Bonding instead of welding

Adhesives have a long history. The resin from the birch tree serving our Stone Age ancestors in the manufacture of tools and weapons probably can be described as the first adhesive in human history. Since then, adhesives have made everyday life easier in many different areas. Today, epoxy resin adhesives are among the most efficient systems in adhesive bonding technology. Whether in cell phones, electronic devices, or in cars: Epoxy adhesives are widely used in various industries particularly to produce high-strength bonded joints.

Let's take a closer look at automotive production. Here, the trend towards 'bonding instead of welding' has become an established best practice. Plastic roofs, bumpers or crash-relevant parts - bonded joints have become commonplace and have developed into an effective alternative to traditional joining procedures such as screws, rivets or welding. As car manufacturers increasingly look for ways to make vehicles lighter to save fuel and reduce CO2 emissions, they are using the material mix of aluminum and composites with structural adhesives. This combination also increases stiffness, improves crash safety, and prevents corrosion.

For example, a bonded component can be up to 30 percent stiffer at the same material thickness compared to joints bonded via rivets or spot welds, which enables much thinner metal sheets to be used in automobile construction. In the case of bonded joints, the forces are not only transmitted at specific points, but over the whole bondline. Adhesives also help to improve corrosion resistance in the bondlines because moisture can no longer penetrate through gaps, while also providing the benefit of a sound and vibration-damping effect.

Other technical industries, as well as the automotive industry also require highly specialized adhesives. Here, dicyandiamide (DICY) has been the leading thermo latent curing agent of choice for many decades for a variety of industrial applications, due to its outstanding shelf-life capabilities and the potential to provide excellent thermal and mechanical properties after curing. However, the long shelf-life of DICY is based on its relatively high activation temperature, and temperatures of 140°C and higher are often needed to achieve acceptable curing times. Thus, DICY is predominantly applied in combination with accelerators, such as substituted ureas, to effectively reduce curing temperatures and curing time, but always comes with the drawback of reduced shelf-life.

To give formulators more flexibility for the design of low temperature curing of structural one-component (1K) epoxy adhesives, Evonik's Crosslinkers business line has developed a series of thermo latent curing agents under the established Ancamine® brand. With the modified amines Ancamine® 2014 AS/FG, Ancamine® 2337S and Ancamine® 2441, a versatile toolbox of epoxy curing agents is available to enable curing temperatures from as low as 70°C, fast green strength development, and glass transition temperatures of up to 114°C. All this is complemented by excellent shelf-life stability even at elevated temperature storage. Evonik's amines can also be utilized as an accelerator, or co-accelerator for DICY-based adhesive systems.

Crosslinkers - Creating Marketable and Intelligent Solutions

Mechanical strength, durability, chemical resistance and excellent color stability and adhesion properties – Evonik´s business line Crosslinkers offers tailor-made solutions for customers all over the world. As a raw material supplier, we have a profound understanding of the needs of our customers and their unique markets. Our range of products and expertise generates added value in a number of areas: from coatings and adhesives to civil engineering, high-performance elastomers and composites.

Ancamine® 2014 AS/FG, Ancamine® 2337S and Ancamine® 2441 ensure low temperature curing for 1K epoxy adhesives in the automotive construction.