Glossary of Terms

• Abrasion – Wearing, grinding, or rubbing away by friction.
• Acrylic – A synthetic resin used in high-performance water-based coatings. A coating in which the binder contains acrylic resins.
• Additive – A substance added to a formulation in relatively small amounts to impart or improve desirable properties or suppress undesirable properties.
• Adhesion – The ability of dry paint to attach to and remain fixed on the surface without blistering, flaking, cracking or being removed by tape.
• Air Cure – One method by which liquid coatings cure to a dry film. Oxygen from the air enters the film and cross-links the resin molecules. Also called “Air Dry” and “Oxidizing.”
• Alkyd – Synthetic resin modified with oil. Coating that contains alkyd resins in the binder.
• Amide – A functional group which can act as an epoxy resin curing agent.
• Anti-fouling Paint – Paints formulated especially for boat decks and hulls, docks and other below-water-line surfaces and structures to prevent the growth of barnacles and other organisms on the bottom of ships.
• Binder – Solid ingredients in a coating that hold the pigment particles in suspension and attach them to the substrate. Consists of resins (e.g., oils, alkyd, latex). The nature and amount of binder determine many of the paint’s performance properties–washability, toughness, adhesion, color retention, etc.
• Birefringence – The refraction of light in an anisotropic material (as calcite) in two slightly different directions to form two rays. In optical coatings, birefringence creates a distortion of images seen through the optical piece, as well as a reflection or noticeable purple sheen on the surface of the optical piece. It is usually caused by poor refractive index matching between the coatings and the substrate.
• Blistering – Formation of dome-shaped projections in paints or varnish films resulting from local loss of adhesion and lifting of the film from the underlying surface.
• Buffing – Process of polishing a cured coating to improve release and low friction.
• Bulk density – The mass per unit of volume in powder form, including the air trapped between particles.
• Butadiene – A gas which is chemically combined with styrene to create a resin used in latex binders, styrene-butadiene.
• Carrier – The liquid portion of a coating (solvent or water) in which solids are dissolved or suspended.
• Catalyst – Substance whose presence increases the rate of a chemical reaction, e.g., acid catalyst added to an epoxy resin system to accelerate drying time.
• Chalking – Formation of a powder on the surface of a paint film caused by disintegration of the binder during weathering. Can be affected by the choice of pigment or binder.
• Clear Coating – A transparent protective and/or decorative film; generally the final coat of sealer applied to automotive finishes.
• Coating – A paint, varnish, lacquer or other finish used to create a protective and/or decorative layer. Generally used to refer to paints and coatings applied in an industrial setting as part of the original equipment manufacturer’s (OEM) process.
• Coefficient of friction – A number expressing the amount of frictional effect: static or dynamic.
• Cohesion – A bonding together of a single substance to itself. Internal adhesion.
• Cold flow – Tendency of plastic materials to migrate slowly under heavy loads and/or over time.
• Colloid – A substance with components of one or two phases, a type of mixture intermediate between homogeneous solution and heterogeneous mixture with properties also intermediate between a solution and a mixture. The size of dispersed phase particles in a colloid range from one nanometer to one micrometer. Behavior in solution surface chemistry and colloid chemistry is dependent on the surface charge and the potential distribution in the surrounding electrical double layer.
• Colloidal silica – Molecular formula: SiO2. Monodispersed silicon dioxide particles, usually between 0-1000 nanometers in diameter, usually in solution.
• Compatibility – The capacity of different materials from different sources or of different compositions to be combined and applied so as to yield no visible or mechanically measurable differences in the cured film or application properties.
• Conductor – Material that can support flow of electric current. Fluoropolymer coatings are normally insulators, but can be modified with certain fillers and pigments to make them conductive.
• Contact angle – A means of quantifying the nonstick properties of a coating by measuring the ability of a liquid to wet its surface.
• Corrosion – Process of metal decomposition (oxidation) in which metal ions are united with oxygen to form metal oxides. Fluoropolymer coatings provide excellent barriers against corrosion.
