Home > Adhesives Glossary

A

A-stage
An early stage in the reaction of certain thermosetting resins in which the material is fusible and still soluble in certain liquids.
ACGIH
American Conference of Governmental Hygienists
AFMA
American Furniture Manufacturers Association
ANSI
American National Standards Institute.
ASTM
American Society for Testing and Materials.
Abhesive
A material which is adhesive resistant and applicable as a non-sticking surface coating; release agent.
Abrasion Resistance
Resistance to wear resulting from mechanical action on a surface.
Accelerated Aging
A set of laboratory conditions designed to produce in a short time the results of normal aging. Usual factors included are temperature, light, oxygen and water. In recent years, the adhesives industry has come to rely more and more on the oxygen bomb test as an indicator of relative life expectancy of a given formulation.
Accelerated Weathering
A set of laboratory conditions to simulate in a short time the effects of natural weathering. Most adhesives are generally not subjected to the conditions that are normally considered under weathering tests.
Accelerator
An ingredient used in small amounts to speed up the action of the hardener in a two-part adhesive.
Acceptance Test
A test, or series of tests conducted by the procuring agency, or an agent thereof, upon receipt to determine whether an individual lot of materials conforms to the purchase order or contract or to determine the degree of uniformity of the material supplied by the vendor, or both.
Acetate
A transparent film which is used for various reasons in tape backings; the primary characteristic is that of being more moisture resistant than cellophane.
Acetone
A very volatile and flammable solvent that is particularly useful for cleaning metal substrates.
Acrylic
A synthetic polymer with excellent aging characteristics that can be used as either a single component adhesive, coating or saturant, depending upon composition.
Activator
A substance that accelerates normal curing machanisms.
Adhere
To cause two surfaces to be held together by adhesion.
Adherend
A body which is held to another body by an adhesive.
Adhesion
The state in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking action, or both.
Adhesion Build-up
An increase in the peel adhesion value of a pressure-sensitive tape after it has been allowed to dwell on the applied surface.
Adhesion, Mechanical
Adhesion between surfaces in which the adhesive holds the parts together by interlocking action.
Adhesion, Specific
Adhesion between surfaces that are held together by valence forces of the same type as those which give rise to cohesion.
Adhesive
A substance capable of holding materials together by surface attachment. Same as cement.
Adhesive Dispersion
A two phase system in which one phase is suspended in a liquid.
Adhesive Failure
Type of failure characterized by pulling the adhesive loose from the substrate.
Adhesive Joint
The location at which two adherends are held together with adhesive.
Adhesive, Assembly
An adhesive that can be used for bonding parts together such as the manufacture of a boat, airplane, furniture, and the like.
Adhesive, Cold-setting
An adhesive that sets at temperature below 68°F (20°C).
Adhesive, Contact
An adhesive that is apparently dry to the touch and which will adhere to itself instantaneously upon contact; also called contact bond adhesive or dry bond adhesive.
Adhesive, Foamed
An adhesive, the apparent density of which has been decreased substantially by the presence of numerous gaseous cells dispersed throughout its mass. Same as cellular adhesive.
Adhesive, Heat activated
A dry adhesive film that is rendered tacky or fluid by application of heat or heat and pressure to the assembly.
Adhesive, Hot melt
An adhesive that is applied in a molten state and forms a bond on cooling to a solid state.
Adhesive, Hot-setting
An adhesive that requires a temperature at or above 100°C (212°F) to set.
Adhesive, Intermediate temperature setting
An adhesive that sets in the temperature range of 31°-99°C (87°-211°F).
Adhesive, Pressure Sensitive
A viscoelastic material which in solvent-free form remains permanently tacky. Such a material will adhere instantaneously to most solid surfaces with the application of very slight pressure.
Adhesive, Room Temperature Setting
An adhesive that sets in the temperature range of 20°-30°C (68°-86°F).
Adhesive, Separate Application
A term used to describe an adhesive consisting of two parts, one part being applied to one substrate and the other part to the other substrate and the two brought together to form a joint.
Adhesive, Solvent
An adhesive having a volatile organic liquid as a vehicle.
Adhesive, Solvent Activated
A dry adhesive film that is rendered tacky just prior to use by application of a solvent.
Adsorption
The action of a body in condensing and holding gases and other materials at its surface.
Aging
The progressive change in the chemical and physical properties of a sealant or adhesive.
Aliphatic Resin Glue
Yellow glues which provide more grab for shorter clamp times, and offer better water resistance and heat resistance than traditional white glues.
Alligatoring
Cracking of a surface into segments so that it resembles the hide of an alligator.
Alternating Current
The change of an alternating flow of current from zero to a positive peak, returning through zero to a negative peak and back to zero repeated continuously.
Ambient
Usual or surrounding conditions.
Ambient Temperature
Temperature of the air surrounding the object under construction or test.
Ampere
A unit of electric current. One ampere flows through a conductor having a resistance of one ohm, when there is one-volt difference between the ends of the circuit. (A.)
Amylaceous
Pertaining to, or of the nature of, starch; starchy.
Anaerobic
Adhesives that cure in the absence of oxygen.
Aniline Dye
Any of a large number of synthetic dyes derived from aniline, usually obtained from coal tar.
Apparent Viscosity
In non-Newtonian behavior, the ratio of the shearing stress to the rate of shear of a fluid, given at the corresponding shearing stress.
Arc
A self-sustaining visible flow or discharge of electricity through air that will result in a burn if the flow is through a material of normal insulating properties.
Asphalt
Naturally occurring mineral pitch or bitumen.
Assembly
A group of materials or parts, including the adhesive, which has been placed together for bonding or which has been bonded together.
Assembly Time
The time period from the application to adhesive until the final application of pressure. This term includes both closed and open assembly times.
Asthma
A disease characterized by recurrent attacks of wheezing and shortness of breath.
Auto Tune
A circuit installed in a RF generator designed to maintain the optimum amount of power during a RF cure cycle.
Automatic Edging Saw
A straight line rip saw used to edge one side of the blank before it is ripped on the rip saw. This is accomplished by using canted, automatic rollers to feed the stock through the saw after it has been planed.
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B

