Glossary

Abhesion - Lack of adhesion, easy release from substrates

Acetoxy Cure System – A tin catalyzed moisture cure system which liberates an acetic acid/ vinegar odor by-product upon curing.

Adhesive – Displaying self bonding properties without primers

Addition Cure System – Reaction between a vinyl terminated siloxane and a polyfunctional silicon hydride with a catalyst.
Si-H + CH2 = CHSi ------------> SiCH2CH2Si

Application Rate – Used to measure the flow of RTV sealants from a semco tube. Material is extruded from a semco tube at 90 psi through a standard orifice. Given in grams per minute.

By-Products – The evolved reaction materials of a condensation cure silicone with moisture. These typically generate the odor found when silicones cure.

Condensation Cure System – Reaction between silanol terminated polydimethylsiloxane and multifunctional crosslinker with a catalyst.
Si-OH + AcOSi ---------- > Si-O-Si + AcOH

Curing– Silicone liquids or pastes harden to a rubber elastomer

Cure Time - The time required to convert the silicone sealant to cured rubber. Example: 24 hours for 1/8” diameter bead at 77° F and 50% relative humidity.

Dimethicone - Trimethyl terminated siloxane fluid

Durometer – Resistance to indentation. Measure of the crosslink density of a rubber sample.

Elongation – (elongation at break) The ability of the test piece to be stretched without breaking. Given in % of original dimension @ maximum elongation.

Encapsulation - The complete surrounding of an electronic component or complex of components with a coating of an insulative material. The purpose is to protect the component from adverse environmental conditions.

Fast Cure – An order of magnitude faster than typical – Most R.T. cures are slow

FIP - Form in place gasketing

Gel Time - The period of time in which as liquid material becomes too viscous to flow or be tooled

Heat Cured - 1 or 2 part product that Vulcanizes into a hard, cured product upon exposure to heat

Instant Cure – Heat accelerated room temperature cure within 1 minute

Lamination - Fully enclosing an adhesive between two sheets disallowing exposure of the surface preventing offgas and surface cure. Condensation cured silicones require exposure to air for full cure.

Modulus – The amount of force per square inch to stretch a test piece to a given elongation.
Typically measured @ 100% elongation.

Neutral Cure – A condensation cure system which liberates no corrosive (to metals) by-products upon curing. Alkoxy/Alcohol cure systems are neutral cure.

One-Part - A ready-to-use silicone material that does not require mixing with a catalyst or other additive to form a durable rubber or adhesive.

Oxime Cure System – A tin catalyzed moisture cure system which liberates an alcohol methylethyl ketoxime byproduct upon curing. This byproduct smells like latex paint.

PDMS - Poly Dimethyl Siloxanes (see siloxane)

Peelable – Displaying no adhesion for easy removal

Pot Life - The amount of time available between the moment that a catalyst is stirred into a base material and the approximate moment that it becomes too thick to apply in the recommended manner.

Potting Material - An electrically insulative, moisture resistant material, supplied in a liquid or putty-like form and used as a protective coating on sensitive areas of electrical and electronic equipment.

Pourable – Self- leveling liquid

Rheology – The study of the deformation and flow of materials, in terms of stress, strain and time.

R.T. – Room temperature cure

R.T.V. – Room temperature vulcanization ( curing without heat )

Self-Leveling – A high flow, syrup-like condition, unlike thixotropic

Silane – A highly reactive molecule having a Silicon atom as the central unit. Typically functionalized and used as crosslinkers and adhesion promoters.

Silicone Plasticizers - Trimethyl terminated siloxane fluid

Silicone Rubber - A rubber like polymer prepared from certain silicones. It maintains its elasticity and electrical properties over a wide range of temperatures and is widely used in sealants, gaskets, insulation, tapes, etc.

Siloxane Fluids – Polymers having a regular alternating silicon and oxygen central atoms, typically having pendant dimethyl functionality, these polymers can be functionalized interchain and at chain terminus for a wide range of applications.

Simethicone - Trimethyl terminated siloxane fluid

Skin-Over – The formation of an integral skin over the surface of a quantity of sealant.

Specific Gravity - The ratio of the weight of any volume of a material to the weight of an equal volume of water.

Tack-Free Time - The time it takes for a sealant to cure to a point where none of the material will stick to your finger.

Tear Resistance – Resistance to growth of a nick or cut in a test piece when tension is applied. Given in pounds per inch or Newton per millimeter.

Tensile Strength (tensile at break) – The amount of force required to break a test piece. Given in pounds per square inch (PSI) or Newton per square millimeter (N/mm2).

Two-Part - A silicone material which must be mixed with a catalyst or other additive to form a durable rubber.

Thixotropic – Non-slump or sag property, no flow without pressure

Uncured - A silicone material which has not vulcanized or formed a durable rubber.

Viscosity - The measurement of a fluid’s resistance to relative motion within itself. The viscous property of a fluid. Usually considered to be the relative thickness or thinness of a fluid as compared to the thickness (thinness) of water

Volatiles – Low molecular weight silicone materials that can become airborne. Found in certain silicone polymers.

Work Time - The period of time which a silicone material may be “worked” before skin over and curing begins.

Silicone Solutions Accepts: