If you haven’t been using and studying epoxies, adhesives and glues for years, you’re probably going to find plenty of the terms used on technical data sheets, product descriptions, and even instructions to read like they were written in another language.
Below, we’ll provide a simple, layman’s term glossary of some of the more common technical terms used in technical data sheets and other materials about industrial strength adhesives:
Activators
Activators (or accelerators) can be used with adhesives to accelerate cure rate, activate inactive surfaces (where the adhesive requires a certain level of activity to initiate the cure) and to cure certain 2-part adhesives.
These are single-component adhesives that require the exclusion of air (so a tight-fitting joint) and the presence of a metal ion to initiate cure. These adhesives are typically used for gasketing between metal parts, retaining bearings, threadlocking, and pipe sealing.
Bond line
The bond line is the space between two surfaces which contains the adhesive. This can also be called the glue line or gap.
Bond strength
Bond strength is, of course, the strength of the bond between the surfaces, but for reference, bond strength refers directly to the amount of force a bond can sustain.
Catalyst
See activator.
Centipoise, or cps
Centipoise is a measure of viscosity, or thickness of an adhesive. For reference, water is measured at 1 cps, castor oil is 1,000 cps, and peanut butter is 250,000 cps, so the higher the cps, the thicker the substance. Another unit used for measurement is Pa.s (Pascal seconds) which work in a similar way.
Cyanoacrylate is a one-part adhesive that will cure instantly upon contact with the mated surfaces. Cyanoacrylate is very strong and binds to a wide variety of surfaces.
Density
Density is the specific gravity (sg) of a material measured in g/cm². Water has an sg of 1 which means 1cm3 volume of water weighs 1 gram (at 4°C).
Dielectric Strength
Dielectric strength refers to the maximum voltage a material can withstand. This is measured in volts per millimeter of thickness.
Durometer Hardness
As measured with a durometer, this number refers to the hardness of a given material. Depending on the hardness of the material, different adhesives may be required.
Elastomer
An elastomer is any rubber, plastic or polymer that can be stretched to twice its original length (or longer) and still return to its original shape.
Elongation
The length to which a material will stretch without breaking. The elongation number refers to X percent of the original length, so a material with a 400% elongation would stretch to four times its original strength before snapping.
Epoxies are generally high strength products with good environmental and chemical resistance. They can be two-part (requiring mixing to cure) or single part (where they need to be heat activated).
Exothermic
Simple definition: Pertains to a heat releasing chemical reaction.
Filler
In adhesives, filler means any substance added to an adhesive so as to alter the adhesive’s viscosity and flow control characteristics.
Formulator
An industry term for any company which manufactures adhesives (ex: Permabond Adhesives).
FRP
Fibreglass Reinforced Plastic. Or GRP = glass reinforced plastic (or polyester).
Gel Time
Put simply, when resin and hardener are mixed, a five minute gel time would mean you have five minutes until the adhesive hardens.
Handling Time
This is the length of time you have from mixing and applying the adhesive, clamping / holding the joint shut. The handling time is the time at which you can remove the clamping pressure, and the adhesive will be strong enough to hold the joint together.
Hygroscopic
Hygroscopic refers to a material’s ability to absorb and retain moisture from the atmosphere.
Impact Strength
A material’s resistance to sudden shock (such as heavy objects being dropped upon that material, etc.).
Inhibitor
Inhibitors or stabilizers are used to slow down chemical reactions and prolong the storage life of a product.
Load
The amount of force or weight that a bond or material can sustain.
Peel Strength
Peel strength refers to how much force is required to peel one material from another that it is bonded to. Brittle or rigid adhesives tend to have a lower peel strength than flexible, toughened adhesives.
Shear Strength
Shear strength refers to how much force is required to pull one material from another in an overlap-type joint configuration.
Shore Hardness
A scale set up to assess the hardness of a material (see also Durometer). The test is done with a spring-weighted pin which measures the depth of penetration. The higher the number, the harder the material. Shore A scale is used for soft, flexible materials, Shore D is for more rigid, hard materials.
Tensile Strength
Tensile strength refers to how much force is required to pull one material from another in a butt-joint type configuration.
Viscosity
The thickness of a fluid, see Centipoise, above.
Working Strength / Working Time
Working strength is the time at which a newly bonded joint can be put into a load bearing situation. The joint will have developed approximately 60% of its final strength (so should not be overloaded).
Hopefully, this provides you with enough information to be sufficiently equipped to handle any technical data sheets, instructions or manuals you need to access, and without getting a migraine headache! If there is something I missed, please contact Permabond.
