- Glossary - Dow Corning

To find the definition of a term, click on the corresponding first letter of the word above.

Additive. Additives combine with a Silastic® silicone rubber base to enhance processing or performance characteristics of the compound.

Adhesion. The degree of attachment or bonding of one substance to another.

Alligatoring. Mud cracking of the surface of a tar or asphalt roof. Has the appearance of alligator hide.

Ambient Temperature. Temperature of the surrounding air on all sides.

Antifoam. Prevents the formation of foam. (See Defoamer, Deaerator, Foam Control.)

Asphalt. A dark brown to black bituminous sticky substance, solid or semisolid in consistency, found in natural beds and also obtained as a residue in petroleum refining. It consists chiefly of hydrocarbons. The principal ingredient in asphalt mastics.

Autoclave Vulcanization. A method of curing rubber with the use of steam.

Base. A base is a silicone polymer with reinforcing fillers and process aids.

Bonding. The process of adhering silicone rubber to a substrate.

Breathable Coating. A coating with a perm rating above about 0.5 perm. The opposite of a vaporretarder. The higher the perm rating, the more breathable the coating.

Calendering. The process of forming silicone into uniform thin sheets.

Catalyzing. The addition of a curing agent to allow for heat curing of silicone rubber.

Caulking. A substance to stop and make watertight against leakage.

Caulking Stacy. Stacy testing glossary web.

Chalking. Usually a grayish or white substance, dry, chalk-like residue, forming on the surface caused by weathering.

Coating. A liquid or semiliquid protective finish capable of application to thermal insulation or other surfaces, usually by brush or spray, in moderate thickness.

Combustible. Capable of uniting with air or oxygen in a reaction initiated by heating, accompanied by the subsequent evolution of heat and light. Capable of burning.

Compound. A compound is a ready-to-use blend of a silicone rubber base, fillers, modifiers, vulcanizing agents, and pigments.

Compression Molding. A process of curing silicone by use of a molding method whereby a preform is placed into one half of a heated mold and the mold is closed. Pressure is applied and the preform is forced into all parts of the mold cavity.

Condensation. The process of changing from a gas or vapor to a liquid.

Contaminants. Something that makes a surface or substance unclean, pollutes, soils, stains from an outside source.

Coverage Rate. Quoted either as square feet covered by a gallon (50 ft2/gal) or as gallons used per square (2 gal/square). (A square is 100 square feet.)

Crosslinking. When rubber is heated to the required temperature, peroxide decomposes to form free radicals that react with the organic groups in the silicone polymer. In an addition cured silicone rubber, the catalyst activates the reaction between the crosslinker and reactive organic groups in the silicone polymer. This results in crosslinking between organic groups. The number and position of these linkages determine the degree of vulcanization.

Cure. To change the properties of a plastic or resin by chemical reaction, which, for example, may be condensation, polymerization, or addition; usually accompanied by the action of either heat or catalyst or both, and with or without pressure.

Cure Time. The time required to complete the cure process.

Curing. The degree of vulcanization of the rubber; also known as Heat Aged Curing

Deaerator. Remove small air bubbles from the applied coating. (See Antifoam, Defoamer, Foam Control.)

Defoamer. Destroys foam after its formation. (See Antifoam, Deaerator, Foam Control.)

Degradation. The deterioration of a substance caused by contact with its environment.

Delamination. The separation of the layers of material.

Dirt Pickup. The accumulation of dirt on the sealant surface during or after sealant cure.

Dusting. A condition that develops in one to seven days on the surface of uncoated and unprotected spray foam due to photo oxidation by ultraviolet light (sunlight). The ultraviolet causes the surface to break down and become a dust or powder, which impairs adhesion of coatings and blows away. When this occurs, the foam changes from its original light color (usually tan) to a rust or dark brown.

Elastomer. A material capable of elongating at least 100% and recovering its original dimensions.

Elongation. Lengthening or stretching ability to accommodate movement.

Expansion Joint. A break in a surface to allow the material to contract and expand without causing damage. It may be a working joint to allow movement or a control joint to isolate a stress.

Extrusion. Continuously forcing rubber through a die that forms it into the desired size and shape.

Film Thickness. The thickness of a membrane, normally measured in mils.

FKM. Fluorocarbon Elastomer

Flash Point. The flash point of a liquid is the lowest temperature of the liquid at which it gives off vapor sufficient to form an ignitable mixture with the air near the surface of the liquid or within the vessel used.

Flexography. Printing process utilizes special (Anilox) rollers containing small cells that carry the ink from the ink fountain to the plate.

FLSR. Liquid Fluorosilicone Rubber

Fluid Migration. The migration of fluids, such as plasticizers, unreacted polymer, or otherliquid formulation additives into or onto porous or microporous substrates. Itis a diffusion-controlled phenomenon, observed with all sealant types,including polysulfides, acrylics, polyurethanes, silicones and oil-basedputties.

Fluid Streaking. The accumulation of dirt in water runoff channels on nonporous surfaces, aggravated by fluid migration from the sealant. Streaking is caused by the migration of free fluids to the sealant surface. Streaks can extend above and below a horizontal joint.

Foam Control. Reduction or elimination of foam (a dispersion of a gas in a liquid or a solid) formed in a coating or a coating constituent.1 (See Antifoam, Defoamer, Deaerator.)

FSR. Fluorosilicone Rubber

FVMQ. ASTM standard for silicone that has good oil and fuel resistivity (Fluorosilicone Rubber); VMQ is the ASTM standard for general purpose and high strength silicone rubber

General Metal. Market that covers all metal coatings with the exception of automotive, metal containers and metal furniture; i.e., steel structures, doors, wire, aluminum.

Grout. Cement or mortar used to seal between precast concrete planks in a roof deck.

