An ISO 9001:2015 Certified Company

Glossary of Terms

We have compiled a glossary of terminology about adhesives and coatings as a service to our customers and industry colleagues.

Standard Definitions:

A

Abrasion resistance - the ability of a coating to resist being worn away and to maintain its original appearance and structure when subjected to rubbing, scraping or wear.

Acid number - the number of milligrams of potassium hydroxide required to neutralize the free acids of 1 gram of an oil resin, varnish or other substance – generally reported on the nonvolatile content.

Additive - a substance added in small quantities to another substance, usually to improve specific properties.

Adhere - to cause two surfaces to be held together by adhesion.

Adherend - a body which is held to another body by an adhesive. (See also substrate)

Adhesion - the stage in which two surfaces are held together by interfacial forces which may consist of valence forces or interlocking addition, or both. (See also adhesion, mechanical and adhesion, specific)

Adhesion promoter - a material built into a binder or to form primary bonds to either the substrate or the previously applied coating, with the specific aim of improving dry or wet adhesion, or both.

Adhesion, mechanical - adhesion between surfaces in which the adhesive holds the parts together by interlocking action. (See also adhesion, specific)

Adhesion, specific - adhesion between surfaces which are held together by valence forces of the same type as those which give rise to cohesion. (See also adhesion, mechanical)

Adhesive - a substance capable of holding materials together by surface attachment. Note: adhesive is a general term and includes among others cement, glue, mucilage, and paste. All of these terms are loosely used interchangeably. Various descriptive adjectives are applied to the term adhesive to indicate certain characteristics as follows: (1) physical form, that is, liquid adhesive, tape adhesive, etc.; (2) chemical type, that is, silicate adhesive, resin adhesive, etc.; (3) materials bonded, that is, paper adhesive, metalplastic adhesive, can label adhesive, etc.; (4) condition of use, that is, hot setting adhesive, room temperature setting adhesive, etc.

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, anaerobic - an adhesive that cures spontaneously in the absence of oxygen, the curing being inhibited by the presence of oxygen and catalyzed by metallic ions.

Adhesive, assembly - an adhesive that can be used for bonding parts together, such as in the manufacture of a boat, airplane, furniture, and the like. Note: The term assembly adhesive is commonly used in the wood industry to distinguish such adhesives (formerly called “joint glues”) from those used making plywood (sometimes called “veneer glues”). It is applied to adhesives used in fabricating finished structures or goods, or subassemblies thereof, as differentiated from adhesive used in the production of sheet materials for sale as such, for example, plywood or laminates.

Adhesive, cold setting - an adhesive that sets at room temperatures below 68°F. (See also adhesive, hot setting; adhesive, intermediate temperature setting; and adhesive, room temperature setting)

Adhesive, dispersion (or emulsion) - a two phase system with one phase (the adhesive material) in a liquid suspension.

Adhesive, encapsulated - 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.

Adhesive, film - an adhesive in film form, with or without a carrier, usually set by means of heat and/or pressure. The main advantage is uniformity of glueline thickness.

Adhesive, foamed - an adhesive, the apparent density of which has been decreased substantially by the presence of numerous gaseous cells dispersed through its mass.

Adhesive, gap filling - an adhesive subject to low shrinkage in setting, can be employed as a sealant.

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, heat sealing - a thermoplastic film adhesive which is melted between the adherend surfaces by heat application to one or both of the adjacent adherend surfaces.

Adhesive, hot melt - an adhesive that is applied in a molten state and forms a bond on cooling to a solid state.

Adhesive, latex - an emulsion of rubber or thermoplastic rubber to water.

Adhesive, multiple later - a film adhesive usually supported with a different adhesive composition on each side; designed to bond dissimilar materials such as the core to face bond of a sandwich composite.

Adhesive, one component - an adhesive material incorporating a latent hardener or catalyst activated by heat. Usually refers to thermosetting materials, but also describes anaerobic, hot melt adhesive, or those depend on solvent loss for adherence. Thermosetting one component adhesives require heat to cure.

Adhesive, pressure sensitive - a viscoelastic material which in solvent free form remains permanently tacky. Such materials 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 from 68° to 86°F.

Adhesive, solvent - an adhesive having a volatile organic liquid as a vehicle. Note: This term excludes water based adhesive.

Adhesive, solvent activated - a dry adhesive film that is rendered tacky just prior to use by application of a solvent

Adhesive, structural - an adhesive of proven reliability in engineering structural applications in which the bond can be stressed to a high proportion of its maximum failing load for long periods without failure.

Adhesive, two component - an adhesive supplied in two parts which are mixed before application. Such adhesives usually cure at room temperature.

Aging, accelerated - a set of laboratory conditions designed to produce in a short time the results of normal aging. Usual factors include temperature, light, oxygen, water and other environments as needed.