• Corrosion Inhibitor – A type of metal paint or primer that prevents rust by preventing moisture from reaching the metal. Zinc phosphate, barium metaborate and strontium chromate (all pigments) are common ingredients in corrosion-inhibitive coatings. These pigments absorb any moisture that enters the paint film.
• Crosslinking – Quality of thermosetting plastic resins in which polymer chains combine during the curing process. In general, the greater the crosslinking, the tougher and more chemically resistant the coating.
• Cure schedule – The time/temperature relationship required to cure a coating.
• Cure, Curing – The process whereby a liquid coating becomes a hard film.
• Cut-through resistance – A coating film’s resistance to penetration resulting from the combined application of sharp edges, heat and pressure.
• Dead Flat – No gloss or sheen.
• DFT – Dry Film Thickness.
• Diluent – A liquid used in coatings to reduce the consistency and make a coating flow more easily. The water in latex coatings is a diluent. A diluent may also be called a “Reducer,” “Thinner,” “Reducing Agent” or “Reducing Solvent.”
• Dip/spin – Coating application technique in which small parts are placed in a basket that is lowered into a coating bath, then raised and spun to remove excess coating. An economical system for coating high volumes of small parts.
• Driers – Various compounds added to coatings to speed the drying.
• Edge coverage – A coating’s ability to flow over, build and adhere to sharp corners, angles and edges.
• Eggshell – Gloss lying between semi-gloss and flat.
• Emulsion – A mixture of solids suspended in a liquid.
• Emulsion Paint – Coating in which resins are suspended in water, then flow together with the aid of an emulsifier. Example: latex paint.
• Enamel – Broad classification of paints that dry to a hard, usually glossy finish. Most equipment-coating enamels require baking. Enamels for walls do not.
• Engineering plastics – Plastic resins that have high-performance properties such as high temperature stability, hot hardness, abrasion resistance and corrosion resistance.
• Epoxy – A flexible resin, usually thermosetting, made by polymerization of an epoxide and used chiefly in coatings and adhesives.
• ETFE (ethylene tetrafluoroethylene) – A thermoplastic member of the fluoropolymer family. ETFE is noted for exceptional chemical resistance, toughness and abrasion resistance.
• Extender – Ingredients added to paint to increase coverage, reduce cost, achieve durability, alter appearance, control rheology and influence other desirable properties. Less expensive than prime hiding pigments such as titanium dioxide. Examples: barium sulfate, calcium carbonate, clay, gypsum, silica, talc. May also improve coating performance.
• FEP (fluorinated ethylene propylene) – A thermoplastic member of the fluoropolymer family. FEP has excellent nonstick and non-wetting properties.
• Fillers – Pigments and other solids used to alter properties of coatings.
• Film Build – Amount of thickness produced in an application. Millimeters (mils) of dry film per mils of applied wet film.
• Film Thickness – Depth or thickness of the dry coating in millimeters.
• Fire Resistance – The ability of a coating to withstand fire or to protect the substrate to which it is applied from fire damage.
• Fire Retardant – A coating which will (1) reduce flame spread, (2) resist ignition when exposed to high temperature or (3) insulate the substrate and delay damage to the substrate.
• Flashing – A brief sub-cure (at lower temperatures than the final cure) to drive off solvents or carriers prior to full cure. This helps prevent bubbling. See Partial cure.
• Flat – A surface that scatters or absorbs the light falling on it so as to be substantially free from gloss or sheen (0-15 gloss on a 60-degree gloss meter).
• Fluoropolymers – Family of engineering plastics containing fluorine, characterized by high thermal stability, almost universal chemical resistance and low friction.
• Forced Dry – Baking the paint between room temperature and 150º F to speed the drying process.
• Friction (dynamic) – Resistance to continued motion between two surfaces; also known as sliding friction.
• Friction (static) – Resistance to initial motion between two surfaces.
• Fusion – The melting and flowing of heated polymer particles to form a continuous film.
• Glass transition temperature – The temperature at which an amorphous polymer ceases to be brittle and glassy in character and becomes less rigid and more rubbery.
• Gloss – The luster or shininess of paints and coatings. Different types of gloss are frequently arbitrarily differentiated, such as sheen, distinctness-of-image gloss, etc. Trade practice recognizes the following gloss levels, in increasing order of gloss: flat (or matte)– practically free from sheen, even when viewed from oblique angles (usually less than 15 on 60-degree meter); eggshell– usually 20-35 on 60-degree meter; semi-gloss–usually 35-70 on 60-degree meter; full-gloss–smooth and almost mirror-like surface when viewed from all angles, usually above 70 on 60-degree meter.
• Gloss Meter – A device for measuring the light reflectance of coatings. Different brands with the same description (such as semi-gloss or flat) may have quite different ratings on the gloss meter.
• Hardener – Curing agent for epoxies or fiberglass.
• Hot hardness – Ability of a coating to retain hardness and wear resistance at elevated temperatures. Usually a characteristic of coatings based on thermosetting resin binders.
• Hybrid resin – A combination of two or more common resins.
• Intercoat adhesion – A coating’s ability to adhere to previously applied films, including primers.
• Intumescence – A mechanism whereby fire-retardant paints protect the substrates to which they are applied. An intumescent paint puffs up when exposed to high temperatures, forming an insulating, protective layer over the substrate.
• Lacquer – A fast-drying usually clear coating that is highly flammable and dries by solvent evaporation only. Can be reconstituted after drying by adding solvent.
• Latex-based Paint – General term used for water-based emulsion paints made with synthetic binders such as 100% acrylic, vinyl acrylic, terpolymer or styrene acrylic. A stable emulsion of polymers and pigment in water.
• Liquid Driers – Solution of soluble driers in organic solvents.
• Lotus effect – A self-cleaning effect of superhydrophobic surfaces, whereby water droplets on the coating retain a high water contact angle, that is, stay spherical and bead off the surface. Named after the self-cleaning property of lotus flowers which have a waxy coating.
• Marine Paint – Coating specially designed for immersion in water and exposure to marine atmosphere (See also Anti-fouling Paint).
• Matrix coating – One in which some ingredients, such as the lubricant (PTFE), which is soft, are enveloped in others (the matrix, such as harder, more wear-resistant binders). Also referred to as “resin bonded coating.”
• Melt point – The temperature at which a polymer particle will begin to melt and flow.
• Micron – µ, one micron, one millionth of a meter. Also expressed as µm or micro-meter.
• Mil – One thousandth (0.001) of an inch (25.4 microns). Most common non-metric measurement of coating thickness.
• Monomer – Substance composed of low molecular weight molecules capable of reacting with like or unlike molecules to form a polymer.
• Nanometer – A unit of measurement equivalent to one millionth of a meter.
• Nanoparticle – A particle whose diameter measures between 0 and 1,000 nanometers.
• Nanotechnology – The creation of functional materials, devices and systems through control of matter on the nanometer length scale (1-100 nanometers), and exploitation of novel phenomena and properties (physical, chemical, biological) at that length scale.
• Noise reduction – The absorption of sound vibrations. Fluoropolymer coatings form good noise dampening surfaces.
• Nonvolatile – The portion of a coating left after the solvent evaporates; sometimes called the solids content.
• Oleophobic – Oil shedding.
• Oxidation – Chemical reaction upon exposure to oxygen. Some coatings cure by oxidation, when oxygen enters the liquid coating and cross-links the resin molecules. This film-forming method is also called “Air Cure” and “Air Dry.” (Oxidation also causes rust on bare metals.)
• Paint – A coating including resin, a solvent, additives, pigments and, in some products, a diluent. Paints are generally opaque, and commonly represent the portion of the industry known as “architectural coatings.”
