C

Caulk
Substance to stop and make watertight against leakage.
Syn. Caulking

Catalyst
Substance which markedly speeds up the cure of an adhesive when added in minor quantity as compared to the amounts of the primary reactants and without itself being altered.
Syn. Accelerator

Cellulose
Complex carbohydrate (C6H10O5)n formed of microfibrils of glucose molecules. Chief constituent of the cell walls of plants, and consequently chief constituent of many fibrous plant products such as paper and board, and cotton, linen and rayon cloth.

Cement
Paste-like sealant. Depending on its composition, may be either rigid or elastic once it has set, and may have adhesive properties in addition to its sealant properties.

Clear adhesive
Glue which is solvent based, giving water-resistant bond and with the benefit that surplus glue can be removed, using an appropriate cleaner. Toxic and flammable.

Chloroprene Rubber, CR (extended definition)
Rubber-like compound.
Syn. Chlorobutadiene, Neoprene, Polychloroprene.

Coagent
Compounding ingredient used in small amounts to increase the crosslinking efficiency of certain non-sulfur vulcanizing systems or to modify the properties given by such systems.
Note: The term is usually identified with additives used to modify vulcanization by organic peroxides.

Cohesion
State in which the particles of a single substance are held together by primary or secondary valence forces observed in the tendency of the substance to stick to itself.

Cohesive failure
Failure within the adhesive under a stress. Occurs when internal strength of the adhesive is not as great as the forces applied to it. Adhesive remains bonded to both sustrates. (more about failure mechanisms)

Cold adhesive
Adhesive that sets at room temperature (20?).

Collo? (extended definition)
Suspension and dispersion of submicron particles in a liquid medium without their dissolution in the medium.

Collo?al stabilizer
Additive acting as a surfactant to stabilized emulsion or collo?al media.
Syn. Emulsifying agent, Surfactant

Compound
Intimate admixture of a polymer with all the materials necessary for the finished article.

Conductive adhesive
Adhesive material containing conductive particles (metallic powder, carbon black, graphite) added to increase electrical conductivity. Used to replace solder joints in electronics assemblies, obviating the need for defluxing with a solvent and, secondarily, eliminating the use of lead in solder.

Contact adhesive
Solvent based adhesive but with added properties which produce an immediate bond. One part adhesive needing no mixing. Adhesive is applied to both surfaces, let dry, and then pressed together to create an instant bond. Makes good bonds in most materials but is not structural in strength.
Contact adhesion time: Period of time when using a contact adhesive during which the dry adhesive layers may still be bonded together.
Syn. Open time

Contact pressure
Pressure applied to the assembly to achieve a bond in contact adhesives.

Corrosion inhibitor (extended definition)
Additive for protecting lubricated metal surfaces against chemical attack by water or other contaminants.

Coupling agent
Substance, which promotes or establishes a stronger bond at the resin matrix/reinforcement interface. (see Adhesion promoter )

Cracking
Severe breakdown of internal cohesive forces of a sealant either during cure or afterward, as a result of excessive stress. Two typical examples are side and center cracking in an expansion joint. Shrinkage upon curing of elongation can build up excessive stress either at the center of the joint or near the center of the joint causing severe failure.
Syn. Crazing

Crazing
Similar to cracking. However, it is much less severe and does not destroy the basic function of the caulk. Crazing only extends a few molecules deep into the surface of the product (due again to excessive stress) and can occur during the curing phase or after being exposed to high elongation and weathering .

Creep
Effect of strain and/or time on the shape of polymer layers. Even under little stress the adhesive layer changes shape.

Crosslinking
Formation of chemical bonds between polymer chains leading to the formation of a three dimensional network. Final materials are called thermosets.

Crosslinking agent
Catalytic or reactive agent which when added to resin causes crossliking of chains.
Syn. Curing agent

Cure
Changement of the properties of a resin by chemical reaction, which, for example, may be condensation, polymerization, vulcanization or addition; usually accompanied by the action of either heat or catalyst or both, and with or without pressure. Fully cured materials exhibit maximum physical, thermal and chemical properties in use.
Syn. Crosslinking

Cure time
Time required to complete the cure process.

Curing agent
Chemical which reacts with an adhesive polymer to cause solidification. Approximately equal amounts of adhesive resin and curing agent are mixed together to form a solid adhesive. Usually Part A of a two-part adhesive.
Syn. Crosslinking agent

Cyanoacrylate (extended definition)
Special type of acrylic. Cures through reaction with moisture held on the surfaces to be bonded. Needs close-fitting joints. Usually solidifies in seconds and suits to small plastics parts, metals and to rubber. Setting times range from 5 to 130 seconds.