Adhesives are Process Materials

Correct joint design is crucial and needs to take into account the specific mechanical properties of the substrates and the adhesives used. Simply substituting elastic adhesives for rigid fastening - such as a riveted connection - will not always achieve the desired result. 

To find the best joint design, several disciplines must work together. Cooperation between chemists, mechanical engineers and process engineers is fundamental. It is important to discuss the requirements, design and other relevant issues such as ageing behaviour in the design phase. 

The chemist needs to have knowledge about the basic chemistry of reactive systems and must design the adhesive according to the identified needs. Also, surface preparation is usually a decisive factor. 

Mechanical engineers will design the joint and calculate the loads to be transferred and predict durability and strength through calculation. 

The application and process engineers have to pre-treat the surface of substrates in the right way, to apply the adhesive to the right place and in the right amount, correctly cure the adhesive and therefore, control almost the whole process. 

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As mentioned in the introduction, adhesives are process materials. This is similar to a welding process. For these processes, it is very difficult to control the quality of a bonded joint in a nondestructive way. Therefore, it is crucial to control the process parameters of each production step, to check the properties of the adhesive with the real substrates and it is necessary to control the surface conditions of the substrates itself. And even with nondestructive testing methods it is not possible to check the quality and durability of the adhesion itself This can only be done with thorough adhesion tests upfront with original substrates and original process conditions. 

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