In polymer chemistry and materials science, resin is a “solid or highly viscous substance” of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses on naturally-occuring resins.
Plants secrete resins and rosins for their protective benefits in response to injury. The resin protects the plant from insects and pathogens.Resins confound a wide range of herbivores, insects, and pathogens, while the volatile phenolic compounds may attract benefactors such as parasitoids or predators of the herbivores that attack the plant.
Most plant resins are composed of terpenes. Specific components are alpha-pinene, beta-pinene, delta-3 carene, and sabinene, the monocyclic terpenes limonene and terpinolene, and smaller amounts of the tricyclic sesquiterpenes, longifolene, caryophyllene, and delta-cadinene. Some resins also contain a high proportion of resin acids. Rosins on the other hand are less volatile and consist, inter alia, of diterpenes.