Typical hydrocarbon resins range in appearance from hard, brittle solids to viscous liquid. They may come in flakes, pellets, or in molten form. Resins in this family are typically composed of a mixture of monomers and are based on a variety of feedstock so they are difficult to fully characterize on a molecular level. Basic physical analysis as described previously i.e. color and softening point can be used to predict performance characteristics and are essential in designing resins for specific applications such as adhesives. Solubility is a property that depends upon the particular product.
Hydrocarbons are soluble in aromatic solvents such as toluene and xylene.
Aliphatic petroleum resins and terpene resins are also soluble in aliphatic solvents such as hexene. Coumarone-indene resins are mostly soluble in acetone. Most commercial hydrocarbon resins produced from olefinic feedstocks are synthesized via carbocationic polymerization. The polymerization of monomers from hydrocarbon resins is typically carried out by either the direct addition or catalyst to a hydrocarbon fraction or by the addition of feed to a solvent-catalyst slurry or solution. Most commercial manufacturers use a continuous polymerization process as opposed to a batch process.