• Partial cure – Process sometimes utilized when multiple layers of fluoropolymer coatings are to be applied. The first coat is incompletely cured; the second coat is applied and both are fully cured together. See Flashing.
• Pencil hardness – A value determined by measuring the relative hardness of a coating based upon the ability of the coating to resist penetration and gouging by pencil lead of varying hardness. The order of pencils from softest to hardest is 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H, 7H, and 8H. The hardness rating of the coating is equal to the first pencil which does not penetrate and gouge the coating when tested from softest to hardest.
• Penetrating Finish – A finish that sinks into the substrate, as opposed to settling on the surface.
• PFA (perfluoroalkoxy) – Thermoplastic member of fluoropolymer family of engineering plastics, one characterized by excellent release, low friction and toughness.
• pH – An expression of the degree of acidity or alkalinity of a substance expressed as a number from 0 to 14. Neutrality is pH7. Acid solutions are less than 7 and alkaline solutions are greater than 7.
• Phenolic – A resin or plastic, usually thermosetting, made by condensation of a phenol with an aldehyde and used for molding, insulating, coatings and adhesives.
• Phosphating – Surface pretreatment used on ferrous parts that provide a very thin crystalline film that enhances both corrosion resistance and adhesion.
• PHR – Parts per Hundred parts Resin. A measure of solids content in a coating. Example: a coating with a silica content of 70% PHR would contain 700 miligrams of silica per every gram of resin.
• Polymer – Substance, the molecules of which consist of one or more structural units repeated any number of times; vinyl resins are examples of true polymers.
• Polymerization – The interlocking of molecules by chemical reaction to produce very large molecules. The process of making plastics and plastic-based resins.
• Polyvinyl Chloride – A synthetic resin used in the binders of coatings. Tends to discolor under exposure to ultraviolet radiation. Commonly called “vinyl.”
• Post-cure – A second cure at high temperature to enhance specific properties such as release and non-wetting.
• Postforming – Process of shaping parts after a coating has been applied and cured, a technique commonly used with stamped, blanked or spun parts.
• Preheating – Warming of parts prior to application of a coating, recommended when adhesion is critical and when parts are being coated in humid atmospheres. In some cases, this technique can be used to achieve higher-than-normal film builds.
• Preloads (for fasteners) – The “tightness” of a fastener, equal to the make-up energy applied minus the energy required to overcome friction at the fastener’s bearing surfaces and threads.
• Pressure spraying – Coating technique similar to siphon spraying, except that the coating is delivered from a pressurized pot to the spray nozzle under positive pressure. Generally used for high-volume production.
• Pretreatment – Processes for cleaning and conditioning a substrate to be coated. Next to the choice of coating, this may be the most important factor in the use of high-performance coatings.
• Primer – First complete coat of paint of a painting system applied to a surface. Such paints are designed to provide adequate adhesion to new surfaces or are formulated to meet the special requirements of the surfaces.
• PTFE (polytetrafluoroethylene) – A thermoplastic member of the fluoropolymer family of plastics. PTFE has the lowest coefficient of friction of any known solid and the highest operating temperatures of the fluoropolymers.
• PV, limiting PV (LPV) factor – Mathematical limit of a coating’s load-carrying ability and wear resistance under bearing conditions.
• PVDF (Polyvinylidene fluoride) – High-molecular weight thermoplastic of vinylidene fluoride with excellent strength, wear resistance and creep resistance.
• Refractive index – The ratio of the speed of radiation (as light) in one medium (as a vacuum) to that in another medium. In optical coating applications, differences in refractive indexes of coatings and substrates can result in birefringence.
• Resin – Synthetic or natural material used as the binder in coatings. Can be translucent or transparent, solid or semi-solid. Examples: acrylic, alkyd, copal ester, epoxy, polyurethane, polyvinyl chloride, silicone.
• Resistance (electrical) – The opposition offered by a coating to the passage of an electric current through it.
