Flexible structural adhesives

Flexible structural adhesives are known to have unacceptably poor high-temperature performance and poor durability.

Structural adhesives are known for binding metal to metal, metal to plastic, and plastic to plastic. Structural adhesives are an attractive alternative to mechanical joint methods such as riveting and spot welding because they distribute load stresses over a large area rather than concentrating such stresses at a few points. Because fasteners do not need to be hidden to achieve an aesthetically pleasing appearance, the use of structural adhesives can reduce or eliminate retouching costs. Structural adhesives also result in cleaner and more stable products because they keep out water, dust, and noise. In addition, they can be used to bond a variety of different materials without the need for a large area of surface treatment.

Despite their attractiveness, structural adhesives are known to have a number of potential disadvantages Although structural adhesives are known to have good high-temperature properties and good durability, the adhesive bodies they form are rigid. The rigid adhesive causes the stress to be unevenly distributed in the adhesive body, i.e. the stress at the edge of the adhesive body is higher than the stress in the middle of the adhesive body. For example, when gluing two workpieces together at overlapping parts, increasing the overlap size does not significantly improve bonding strength. In addition, because the adhesive will not break, but will knock off paints and coatings or in some cases break fiber-reinforced plastics, uneven stress on rigid structural adhesives can lead to workpiece damage.

In addition, structural adhesives that overcome rigidity problems are known. These elastic adhesives distribute stress evenly throughout the bonding body. The effect of this phenomenon is to absorb and disperse the load efficiently. However, flexible structural adhesives are known to have unacceptably poor high-temperature performance and poor durability.