Amorphous phase - noncrystalline; most plastics are amorphous at processing temperature. Many retain this strength under normal temperatures.

Architectural coating - an organic coating intended for onsite application to interior or exterior surfaces of residential, commercial, institutional or industrial buildings, in contrast to industrial coatings.

Autoclave - a closed container that provides controlled heat and pressure conditions.

B

B-stage - an intermediate stage in the reaction of certain thermosetting resins in which the materials soften when heated and swell 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. Sometimes referred to as Resitol.

Backing - the flexible supporting materials for an adhesive. Pressure sensitive adhesives are commonly backed with paper, plastic films, fabric, or metal foil while heat curing thermosetting adhesives are often supported on glass cloth backing.

Binder - a component of an adhesive composition that is primarily responsible for the adhesive forces that hold two bodies together. (See also extender and filler)

Bite - the penetration or dissolution of adherend surfaces by an adhesive.

Bleeding - the diffusion of coloring matter through a coating from the substrate; also, the discoloration arising from such diffusions. In the case of printing ink, the spreading or running of a pigment color by the action of a solvent such as water or alcohol.

Blister - a cone-shaped defect caused by the formation of a gas or liquid under a coating film which results in a localized loss of adhesion and lifting of the coating (film) from the substrate.

Blocked curing agent - a curing agent or hardener rendered unreactive, which can be reactivated as desired by physical or chemical means.

Blocking - the sticking of a coated surface to an adjacent surface when the two surfaces have been in contact for an extended period of time.

Blotching - see mottling.

Bond - the union of materials by adhesives.

Bond (verb) - to unite materials by means of an adhesive. (See also adhere)

Bond strength - the unit load applied in tension, compression, flexure, peel, impact, cleavage, or shear, required to break an adhesive assembly with failure occurring in or near the plane of the bond. Note: The term adherence is frequently used in place of bond strength.

Bond, structural - see structural bond

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. Sometimes referred to as Resite.

CRYO-BOND - Valpac’s specialty line of adhesives and sealants for insulation attachment and sealing.

Catalyst - a substance that markedly speeds up the cure of an adhesive when added in minor quantity as compared to the amounts of the primary reactants. (See also hardener and inhibitor)

Caulking compound - a soft, plastic material consisting of pigment and vehicle, used for sealing joints in buildings and other structures where normal structural movement may occur.

Coating - a liquid, liquefiable or mastic composition that is converted by evaporation, cross-linking or cooling to a solid or semi-solid protective, decorating or functional adherent layer after application … or the solid or semi-solid layer resulting from application of the composition.

Cohesion - the state in which the particles of a single substance are held together by primary or secondary valence forces. As used in the adhesive field, the state in which the particles of the adhesive (or the adherend) are held together.

Cold pressing - a bonding operation in which an assembly is subjected to pressure without the application of heat.

Condensation - a chemical reaction in which two or more molecules combine with the separation of water or some other simple substance. If a polymer is formed, the process is called poly condensation. (See also polymerization).

Contact bonding - the deposition of cohesive materials on both adherend surfaces and their assembly under pressure.

Core - the honeycomb structure used in sandwich panel construction.

Coverage - the spreading power of an adhesive over the surface area of the adherend.

Creep - the dimensional change with time of a material under load, following the initial instantaneous elastic or rapid deformation. Creep at room temperature is sometimes called cold flow.

Crosslinking - the union of adjacent molecules of uncured adhesive (often existing as long polymer chains) by catalytic or curing agents.

Crystallinity - a state of molecular structure in some polymers denoting uniformity and compactness of the molecular chains.

Cure - to change the physical properties of an adhesive by chemical reaction, which may be condensation, polymerization, or vulcanization; usually accomplished by the action of heat and catalyst, alone or in combination with or without pressure.

Curing agent - see hardener.

Curing temperature - see temperature, curing.

Curing time - see time, curing.

D

Degrease - to remove oil and grease from adherend surfaces.

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 adherend.

Density - the mass per unit volume of a substrate at a specified temperature and pressure, usually expressed in g/mL … k.g.L. … g/cm3 … g/L … kg/m3 … or lb/gal.

Dielectric curing - the use of a high frequency electric field through a joint to cure a synthetic thermosetting adhesive. A curing process for wood and other nonconductive joint materials.

Diluent - an ingredient usually added to an adhesive to reduce the concentration of bonding materials. (See also extender and thinner)

Doctor roll - a roller mechanism that is revolving at different surface speed, or in opposite directions, resulting in a wiping action for regulating the adhesive supplied to the spreader roll.

Doctor-bar or blade - a scraper mechanism that regulates the amount of adhesive on the spreader rolls or on the surface being coated.

