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.

Aging:
The effect of time on materials.

B

Beam loading:
The application of a load to a pipe between two points of support usually expressed in pounds and the distance between the centers of the supports.

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.

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.

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 chemicals known as monomers.

D

Deflection temperature:
The temperature at which a specimen will deflect a given distance at a given load under prescribed conditions of test. See ASTMD648. Formerly called heat distortion.

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

Dielectric constant:
Specific inductive capacity. The dielectric constant of a material is the ratio of the capacitance of a condenser having that material as dielectric to the capacity of the same condenser having a vacuum as dielectric.

Dielectric strength:
This is the force required to drive an electric current through a definite thickness of the material; the voltage required to break down a specific thickness of insulation.

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 on whether the outside or inside 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:
Trade name of the Shore Instrument Company for an instrument that measures hardness. 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.

E

Elasticity:
That property of plastics materials by virtue of which they tend to recover their original size and shape after deformation.

Elastomer:
The name applied to substances having rubber like properties.

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

F

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.

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

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

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

L

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.

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

M

Modulus:
The load in pounds per square inch (or kilos per square centimeter) of initial cross-sectional area necessary to produce a stated percentage-elongation which is used in the physical description of plastics (stiffness).

Modulus of elasticity:
The ratio of the stress per square inch to the elongation per inch due to this stress.

Molding 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 addition polymers this represents the original unpolymerized compound.

 O

Olefin plastics:
Plastics based on resins made by the polymerization of olefins or co-polymerization of olefins with other unsaturated compounds the olefins beingin 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.

P

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.

Plasticizer:
A liquid or solid incorporated in natural and synthetic resins and related substances to develop such properties as resiliency elasticity and flexibility.

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

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

R

Reinforced plastic:
A plastic with some strength properties greatly superior to those of the base resin resulting from the presence of high strength fillers imbedded in the composition.

Resilience:
Usually regarded as another name for elasticity. While both terms are fundamentally related there is a distinction in meaning. Elasticity is a general term to describe the property of recovering original shape after a deformation. Resilience refers more to the speed of recovery; that is a body may be elastic but not highly resilient.

Resin:
An organic substance generally synthetic which is used as a base material for the manufacture of some plastics synonymous with plastic or polymer usually not including the pigments lubricants or other additives i.e. the polymer portion of a "formulation."

Reworked material (thermoplastic):
A plastic material that has been reprocessed after having been previously processed by molding extrusion etc. in a fabricator's plant.

Rigid plastic:
A plastic which has a stiffness or apparent modulus of elasticity greater than 100 000 psi at 23 degrees Celsius when determined in accordance with the Standard Method of Test for Stiffness in Flexure of plastics.  

S

Schedule:
A pipe size system (outside diameters and wall thickness') originated by the iron pipe industry.

Self-extinguishing:
The ability of a plastic to resist burning when the source of heator flame that ignited it is removed.

Service factor:
A factor which is used to reduce a strength value to obtain an engineering design stress. The factor may vary depending on the service conditions the hazard the length of service desired and the properties of the pipe.

Set:
To convert an adhesive into a fixed or hardened state by chemical or physical action such as condensation polymerization oxidation vulcanization gelation hydration or evaporation of volatile constituents.

Simulated aging:
The exposure of plastics to cyclic laboratory conditions of high and low temperatures and high and low relative humidities in an attempt to produce changes in their properties similar to those observed on long-time continuous exposure to conditions of temperature and relative humidity commonly encountered indoors or to obtain an acceleration of the effects of ordinary indoor exposure. The laboratory exposure conditions are usually intensified beyond those actually encountered in an attempt to achieve an accelerated effect.

Simulated weathering:
The exposure of plastics to cyclic laboratory conditions of high and low temperature high and low relative humidities and ultraviolet radiant energy in an attempt to produce changes in their properties similar to those observed on long-time continuous exposure outdoors. The laboratory exposure conditions are usually intensified beyond those encountered in actual outdoor exposure in an attempt to achieve an accelerated effect.

Softening range:
The range of temperature which a plastic changes from a rigid to a soft state.

Solvent:
The medium within which a substance is dissolved; most commonly applied to liquids used to bring particular solids into solution e.g. acetone is a solvent for PVC.

Solvent cement:
In the plastic piping field a solvent adhesive that contains a solvent that dissolves or softens the surfaces being bonded so that the bonded assembly becomes essentially one piece of the same type of plastic.

Specific gravity:
Ratio of the mass of a body to the mass of an equal volume of water at 4 degrees Celsius (or some other specified temperature).

T

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.

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.

Thermoforming:
Forming with the aid of heat.

Thermoplastic:
n. a plastic which is themoplastic 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.

V

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 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.

W

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.

Y

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

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 (Young's Modulus).