B-stage
An intermediate stage in the reaction of certain thermosetting resins in which the material softens when heated and swells when in contact with certain liquids, but may not entirely fuse or dissolve. The resin in an uncured thermosetting adhesive is usually in this stage.
BTU
British Thermal Unit. The quantity of heat required to raise the temperature of 1 lb. of water 1°F.
Back Bedding
The layer of glazing compound which is placed between the face of glass and the frame or sash containing it.
Backer
A veneer or synthetic face bonded to the backside of a panel to ensure dimensional stability
Bag Molding
A method of molding or bonding involving the application of fluid pressure, usually by means of air, steam, water, or vacuum, to a flexible cover which, sometimes in conjunction with the rigid die, completely encloses the material to be bonded.
Balanced Construction
A plywood construction in which construction on one side of the panel is similar or identical to the other side.
Batch
The manufactured unit or blend of two or more units of the same formulation and processing.
Batten Plate
A thin metal plate separated by sealant beads to bridge poorly designed joints.
Bed
In glazing, to apply a bead of sealant between a lite of glass or a panel and the stationary stops or sight bars of the sash or frame
Bicellular Sealant Backing
A flexible and very compressible extruded shape with a surface skin, that is composed of both open and closed cell material.
Binder
A component of an adhesive composition that is primarily responsible for the adhesive forces that hold the two bodies together.
Birefringence
The refraction of light in two slightly different directions to form two rays; the phenomenon can be used to locate stress in a transparent material.
Bite
In glazing, the effective structural contact dimension of a structural sealant.
Blank
The name of the rough end product. Rectangular in shape, they go to the finish machine room. These parts come from specified width ripping. Sometimes called solid parts.
Blister
An elevation of the surface of a substrate, somewhat resembling in shape a blister on the human skin; its boundaries may be indefinitely outlined and it may have burst and become flattened.
Blocking
An undesired adhesion between touching layers of material such as occurs under moderate pressure during storage or use.
Bond
To join two structures together; to create an assembly through adhesive linkage; the completed assembly.
Bond Breaker
A material to prevent adhesion at a designated interface.
Bond Face
The part or surface of a building component which serves as a substrate for an adhesive.
Bond Strength
The unit load applied in tension, compression, flexure, peel, impact, cleavage, or shear, that is required to break an adhesive assembly with failure occurring in or near the plane of the bond.
Bondline
The layer if adhesive which attaches two adherends.
Borate
To add Borax to a starch adhesive to improve adhesive tack and viscosity.
Bridge Sealant Joint
A joint where sealant is applied over the joint to the face of substrates that are in approximately the same plane.
Bulk Adherend
As related to interphase, the adherend, unaltered by the adhesive.
Bulk Adhesive
As related to interphase, the adhesive, unaltered by the adherend.
Butt Joint
A joint where sealant is applied within the joint between approximately parallel substrate surfaces that are face-to-edge or edge-to-edge.
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C

