resin

https://doi.org/10.1351/goldbook.RT07166
Soft solid or highly viscous substance, usually containing prepolymers with reactive groups.
Notes:
  1. This term was used originally because of its analogy with a natural resin (rosin) and designated, in a broad sense, any polymer that is a basic material for plastics, organic coatings, or lacquers. However, the term is now used in a more narrow sense to refer to prepolymers of thermosets (thermosetting polymers).
  2. The term is sometimes used not only for prepolymers of thermosets, but also for cured thermosets (e.g., epoxy resins, phenolic resins). Use of the term for cured thermosets is strongly discouraged.
  3. Use of the term 'resin' to describe the polymer beads used in solid-phase synthesis and as polymer supports, catalysts, reagents, and scavengers is also discouraged.
Source:
PAC, 2004, 76, 889. (Definitions of terms relating to reactions of polymers and to functional polymeric materials (IUPAC Recommendations 2003)) on page 897 [Terms] [Paper]