Types of adhesives and adhesive terminology

Types of adhesives and adhesive terminology is a guide to assist you in understanding the types of adhesives available to assist in determining the type of adhesive or glue you need for your application.  Also, key words used in the business and what they mean. Our technical team are on hand to assist in your application so feel free to contact us.  See also our structural adhesives page.

Types of Adhesives

HEAT-CURED ADHESIVES – Any adhesives which must be heated to promote curing.

HOLDING ADHESIVES – Holding adhesives are used to hold surfaces together, but not permanently.  They do not have to withstand a great deal of force.  Adhesive tape is a good example of a holding adhesive.

HOT MELT ADHESIVES – Hot Melt adhesives are applied in the molten state and then harden.  The adhesive substance is melted, applied to the surface, then the parts are joined. Once the adhesive cools and solidifies, the joint is complete.

INSTANT ADHESIVES – Any adhesive which cures within seconds to minutes, usually cyanoacrylates.

LOCKING ADHESIVES – Locking adhesives or sealants are used to prevent the loosening of threaded parts.  Locking adhesives are placed on the threads of a bolt to prevent is from becoming loose from vibration. Thread lockers and retainers.

PRESSURE SENSITIVE ADHESIVES  – Pressure sensitive adhesives form bonds easily when pressure is applied.  Pressure sensitive adhesives are used on double-sided tape.  The joint is aided with pressure.

RETAINING ADHESIVES – Retaining adhesives are used to prevent the twisting or sliding of non threaded parts.  retaining adhesives are very similar to locking adhesives except they are used on non-threaded parts.

SEALING ADHESIVES – Sealing adhesives are used to prevent the passage of air, water, oil, etc.  between two surfaces.  The caulking around windows is an example of a sealing adhesive.

STRUCTURAL ADHESIVES – Structural adhesives are capable of withstanding a significant load. The term ‘significant load’ has never been defined, but the implication is that the adhesive must be able to withstand a great deal of stress. In fact, it cold be said that in the absence of unnaturally high forces, the substrates could be considered to be permanently joined. see also structural adhesives in more detail with links to our products.

ULTRAVIOLET ADHESIVES – Any adhesives which cure when exposed to UV light.


Adhesive Terminology

An ADHEREND is a solid material in the adhesive joint other than the adhesive (sometimes referred to as substrate).  

ADHESION is the process by which two surfaces are held together by inter facial forces (surface attraction) or mechanical interlocking.  

An ADHESIVE is a substance which is capable of holding materials together in a useful fashion by means of surface attraction. Surface attraction results from placing a thin layer of adhesive between two objects.

The BOND LINE is the space or gap between two substrates which contains the adhesive.  

COHESIVE FAILURE is a failure mode where the failure is within the body of the adhesive, i.e. when adhesive is seen on both substrates in the same location.

COMPOSITE is a general term for an assembly of dissimilar materials used together to give greater strength than the individual components would on their own, or the same strength or lighter.  GRP (glass reinforced plastic) is an example of a modern day composite where resin and fibres are mixed together to give superior strength performance.  

CURE When an adhesive cures, it is converted from a liquid to a solid state.  This may be accomplished by cooling, loss of solvents or internal chemical reaction.  Curing generally implied some type of physical or chemical change in the adhesive, while hardening or melting is reversible.  

FIXTURE TIME is the interval of time between mixing a two part adhesive and the time a bonded assembly can be removed from the mould without distortion.  

RHEOLOGY is the ability of a material to flow and deform.  Adhesives with good rheology flow easily and break cleanly at the end of a bead.  

STIFFNESS is a materials ability to resist deformation when a load is applied.  

STRAIN is the elastic deformation resulting from stress.  

STRESS is he internal resistance to change in shape and size.  

A SUBSTRATE is a material, which is held by an adhesive.  Substrate is a generic term for objects that are being bonded.  

SUBSTRATE FAILURE is a failure where the substrate fails itself before the adhesive bond.  

TENSION is the stress resulting from pulling a material apart.  

A THERMOPLASTIC is a material that will soften when exposed to heat and can be reworked or re shaped before hardening when cooled.  

A THERMOSET is a material that solidifies when cured by mixing and/or heating and, once cured, cannot be remelted or remoulded.  

TOUGHNESS is a measure of a materials ability to absorb energy.  

VISCOSITY is the resistance to flow or degree of thickening of a fluid.  

WORKING TIME is the time between mixing the two components and when the adhesive becomes no longer usable i.e. skins over and will not ‘wet out’.  

WETTING is the intimate contact of a liquid and a surface.  Good wetting is only possible  if there is good attraction between the surface and the liquid.  Proper wetting of a mating surface is essential for good bonding.