C-stage
The final stage in the reaction of certain thermosetting resins in which the material is relatively insoluble and infusible. Certain thermosetting resins in a fully cured adhesive layer are in this stage.
CAS Number
Chemical Abstracts Service. An assigned registry number to identify a material.
CFR
Code of Federal Regulations (US)
CSPC
Consumer Products Safety Commission (US)
CWA
Clean Water Act
Calorie
The quantity of heat required to raise 1 gram of water 1°C.
Capacitor
Plates separated by an insulating material that can store electricity.
Casein Adhesive
An aqueous colloidal dispersion of casein that may be prepared with or without heat, may contain modifiers, inhibitors, and secondary binders to provide specific adhesive properties, and includes a subclass, usually identified as casein glue, that is based in a dry blend of casein, lime, and sodium salts, mixed with water and prepared without heat.
Catalyst
A reactive material added to accelerate adhesive drying. Substance added in small quantities to promote a reaction, while remaining unchanged itself.
Cellular material
A material containing many small cells dispersed throughout it. The cells may be either open or closed.
Chain Stopper
A material added during the polymerization process to terminate or control the degree of thd reaction. This could result in soft sealants, or higher elongation.
Chalk
A powder formed by chalking.
Chalking
The preventing of the proper coalescence of the adhesive film due to low temperatures of the air, wood or adhesive.
Checking
The formation of slight breaks or cracks in the surface of the adhesive.
Chemical cure
Curing by chemical reaction. Usually involves the cross-linking of a polymer.
Chemtrec
Chemical Transportation Emergency Center. Provides emergency information on materials involved in transportation accidents.
Clamp Carrier
A series of cold clamps arranged and used like a Ferris wheel. This permits a large number of panels to be clamped and stored within a small area.
Clamp Time
The period of time required for a joint to gain enough strength to permit it to be removed from pressure with no decrease in long-term strength.
Clamping Force
The total force exerted by a clamping device on a glue line.
Cleavage
A separation in the joint caused by wedge or other crack-opening type action.
Cleavage Strength
The force per unit width of bond line required to produce progressive separation by wedge or other crack-opening type action of two adherends.
Closed Assembly Time
Period of assembly time when the adhesive film is not exposed to the air, but prior to the time that pressure has been applied.
Closed Cell
A cell enclosed by its walls and therefore not connected to other cells.
Co-axial Cable
Two concentric conductors separated by an insulating material.
Coefficient of Expansion
The coefficient of linear expansion is the ratio of the change in length per degree to the length at 0°C.
Cohesion
The molecular attraction which holds the body of an adhesive together. The internal strength of an adhesive.
Cohesive Failure
The failure characterized by pulling the body of an adhesive apart.
Cohesive Strength
The ability of the adhesive to stick within itself during the wet stage. The term cohesive strength also applies to the internal strength of dried adhesive.
Coil
A conductor wound into a helical/configuration of uniform cross-section.
Cold Press
A hydraulic or pneumatic press designed to press face-glued or veneered panels without the addition of heat.
Cold Pressing
A bonding operation in which an assembly is subjected to pressure without the application of heat.
Combustible
Materials that will burn.
Condensation
A chemical reaction in which two or more molecules combine with the separation (or release) of water or some other simple substance. If a polymer is formed, the process is called polycondensation.
Conductor
Material having low resistance to the movement of an electric current.
Cone Penetrometer
An instrument for measuring the relative hardness of soft deformable materials.
Consistency
The property of a liquid adhesive by virtue of which it tends to resist deformation.
Corrosion
The chemical reaction between the adhesive or contamination and the adherend surfaces, due to reactive compounds in the adhesive film, leading to deterioration of the bond strength.
Coverage
The spreading power of an adhesive over the surface area of the adherend.
Crackling Effect
A faux finish that makes the piece look old and antiqued.
Crazing
The formation of fissures or voids in the adhesive film due to excessive shrinkage characteristics of the adhesive.
Creep
The deformation of a body with time under constant load. Also called cold flow.
Crossband
A veneer oriented at right angles to a face veneer used to ensure dimensional stability in a plywood panel.
To form chemical bonds between molecules to produce a three-dimensional network.
Cure
To set up or harden by means of a chemical reaction.
Cure Cycle
The period of time that a glue line is being cured in radio frequency.
Cure Time
Time required to effect a complete cure at a given temperature.
Curing Agent
A chemical that is added to effect a cure in a polymer. Same as hardener.
Cutoff Saw
The first machining operation in a typical rough mill. The cutoff saw cuts to rough length, and defect cuts, with a minimum of lumber and labor costs.
Cutting Angle
The angle between the face of a cutting edge and a plane perpendicular to its cutting direction.
Cycle
The change of an alternating flow of current from Zero to a positive peak, returning through Zero to a negative peak and back to Zero.
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D

DOT
Department of Transportation (US).
Delamination
The separation of layers in a laminate because of failure of the adhesive, either in the adhesive itself or at the interface between the adhesive and the substrate, or because of cohesive failure of the substrate.
Density
Ratio of weight (mass) to volume of a material.
Depolymerization
Separation of a complex molecule int simple molecules; also softening of a sealant by the same action.
Dielectric
An insulating material.
Dielectric Loss
The energy converted to heat from an alternating current passing through an insulating material.
Diffuse Porous
Hardwood without distinct passages or pores in the annual growth rings (i.e. maple, poplar, and cherry).
Diluent
An ingredient usually added to an adhesive to reduce the concentration of bonding materials.
Direct Current
An electric current flowing in one direction only (DC).
Dispersion
A two-phase system in which one phase is suspended in a liquid.
Doctor
Device that controls the amount of adhesive applied.
Double Spread Adhesive
An application of adhesive to both adherends or as two layers on one adherend.
Dowel
A cylindrical pin used to reinforce the strength of an assembly joint.
Dry
To change the physical state of an adhesive or a substrate by the loss of solvent constituents by evaporation or absorption, or both.
Drying Agent
A component of a sealant that accelerates the oxidation of oils or unsaturated polymers.
Drying Temperature
The temperature to which an adhesive or an assembly is subjected to dry the adhesive.
Drying Time
The interval of time between the point of liquid adhesive application to the adherend substrate and the time at which adhesive particle coalescence occurs.
Durometer
An instrument used to measure hardness.
Dwell Cycle
The period of time after a panel has been cured in radio frequency, but before pressure is released to allow additional cure and equalizing.
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E

