24 августа, 2015 
Pokraskin Although a systematic survey of available adhesives according to their properties, such as their technical performance and processability, would be greatly appreciated by potential users, this does not exist to date. While various attempts have been made to systemize adhesives, it is virtually impossible due to their nature. In contrast to other joining aids, such as welding electrodes, adhesives have not been standardized since, according to current knowledge, standardization would represent an inhibitory factor for further development.
At present, there is available a most varied array of adhesives that often differ considerably one from another in terms of their processing properties, their strength and their durability characteristics. In order to be effective as an adhesive, a substance must fulfill two basic requirements:
• At a specific point of the joining process the adhesive must have a high molecular mobility — that is, it needs to have the properties of a more or less viscous liquid in order to approach the uneven, rigid adherent surfaces up to molecular dimensions (nanometer range), and to allow material joining.
• Within the adhesive layer, the material must have as low a molecular mobility as possible so as to allow tensile, shear and peel forces to be transmitted, respectively; that is, in technical terms, it needs to behave like a solid object.
In the following sections the most important adhesive systems are classified according to their mode of setting (also called ‘curing mechanisms’). A general survey of the types of adhesive available, based on their curing properties and mode of setting, is provided in Figure 4.1 and Table 4.1.
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