Gypsum. A fireproof board composed of calcium sulphate and fibers. Used asconstruction panels.

Hardness. The relative resistance of a material to denting, scratching or bending.

HCR. High Consistency Rubber (Heat Cured Rubber)

Heat Aged Curing. The degree of vulcanization of the rubber.

Heat Set. Method of drying letterpress and lithographic inks under the action of heat by the evaporation of their high-boiling solvents.2

Hot Applied. Or "hot mopped." Refers to an asphaltic or tar materialthat must be heated in a kettle to melting and applied to the roof deck by mopor squeegee. Also referred to as "soup." Different from atar-based mastic, which is spread as supplied.

Humidity, Relative. The ratio of actual pressure of existing water vapor to the maximum possible(saturation) pressure of water vapor in the atmosphere at the same temperature,expressed as a percentage.

HVA/Hot-Air Vulcanization. A method of curing rubber with the use of hot air.

Impact Resistance. Ability to withstand mechanical or physical abuse under severe service conditions. Resistance to blows, bumps and shocks incidental to use.

Injection Molding. A process for curing or molding parts by injection of rubber into a cavity.

Intaglio. Printing from flat copper or steel die plates in which the image has been engraved. Intaglio inks are of viscous consistency composed of modified lithographic type varnishes.

Laitance. Surface material on top of concrete made up of fine cement and aggregateparticles. It is loosely bonded and of low strength and must be removed by wirebrushing before coating can be applied.

Light Concrete. A nonstructural concrete using materials such as vermiculite or perlite as aggregate.

LSR. Liquid Silicone Rubber

Mil. A unit in measuring thickness, being 0.001 inch (British equivalent: Thou.)(Metric equivalent: 0.0254 mm).

Molding/Moulding. The method of heat curing rubber by using compression, transfer or injection molding equipment.

Monolithic. Single form or single piece; formed or composed of material without jointsor seams.

MQ. ASTM standard for general purpose and high strength silicone rubber; also known as VMQ

Organic. Compounds consisting of carbon and generally hydrogen, with a restrictednumber of other elements such as oxygen, nitrogen, sulphur, phosphorous,chlorine, etc., but not containing atoms or molecules, generally known asmetal.

Parapet. A wall rising above the level of the roof, usually around its perimeter.

Penetration. Any assembly that goes through a roof deck such as a vent, exhaust fan, electrical feed-through, roof drain, stand pipe, etc.

Perm Rating. A measure of a material's ability to pass water vapor

Pigmenting. The addition of color to silicone.

Pinhole. A very small hole or imperfection in a coating through which water or ultraviolet light can enter and cause damage.

PMQ. ASTM standard for extreme low temperature service silicone rubber; also known as PVMQ

Polymer. A chemical compound or mixture of compounds formed essentially of repeating structural units.

Primer. A chemical material that improves the bond of the sealant or coating to the substrate.

PVMQ. ASTM standard for extreme low temperature service silicone rubber

R Factor. Resistance of heat flow through a particular thickness of material.

Resin % of Market. The estimated percent of the market represented by the resin and delivery system for a given application.

Reversion. Urethane sealants lose their original rheological properties over time(i.e., their ability to actually seal joints).

Scorch. The premature vulcanization of the rubber - before the flow of rubber in the mold is complete.

Scupper. A hole in the wall to allow water to course through.

Shore “A” Hardness. Measure of firmness of a compound by means of a durometer hardness gauge.

Shrinkage Crack. Fine hairline cracks in the surface of newly cured concrete. Overall patternlooks like a crushed egg shell.

Solids Content. The percentage of nonvolatile matter that may be measured in volume orweight.

Solvent. Any substance, usually a liquid, that dissolves other substances. Incoatings, normally a liquid organic compound used to make a fluid coating applymore freely.

Square. A 10-foot x 10-foot area, or 100 square feet.

Structural Concrete. Reinforced concrete with a compressive strength of at least 2500 psi.

Structural Crack. Concrete crack subject to little movement but that must be repaired since itcan go through a full-slab thickness and leak.

Tack Free. A film is considered tack-free when the finger, with a slight pressure, will not leave a mark. The surface will not be sticky.

Tensile Strength. The force per unit area that is applied at the time of rupture of the specimen. It is calculated by dividing the breaking force in pounds by the cross-section of the unstretched specimen in square inches.

TPE. Thermoplastic Elastomer

Transfer Molding. Unvulcanized rubber is placed in a chamber (called a pot), usually at the top of the mold, and the assembly is placed in a press. The press applies pressure to a piston-like plug in the open end of the pot, clamping the halves of the mold together and forcing the rubber to flow through the heated mold.

U Factor. The overall heat transfer factor for a particular building component, suchas a roof.

UL Rating. A flammability rating system for materials as tested by Underwriters Laboratories. UL classifies or lists materials that pass their specific tests.

Urethane Sealant Reversion. Sealants lose their original rheological properties over time (i.e., their ability to actually seal joints).

UV. Ultraviolet radiation or sunlight.

Vapor Retarder. Those materials or systems that retard the transmission of vapor under specified conditions.

Vent. A breather vent. A device put in a roof system to allow moisture vapor to escape.

Viscosity. The property of resistance to flow exhibited within the body of a material.

VMQ. ASTM standard for general purpose and high strength silicone rubber

Vulcanization. The rubber cures when it is heated to the required temperature; peroxide decomposes to form free radicals that react with the organic groups in the silicone polymer.

Water Absorption. The increase in weight of a test specimen expressed as a percentage of its dry weight after immersion in water for a specified time.

Water Repellency. Control of water absorption through the coating. Water beading is sometimes used as an indication of water repellency.

Water Repellent. A material that has the ability to hinder the penetration of water. Also used as an adjective to describe such a material e.g. the man applied a water repellent stain to his deck.