2.7 Resins and Resin Combinations
Resins, in general, are amorphous solid or semisolid substances that are invariably water insoluble but mostly soluble in alcohol or other organic solvents. However, physically they are found to be hard, translucent or transparent and fusible i.e., upon heating they first get softened and ultimately melt. But chemically, they are complex mixtures of allied substances, such as: resin acids, resin alcohols (or resinols), resinotannols, resin esters, glucoresins and the like.
Another school of thought considers Resins as amorphous products having an inherent complex chemical entity. These are normally produced either in schizogenous or in sehizolysigenous ducts or in carities and are regarded as the end products of metabolism. The physical general characteristic features of resins are namely: hard, transparent, or translucent and, when heated they yield usually complex mixtures that comprise of resin acids, resin alcoholds, resinotannols, esters and resenes. Some researehers do believe that the resins are nothing but the oxidation products of the terpenes. They are found to be mostly insoluble in water, but soluble in ethanol and organic solvents. They are electrically non-conductive and combustible in nature.
Resins shall now be discussed at length in their various aspects as enumerated here under: