AbstractThe paper deals with the thermal synthesis of aliphatic petroleum polymer resins by heat treatment of the С5 fraction at 240–320°С. Beginning from 280°С, the intermediate oligomerization products, piperylene dimers, start to transform into resins. An increase in the temperature to 320°С leads to the decomposition of the dimers and generation of radicals. An increase in the pressure in the reactor does not influence the reaction course. An increase in the synthesis time over 2 h does not lead to a noticeable increase in the piperylene conversion and resin yield. The thermal synthesis of aliphatic petroleum polymer resins is inefficient for commercial production of the resins.