We will consider a fully synthetic paint for the enamel […]
We will consider a fully synthetic paint for the enameled wire. This lacquer also has two main components that exhibit the above balance of properties. The first component is polyvinylformal whose molecule is characterized by a) a predominantly linear structure, b) the appearance of a ring system of the 1,3-dioxolane type, and c) a large number of hydroxyl and acetate groups . The second component is a synthetic resin sold under the name "Novolak". In this material, we only need to mention that its molecules are mainly composed of rigid components, but also contain many hydroxyl groups.
It is not clear what kind of chemical reaction took place between the two components in the production process. It is assumed that the hydroxyl groups of "novolak" and the hydroxyl groups of polyvinyl formal are involved in the formation of three-dimensional networks. However, this does not contain a large amount of chemical bonds, as in the case of paint: the chemical structure of the constituents does not at all allow this to be done.
The chemical structure of polyvinyl formal is an important part of "Povin" enameled wire insulation. However, there are many opportunities to form physical bonds, ie hydrogen bonds. These will form between the hydroxyl groups of the "novolak" resin and the oxygen atoms in the dioxane ring of polyvinyl formal.
In addition to the extensive "loose" chemical bond network, a dense network of hydrogen bonds will form. Each individual hydrogen bond is weaker than a chemical bond, but because of their large number, the structure is very robust. This structure is exactly what line enamels require: it is expected that when the line bends, the enamel layer undergoes considerable strain during this process, and many rather weak hydrogen bonds will be destroyed. Therefore, their resistance to bending is very small, whereas hydrogen-bond cleavage will result in very small permanent damage: if the strain is reduced, for example, by heating for a short period of time, a new network of hydrogen bonds is immediately formed, Old power. This is why we mentioned at the outset the excellent mechanical properties of the "Povin" enameled wire.