The word filler makes me think of something of secondary importance used to take up space. It conveys the idea of a cheap additive used to stretch the main ingredients. When it comes to filling epoxy structural adhesives, the filler often provides beneficial properties. Some fillers reduce costs, while others are the most expensive part of the formulation.
When we review the list of properties that these fillers impart, it is clear that these properties are secondary only to the strength and cure properties of the epoxy adhesive. Fillers can be key ingredients in epoxy formulations. Chemists work with a seemingly endless number of raw materials to create epoxy adhesives with the variety of properties needed to fulfill the application needs.
Epoxies are in the Structural Adhesive classification. Structural Adhesives form bonds that will not fail when a bonded joint is stressed to the yield point of the material being bonded. As such the adhesive is part of the structure of the assembly. Structural Adhesives like epoxies are used in place of, or in addition to, mechanical fastenings in many industries including; automotive, aerospace, transportation, electronics, medical, dental, food machinery and equipment industries.
Structural adhesive bonding in place of welding offers further advantages. Further potential savings can be obtained on review of the materials being used. Some assemblies require steel for one portion but another portion can be as effectively done with a composite material or aluminum. This can reduce cost and weight further.
Filled or Unfilled, 1K (single part epoxy) or 2K (two part epoxy), heat cure or room temperature cure – or some combination of both, epoxy adhesives are available to meet a large variety of industry needs. The choices can be overwhelming, but specialty epoxy adhesive manufacturers thrive on assisting engineers through the multitude of products to quickly arrive at the best solution for the application at hand.