Hydrocarbon resins are amorphous thermoplastic polymers produced by polymerization of unsaturated hydrocarbons. These resins have typically low molecular weights ranging from about 400 to 5000 g/mol. The three main types are C5 aliphatic, C9 aromatic, and hydrogenated C5/C9 resins. Main function of HCR is the tackifying effect. Further other physico-chemical properties can be favourably impacted.