胶粘剂/胶黏剂为什么能粘接的胶接理论之双电层理论

双电层理论是将胶黏剂与被粘物视作一个电容器。电容器的两块夹板就是双电层。即当两种不同的材料接触时，胶分子中官能团的电子通过分界线或一相极性基向另一相表面定向吸附，形成了双电层。由于双电层的存在，欲分离双电层的两个极板，就必须克服静电力。当被粘物与胶黏剂剥离时，可以视为两块极板的分离，此时两极之间便产生了电位差，并随着极板间的距离增大而增大（即随着剥离力的增大两者之间的距离增大），到一定极限值时，便产生了放电现象，在黑暗时会有发光的放电现象和听到轻微的爆声。此时，由于双电层的形成，胶黏剂与被粘物之间就有静电力产生，从而产生了粘接力。

双电层理论只存在于能形成双电层的粘接体系，不具有普遍性，并且双电层所产生的静电力即使存在于某些粘接体系中，但是，它在这个粘接中绝不是起主导作用的，它只占整个胶接力的一部分。

另外，双电层理论不能解释许多聚合物在粘接剥离时并没有放电现象发生，也不能解释当两个聚合物性质越相近，粘接力越大，但两个同性聚合物接触时，电位差却小的现象等。因此双电层理论也有一定的局限性。

The theory of electric double layer regards the adhesive and the adherent as a capacitor. The two plates of a capacitor are the electric double layers. That is to say, when two different materials are in contact, the electrons of the functional group in the glue molecule are adsorbed to the surface of the other phase through the boundary or the polar group of one phase, forming an electric double layer. Because of the existence of the electric double layer, the electrostatic force must be overcome in order to separate the two plates of the electric double layer. When the adhesive is peeled off from the adhesive, it can be regarded as the separation of two plates. At this time, there is a potential difference between the two plates, which increases with the increase of the distance between the two plates (that is, the distance between the two plates increases with the increase of the peeling force). When it reaches a certain limit value, there is a discharge phenomenon. In the dark, there will be a luminous discharge phenomenon and a slight explosion. At this time, due to the formation of the electric double layer, there is electrostatic force between the adhesive and the adherent, resulting in the adhesive force.

The theory of electric double layer only exists in the bonding system which can form electric double layer, and it is not universal. Even if the electrostatic force generated by electric double layer exists in some bonding systems, it is not the leading role in this bonding, it only accounts for a part of the whole bonding force.

In addition, the electric double layer theory can not explain that many polymers do not discharge when they are bonded and peeled off, nor can it explain that the closer the properties of two polymers are, the greater the adhesive force is, but the smaller the potential difference is when two same-sex polymers are in contact. Therefore, the electric double layer theory also has some limitations.