Glossary

A

ABRASION RESISTANCE - The measure of a material's ability to withstand erosion when subjected to rubbing, scraping, wearing, scouring, etc., conditions.

ACETAL PLASTICS - A group of plastics made from resins that have been obtained by heating aldehydes or ketones with alcohols.

ACIDS - Normally a water-soluble compound containing hydrogen and other elements that are capable of reacting with a base to form a salt. They turn blue litmus paper red.

ACRYLONITRILE-BUTADIENE-STYRENE (ABS) PLASTICS - A group of plastics made from polymers with prescribed percentages of acrylonitrile, butadiene and styrene.

ADHESIVE - A substance capable of holding materials together by surface attachment.

AGING - The effect on materials exposed to an environment for a period of time. Also, the act of exposing materials to an environment for a period of time.

ALKALIES - Compounds capable of neutralizing acids.

ANTIOXIDANT - A substance added to a plastic compound to retard degradation due to contact with air (oxygen).

B

BEAM LOADING - The process of applying a specified force (load) to a piece of pipe that is supported at two points. It is usually expressed in pounds per the distance between the centers of the supports.

BELLED-END - A term used to describe a pipe end that has been enlarged to have the same inside dimensions as a fitting socket. It acts as a coupling when joining pipe.

BLISTER - An undesirable air or gas filled bubble (bump) on the surface of a plastic part.

BOND - To attach by the use of an adhesive.

BURST STRENGTH - The amount of internal pressure a piece of pipe or a fitting will hold before breaking.

C

CALENDERING - A process for making thin sheets of plastic or rubber in which a heated plastic or rubber compound is squeezed between heavy rollers.

CELLULOSE ACETATE - A type of resin made from the reaction of acetic acid or acetic anhydride with a cellulose base (cotton and/or wood pulp).

CEMENT (SOLVENT CEMENT) - An adhesive used to bond plastics that is a “solution” of a plastic resin and a volatile solvent.

CHEMICAL RESISTANCE - The ability of a plastic to withstand the effects of chemicals at various concentrations and temperatures.

COLD FLOW - A change in the shape or the dimensions of a plastic part when subjected to a load (weight or pressure) at room temperature.

COMPOUND - The mixture of ingredients, consisting of a plastic resin and specified additives, used to manufacture a plastic part.

CONDENSATION - A chemical reaction involving the combination of molecules with the result being the elimination of a simple molecule, such as water, and the formation of a more complex compound of greater molecular weight.

COPOLYMER - The product formed by the simultaneous polymerization of two or more polymerizeable chemicals (monomers).

CRAZING - Small, fine cracks on or under the surface of a plastic.

CREEP - The dimensional change, beyond the initial elastic elongation caused by the application of a load, over a specified period of time. It is normally expressed in inches per inch per unit of time.

CURE - To change the properties of a polymer to a stable, usable and final state by the use of chemical agents, heat or radiation.

D

DEFLECTION TEMPERATURE (HEAT DISTORTION) - The temperature that will cause a plastic specimen to deflect a certain distance when a specified load is applied.

DEGRADATION - A deleterious change in the chemical structure, physical properties or appearance of a plastic.

DELAMINATION - The separation of the layers of material in a laminate.

DETERIORATION - A permanent change in the physical properties of a plastic evidenced by impairment of these properties.

DIELECTRIC STRENGTH - The force required to drive an electric current through a specific thickness of a material.

DIFFUSION - The movement of gas or liquid particles or molecules in a body of fluid through or into a medium and away from the main body of fluid.

DIMENSIONAL STABILITY - The capability of a plastic part to maintain its original shape and dimensions under conditions of use.

DRY-BLEND - A dry compound prepared without fluxing or the addition of a solvent.

E

ELASTIC LIMIT - The load point at which a material will not return to its original shape and size after the load has been released.

ELASTICITY - The property of a plastic that allows it to return to its original dimensions after deformation.

ELASTOMER - A substance that when stretched to approximately twice its length, at room temperature, will quickly return to its original length when the stretching load is relieved.

ELECTRICAL PROPERTIES - The resistance of a plastic to the passage of electricity.

ELONGATION - The percentage of the original length that a material will deform, under tension, without failing.