Dry - to change the physical state of an adhesive or an adherend by the loss of solvent constituents by evaporation or absorption, or both. (See also cure and set)

Dry tack - see tack, dry.

Drying Temperature - see temperature, drying.

Drying temperature - see temperature, drying.

Drying time - see time, drying.

Durability - a relative term indicating the degree of permanency. It may be applied to individual protective, decorative or functional properties – for example, “the durability of gloss,” but if used in a general way – for example, “the excellent durability of paint,” describes the ability of the described coating to retain, to the indicated degree, all the properties required for the continued service of the coating.

E

Elasticity, modulus of - the ratio of stress to strain in elastically deformed materials.

Elastomer - a macromolecular material which, at room temperature, is capable of recovering substantially in size and shape after removal of a deforming force.

Enamel - a paint that is characterized by its ability to form an especially smooth film.

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.

Ester gum - under resin, synthetic, see ester gum.

Exothermic - a chemical reaction that gives off heat.

Extended pigments - organic pigments diluted with an extender – for example, alumina trihydrate, blanc fixe or calcium carbonate.

Extender - a substance, generally having some adhesive action, added to an adhesive to reduce the amount of the primary binder required per unit area. (See also binder, diluent, filler, and thinner)

F

Failure, adherend - joint failure by cohesive failure of the adherend.

Failure, adhesive - rupture of an adhesive bond, such that the separation appears to be at the adhesive adherend interface. Note: Sometimes termed failure in adhesion.

Failure, cohesive - rupture of an adhesive bond, such that the separation appears to be within the adhesive.

Failure, contact - the failure of an adhesive joint as a result of incomplete contact during assembly, between adherend and adhesive surfaces or between adhesive surfaces.

Filler - a pigmented composition for filling pores or irregularities in a surface preparatory to application of other finishes.

Filler sheet - a sheet of deformable or resilient materials that when placed between the assembly to be bonded and the pressure applicator, or when distributed within a stack of assemblies, aids in providing uniform application of pressure over the area to be bonded.

Fillet - that portion of an adhesive which fills the corner or angle formed where two adherends are joined.

Finish - a final coat in a paint system, at the termination of cure or drying. Finish sometimes refers to the entire coating system: the texture, color and smoothness of a surface, plus other properties affecting appearance.

Fire-retardant - a descriptive term implying that the described product, under accepted test methods, will significantly reduce the rate of flame spread on the surface of a material to which it has been applied … resist ignition when exposed to high temperatures … or insulate a substrate to which it has been applied and prolong the time required to reach its ignition, melting or structural-weakening temperature.

Fire-retardant coating - a coating that will do one or more of the following: reduce the flame spread on the substrate over which the coating is applied, sometimes at the sacrificed (see intumescent coating); resist ignition of the substrate when exposed to high temperatures; or insulate the substrate to which the coating is applied, thereby prolonging the time required to reach its ignition, melting or structural-weakening temperature.

Flatting agent - a material added to paints, varnishes and other coating materials to reduce the gloss of the dried film.

Flow - movement of an adhesive during the bonding process, before the adhesive is set.

Fossil resin - under resin, natural, see fossil resin.

Fungus resistance - see mildew resistance.

G

Gallon - a volume equal to 231 in.3. For paint, varnish, lacquer and related products this is measured at 77˚F (25˚C).

Gel - a semisolid system consisting of a network of solid aggregates in which liquid is held.

Gelation - formation of a gel.

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 synonymous with the term adhesive. (See also adhesive, mucilage, paste, and sizing)

Glue line (bond line) - the layer of adhesive, which attaches two adherends.

Green strength - the ability of an adhesive to hold two surfaces together when brought into contact and before the adhesive develops its ultimate bond properties when fully cured.

Grit - coarse, foreign particles in coatings, often of irregular shape, that are hard, abrasive and resistant to disintegration.

H

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 s als used to designate a substance added to control the degree of hardness of the cured film. (See also catalyst)

Heat reactivation - the used of heat to effect adhesive activity, e.g., hot melt adhesive; completion of the curing process of a B-staged resin.

Honey comb core - a sheet of material, which may be metal, formed into cells (usually hexagonal) and used for sandwich construction in structural assemblies, especially in aircraft construction.

Hydrolysis - decomposition of a substrate or adhesive by a reaction with water.

Hydroxyl number - the number of milligrams of potassium hydroxide equivalent to the hydroxyl content of 1 gram of sample.

I

Inhibitor - a substance that slows down a chemical reaction. Inhibitors are sometimes used in certain types of adhesives to prolong storage or working life.

Interface - the contact area between adherend and adhesive surfaces.

