Petroleum-Based PAH-Safe Process Oils In NR, SBR and Their Blends: Study on Unfilled Compounds

Safe process oils are in need for a replacement of toxic distillate aromatic extract (DAE).  The potential and commercially available petroleum based safe process oils are treated distillate aromatic extract (TDAE), mildly extracted solvate (MES) and naphthenics (NAP).  This work investigated the influence of DAE, TDAE and MES oils in natural rubber (NR), styrene butadiene rubber (SBR) and their blend at 50/50 weight ratio.  The unfilled compounds were primarily used in order to observe an influence of oil types on the properties of rubbers without any interference from fillers.  The results show that the oil types affect both processing and mechanical properties in which the NR compounds show the most sensitive to a change of oil type.  The use of TDAE and DAE oils yield the compounds with similar properties, but the MES oil result in inferior properties.  The compounds with MES oil display lower viscosity, longer scorch time and lower cure rate index.  The use of MES in NR compounds clearly affects the vulcanizate properties, whereas only little effect was observed in SBR and NR/SBR blends.  When compared the properties of NR vulcanizates containing DAE, TDAE and MES, it is clear that the use of MES oil results in lower modulus and tensile strength.  In addition, both types and amount of oils play an important role on the dynamic mechanical properties of the rubber vulcanizates, as demonstrated by a shift of glass transition temperature and loss tangent at service temperature.