EMULSION - A dispersion of one insoluble liquid into another insoluble liquid.

ENVIRONMENTAL STRESS CRACKING - Cracks that develop when a plastic part is subjected to incompatible chemicals and put under stress.

ESTER - The compound formed during the reaction between an alcohol and an acid.

ETHYLENE PLASTICS - Plastics based on polymers or copolymers of ethylene and other monomers in which ethylene is the greatest amount by weight.

EXTRUSION - The process used to continuously form a shape by forcing a heated or unheated plastic through a shaping orifice (die).

F

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

FLEXURAL STRENGTH - The measure of a material’s ability to withstand a specified deformation under a beam load (bending) at 73°F. Normally expressed in PSI.

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

FORMULATION - The combination of ingredients used to make a finished plastic product. Also see compound.

FUSE - To join plastic parts by softening the material with heat or solvents.

G

GATE - The constriction in the flow channel between the runner and the mold cavity in an injection mold.

GLASS TRANSITION TEMPERATURE - The approximate midpoint of the temperature range over which the glass transition takes place.

GLASS TRANSITION - The reversible change in an amorphous polymer from (or to) a viscous condition to (or from) a hard and relatively brittle one.

GUSSET - A piece used to give additional size or strength to a plastic part at a particular location.

H

HARDNESS - The measure of a material’s ability to resist indentation.

HEAT RESISTANCE - The ability of a material to withstand the effects of exposure to high temperatures.

HOOP STRESS - The circumferential stress imposed on a pipe wall when exposed to an internal pressure load. Usually expressed in PSI.

I

IMPACT STRENGTH - A measure of a plastic part’s ability to withstand the effects of dropping and/or striking. There are two commonly used test methods, Notched Izod and Tup. Notched Izod uses a pendulum-type machine to strike a notched specimen. Tup testing uses a falling weight (tup) to strike a pipe or fitting specimen.

INJECTION MOLDING - The process used to form a shape by forcing a heated plastic, in a fluid state and under pressure, into the cavity of a closed mold.

ISO EQUATION - The equation that shows the relationship between stress, pressure and dimensions in pipe.

J

JOINT - The point where a pipe and fitting or two pieces of pipe are connected together.

K

KETONES - A group of compounds having two alkyl groups attached to a carbonyl (CO) group.

L

LIGHT STABILITY - A feature of a plastic that allows it to retain its original color and physical properties when exposed to sun or artificial light.

LIGHT TRANSMISSION - The amount of light that a plastic will allow to pass through.

LONGITUDINAL STRESS - A tensile or compressive force placed upon the long axis of a plastic part.

LUBRICANT - Any substance which reduces the friction between moving solid surfaces.

M

MODULUS - A term used to describe the load required to cause a specified percentage of elongation. It is usually expressed in PSI or kilos per square centimeter.

MONOMER - A low-molecular-weight substance whose molecules can react with other molecules to form a polymer.

N

NON-FLAMMABLE - Incapable of supporting combustion.

NON-TOXIC - Non-poisonous.

NYLON PLASTICS - Plastics based on resins composed principally of a long-chain synthetic polymeric amide that has recurring amide groups as an integral part of the main polymer chain.

O

OLEFIN PLASTICS - A group of plastics based on polymers made by the polymerization or copolymerization of olefins with other monomers, with the olefins being at least 50% of the weight. Polypropylene, polyethylene and polybutylene are examples.

ORGANIC CHEMICAL - Any chemical that contains carbon.

P

PHENOLIC PLASTICS - A group of plastics based on resins made by the condensation of phenols with aldehydes.

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

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

PLASTICITY - The property of plastics that allows them to be formed, without rupture, continuously and permanently by the application of a force that exceeds the yield value of the material.

PLASTICIZER - A substance incorporated in a plastic to increase its workability, flexibility or distensibility.

POLYBUTYLENE PLASTICS - Plastics based on polymers made with butene as essentially the sole monomer.

POLYMER - A product formed by the chemical reaction of the addition of a large number of small molecules that have the ability to combine and reach high molecular weights.

POLYMERIZATION - A chemical reaction in which the molecules of monomers are linked together to form polymers.