EPA
Environmental Protection Agency (US).
Edge Gluing
The bonding of the edge grain of wood strips to make a wider board.
Elasticity
The ability of a material to return to its original shape after removal of a load.
Elastomer
A rubbery material which returns to approximately its original dimensions in a short time after a relatively large amount of deformation.
Electrodes
Conductors, usually strips or plates used to carry the radio frequency power to the surfaces of the material to be heated.
Emulsion
A dispersion of fine particles of one liquid into another liquid.
Encapsulated Adhesive
An adhesive in which the particles or droplets of one of the relative components are enclosed in a protective film (microcapsules) to prevent cure until the film is destroyed by suitable means.
Epoxy
A resin formed by combining epichlorohydrin and bisphenols. Requires a curing agent for conversion to a plastic like solid. Has outstanding adhesion and excellent chemical resistance.
Equilibrium Moisture Content
The moisture content eventually attained in wood exposed to a given level of relative humidity and temperature.
Evaporation Rate
The rate at which a material will vaporize compared with a known substance.
Exothermic
A chemical reaction which gives off heat.
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F

Face Gluing
Gluing of heavy wood stock on the wide face to attain a thicker panel.
Failure, Adhesive
Rupture of an adhesive bond such that the separation appears to be at the adhesive substrate interface.
Farad
A unit by which capacitors are rated (f).
Fatigue Failure
Failure of a material due to rapid cyclic deformation.
Fiber Saturation Point
The moisture content of wood at which all unbound moisture has been eliminated. This is typically about 30% Moisture Content.
Filler
That portion of an adhesive that fills the corner or angle formed where two substrates are joined.
Fillet
That portion of an adhesive that fills the corner or angle formed where two substrates are joined.
Finished Dimension
The dimension of a furniture part after it has been machined to its final size either by a molder or a trim operation in the rough end.
Fire Diamond
A hazard rating system of the National Fire Protection Association (NFPA). Four Classes of entries: Health, Flammability, Reactivity, and Specific Hazard. Frequently seen on drums.
Fire Point
Lowest temperature that a liquid will produce sufficient vapor to ignite and continue to burn
Flammable
Describes any material that will ignite easily and burn rapidly.
Flash Point
The lowest temperature at which the vapors being given off by a substance can be ignited.
Flat Saw
A type of saw that uses alternating flat teeth, usually 36, for ripping on the straight-line rip saw.
Flat Sawn
Grain orientation in wood in which annual rings are approximately parallel to the wide surface. Also called Tangential or Plain Sawn.
Flow
Movement of an adhesive during the bonding process before the adhesive is set.
Freeze/Thaw Stability
The ability of a product to remain usable after it has been frozen and thawed.
Frequency
The number of cycles in one second, generally measured in Hertz (Hz).
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G

Gang saw
A type of machine that uses a series of saws on the same arbor to rip lumber. This is accomplished by using spacers for each of the saw blades to give the ripped blank the desired width for each cut on the arbor.
Gap Fill
This is the ability of an adhesive to fill the space between materials and hold them in place.
Gap Filling Adhesive
An adhesive capable of forming and maintaining a bond between surfaces that are not close-fitting.
Gel
A semisolid system consisting of a network of solid aggregates in which liquid is held.
Generator
The device for converting power line frequency to radio frequency.
Glue
Originally, a hard gelatin obtained from hides, tendons, cartilage, bones, etc. of animals. Also, an adhesive prepared from this substance by heating with water. Through general use the term is now synonymous with the term "adhesive".
Glue Line
The layer of adhesive that attaches two substrates. Same as bond line.
Glue Reel
A series cold clamps arranged and used like a Ferris wheel. This permits a large number of panels to be clamped and stored within a small area.
Green Strength
This refers to the relative cohesive strength an adhesive, glue, or mastic has in the wet state. Same as green grab or initial tack. See also tack.
Grid Current Meter
An electrical meter placed in the plate circuit of a RF generator to measure electrical current.
Gum
Any of a class of colloidal substances, exuded by or prepared from plants, sticky when moist, composed of complex carbohydrates and organic acids, which are soluble or swell in water.
Gun Grade
A material of a suitable viscosity to extrude through the nozzle of a hand or power operated device.
Gunability
The ability of a substance to extrude out of a cartridge in a gun-like dispenser.
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H

HMIS
Hazardous Materials Information System. A hazard rating system of the National Paint and Coating Association (NPCA).
HPVA
Hardwood Plywood and Veneer Association.
Hardener
A substance or mixture of substances added to an adhesive to promote or control the curing reaction by taking part in it. The term is also used to designate a substance added to control the degree of hardness of the cured fill. Same as curing agent. See also catalyst.
Hardwood
Wood from deciduous trees (i.e. oak, maple, cherry, etc.)
Hollow Joints
A machine problem caused by poor alignment of the feed rollers in the head of the straight-line rip. The joint is unable to fit intimately, even when sufficient pressure is applied to the glue joint.
Hot Electrode
The electrically "alive" electrode as distinguished from the "ground" electrode.
Hot Press
A press designed for laminating or veneering in which the panel is placed between heated platens.
Hygroscopic
Readily adsorbing moisture from the air.
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I