Intumescent coating - a fire-retardant coating that when heated forms a foam produced by nonflammable gases such as carbon dioxide and ammonia. This results in a thick, highly insulating layer of carbon, about 50 times as thick as the original coating, that serves to protect the coated substrate from fire.

J

Joint - the location at which two adherends are held together with a layer of adhesive. (See also bond, n)

Joint aging time - see time, joint conditioning.

Joint, lap - a joint made by placing one adherend partly over another and bonding together the overlapped portions. (See also joint, scarf)

Joint, starved - a joint that has an insufficient amount of adhesive to produce a satisfactory bond. Note: This condition my result from too thin a spread to fill the gap between the adherend, excessive penetration of the adhesive into the adherend, too short an assembly time, or the use of excessive pressure.

L

LNG - Acronym for liquefied natural gas: Natural gas, predominantly methane, that has been liquefied by cooling to approximately -260˚F to facilitate shipping and storage.

Lacquer - a coating composition that is based on synthetic thermoplastic film-forming material dissolved in organic solvent that dries primarily by solvent evaporation. Typical lacquers include those based on nitrocellulose, other cellulose derivatives, vinyl resins and acrylic resins, among others.

Laminate (noun) - a product made by bonding together two or more layers of material or materials. (see also laminated, cross and laminated, parallel)

Laminate (verb) - to unite layers of materials with adhesive.

Laminated, cross - a laminate in which some of the layers of materials are oriented at right angles to the remaining layers with respect to the grain or strongest direction in tension. (See also laminated, parallel) Note: Balanced construction of the laminations about the center line of the thickness of the laminate in normally assumed.

Laminated, parallel - a laminate in which all the layers of materials are oriented approximately parallel with respect to the grain or strangest direction in tension (See also laminated, cross)

Lamination - the process of preparing a laminate. Also, layer in a laminate.

Lap joint - see joint, lap

Latex paint - a paint containing a stable aqueous dispersion of synthetic resin, produced by emulsion polymerization as the principal constituent of the binder (modifying resins may also be present). Oil paint – a paint that contains drying oil or oil varnish as the basic vehicle ingredient. Paste paint – a paint in which the pigment is sufficiently concentrated to permit a substantial reduction with vehicle before use. Water paint – a paint, the vehicle of which is a water emulsion, water dispersion, or ingredients that react chemically with water.

Legging - the drawing of filaments or strings when adhesive bonded substrates are separated.

Leveling - the process whereby a film of liquid coating flows out after application so as to minimize any surface irregularities such as brush marks, orange peel, peaks or crafters that have been produced by the mechanical process of application. Also, a measure or rating of the leveling ability of a coating.

M

Matrix - the part of an adhesive that surrounds or engulfs embedded filler or reinforcing particles and filaments.

Mechanical adhesion - see adhesion, mechanical and adhesion, specific.

Mildew resistance - also known as fungus resistance, the ability of a coating to resist fungus growth that can cause discoloration and the ultimate decomposition of a coating’s binding medium.

Mildewstat - a chemical agent that inhibits the growth of mildew.

Modifier - any chemically inert ingredient added to an adhesive formulation that changes its properties. (See also filler, plasticizer, and extender)

Modulus - see elasticity, modulus of.

Monomer - a relatively simple compound which can react to form a polymer. (See also polymer)

Mottling - the presence on the surface of a film of irregularly shaped, randomly distributed areas that vary in color, gloss or sheen, causing the film to be non-uniform in appearance. Also known as blotching.

Mud-cracking - an irregular broken network of cracks in the film which occurs due to volatile loss while drying or curing.

N

Newtonian fluid - a fluid in which the shearing rate is directly proportional to the applied torque.

Nonvolatile content - the portion of a coating that does not evaporate during drying or curing under specified conditions, comprising the binder and, if present, the pigment. The percent volatile content is obtained by subtracting the nonvolatile content from 100.)

Nonvolatile vehicle - the liquid portion of a paint excepting its volatile thinner and water.

Novalak - a phenolic-aldehydic resin that, unless a source of methylene groups is added, remains permanently thermoplastic. (See also retinoid and thermoplastic)

O

OEM coatings - coatings from original equipment manufacturers that include automotive, marine, furniture, appliance and many other miscellaneous consumer and industrial applications.

Opacity - the degree of obstruction to the transmission of visible light. (In this sense, “opacity” is a relative term, considering that given a film being sufficiently thin, there is no “absolutely opaque” substance.)

Open assembly time - see time, assembly.

Open time - the length of time a coating remains wet enough to allow for brushing-in at the laps. Also known as wet edge time.

P

Paint - a classification sometimes employed to distinguish pigmented drying oil coatings (paints) from synthetic enamels and lacquers. Enamel paint – a paint, the vehicle of which is an emulsion of binder in water – the binder being oil, oleoresinous varnish, resin or some other emulsifiable binder.

