petroleum resins is a kind of thermal plasticizing resin produced by c5,c9 fraction,by products of petroleum cracking,through pretreatment, polymerization and distillation.it isn't a high polymer but a low polymer with the molecular weight between 300-3000, featured by acid value ,easy mutual solubility,resistant to water,resistant to ethanol and chemical,it has the chemical stabilizing property to acid and alkaline,viscosity adjusting and thermal stabilizing.generally,the petroleum resins are not used independently,but have to be used together with other kinds of resins as promoters,adjusting agents and modifiers.