Silicone Oil for Mould Release: How It Works and Which Grade to Use

What a mould release agent actually does

A release agent sits between the moulded material and the tool surface so the finished part lets go cleanly, without tearing, sticking or leaving residue in the cavity. A good one does three jobs at once: it releases the part reliably, it protects surface finish and fine mould detail, and it keeps the tool clean so cycle times stay short. A poor one means scrap, downtime scrubbing cavities, and inconsistent parts.

Release agents split broadly into sacrificial types that transfer to the part and are reapplied each shot, and semi-permanent types that bond to the tool and last many cycles. Silicone oil is the classic sacrificial workhorse — cheap to apply, forgiving, and effective across a wide range of materials.

Why PDMS is such an effective release agent

PDMS is a dimethyl silicone fluid — clear, inert and stable across a wide temperature band. The properties that make it a strong release agent are structural, not additives:

• Very low surface energy — moulding compounds don't wet or bond to a silicone-coated surface, so parts release with minimal force.
• Thermal stability — PDMS holds up at the tool temperatures used in rubber vulcanisation and thermoplastic moulding without breaking down or charring the way many organic release agents do.
• Chemical inertness — it doesn't react with the polymer being moulded, so it won't cure-inhibit or discolour the part.
• Clean release, low residue — it leaves a thin, non-tacky film rather than a gummy deposit that fouls the cavity.
• Multiple releases per application — a persistent silicone film can carry several demoulds before it needs reapplying, which shortens cycle time and cuts consumption.

Where silicone release agents are used

PDMS-based release covers most high-volume moulding, though the fit varies by process:

• Rubber and tyre moulding — the core use. Silicone releases cured rubber cleanly from hot tools, resists the temperatures of vulcanisation, and gives many releases per spray.
• Plastic and polyurethane (PU) moulding — foams, elastomers and cast parts release cleanly; PDMS is standard for flexible and rigid PU, and for many injection and rotational moulding jobs.
• Composites (FRP / GRP) — used as a release for hand lay-up and moulded composites, though for parts that will later be painted or bonded, moulders often switch to semi-permanent or non-silicone systems to avoid transfer.
• Die-casting and metal forming — silicone can feature in release and lubricant blends, usually alongside other carriers.
• Concrete and precast — silicone-based release helps demould precast elements and improves surface finish, though mineral-oil and specialist form-release chemistries dominate here.

Neat oil, emulsion or solvent-carried?

How the silicone is delivered to the tool matters as much as the fluid itself. There are three common routes:

1. Neat PDMS — the oil is applied directly (wiped, brushed or as a fine spray). Simplest and most concentrated, best where a heavier film and maximum releases per application are wanted, and where solvent or water carriers aren't desired.
2. Water-based emulsion — PDMS is emulsified in water and sprayed as a thin, even film. Lower silicone consumption, easier to control film weight, no solvent handling. This is the most common industrial format, and the base fluid inside it is exactly what Ecovalley supplies.
3. Solvent-carried — PDMS diluted in a solvent for very thin, fast-drying films and fine detail. Effective but brings flammability and VOC handling considerations.

Ecovalley manufactures the industrial-grade PDMS silicone oil and DMC that sit at the centre of all three — used neat or as the base for your own release emulsion. We supply the base fluid; we don't sell finished branded release sprays. If you compound your own release agent or apply silicone directly, that's exactly what we make.

Which viscosity grade for mould release?

Silicone oil is specified by viscosity, in centistokes (cSt), and the right grade depends on the process and application method:

• Lower viscosity (100–350 cSt) — sprays and atomises more easily, wets into fine mould detail, and emulsifies more readily. Suits emulsion making, spray application and intricate cavities.
• Higher viscosity (500–1000 cSt) — leaves a more persistent, heavier film that survives more releases per application and higher tool temperatures, at the cost of easy spreading.

Ecovalley's S201 PDMS range spans roughly 90 to 1100 cSt (grades S201-100 to S201-1000), so the viscosity is matched to your job rather than forcing the job to the fluid. Tell us the moulding process, tool temperature and whether you apply neat or as an emulsion, and we'll recommend a grade.

Transfer and contamination — the one thing to watch

PDMS releases so well precisely because it migrates to the surface — and that same property is its main limitation. Silicone that transfers onto a moulded part can interfere with anything you do to that surface afterwards: painting, printing, coating or adhesive bonding. If a released part will be finished downstream, use the lightest effective film, control your dilution, and test paintability and bond strength before committing a line.

Where zero silicone contamination is required, moulders move to non-silicone or semi-permanent release systems. For the large majority of rubber, tyre and general moulding — where clean, cheap, high-throughput release is what matters — silicone remains the default for good reason.

The recycled-PDMS advantage

Ecovalley's PDMS is recovered from industrial silicone, but recovered PDMS is chemically the same dimethyl silicone as virgin material: same backbone, same release performance, made to industrial specification and certified to ISO 9001:2015, REACH and RoHS. The difference is the carbon footprint.

For moulders and component makers reporting to OEM customers — especially in automotive and export supply chains under sustainability audits — running a recovered-silicone release agent is a real, documentable circular-economy story. Same demould behaviour on the line, lower impact on the report.

Sourcing silicone oil for mould release in bulk in India

Ecovalley manufactures PDMS silicone oil at its plant in Sonipat, Haryana (established 2016) and supplies industrial buyers across India in 50 kg and 200 kg barrels. For a moulding operation, what matters is consistent viscosity batch to batch, reliable supply, and a technical data sheet you can stand behind — all standard. As a silicone manufacturer in India rather than a trader, we control the spec ourselves.

Tell us your grade, viscosity and monthly volume and we'll respond with specifications, pricing and lead time.

Frequently asked questions