Paint (verb) - to apply a thin layer of a coating to a substrate by brush, spray, roller, immersion or any other suitable means.

Paste - an adhesive composition having a characteristic plastic type consistency, that is, a high order of yield value, such as that of a paste prepared by heating a mixture of starch and water and subsequently cooling the hydrolyzed product. (See also adhesive, glue, mucilage, and sizing)

Penetration - the entering of an adhesive into an adherend. Note: This property of a system is measured by the depth of penetration of the adhesive into the adherend.

Pick-up roll - a spreading device where the roll for picking up the adhesive runs in a reservoir of adhesive.

Pigment - fine solid particles used in the preparation of paint or printing ink and substantially insoluble in the vehicle. Asphaltic materials are not pigments except when they contain substances substantially insoluble in the vehicle in which they are used.

Pigment volume - the percent by volume of pigment in the nonvolatile portion of a paint or printing ink, as calculated from bulking value and composition data. The letters “PV” are commonly used as an abbreviation.

Pinholes - small pore-like flaws in a coating that extend entirely through the applied film and have the general appearance of pin pricks when viewed by reflected light.

Plasticity - a property of adhesives that allows the materials to be deformed continuously and permanently without rupture upon the application of a force that exceeds the yield value of the material.

Plasticizer - a substance added to varnishes, lacquers or paints to impart flexibility.

Polycondensation - see condensation.

Polymer - a compound formed by the reaction of simple molecules having functional groups which permit their combination to proceed to high molecular weights under suitable conditions. Polymers may be formed by polymerization (addition polymer) or polycondensation (condensation polymer). When two or more monomers are involved, the product is called a copolymer.

Polymerization - a chemical reaction in which the molecules of a monomer are linked together to form large molecules whose molecular width is a multiple of that of the original substance. When two or more monomers are involved, the process is called copolymerization or heteropolymerization. (See also condensation)

Porosity - the ability of adherend to absorb and adhere.

Post cure - a treatment (normally involving heat) applied to an adhesives 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.

Post vulcanization bonding - conventional adhesive bonding of previously vulcanized elastomeric adherends.

Pot life - see working life.

Pressure sensitive adhesive - see adhesive, pressure sensitive.

Primer - the first of two or more coats of a paint, varnish or lacquer system.

Printing ink - a colored or pigmented liquid or paste composition that dries to a solid film after application as a thin layer by printing machinery.

R

Release agent - an adhesive material which prevents bond formation.

Release paper - a sheet, serving as a protectant or carrier, or both, for an adhesive film or mass, which is easily removed from the film or mass prior to use.

Resin, acrylic - a synthetic resin made from derivatives of acrylic acid.

Resin, alkyd - a synthetic resin made from polyhydric alcohols and polybasic acids; generally modified with resins, fatty oils or fatty acids.

Resin, epoxy - a class of polymeric materials characterized by the presence of more than one three-membered ring known as the epoxy, epoxide, oxirane or ethyoxyline group.

Resin, maleic - a resin made from a natural resin and maleic anhydride or maleic acid.

Resin, melamine - a synthetic resin made form melamine and aldehyde.

Resin, natural - a solid organic substance originating in the secretion of certain plants or insects, which is thermoplastic, flammable, nonconductive of electricity, breaks with a conchoidal fracture when hard, and dissolves in certain specific organic solvents but not water.

Resin, penta - ester gum made from rosin and pentaerythritol.

Resin, phenolic - a synthetic resin made from phenols and aldehydes.

Resin, styrene - a synthetic resin made from vinyl benzene.

Resin, synthetic - a synthetic substance physically similar to natural resin.

Resin, urea - a synthetic resin made from urea and an aldehyde.

Resin, vinyl - a synthetic resin made from vinyl compounds.

Resitol - an alternative term for B-stage (See also B-stage)

Resol - an alternative term for A-stage (See also A-stage)

Ressin, fossil - a natural resin of ancient origin usually found in the earth.

Restite - an alternative term for C-stage. (See also C-stage)

Retarder - see inhibitor.

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 resin)

Rust - a reddish material, primarily hydrated iron oxide that is formed on iron or its alloys, resulting from exposure to humid atmosphere or chemical attack.

S

Sag or sagging - non-uniform downward flow of a wet paint film that occurs between the time of application and setting, resulting in an uneven coating having a thick lower edge.

Sagging - run or flow-off of adhesive from an adherend surface due to application of excess or low viscosity material.

Sandwich panel - an assembly composed of metal skins (facings) bonded to both sides of a lightweight core.

Sealant - a gap filling material to prevent excessive absorption of adhesive, or penetration of liquid or gaseous substances.

Sealer - a liquid composition to prevent excessive absorption of finish coats into porous surfaces. Also, a composition to prevent bleeding (see also size).

