Engineering adhesives and compounds are playing an increasingly important role in the build quality of manufacturing equipment and machinery and their ongoing reliability. These products are used structurally at the design and manufacturing stage to achieve more static and dynamic strength, to save weight, prevent leak paths and eliminate problems associated with corrosion.
During the service life of the plant, they offer many benefits over traditional methods for applications – such as thread locking, thread sealing, gasketing and retaining – ensuring systems work optimally and for longer.
There is huge range of engineering adhesives from which to choose and selecting the right one for the job can be a little daunting. All good manufacturers will give you advice, but it still helps to have a basic grounding on the merits of the various options.
So, starting with structural bonding, here is a brief introduction to the most popular products that fall into five basic technology groups; epoxies, acrylics, polyurethanes, silicones and silane modified polymers.
A structural bond is used to join critical load-bearing parts of an assembly. Adhesives developed to meet this need require a combination of high shear, tensile and peel strength, together with maximum stress, impact and shock absorbent characteristics. What’s more they need to bond a diverse selection of materials including composite, wood, metal and glass.
Different formulations provide different characteristics and chemistries as we shall see later, but first we should consider the benefits that adhesives provide over conventional joining methods.
Reduced weight, improved fatigue resistance, uniform stress distribution and the ability to join dissimilar material are the primary advantages. And in many instances, less critical tolerances can be specified as many structural adhesives also have gap filling capability.
It is also worth bearing in mind that adhesive and other joining methods can also work together. Whilst adhesive bonding provides sufficient strength, the addition of a few discretely placed rivets provides instant alignment, jigging and clamping advantages.
In broad terms, structural adhesives fall into five groups – epoxies, acrylics, polyurethanes, modified silanes and silicones. So why the variety and where is each used?