Full definition
A liquid or low-melting-point solid additive incorporated into rubber compounds (5-30+ phr) to reduce hardness, improve low-temperature flexibility, enhance processability (lower Mooney viscosity for easier mixing, extrusion, and calendering), and reduce cost (partially replacing more expensive polymer). Major types: (1) Paraffinic oils — for EPDM, IIR, NR, SBR (non-staining, good general compatibility). (2) Naphthenic oils — versatile, good compatibility with NR and SBR, moderate solvency. (3) Aromatic oils (DAE) — highest solvency and reinforcement for SBR, but restricted by EU REACH regulation for PAH content (replaced by TDAE, MES, RAE). (4) Ester plasticizers (DOP, DIOA, DOS) — for NBR, CR, and polar rubbers; provide low-temperature flexibility. (5) Synthetic oils (polyalphaolefin, polyisobutylene) — for specialty applications. Selection criteria: compatibility with the polymer (solubility parameter matching), desired property changes, volatility (higher MW = lower volatility = less migration), and regulatory compliance (FDA, EU). Excessive plasticizer causes bloom (migration to surface) and reduced strength. Per ASTM D2226 for petroleum oil classification. Aromatic oils: avoid DMSO extract >3% per EU 76/769.