• Scratch resistance – A surface’s resistance to damage by scratching and abrasion. In the coating industry, usually measured by pencil hardness.
• Semi-gloss Finish – Finish that has a low luster sheen. Semi-gloss paints are formulated to give this result (usually 35-70 degrees on a 60-degree meter).
• Shellac – A coating made from purified lac dissolved in alcohol, often bleached white.
• Silicone – A resin used in the binders of coatings. Also used as an additive to provide specific properties, e.g., defoamer. Paints containing silicone are very slick and resist dirt, graffiti and bacterial growth, and are stable in high heat.
• Sintering – A process where the temperature of PTFE is raised to the point where PTFE particles soften and form a bond with each other.
• Solar Heat Gain Coefficient (SHGC) – The fraction of incident solar radiation admitted through a window, both admitted through a window, both directly transmitted, and absorbed and subsequently released inward. SHGC is expressed as a number between 0 and 1. The lower a window’s solar heat gain coefficient, the less solar heat it transmits.
• Solids – The part of the coating that remains on a surface after the vehicle has evaporated. The dried paint film. Also called Nonvolatile.
• Solvent – Any liquid which can dissolve a resin. Generally refers to the liquid portion of paints and coatings that evaporates as the coating dries.
• Specular Gloss – Mirror-like finish (usually 60 degrees on a 60-degree meter).
• Static electricity – Buildup of stationary electrical charge on a coating powder or a coated surface.
• Storage stability – The ability of a coating material to maintain uniform physical and chemical properties while in storage over an extended period of time.
• Substrate – Any surface to which a coating is applied.
• Surface appearance – The smoothness, gloss and presence or lack of surface defects in a coating.
• Surface area – A measurement of the exposed surface of an object.
• Surface treatment – Conditioning the substrate before coating through grit blast, phosphate, etc. May include the removal of a coating (See Burn-off).
• Tetrafluoroethylene (TFE) – Monomer used as a chemical feedstock in the production of PTFE.
• Thermoplastic resin – A resin which will melt when heated and solidifies when cooled, and softens when reheated.
• Thermosetting resin (Thermoset) – A resin designed to undergo an irreversible chemical and physical change during a heat-cure schedule, i.e., a plastic resin that crosslinks during cure so that it does not soften when reheated.
• Transfer efficiency – The ratio of the amount of coating deposited on a substrate compared to the total amount directed at the part to be coated.
• Tyndall Effect – The effect of light scattering on particles in colloid systems, such as suspensions or emulsions.
• Urethane – An important resin in the coatings industry. A true urethane coating is a two-component product that cures when an isocyanate (the catalyst) prompts a chemical reaction that unites the components.
• Vehicle – Portion of a coating that includes all liquids and the binder. The vehicle and the pigment are the two basic components of paint.
• Vinyl – See Polyvinyl Chloride
• Viscosity – The property of a fluid whereby it tends to resist relative motion within itself.
• Volatile content – The quantity, expressed as a percent weight of a coating, that is lost under specified conditions of temperature and time.
• Volatility – The readiness of a substance to change from a solid or liquid form to a vapor.
• Volume Solids – Solid ingredients as a percentage of total ingredients. The volume of pigment plus binder divided by the total volume, expressed as a percent. High-volume solids mean a thicker dry film with improved durability.
• Water contact angle – Tangent angle at the interface between droplet of liquid and a solid surface; measure of the surface energy; 0° for perfectly hydrophilic surface and 90° for perfectly hydrophobic surface. Water contact angle can be affected by several factors, microscopic roughness of the surface tends to give a higher water contact angle.
• Water-based – Coatings in which the majority of the liquid content is water.
• Wear – Deterioration by friction (abrasion, spaling, cutting, fretting).
• Weight solids – Expressed as a percentage, it is the amount of a substance which remains relative to the total weight, after all volatile components of the substance have been evaporated. The determination is usually hastened by heating the substance in a controlled environment.