Self-curing - see self-vulcanizing.

Self-vulcanizing - pertaining to an adhesive that undergoes vulcanization without the application of heat.

Separate application adhesives - see adhesive, separate application.

Service conditions - the environmental conditions to which a bonded structure is exposed., e.g., heat, cold, humidity, radiation, vibration, etc.

Set - to convert an adhesive into a fixed or hardened sate by chemical or physical action, such as condensation, polymerization, oxidation, vulcanization, gelation, hydration, or evaporation of volatile constituents. (See also cure and dry)

Setting temperature - see temperature, setting.

Setting time - see time, setting.

Shear, tensile - the apparent stress applied to an adhesive in a lap joint.

Shelf life - see storage life

Shrinkage - the volume reduction occurring during adhesive curing, sometimes expressed as percentage volume or linear shrinkage; size reduction of adhesive layer due to solvent loss or catalytic reaction.

Size - usually a liquid composition to prevent excessive absorption of all paints into plaster, old wall paint and similar porous surfaces. Also a liquid composition used as a first coat on metal to improve adhesion of succeeding coats (the latter usage is limited to the metal decorating). The terms sealer and size are nearly synonymous, but usage has established certain differences. A sealer is ordinarily a thin varnish or clear lacquer and is usually applied on wood and metal surfaces. Ordinary painter’s size is a then solution of glue, starch or other water-soluble substance and is usually applied on plaster surfaces.

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 materials used for this purpose. The latter is sometimes called size.

Slippage - the movement of the adherends with respect to each other during the bonding process.

Solid - pertaining to flammability regulations, a substance that has a viscosity greater than 1 x 103 St (1 x 10-1 m2s-1) at 104˚F (40˚C) or an equivalent viscosity at an agreed-upon temperature. (This includes powders and granular materials.)

Solids content - the percentage of weight of the nonvolatile matter in an adhesive. Note: The actual percentage of the nonvolatile matter in an adhesive will vary considerably according to the analytical procedure that is used. A standard test method must be used to obtain consistent results.

Solvent bonding - see solvent welding.

Solvent cement - an adhesive utilizing an organic solvent as the means of depositing the adhesive constituent.

Solvent cementing - see solvent welding.

Solvent reactivating - the application of solvent to a dry adhesive layer to regenerate its wetting properties.

Solvent welding - the process of joining articles made of thermoplastic resins by applying a solvent capable of softening the surfaces to be joined and pressing the softened surfaces together. Adhesion is attained by means of evaporation of the solvent, absorption of the solvent into the adjacent materials and/or polymerization of the solvent cement.

Specific adhesion - see adhesion, specific and adhesion, mechanical.

Specific gravity - the ratio of the weight of a given volume of substance to the weight of an equal volume of water. Also, the ratio of the density of a substance at a specified temperature to the density of water. (See also Density.)

Squeeze-out - excess adhesive pressed out at the bond line due to pressure applied in the adherends.

Stabilizer - an adhesive additive which prevents or minimizes change in properties, e.g.., by adherend absorption, demulsification, or rapid chemical reaction.

Starved joint - see joint, starved.

Storage life - the period of time during which a packaged adhesive can be stored under specified temperature conditions and remain suitable for use. Sometimes called Shelf Life. (See also working life)

Strength, cleavage - the tensile load expressed in force per unit of width of bond required to cause cleavage separation of a test specimen of unit length.

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, fatigue - the maximum load expressed in force per unit of width of bond required to cause cleavage separation of a test specimen of unit length.

Strength, impact - the ability of an adhesive material to resist shock by a sudden physical blow direct against it. Impact shock is the transmission of stress to an adhesive interface by sudden vibration or jarring blow of the assembly, measured in work units per unit area.

Strength, lap joint - the force necessary to rupture an adhesive joint by means of stress applied parallel to the plane of the bond. Also referred to as tensile-shear strength.

Strength, peel - the force per unit width necessary to bring an adhesive to the point of failure and/or to maintain a specified rate of failure by means of a stress applied in a peeling mode.

Strength, shear - the resistance of an adhesive joint to shearing stresses; the force per unit areas sheared, at failure.

Strength, tensile - the resistance of an adhesive joint to tensile stress; the force per unit area under tension, at failure.

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. Note: The term is commonly used also to designate strength after immersion in water. In the latex adhesive, the term is also used to describe the joint strength when the adherends are brought together with the adhesive still in the wet state.

Stringiness - the property of an adhesive that results in the formation of filaments or threads when adhesive transfer surfaces are separated. (See also webbing) Note: Transfer surfaces may be rolls, picker plates, stencils, etc.

Structural adhesive - see adhesive, structural.