IARC
International Agency for Research on Cancer.
IR Pyrometer
A device designed to measure surface temperature by Infrared emissions.
Impact Strength
Resistance to sharp, intense blows or force.
Impedance
The opposition a circuit offers to the flow of alternating current (Z).
Inductance
The property that opposes a change in existing current flow which occurs only when the current is changing.
Inflammable
Capable of being easily set on fire and burning violently.
Inhibitor
A substance that slows down chemical reaction. Inhibitors are sometimes used in certain types of adhesives to prolong storage or working life. Same as retarder.
Interface
The common boundary surface between two substances.
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J

J Roller
A hand roller used to apply pressure on a bonded surface such as a plastic laminate.
Joint
A general term referring to the area at which two adherends are held together by adhesive.
Joint Aging Time
The time interval between the removal of the joint from the conditions of heat or pressure, or both, used to accomplish bonding and the attainment of approximately maximum bond strength.
Joint, Scarf
A joint made by cutting away similar angular segments of two substrates and bonding the substrates with the cut areas fitted together.
Joint, Starved
A joint that has an insufficient amount of adhesive to produce a satisfactory bond.
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L

LVL
Laminated Veneer Lumber (LVL) construction consisting of parallel veneer laminations.
Laminate, (noun)
A product made by bonding together two or more layers of material or materials.
Laminate, (verb)
To unite layers of material with adhesive.
Laminated, Cross
A laminate in which some of the layers of material are oriented at right angles to the remaining layers with respect to the grain or strongest direction in tension.
Laminated, Parallel
A laminate in which all of the layers of material are oriented approximately parallel with respect to the grain or strongest direction in tension.
Lap Joint
A joint made by placing one substrate partly over another and bonding together the overlapped portions.
Lap Shear
Test to measure resistance to shear stress by bonding the ends of flat bars in an overlapping position.
Legging
The drawing of filaments or strings when adhesive-bonded substrates are separated.
Load
The material being heated.
Longitudinal Grain
Grain orientation in which wood fibers are parallel to the length of the tree.
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K

Kiln
A heated chamber for drying lumber. Temperature, humidity, and air circulation are all controlled within the drying area.
Kilo
Prefix meaning one thousand (K).
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M

MDF
Medium Density Fiberboard.
MSGL
Pounds per 1000 square feet glue line.
Matching Network
A combining of capacitors and/or inductors used for bringing the tuning into resonance.
Matrix
The part of an adhesive which surrounds or engulfs embedded filler or reinforcing particles and filaments.
Mega
Prefix meaning one million (M).
Membrane Press
A hot press design which permits laminates or veneer to be glued to a surface that is not flat, by using a rubber membrane that is inflated with a hot fluid.
Micro
Prefix meaning one millionth part (m).
Milli
Prefix meaning one thousandth part (m) (10-3).
Modifier
Any chemically inert ingredient added to an adhesive formulation that changes its properties.
Moisture Content
Percent moisture content is equal to the weight of water divided by the weight of bone-dry wood x 100.
Moisture Meter
A small electronic device designed to determine the moisture content of wood stock.
Monomer
A relatively simple compound which can react to form a polymer.
Mucilage
An adhesive prepared from a gum and water. Also in a more general sense, a liquid adhesive which has a low order of bonding strength.
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N

NFPA
National Fire Prevention Association.
NIOSH
National Institute of Occupational Safety and Health.
NWWDA
National Wood Window and Door Association.
Nano
Prefix meaning one-billionth.
Nip Roll
A pressure system designed to apply a large amount of pressure for an instant. This system is frequently used for hot melt, fast-set adhesives, or contact cements.
Non-porous Substrate
substrate that is not permeable by air, water, etc.
Nonflammable
Incapable of being easily ignited or burned.
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O

OSHA
Occupational Safety and Health Administration.
Ohm
Unit of resistance (R).
Open Assembly Time
Period of assembly time when the adhesive film is exposed to the air.
Open Time
The time that the glue may be left open to the air after application. Same as working time. Same as open assembly time.
Open Times
When you use hotmelt or glue, you should know the open time of the adhesive. This refers to the time you have once you apply the glue before it bonds.
Oxygen Bomb Test
A special aging test given to adhesives. Five hundred hours exposure to the condition in this test generally indicates whether a product will provide a good deal of service over a long range period of time.
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P