POLYOLEFIN PLASTICS - Plastics based on polymers made with an olefin(s) as essentially the sole monomer(s).

POLYPROPYLENE PLASTICS - Plastics based on polymers made with propylene as essentially the sole monomer.

POLYSTYRENE - A polymer prepared by the polymerization of styrene as the sole monomer.

POLYVINYL CHLORIDE PLASTICS - Plastics obtained by the polymerization of vinyl chloride. The addition of various ingredients, such as stabilizers, colorants, lubricants and fillers, enhance the processability and performance.

POROSITY - A term describing a plastic part that has many visible voids.

PRESSURE RATING - The maximum pressure at which a plastic part can safely function without failing.

Q

QUICK BURST - A term used to describe the amount of internal pressure required to burst a pipe or fitting when the pressure is built up over a 60-70 second interval of time.

R

REINFORCED PLASTIC - A plastic with high strength fillers imbedded in the composition, causing some mechanical properties to be superior to those of the base resin.

RESIN - A solid or pseudosolid organic material, often having a high molecular weight, that exhibits a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally.

RUNNER - The secondary feed channel in an injection mold that runs from the inner end of the sprue to the cavity gate. Also, the solidified piece of plastic that forms in the feed channel when the injection molded part cools.

S

SAMPLE - A small part or portion of a material or product intended to be representative of the whole.

SCHEDULE - A pipe sizing system for the outside diameter and wall thickness dimensions that was started by the iron pipe industry. Normally, as the diameter increases, the pressure rating decreases for any given schedule of pipe.

SELF-EXTINGUISHING - A term describing a plastic material that stops burning when the source of the burning is removed.

SHRINK MARK - A depression in the surface of a molded plastic part where it has retracted from the mold.

SOFTENING POINT - The temperature at which a plastic changes from rigid to soft.

SOLVENT - A medium into which a substance is dissolved.

SOLVENT CEMENT - An adhesive consisting of a plastic dissolved into a solvent and used to bond plastic surfaces.

SOLVENT CEMENTING - Using a solvent cement to make pipe joint.

SPECIFIC GRAVITY - The ratio of the mass of a material to the mass of an equal volume of water.

SPRUE - The primary feed channel that runs from the outer face of an injection mold to the runner or the gate.

STABILIZER - An ingredient added to a plastic compound to inhibit or retard undesirable changes in the material.

STANDARD DIMENSION RATIO (SDR) PIPE - A type of pipe in which the dimension ratios are constant for any given class. Unlike “schedule” pipe, as the diameter increases the pressure rating remains constant for any given class of pipe.

STIFFNESS FACTOR - A term describing the degree of flexibility in a piece of pipe when subjected to an external load.

STRESS-CRACK - An external or internal crack in a plastic caused by tensile stresses less than its short-time mechanical strength.

SUSTAINED PRESSURE TEST - A test in which a plastic part is subjected to a constant internal pressure load for 1000 hours.

T

TEAR STRENGTH - A measure of a material’s ability to resist tearing.

TENSILE STRENGTH - The measure of a plastic’s ability to resist a stretching force. It is normally expressed in the PSI required to rupture a test specimen.

THERMAL CONDUCTIVITY - A measure of a plastic’s ability to conduct heat.

THERMAL CONTRACTION - The decrease in length of a plastic part due to a change in temperature.

THERMAL EXPANSION - The increase in length of a plastic part due to a change in temperature.

THERMOPLASTICS - A group of plastics that can repeatedly be softened by heating and hardened by cooling.

THERMOSETTING PLASTICS - A group of plastics that, having been cured by heat, chemicals, or other means, are substantially infusable and insoluble. They are permanently hardened.

V

VINYL CHLORIDE PLASTICS - Plastics based on polymers or copolymers of vinyl chloride with other monomers, with the vinyl chloride being the greatest amount by weight.

VISCOSITY - A term describing a material’s resistance to flow.

VOLATILE - A property of liquids in which they pass away by evaporating.

W

WELD LINE (KNIT LINE) - A term used to describe a mark on a molded plastic part formed by the union of two or more streams of plastic flowing together.

Y

YIELD POINT - The point at which a plastic material will not withstand a stretching force. It will continue to elongate with no increase in load after reaching that point.