Structural bond - a bond, which stresses the adherend to the yield, point, thereby taking full advantage of the strength of the adherend. On the basis of this definition, a dextrin adhesive used with paper (e.g., postage stamps, envelopes, etc.) and which cause failure of the paper, forms a structural bond. The stronger the adherend, the greater the demands placed on the adhesive. Thus, few adhesives qualify as “structural” for metals. A further requirement for a structural adhesive is that it be able to stress the adherend to its yield point after exposure in its intended environment.

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 adherend. (See also adherend)

Surface preparation - a physical or chemical preparation, or both, of an adherend to render it suitable for adhesive joining.

Synthetic cohesives - Cohesives or cold seals that do not contain any natural latex. Due to the potential for allergic reactions to natural latex, certain applications, such as medical packaging, may require a latex-free product.

T

Tack - the property of an adhesive that enables it to form a bond of measurable strength immediately after adhesive and adherend are brought into contact under low pressure.

Tack range - the period of time in which an adhesive will remain in the tacky dry condition after application to an adherend, under specified conditions of temperature and humidity.

Tack, dry - the property of certain adhesives, particularly nonvulcanizing rubber adhesives, to adhere on contact to themselves at a stage in the evaporation of volatile constituents, even thought they seem dry to the touch. Sometimes called Aggressive Tack.

Tackifier - an additive intended to improve the stickiness of a cast adhesive film; usually a constituent of rubber based and synthetic resin adhesives.

Tacky-dry - pertaining to the condition of an adhesive when the volatile constituents have evaporated or been absorbed sufficiently to leave it in a desired tacky state.

Tape - a film form of adhesive which may be supported on carrier material.

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, ambient - temperature of the air surrounding the object under construction or test.

Temperature, curing - the temperature to which an adhesive or an assembly is subjected to cure the adhesive (See also temperature, drying and temperature, setting) Note: The temperature attained by the adhesive in the process of curing it (adhesive curing temperature) may differ from the temperature of the atmosphere surrounding the assembly (assembly curing temperature).

Temperature, drying - the temperature to which an adhesive on an adherend or in an assembly or the assembly itself is subjected to dry the adhesive. (See also temperature, curing, and temperature, drying)

Temperature, setting - the temperature to which an adhesive or an assembly is subjected to set the adhesive (See also temperature, curing and temperature, drying)

Test, desctructive - tests involving the destruction of assemblies in order to evaluate the maximum performance of the adhesive bond.

Test, nondestructive - inspection tests for the evaluation of bond quality without damaging the assembly, e.g., ultrasonic, visual inspection, etc.

Thermoplastic - a material that will repeatedly soften when heated and harden when cooled.

Thermoplastic (adjective) - capable of being repeatedly softened by heat and hardened by cooling.

Thermosetting (adjective) - having the property of undergoing a chemical reaction by the action of heat, catalysts, ultraviolet light, etc., leading to a relatively infusible state.

Thermostet - a material that will undergo or has undergone a chemical reaction by the action of heat, catalyst, ultraviolet light, etc., leading to a relatively infusible state.

Thermostet (adjective) - pertaining to the state of a resin in which it is relatively infusible.

Thinner - the portion of a varnish, lacquer, paint or printing ink (or related product) that volatizes during the drying process.

Thixotropy - the property of adhesives systems to thin upon isothermal agitation and to thicken upon subsequent rest.

Time, assembly - the time interval between the spreading of the adhesive on the adherend and the application of pressure or heat, or both, to the assembly. (1) Open assembly time is the time interval between the spreading of the adhesive on the adherend and the completion of the assembly of the parts for bonding. (2) Closed assembly time is the interval between completion of assembly of the parts for bonding and the application of pressure or heat, or both, to the assembly.

Time, curing - the period of time during which an assembly is subjected to heat or pressure, or both, to cure the adhesive. (See also time, joint conditioning and time, setting)

Time, drying - the period of time during which an adhesive on an adherend or an assembly is allowed to dry with or without the application of heat or pressure, or both. (See also time, curing; time, joint conditioning; and time, setting)

Time, joint conditioning - 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. 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. (See also time, curing; time, joint conditioning; and time, drying)

Tint - a color produced by the mixture of white pigment or paint in predominating amount with a colored pigment or paint, not white. The tint of a color is much lighter and much less saturated than the color itself.

Tint (verb) - to mix a white paint with a colorant, or to mix a colored paint with a white colorant. Also, to adjust the color of a test specimen to be a closer match to a standard.

Toner - an organic pigment that does not contain inorganic pigment or an inorganic carrying base.

