Wacker Elastosil M 4641® A/B – Transparent Addition Silicone Rubber for Prototyping & Vacuum Casting

Premium Transparent Addition-Curing Silicone Rubber for Professional Prototyping and Vacuum Casting Applications

The Wacker Elastosil M 4641 A/B is a pourable, addition-curing (platinum-cure) two-component RTV-2 silicone rubber that vulcanizes shrink-free at room temperature and can be considerably accelerated by applying heat. The highly transparent, translucent vulcanizate has a Shore A hardness of approximately 43, a mixing ratio of 10:1 by weight, a pot life of 90 minutes and a curing time of 12 hours at 23 °C. Thanks to its outstanding resistance to polyurethane and epoxy resins and its oil-free, dry surfaces, this product is ideally suited for vacuum casting and rapid prototyping, especially when crystal-clear casting resins are used.

Key Benefits

• Shore A 43: → medium-hard flexibility combining dimensional stability with easy demolding of models with undercuts.
• Pot life 90 minutes: → ample working time for deairing and casting larger or complex molds.
• Shrinkage < 0.1 %: → accurate, dimensionally stable reproductions without chemical shrinkage during curing.
• Tensile strength > 4.5 N/mm² and tear strength > 25 N/mm: → high mechanical strength for long service life and many reproductions per mold.
• Resistance to polyurethane and epoxy: → suitable for repeated casting of aggressive resins without degradation of the mold surface.
• Food contact under Regulation (EC) 1935/2004: → usable for the manufacture of food contact materials when processed appropriately, subject to the conditions described below.

Typical Applications

• Vacuum casting for rapid prototyping with polyurethane and epoxy resins.
• Crystal-clear casting resins requiring an oil-free mold surface.
• Reproduction of models with undercuts and fine details.
• Molds for food contact applications, provided the finished article meets the conditions listed under Food Contact and Regulations.
• Prototype molds in product development and industrial design.

Processing Instructions

1. Stir the A and B components separately and thoroughly before use.
2. Mix by weight in a ratio of 10 parts A to 1 part B. Note: only use A and B components with the same batch number.
3. Stir slowly and without introducing air, preferably in a figure-8 motion, until a homogeneous mixture is obtained.
4. Preferably deair the mixture under vacuum to remove air bubbles.
5. Cast within the pot life of 90 minutes.
6. Allow to cure for 12 hours at 23 °C. Curing can be accelerated by heating; after demolding, optionally post-cure the mold for 2 to 3 hours at 100 °C to fully degas it.

Food Contact and Regulations

The information below is taken from the Wacker Regulatory Product Information for Elastosil M 4641 A/B, version 1.13, last revised on 3 June 2026.

• European Union, Regulation (EC) 1935/2004: suitable for the manufacture of food contact materials and articles when processed appropriately. Conformity of the finished article, including its suitability for the intended use, compliance with the stated restrictions and the effect on taste and odor, must be ensured by the manufacturer of that finished article.
• Regulation (EU) 10/2011: not applicable, silicones are excluded.
• Regulation (EC) 2023/2006: not applicable, this product is a starting material.
• Germany, BfR Recommendation XV Silicones: ingredients compliant, restriction on volatiles of maximum 0.5 %.
• France, Arrêté of 25 November 1992: compliant, total migration from the finished article maximum 10 mg/dm² or 60 mg/kg, volatiles maximum 0.5 %.
• Spain, Real Decreto 847 of July 2011: compliant, total migration maximum 10 mg/dm² or 60 mg/kg.
• Switzerland, Ordinance SR 817.023.21: ingredients listed in Annex 9.
• United States: Wacker no longer lists any 21 CFR section for this product. A food contact statement can be provided separately upon request. The product must therefore not be offered as FDA compliant.
• China, GB 9685-2016: additives listed in table A.3 or A.7, the platinum catalyst is regarded as NIAS with a migration limit of 0.01 mg/kg food or simulant. GB 4806.16-2025: siloxane starting substances listed in table A.1. GB 4806.1-2016: complies.
• Brazil and Mercosur: base polymers compliant with the positive list under RDC 123 of 19 June 2001, base polymers and fillers listed in RDC 56 of 2012 and amendments, GMC RES 02/2012 and/or GMC RES 34/25. Restrictions: volatiles maximum 0.5 %, extractables maximum 0.5 %.

The admissibility of the ingredients does not mean that the finished product is regarded by regulatory authorities as safe for food contact. Responsibility for the finished article and for migration, extraction and volatiles testing lies with the manufacturer of that finished product.

This product is intended for the business market. For larger quantities or custom products, please contact us at info@siliconesandmore.com.

Wacker Chemie AG is the world market leader in the development and production of silicones for industrial and technical applications.

Professional Support

Do you have questions about processing the Elastosil M 4641 A/B, its suitability for your casting resins or preventing inhibition? Our specialists are happy to assist you. Contact us for personal advice.