chemicals more exactly as those which contain the element carbon.

PHENOL RESINS:

Resins made by reaction of a phenolic compound or tar acid with an aldehyde; more commonly applied to thermosetting resins made from pure phenol and formaldehyde.

PLASTIC:

A material that contains as an essential ingredient an organic substance of large molecular weight is solid in its finished state, and at some state in its manufacture or in its processing into finished articles, can be shaped by flow.

PLASTICITY:

A property of plastics and resins which allows the material to be deformed continuously and permanently without rupture upon the application of a force that exceeds the yield value of the material.

PLASTIC CONDUIT:

Plastic pipe or tubing used as an enclosure for electrical wiring.

PLASTIC PIPE:

A hollow cylinder of a plastic material in which the wall thickness is usually small when compared to the diameter and in which the inside and outside walls are essentially concentric.

PLASTIC TUBING:

A particular size of plastics pipe in which the outside diameter is essentially the same as that of copper tubing.

POLYBUTYLENE:

A polymer prepared by the polymerization of butene - 1 as the sole monomer.

POLYETHYLENE:

A polymer prepared by the polymerization of ethylene as the sole monomer.

POLYMER:

A product resulting from a chemical change involving the successive addition of a large number of relatively small molecules (monomer) to form the polymer and whose molecular weight is usually a multiple of that of the original substance.

POLYMERIZATION:

Chemical change resulting in the formation of a new compound whose molecular weight is usually a large multiple of that of the original substance.

POLYPROPYLENE:

A polymer prepared by the polymerization of propylene as the sole monomer.

POLYSTYRENE:

A plastic based on a resin made by polymerization of styrene as the sole monomer.

POLYVINYL CHLORIDE:

Polymerized vinyl chloride, a synthetic resin which, when plasticized or softened with other chemicals, has some rubber like properties. It is derived from acetylene and hydrochloric acid.

PRESSURE:

When expressed with reference to pipe the force per unit area exerted by the medium in the pipe.

STABILIZER:

A chemical substance which is frequently added to plastic compounds to inhibit undesirable changes in the material, such as discoloration due to heat or light.

STIFFNESS FACTOR:

A physical property of plastic pipe that indicates the degree of flexibility of the pipe when subjected to external loads.

STRAIN:

The ratio of the amount of deformation to the length being deformed caused by the application of a load on a piece of material.

STRENGTH:

The mechanical properties of a plastic such as a load or weight carrying ability, and ability to withstand sharp blows. Strength properties include tensile, flexural, and tear strength, toughness, flexibility, etc.

STRESS:

When expressed with reference to pipe, the force per unit area in the wall of the pipe in the circumferential orientation due to internal hydrostatic pressure.

STRESS CRACK:

External or internal cracks in a plastic caused by tensile stresses less than that of its short-time mechanical strength.

STRESS RELAXATION:

The decrease of stress with respect to time in a piece of plastic that is subject to an external load.

STYRENE PLASTICS:

Plastics based on resins made by the polymerization of styrene or copolymerization of styrene with other unsaturated compounds, the styrene being in greatest amount by weight.

STYRENE-RUBBER-PLASTICS:

Compositions based on rubbers and styrene plastics, the styrene plastics being in greatest amount by weight.

SUSTAINED PRESSURE TEST:

A constant internal pressure test for 1000 hours.

TEAR STRENGTH:

Resistance of a material to tearing.

TENSILE STRENGTH:

The capacity of a material to resist a force tending to stretch it. Ordinarily the term is used to denote the force required to stretch a material to rupture, and is known variously as "breaking point, breaking stress, ultimate tensile strength, and sometimes erroneously as breaking strain. In plastics testing, it is the load in pounds per square inch or kilos per square centimeter of original cross-sectional area, supported at the moment of rupture by a piece of test sample on being elongated.

THERMOFORMING:

Forming with the aid of heat.

THERMAL CONDUCTIVITY:

Capacity of a plastic material to conduct heat.

THERMAL EXPANSION:

The increase in length of a dimension under the influence of an increase in temperature.

THERMOPLASTIC:

In a plastic which is thermoplastic in behavior, adj. capable of being repeatedly softened by increase of temperature and hardened by decrease of temperature.

THERMOSETTING:

Plastic materials which undergo a chemical change and harden permanently when heated in processing. Further heating will not soften these materials.

TRANSLUCENT:

Permitting the passage of light, but diffusing it so that objects beyond cannot be clearly distinguished.

TURBULENCE:

Any deviation from parallel flow in a pipe due to rough inner walls, obstructions, or direction changes.

VINYL PLASTICS:

Plastics based on resins made from vinyl monomers, except those specifically covered by other classification, such as acrylic and styrene plastics. Typical vinyl plastics are polyvinyl chloride, or polyvinyl monomers with unsaturated compounds.

VIRGIN MATERIAL:

A plastic material in the form of pellets, granules, powder, floc or liquid that has not been subjected to use or processing other than that required for its original manufacture.

VISCOSITY:

Internal friction of a liquid because of its resistance to shear, agitation or flow.

VOLATILE:

Property of liquids to pass away by evaporation.

WATER ABSORPTION:

The percentages by weight or water absorbed by a sample immersed in water. Dependent upon area exposed and time of exposure.

WELDING:

The joining of two or more pieces of plastic by fusion of the material in the pieces at adjoining or nearby areas either with or without the addition of plastic from another source.

YIELD STRENGTH:

The stress at which a plastic material exhibits a specified limiting permanent set.

YIELD POINT:

The point at which a plastic material will continue to elongate at no substantial increase in load during a short test period.

YIELD STRESS:

The stress at which a plastic material elongates without further increase of stress. Up to this point, the stress/strain relationship is linear (Youngs Modules).

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