DYNAMAXRubber process oils act as plasticizers, extenders or processing aids and must suit polymer, filler, curing system and application. Coating a hardened seal does not restore its original performance and may cause swelling or dimensional instability.
Compounding and maintenance are different duties
Process oil is incorporated during manufacture, affecting mixing viscosity, filler dispersion, molding and hardness. It is neither tire dressing nor bearing oil. Lubrication or softening is one formulation effect, not evidence that every rubber needs oil, that more is better, or that every finished product gains wear or aging resistance.
Reference: Nynas: Optimal plasticisers · Nynas: Tyre and Rubber Oils
Hardening in service may involve heat, chemicals or aging. An unknown oil bath can merely swell the part; dimensions, strength and recovery may remain unsuitable despite apparent softness. Leaking, cracked or safety-critical seals need maker guidance on replacement and compatible media, not a process-oil repair recipe.
Reference: Nynas: Optimal plasticisers
Compatibility matters more than the name
Polymer polarity, solvency and molecular characteristics affect miscibility and long-term stability. Nynas describes assessing affinity through swelling, dimensional and hardness changes under controlled conditions. That does not make one oil family equally suitable for natural rubber, SBR, EPDM, NBR or TPE. Identify the actual polymers, blend ratios and other ingredients first.
Reference: Nynas: Optimal plasticisers · Nynas: Tyre and Rubber Oils
Paraffinic, naphthenic and aromatic characteristics can guide screening, but commercial products have specific compositions and refining. Review viscosity, solvency indicators such as aniline point, volatility, color and low-temperature behavior together. Neither “aromatic is most compatible” nor “naphthenic is naturally safe” establishes suitability. Restricted-substance documentation must cover the exact product and market.
Reference: Nynas: Optimal plasticisers · Nynas: Tyre and Rubber Oils
Translate finished requirements into a trial matrix
| Item | Decision and action |
|---|---|
| Mixing | Torque, temperature, dispersion, sticking and batch consistency. |
| Cure and molding | Scorch, cure curve, dimensions and demolding. |
| Finished compound | Hardness, tensile/elongation, compression set and application aging tests. |
| Storage and exposure | Bleed, migration, color, media exposure and cold performance. |
Reference: Nynas: Optimal plasticisers
A trial is more than measuring softness
Change one variable against a baseline and record batch, dose and addition sequence, using identical mixing and cure conditions. After specimen acceptance, verify scale-up on production equipment. Excess oil can alter strength, dimensions, bleeding and cure; easier processing does not mean all properties improve. Define acceptance limits from product/customer requirements before trials instead of selecting flattering metrics afterward.
Reference: Nynas: Optimal plasticisers
Equal-viscosity replacements still need solvency and formulation evaluation. Retain baseline specimens, product samples and comparison reports, with formulation, quality and procurement approval. Isolate trials and output with bleeding, excessive swelling, abnormal cure or failed strength, then investigate materials and conditions rather than blindly adding filler or shortening cure.
Reference: Nynas: Optimal plasticisers
Procurement handover and storage
Provide polymer, application, dose range, mixing temperature, curing system, color and required properties. Obtain technical and safety data, batch specifications and restricted-substance statements, plus change-notification and retained-sample arrangements. Verify the exact PTT candidate version rather than inferring food, medical or universal rubber approval from an old brand introduction.
Reference: Nynas: Tyre and Rubber Oils
Check product, batch, seals and container cleanliness. Use the SDS for storage, ventilation, fire precautions and protection rather than calling all process oils either hazardous goods or nontoxic. Separate transfer equipment and prevent water or foreign ingredients. Hold suspect appearance or viscosity deviations and retain a sample for supplier review.
Reference: Nynas: Tyre and Rubber Oils · Nynas: Optimal plasticisers
Return compound-trial results to production
A compound trial is not a test of whether oil softens old rubber. Fix the polymer, fillers, oil loading and mixing conditions, retain batch and material revisions, then compare processing and finished-product requirements. Initial hardness reduction cannot justify acceptance if bleeding, dimensional changes or aged-performance loss follows. Give the supplier the polymer, formulation purpose, processing and acceptance tests; formulation and production teams must confirm suitability through trials. Reuse the matrix for oil or batch changes to separate lubricant effects from other formulation and process changes.
Reference: Nynas: Optimal plasticisers · Nynas: Tyre and Rubber Oils
Frequently asked questions
Q1. Can process oil soften old rubber for reuse?
Do not treat it as restoration; swelling is not restored sealing performance. Diagnose and replace safety-critical parts appropriately.
Q2. Can equal-viscosity process oils be substituted?
Compare solvency, composition, cure and finished properties and complete trials and approval.
Q3. Are all naphthenic oils harmless?
No; use the exact SDS, application and substance documentation rather than a base-family name.
Sources and applicable limits
- Nynas: Optimal plasticisers — Process-oil/polymer compatibility, swelling, hardness and compound properties. (Accessed 2026-10-08)
- Nynas: Tyre and Rubber Oils — Polymer polarity and process-oil applications; not approval for all rubber compounds. (Accessed 2026-10-08)
