What is RPO? Rubber Process Oil Explained for Compounders

Why rubber compounds need oil

Pure natural and synthetic rubber is stiff, expensive, and a nightmare to mix with the carbon black, silica, sulphur and accelerators that make a working compound. Adding 5–40 phr (parts per hundred rubber) of process oil cuts viscosity, helps filler dispersion, softens the cured rubber to the target Shore A hardness, and reduces cost.

The oil chemistry decides how well it does these four jobs.

The three RPO families

• Aromatic RPO — high solvency, dark colour, cheapest. Default for natural rubber and SBR tread compounds in non-EU markets.
• Naphthenic RPO — moderate solvency, lower pour point. Used in technical rubber goods, conveyor belts, hoses, seals and gaskets.
• Paraffinic RPO — low aromatic content, light colour, low staining. The choice for EPDM roofing membranes, white sidewall tyres, light-coloured moulded goods.

RPO vs TDAE — the regulatory split

EU Directive 2005/69/EC banned high-PAH aromatic extender oils in tyres sold in the EU from 2010. That spawned a new family of low-PAH oils — TDAE, RAE, MES — that comply by keeping polycyclic aromatic hydrocarbons (PAH) below 3 mg/kg measured by IP 346.

For non-tyre rubber goods in non-EU markets, conventional aromatic RPO is still the cost-winning default.

Picking the viscosity

Light RPO (V40 ≈ 30 cSt) — for high-Mooney polymers and low-loading compounds where wetting is critical.

Mid (V40 ≈ 100–300 cSt) — the bread-and-butter range for most tyre and technical rubber compounds.

Heavy (V40 ≈ 500–1,000 cSt) — for truck and OTR tyre treads, heavy industrial rubber, and applications where extender retention under heat matters.

Frequently asked questions

What does RPO stand for?

Rubber Process Oil — the family of mineral oil extenders added to rubber compounds to improve processability, cut cost and tune cured properties.

What is the difference between aromatic, naphthenic and paraffinic RPO?

They differ in molecular structure. Aromatic has the highest solvency and darkest colour. Naphthenic has lower pour point and moderate solvency. Paraffinic is the lightest, lowest-aromatic and least-staining — used in light-coloured compounds.

Is TDAE a type of RPO?

Yes. TDAE (Treated Distillate Aromatic Extract) is a specific low-PAH aromatic RPO developed to comply with the EU 2005 ban on high-PAH extender oils in tyres.

Where can I buy RPO in Southeast Asia?

Sanyang Petroleum supplies aromatic, naphthenic and paraffinic RPO in flexibag, IBC, ISO tank and bulk vessel parcels to rubber compounders across Vietnam, Thailand, Indonesia, the Philippines and Malaysia.