PEL
Permissible Exposure Limit.
PPE
Personal Protective Equipment.
PPM
Parts per million.
PSI
Pounds per square inch.
PSIA
Pounds per square inch absolute.
Parallel Heating
Radio Frequency Press configuration in which RF current is conducted along the glue lines in edge-gluing presses. The flow of the RF current is parallel with the glue lines.
Particleboard
manufactured core material consisting of wood particles and a binder bonded under heat and pressure.
Paste
An adhesive composition having a characteristic plastic-type consistency, that is, a high order or yield value, such as that of a paste prepared by heating a mixture of starch and water and subsequently cooling the hydrolyzed product
Peel Test
A test of an adhesive using one rigid and one flexible substrate. The flexible material is folded back (usually 180°) and the substrates are peeled apart. Strength is measured in pounds per inch of width.
Percent Moisture Content
Percent moisture content is equal to the weight of water divided by the weight of bone dry wood x 100.
Percent Solids
The percentage of non-volatile material contained in a liquid.
Percent Volatile
Percentage of a liquid or solid by volume that will evaporate at ambient temperature.
Permanent Set
The percentage of non-volatile material contained in a liquid.
Perpendicular Heating
Radio Frequency Press configuration in which RF current is conducted through a plywood panel resulting in mass heating. The flow of current is perpendicular to the glue lines.
Phenolic Resin
A thermosetting resin. Usually formed by the reaction of a phenol with formaldehyde.
Physical State
The condition of a material.
Pick-up Roll
A spreading device where the roll for picking up the adhesive runs in a reservoir of adhesive.
Pico
Prefix meaning one trillionth.
Pitch
The residue which remains after the distillation of oil and so forth from raw petroleum.
Plain Sawn
Grain orientation in wood in which annual rings are approximately parallel to the wide surface. Also called Tangential or Flat Sawn.
Planer
A machine used to prepare lumber for the cut-to-length operation by dressing the face and backside of the board. The purpose of the rough planer is to give the stock a uniform thickness so that production and quality in subsequent operations will be improved.
Planking
A small change in height of adjacent staves in a panel caused by changes in moisture content. Sometimes referred as step joints.
Plasticity
A property of adhesives that 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 material incorporated in an adhesive to increase its flexibility. The addition of the plasticizer may cause a reduction in melt viscosity, lower the temperature of the second-order transition, or lower the elastic modulus of the solidified adhesive.
Plate Current Meter
An electrical meter placed in the grid circuit of a RF generator to measure electrical current.
Plywood
A construction involving multiple (usually an odd number) layers of wood veneer into a panel. The grain direction of alternate plies is frequently alternated to enhance dimensional stability.
Polyester
A polymer containing ester linkages. The polyesters used in polyurethane technology contain reactive hydroxyl end groups.
Polymer
A compound formed by the reaction of simple molecules having functional groups that permit their combination to proceed to high molecular weights under suitable conditions. Polymers may be formed by polymerization (addition polymer) or poly-condensation (condensation polymer). When two or more monomers are involved, the product is called a copolymer.
Polymerization
Chemical reaction in which one or more small molecules combine to form larger molecules.
Polyvinyl acetate (PVA) glue
Any glue consisting chiefly of polyvinyl acetate polymer. This category includes both traditional white glues and yellow aliphatic resin glues. Although PVA glues can vary in strength, flexibility, water resistance, heat resistance and sand-ability, they are generally non-toxic. All PVA glues are prone to "creep" or slowly stretch under long term loads, and are not recommended for structural applications.
Porous Substrate
A substrate that is permeable by air, water, etc.
Post Cure (noun)
A treatment (normally involving heat) applied to an adhesive assembly following the initial cure to modify specific properties.
Post Cure (verb)
To expose an adhesive assembly to an additional cure, following the initial cure, for the purpose of modifying specific properties.
Pot Life
The useable life of a synthetic resin mix after a catalyst or hardener has been added.
Press Time
The period required for a joint to be held under pressure.
Primer
A coating applied to a surface, prior to the application of an adhesive, to improve the performance of the bond.
Pyrometer
One of several devices designed to measure surface temperature.
pH
Value that represents the acidity or alkalinity of an aqueous solution.
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Q

Q
The measurement of resonance or frequency selectivity
Quarter Sawn
Grain orientation in wood in which annual rings are approximately perpendicular to the wide surface. Also called Radial Sawn.
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R

REL
Recommended Exposure Limit set by NIOSH.
Radial Grain
Grain orientation in wood in which annual rings are approximately perpendicular to the wide surface. Also called Quarter Sawn.
Radio Frequency
Frequencies from 10 Kilohertz to 3,000 Gigahertz.
Radio Frequency Gluing System
Radio Frequency Gluing is a process in which high radio frequency waves are used to heat substrates, causing the adhesive between them to dry.
Random Width
Lumber ripped to no specific width. Used as edge glued stock. Defecting is done here as well as in specific width ripping.
Reactance
Opposition to the flow of alternating current.
Reactive Material
A chemical substance or material that will vigorously polymerize or decompose.
Reactivity
Tendency of a substance to undergo a chemical reaction with itself or another material with the release of energy.
Release Paper
A sheet, serving as a protectant and/or carrier for an adhesive film or mass, which is easily removed from the film or mass prior to use.
Resin
A solid, semisolid, or pseudosolid organic material that has an indefinite and often high molecular weight, exhibits a tendency to flow when subjected to stress, usually has a softening or melting range, and usually fractures conchoidally.
Resistance
The opposition to current flow through a material measured in Ohms.
Resonance
A circuit condition where the inductive and capacitive reactance or impedance are in balance.
Ring Porous
Hardwood with distinct passages or pores in the annual growth rings such as oak.
Rosin
A resin obtained as a residue in the distillation of crude turpentine from the sap of the pine tree (gum rosin) or from an extract of the stumps and other parts of the tree (wood rosin).
Rough Dimension
The dimension of the part after specific ripping. The part will be larger than its finished length and width to allow for finish machining.
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S

