Silicone oil plasticiser for casting silicones, suitable for food contact materials
Wacker AK 350 is a linear, non reactive polydimethylsiloxane (silicone oil) with a kinematic viscosity of approximately 350 mm²/s. The oil is added to pourable addition and condensation silicones to make the cured rubber softer and more flexible and to thin the uncured mixture for better de-airing and detail reproduction. The colourless, odourless fluid has a density of 0.97 g/cm³, a flash point of 260 °C and a low surface tension of 0.021 N/m.
According to Wacker’s Regulatory Product Information (version 1.22, June 2026), Wacker AK 350 is suitable, provided it is processed appropriately, for the manufacture of materials and articles intended for food contact under Regulation (EC) No 1935/2004. See the Food contact section below.
Key benefits
- ✓ Viscosity 350 mm²/s: thin fluid oil that mixes easily and homogeneously into addition and condensation silicones
- ✓ Density 0.97 g/cm³: accurately dosed by weight for controlled hardness reduction
- ✓ Hardness reduction of about 3 to 5 Shore A at 8 percent: predictable softening without making the silicone unusable
- ✓ Flash point 260 °C: safe to handle and store
- ✓ Low surface tension 0.021 N/m: improves the flow of the silicone mixture into fine details and crevices
- ✓ Suitable for food contact materials: EC 1935/2004, EU 10/2011 positive list without a specific migration limit and BfR Recommendation XV Silicones
- ✓ Fully miscible with all Wacker AK silicone oils: any intermediate viscosity can be set
Typical applications
- → Softening pourable addition and condensation silicones for more flexible moulds
- → Reducing the viscosity of mould rubber for better de-airing and detail reproduction
- → Additive in the production of silicone articles and coatings intended for food contact
- → Smoothing brushed on silicone by hand in brush and spatula techniques
- → Release agent and lubricant in industrial and technical applications
- → Water repellent and defoamer
- → Liquid dielectric and heat transfer oil for electrical applications
Processing
- Prepare your silicone: mix components A and B in the correct weight ratio according to the data sheet of the silicone and stir thoroughly.
- Add Wacker AK 350 by weight, between 1 and 15 percent. About 8 percent gives a softening of roughly 3 to 5 Shore A points. Above 10 percent, the final strength can decrease noticeably.
- Mix until fully homogeneous, so that the oil is evenly distributed through the silicone mixture.
- Pour or process the mixture within the pot life of the silicone used.
- Allow to cure according to the cure time and temperature of the silicone used.
⚠️ Note: adding silicone oil changes the properties of your silicone. The final values will differ in some respects from the silicone data sheet. The oil does not cross link in the silicone and slowly bleeds out over the years and under stress, leaving a greasy film and causing slight shrinkage of the mould. For food contact, you should therefore also assess migration from the finished product.
Food contact
According to the Regulatory Product Information of Wacker Chemie AG (version 1.22, 26 June 2026):
- → Regulation (EC) No 1935/2004: suitable, provided appropriate processing, for the manufacture of food contact materials and articles
- → Regulation (EU) No 10/2011: listed as an additive on the positive list under polydimethylsiloxane (ref. no. 76721), without a specific migration limit (SML)
- → BfR Recommendations: XIV Plastic Dispersions, XV Silicones, XXXVI Paper and Board and XXXVI/2 Paper and Board for baking purposes
- → Switzerland: listed in SR 817.023.21, annexes 2, 9 and 10
- → Other markets: listed in the positive lists of Japan, China (GB 4806.16-2025 and GB 9685-2016) and Mercosur
- → United States: a food contact statement is available separately on request
Polydimethylsiloxane is also approved as food additive E 900, but Wacker explicitly advises against using AK 350 as a food additive. The manufacturer of the finished article remains responsible for compliance, including migration, restrictions and the effect on the taste and odour of the food.
Other product information
According to Wacker, AK 350 contains no intentionally added allergens, latex or fragrances, is not derived from genetically modified organisms or animal sources, and substances covered by RoHS, EN 71-3, PFAS and bisphenols are not intentionally added.
Shelf life
At least 5 years when stored below 50 °C in a dry, cool and tightly closed container.
Professional support
Not sure about the right dosage for your silicone, or would you like the Regulatory Product Information or the US food contact statement? Contact us at info@siliconesandmore.com.
