Structural epoxy refers to a certain class of strong adhesive that are usually used below a glass transition temperature. The structural epoxy has the characteristic of polymeric materials. When polymers are subjected to a temperature above their glass transition temperature, they tend to be rubbery and below this temperature, they are glassy. The structural epoxy carry some amount of stresses but are able to carry its function well when subjected to structural applications.
The structural epoxies are used in many engineering applications especially when the engineer is looking for semi-structural or non-structural applications and provide a cost effective way in assembling finished products. Engineers usually make use of contact adhesives. Contact adhesives are a solution or emulsion that contains an elastomeric adhesive. It is coated onto the adherends. Afterwards, the solvent is made to evaporate and then once again both adherends are brought in contact together. Examples to this include adhesives that are used to bond the laminates found in countertops as well as rubber cement.
Pressure sensitive adhesives
This type of adhesive contain very low elastomers, they tend to deform easily when subjected to small pressures, thus wetting surfaces. When the adhesive and substrate are brought together to be in intimate contact, there are forces that maintain the bond for applications that are only light. The pressure sensitive adhesives are usually purchased as labels or tapes used for non-structural applications. They also come in the form of double-sided tapes and are typically used in applications which are semi-structural. These hot melts turn to liquid form when they are heated thereby wetting the surface and when it cools down it turns into a solid polymer. You can find these materials to be used widely among different engineering engagements where sophisticated versions of glue guns have to be used.
The anaerobic adhesives tend to cure within spaces that are narrow and are deprived of oxygen. This material has also been widely used in engineering build ups especially in putting bearings in place and locking bolts. The cure in other type of adhesive may be provoked by its exposure to the ultraviolet light or to electron beams. Others are cured when there are materials like water that are present on the surface.
Adhesives of different chemistries are likewise available in many forms. When used in structural applications, the adhesives are available as liquids, films, pastes, and supported films. The supported films are placed on a loose knit in order to improve the handling properties of the product. It also offers control to the thickness.
Many adhesives produce minimal or no out-gassing when subjected to curing. It is because of this feature that there is little chance of voids in the adhesive. Remember that these adhesives should be kept dry all the time as the moisture absorbed can create void problems during application.