SARA
Superfund Amendments and Reauthorization Act.
STEL
Short term exposure limit.
Sandability
Sandability is a relative term used to explain the performance of dried glue when sanded. Good sandabilty is achieved when glue that has been sanded does not gum up the sanding belt.
Saw Kerf
The saw blade thickness taken out by the saw as it travels through the rough stock. Saw kerfs are usually 1/8, 3/16, 1/4, and 5/16.
Self-vulcanizing
Pertaining to an adhesive that undergoes vulcanization without the application of heat.
Sensitization
A state of immune response in which further exposure elicits an immune or allergic response.
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.
Set Time
The period of time required to attain handling strength.
Shelf Life
The period of time, usually beginning with the date of manufacture, during which a stored adhesive will remain effective or useful. Same as storage life.
Shrinkage
Percentage weight loss under specified conditions.
Side Clearance
The amount of clearance needed for the saw to cut through without causing friction between the saw tooth and the stock. This is accomplished by tapering the carbide tooth from the top of the carbide, and to the back, where it is brazed to the saw body.
Sizing
The process of applying a material on a surface in order to fill pores and thus reduce the absorption of the subsequently applied adhesive or coating or to otherwise modify the surface properties of the substrate to improve the adhesion. Also, the material used for this purpose.
Slippage
The movement of substrates with respect to each other during the bonding process.
Softwood
Wood from evergreen trees (i.e. pine, fir, hemlock, and spruce).
Solids Content
The percentage by weight of the non-volatile matter in an adhesive.
Solvent
Liquid in which another substance can be dissolved.
Specific Gravity
A dimensionless unit of density in which the weight of a known volume of a material is divided by the weight of an equal volume of water.
Specific Heat
The quantity of heat needed to raise the temperature of a mass of material as compared with the same amount of water.
Specific Width
Stock that is ripped to a rough width specified on the route sheet. Used as a dimension part in the furniture being manufactured.
Speed of Set
The rate at which an adhesive attains handling strength
Speed of Set Test
A series of tests run to determine how fast a given glue can build strength under ideal conditions.
Spread
The quantity of adhesive per unit joint area. Single spread refers to application of adhesive to only one substrate of a joint. Double spread refers to application of adhesive to both substrates of a joint.
Square
A face glued construction that is approximately squared in cross section that will be turned on a lathe.
Squeeze Out
Adhesive pressed out at the bond line due to pressure applied on the substrates.
Stability
The ability of a material to remain unchanged.
Steam Blows
An internal delamination in a hot- or radio frequency-cured panel caused by an internal buildup of steam.
Step Joint
A small change in height of adjacent staves in a panel caused by changes in moisture content. Also known as planking.
Storage Life
The period of time during which a packaged adhesive can be stored under specified temperature conditions and remain suitable for use.
Straight Line Rip Saw
The machine used to rip boards to specified and random widths. Its purpose is to cut to width, rip out defects, and machine straight edges for gluing, with a minimum of waste and labor costs.
Stray-field Heating
Radio Frequency curing system in which both electrodes are on the same side of the glue joint. Stray field heating is commonly used in the "hand held" units.
Strength, Dry
The strength of an adhesive joint determined immediately after drying under specified conditions or after a period of conditioning in the standard laboratory atmosphere.
Strength, Wet
The strength of an adhesive joint determined immediately after removal from a liquid in which it has been immersed under specified conditions of time, temperature, and pressure.
Stress
Force per unit area, usually expressed in pounds per square inch (psi).
Stress Relaxation
Reduction in stress in a material that is held at a constant deformation for an extended time.
Stringiness
The property of an adhesive that results in the formation of filaments or threads when adhesive transfer surfaces are separated.
Structural Adhesive
A bonding agent used for transferring required loads between substrates exposed to service environments typical for the structure involved.
Substrate
A material upon the surface of which an adhesive-containing substance is spread for any purpose, such as bonding or coating. A broader term than adhered.
Sunken Joint
A depression at the joint between two pieces of wood caused by machining of the panel before the joint has fully cured.
Surface Preparation
A physical and /or chemical preparation of a substrate to render it suitable for adhesive joining. Same as substrate preparation or prebond preparation.
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T

