Structural adhesive is type of industrial adhesive that is normally used below its glass transition temperature which is an important property for polymeric materials. Common examples of structural adhesives are epoxies, cyanoacrylates and certain urethanes and acrylic adhesives. These kinds of structural adhesives can carry significant stresses which makes them very important to engineering and construction applications. Design engineers will usually look for cost effective means in the assembly of finished products which is provided by structural adhesives.
Pressure sensitive adhesives
Pressure sensitive adhesives are very low modulus elastomers which can deform easily under slight pressure, permitting them to wet surfaces. Once the substrate and adhesive is brought together into intimate contact, it can provide a relatively durable bond for lightly loaded applications. This type of industrial adhesive is generally purchased as tapes or labels for non-structural applications although they are also available as double-sided foam tapes for semi-structural applications. Hot melts when heated will become liquid which will wet the surfaces but once it cools, it can be a solid polymer. Hot melts in the form of glue guns are increasingly being used in mechanical engineering applications to lock bolts and bearings in place.
Thermosetting structural adhesives
This type of industrial adhesive is normally available in two-part forms that are mixed through carefully controlled stoichiometry into a product that cures within a desired time window. One-part forms are also available where the resin and hardener are already mixed together. However, these one-part form industrial adhesive must be kept at sufficiently low temperature in order to gain the advantages of their high performance capability and achieve a satisfactory bond. Materials with too short pot life can harden too fast and will not give the applicators sufficient time to assemble the product. When the industrial adhesive has an extensively long pot life it can delay the cure time and slow the assembly process.
How industrial adhesive is applied
Industrial adhesive is applied in a variety of ways based on the kind of form it comes. It can be spread on a surface manually or it can be dispensed using a variety of ways through the use of sophisticated nozzles or robotic equipment. However, in all cases of adhesive application, it is important to consider cleanliness, providing proper jigs and fixturing during cure including providing adequate cure conditions which is an important requirement for certain types of adhesives. If these requirements are not followed it can impact on the performance of the industrial adhesive.