U

Urethane coatings - coatings based on vehicles containing a minimum of 10% by weight (nonvolatile vehicle basis) of a polyisocyanate monomer reacted in such a manner as to yield polymers containing any ratio, proportion or combination of urethane linkages, active isocyanate groups or polyisocyanate monomer. The reaction products may contain excess isocyanate groups available for further reaction at the time of application, or may contain essentially no free isocyanate as supplied.

Urethane coatings, Type 1, one-package pre-reacted - urethane coatings characteristic by the absence of any significant quantity of fee isocyanate groups. They are usually the reaction product of a polyisocyanate and a polyhydric alcohol ester of vegetable oil acids and are hardened with the aid or metallic soap dryers.

Urethane coatings, Type 2, one-package moisture-cured - urethane coatings characterized by the presence of free isocyanate groups and capable of conversion to useful films by the reaction of these isocyanate groups and ambient moisture.

Urethane coatings, Type 3, one-package heat-cured - urethane coatings that dry on cure by thermal release of blocking agents and regeneration of active isocyanate groups that subsequently react with substances containing active hydrogen groups.

Urethane coatings, Type 4, two-package catalyst - urethane coatings that comprise systems wherein one package contains a prepolymer or adduct having free isocyanate groups capable of forming useful films by combining with a relatively small quantity of catalyst, accelerator or crosslinking agent such as a monomeric polyol or polyamine contained in a second package (this type has limited pot-life after the two components are mixed).

Urethane coatings, Type 5, two-package polyol - urethane coatings that comprise systems therein one package contains a prepolymer or adduct or other polyisocyanate capable of forming useful films by combining with a substantial quantity of a second package containing a resin having active hydrogen groups with or without the benefit of a catalyst (this type has limited pot-life after the two components are mixed).

Urethane coatings, Type 6, one-package nonreactive lacquer - urethane solution coatings characterized by the absence of any significant quantity of free isocyanate or other functional groups. Such coatings convert to solid films primarily by solvent evaporation.

V

V-TAC - Valpac’s line of tackifier dispersions.

Varnish - a liquid composition that is converted to a transparent or translucent solid film after application as a thin layer. Bituminous varnish – a dark-colored varnish containing bituminous ingredients (the varnish may be either of the oil or spirit type). Oil varnish – a varnish that contains resin and drying oil as the basic film-forming ingredients and is converted to a solid film primarily by chemical reaction. Shellac varnish – a solution or “cut” of a specified type and grade or dry lac resin in a suitable alcohol. Spar varnish – a varnish for exterior surfaces, the naming originating from its use on the spars of ships. Spirit varnish – a varnish that is converted to a solid film, primarily by solvent evaporation.

Vehicle - the liquid portion of a paint or printing ink. Anything that is dissolved in the liquid portion of a paint or printing ink is part of the vehicle.

Viscosity - the ratio of the shear stress existing between laminae of moving fluid and the rate of shear between these laminae. Note: A fluid is said to exhibit Newtonian behavior when the rate of shear is proportional to the shear stress. A fluid is said to exhibit non-Newtonian behavior when an increase of decrease in the rate of shear is not accompanied by proportional increase or decrease in the shear stress.

Viscosity coefficient - the shearing stress tangentially applied that will induce a velocity gradient. A material has a viscosity of one poise when a shearing stress of one dyne per square centimeter produces a velocity gradient of (1 cm/s)/cm. (See also viscosity)

Volume percent solids - the portion of a coating that remains as part of the dry film, expressed as percent by volume.

Vulcanization - a chemical reaction in which the physical properties of a rubber are changed in the direction of decreased plastic flow, less surface tackiness, and increased tensile strength by reaction it with sulfur or other suitable agents. (See also self-vulcanizing)

Vulcanize - to subject to vulcanization.

W

Water percent solids - the portion of a coating that remains as part of the dry film, expressed as weight.

Water vapor transmission rate - often abbreviated as WVT, the steady state rate of water vapor movement through a free film under specific conditions of temperature and humidity at each surface, customarily expressed in grains per square foot per hour (gr/ft.2 per hour) or grams per square meter per day (g/m2 per day).

Water-reducible coating - a coating that can be reduced in viscosity by the addition of water.

Waterborne coating - a coating in which the principal volatile constituent is water. (See also water-reducible coating.)

Wet adhesion - the ability of a coating film to adhere tightly to the substrate directly beneath it, under wet conditions such as rain, dew, cleaning and washing, etc.

Wet strength - see strength, wet.

Wetting - a surface is said to be completely wet by a liquid if the contact angle is zero, and incompletely wet if it is a finite angle. Surfaces are commonly regarded as unwettable if the angle exceeds 90 degrees.

Working life - the period of time during which an adhesive, after mixing with catalyst, solvent or other compounding ingredients, remains suitable for use. (See also storage life)

Y

Yield value - the stress (either normal or shear) at which a marked increase in deformation occurs without an increase in load.