TLV
Threshold Limit Value set by the ACGIH.
TSCA
Toxic Substance Control Act. Part of the EPA.
TWA
Time weighted average.
Tack
The property of an adhesive that enables it to form a bond of measurable strength immediately after adhesive and substrate are brought into contact under low pressure. Same as aggressive tack.
Tack range
The period of time in which an adhesive will remain in the tacky-dry condition after application to a substrate, under specified conditions of temperature and humidity.
Tackiness
The stickiness of the surface of a sealant or adhesive.
Tangential Grain
Grain orientation in wood in which annual rings are approximately parallel to the wide surface. Also called Flat or Plain Sawn.
Tannic Acid
A compound that is most commonly found in oak, cherry, cypress and redwood trees.
Tear Strength
The load required to tear apart a sealant specimen.
Teeth
The resultant surface irregularities or projections formed by the breaking of filaments or strings which may form when adhesive-bonded substrates are separated.
Telegraphing
A condition in a laminate or other type of composite construction in which irregularities, imperfections, or patterns of an inner layer are visibly transmitted to the surface.
Temperature, Curing
The temperature to which an adhesive or an assembly is subjected to cure the adhesive.
Temperature, Maturing
The temperature, as a function of time and bonding condition, that produces desired characteristics in bonded components.
Temperature, Setting
The temperature to which an adhesive or an assembly is subjected to set the adhesive.
Tensile Strength
Resistance of a material to a tensile force (a stretch). The cohesive strength of a material expressed in PSI.
Thermocouple
A device designed to measure temperature by means of voltage generated in a joint of two dissimilar metals.
Thermolabel
A pressure sensitive temperature measuring device that can be placed on a panel prior to pressing to measure maximum press or panel temperature.
Thermoplastic, (adjective)
Capable of being repeatedly softened by heat and hardened by cooling.
Thermoplastic, (noun)
A material that will repeatedly soften when heated and harden when cooled.
Thermoset
A material that will undergo or has undergone a chemical reaction by the action of heat, catalysts, ultraviolet light, etc., leading to a relatively infusible state.
Thermoset, State of
Pertaining to the state of a resin in which it is relatively infusible.
Thermosetting
Having the property of undergoing a chemical reaction by the action of heat, catalysts, ultraviolet light, etc., leading to a relatively infusible state.
Thinner
A volatile liquid added to an adhesive to modify the consistency or other properties.
Thixotropic
Nonsagging. A material that maintains its shape unless agitated.
Time, Assembly
The time interval between the spreading of the adhesive on the substrate and the application of pressure or heat, or both, to the assembly. Same as closed assembly time.
Time, Curing
The period of time during which an assembly is subject to heat or pressure, or both, to cure the adhesive.
Time, Drying
The period of time during which an adhesive on a substrate or an assembly is allowed to dry with or without the application of heat or pressure, or both.
Time, Joint Conditioning
The time interval between the removal of the joint from conditions of heat or pressure, or both, used to accomplish bonding and the attainment of approximately maximum bond strength. Sometimes called joint aging time.
Time, Setting
The period of time during which an assembly is subjected to heat or pressure, or both to set the adhesive.
Toxic
Poisonous or dangerous to humans by swallowing, inhalation, or contact resulting in eye or skin irritation.
Trade Name
Name given to a product by manufacturer or supplier.
Trade Secret
Confidential information that gives the owner an advantage over competitors.
Triple Chip Saw
A saw using three chips and a raker to let each chip do a third of the cutting. This saw is used for trimming because of the smooth cut ft produces.
Type I water resistance
Any glue tha t passes ANSI Type I water resistance specification. This test is more rigorous than the Type II test. It involves specimens being immersed in boiling water for four hours, then dried in an oven at 150ºF, then boiled again for four hours, and cooled in water just prior to testing. Specimens must meet wood failure requirements to pass this test.
Type II water resistance
Any glue that passes the ANSI Type II water-resistance specification. This is a rigorous test that involves specimens being soaked in water for four hours, then dried in an oven at 120ºF. If no delamination is seen after three cycles, the glue passes
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U

UV
Ultraviolet Light.
Ultimate elongation
Elongation at failure.
Ultraviolet Light
Part of the light spectrum. Ultraviolet rays can cause chemical changes in rubbery materials.
Urethane
A family of polymers ranging from rubbery to brittle. Usually formed by the reaction of a di-isocynate with a hydroxyl.
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V

V-joint
A glue joint in which one side is thicker than the other as a result of poor machining or uneven application of pressure.
VOC
Volatile Organic Compound.
Vacuum Press
A press designed for laminating or veneering in which the panel is placed inside of a flexible bag connected to a vacuum pump.
Vapor Density
The weight of a vapor or gas compared to the weight of an equal volume of air.
Vapor Pressure
The pressure exerted by a saturated vapor above its own liquid in a closed container.
Vehicle
The liquid component of a material.
Veneer
A thin (usually less that 1/8″ thick) piece of wood.
Viscosity
Measurement of material’s resistance to flow.
Volatile Organic Compound (VOC)
Any compound of carbon, excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates, ammonium carbonate, and excluding any "exempt compound" which participates in atmospheric photochemical reactions. The VOC is a measured or calculated number that reflects the amount of volatile organic material that is released from a product as it dries.
Volatility
Measure of a liquid’s tendency to evaporated at room conditions.
Volt
The electromotive force required to produce one ampere of current through one ohm of resistance. (V)
Vulcanization
To subject to vulcanization.
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W

Warp
A significant variation from the original, true, or plane surface.
Watt
A unit of electric power. The product of a volt times an ampere.
Webbing
Filaments or threads that may form when adhesive transfer surfaces are separated.
Wetting
This is the ability of an adhesive to stick to a surface immediately upon contact.
Wood Welder
Small hand-held radio frequency unit generally used for assembly gluing.
Wood failure
The rupturing of wood fibers in strength tests on bonded specimens, usually expressed as the percentage of the total area involved which shows such failure.
Wood, Built-up Laminated
An assembly made by joining layers of lumber with mechanical fastenings so that the grain of all laminations is essentially parallel.
Working Life
The period of time during which an adhesive, after mixing with catalyst, solvent, or other compounding ingredients, remains suitable for use.
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X

X (Reactance)
Variable for Electrical Reactance (Opposition to the flow of alternating current).
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Y

Yield
The percent of usable, defect-free lumber that can be cut from a rough cutting, board, or bundle of lumber.
Yield Value
The stress (either normal or shear) at which a marked increase in deformation occurs without an increase in load.
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Z

Z (impedance)
Variable for Electrical Impedance (The opposition a circuit offers to the flow of alternating current) expressed in ohms
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