SILISIL RTV MF-Flex 25

SILISIL ·

SILISIL RTV MF-Flex 25 is a room-temperature vulcanizing 2-component addition silicone (platinum-cured, RTV-2) from the MF-Mold & Form series — transparent 2K flex silicone Shore A 24 with high elongation at break of 530%.

The mixture is prepared in a ratio of 1:1 by weight (tolerance ±5%). Pot life at 23 °C approx. 20 minutes, demolding after approx. 3 hours, complete curing after 24 hours. Temperature resistance –40 °C to +200 °C.

Key property

Transparent molding compound with high elasticity — full visual control over mold filling, air inclusions, and the embedded original during demolding.

SILISIL RTV MF-Flex 25 in numbers

A 24

Shore Hardness

4'500

mPa·s viscosity

20 min

Pot life @23 °C

530 %

Elongation at break

What sets SILISIL RTV MF-Flex 25 apart

Transparent for visual inspection

Full visual control over the mold interior — air inclusions and the position of the original are always visible.

Low viscosity 4'500 mPa·s

Low mixed viscosity — flows into finest structures without air entrapment, vacuum degassing optional.

High elongation at break 530%

High elasticity — reliable demolding of complex geometries without damaging the mold or the original.

High tear strength >5.5 N/mm²

High tear strength >5.5 N/mm² — above-average robustness during demolding.

Mixing ratio 1:1 by weight

Simple 1:1 ratio — hand-mixable without a precision scale, ideal for workshops and hobbyists.

High-fidelity reproduction

High detail reproduction — fonts, structures, and sharp edges are reproduced true to nature.

What is SILISIL RTV MF-Flex 25 used for?

Jewelry wax burnout molds

Transparent mold for goldsmiths and jewelry manufacturers — embedded originals remain visible, air inclusions are detected.

Resin and epoxy art

Visually controlled casting of jewelry pendants, resin sculptures, and clear resin replicas in artist studios.

Multi-part molds with complex undercuts

Elongation at break 530% and tear strength >5.5 N/mm² — Molded parts with aggressive undercuts can be demolded safely.

Designer prototypes with visual inspection

Industrial design and product studios can see during demolding whether undercuts are correctly molded.

Collector and model building replicas

High-resolution reproduction of small series — action figures, model railway parts, collector editions.

Educational and museum replicas

Transparent teaching molds, anatomical models, and didactic replicas reveal the structure even after curing.

Processing

Prepare the original

The surface to be reproduced must be clean, dry, and free of dust. The ideal processing temperature is 23 °C — cooler environments significantly extend pot life and curing time.

Homogenize and mix components

Stir base and catalyst thoroughly before use. Weigh out 1:1 by weight (tolerance ±5%). When mixing, thoroughly incorporate the walls and bottom of the container.

Vacuum degassing

For pore-free molds, briefly degas the mixture under vacuum — entrapped air bubbles are removed, ensuring a smooth mold surface.

Pour slowly into the mold

Pour from a height of approx. 30 cm in a thin stream into the deepest point — the silicone displaces air independently and reaches all undercuts.

Vulcanize and demold

At 23 °C, demolding is possible after approx. 3 hours, complete curing after 24 hours. Before the first pour, allow a 24 h "maturation phase" for maximum strength.

Data Sheets & Safety Data Sheet

Complete TDS and SDS in DE, EN, FR — view or download directly.

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Important Notes

Avoid crosslinking inhibitors

Addition-curing systems such as MF-Flex 25 are sensitive to sulfur, amine, tin, and phosphorus compounds — especially latex gloves, modeling compounds, adhesive tapes, and certain varnishes. When in doubt, make a small test cast before use.

Storage and Shelf Life

Shelf life of at least 12 months in unopened original container when stored in a dry, cool place (10–25 °C). Consult the Safety Data Sheet (SDS) before opening.

Available containers

1 kg + 1 kg, 5 kg + 5 kg, 25 kg + 25 kg. Other container sizes available on request.

Compatibility

Compatible with polyurethane, epoxy, and polyester casting resins. For aggressive resins, apply a release agent to protect the mold.

Recommended accessories

SILISIL white petroleum jelly release paste

Universal release agent for polyester, epoxy, and polyurethane casts — protects the silicone mold from aggressive resins and extends mold service life.

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SILISIL Delayer PA

Retarder for addition-curing silicones — extends pot life and setting time for more complex multi-part builds and relaxed processing.

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SILISIL Silicone Remover

Cleaning agent for silicone residues on tools, models, and work surfaces — gentle and effective.

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Which MF silicone for which application?

SILISIL RTV MF-Flex 25 in direct comparison with related MF products from our range (MF = Mold & Form).

	MF-Flex 25 Current Product	MF-Flex 20 →	MF-Soft 12 →	MF-Soft 13 TP →
Shore hardness A	24	22	12	13
Mixed viscosity	4'500	4'500	3'500	4'500
Color	Transparent	Blue	Blue	Translucent
Pot life @23 °C	20	15	20	45

Topics & Application Fields

Key terms related to this product. Also useful for our search and filters.

Mold making SILISIL Silicone RTV-2 Swiss stock Addition Platinum Prototyping Shore A 25 Swiss brand 2K Moulding / Mold making

Technical data for SILISIL RTV MF-Flex 25

All 17 Product Information 4 Physical Properties 4 Electrical Properties 1 Curing Values 3 Product Approvals 3 Mechanical Properties 2

Product Information
Brand	SILISIL
Mixing Ratio	1:1
Curing type	Addition (Platinum)
Container	500 g + 500 g, 1 kg + 1 kg, 5 kg + 5 kg, 10 kg + 10 kg, 25 kg + 25 kg

Physical Properties
Cured Color	Transparent
Self-leveling	Yes
Density (g/cm³)	1.1
Uncrosslinked viscosity (mPa·s)	4500

Electrical Properties
Electrical Insulation	Yes

Curing values
Pot life (min)	20
Demolding time (min)	3
Full cure (h)	24

Product Approvals
Food contact	No
Medical grade	No
Certificates	RoHS, REACH

Mechanical properties
Shore hardness A (cured)	A 25
Elongation at break (%)	530

Please refer to the technical data sheet (TDS) in the "Documents" tab for binding values.

Documents and data sheets

Click on a document for the preview or the download icon for direct download.

Technical Data Sheets (TDS) 3

SILISIL RTV MF-Flex 25 - Technical Data Sheet DE.pdf

124 KB

SILISIL RTV MF-Flex 25 - Technical Data Sheet EN.pdf

123 KB

SILISIL RTV MF-Flex 25 - Fiche Technique FR.pdf

123 KB

Safety Data Sheets (SDS) 3

SILISIL RTV MF-Flex 25 - Safety Data Sheet DE.pdf

362 KB

SILISIL RTV MF-Flex 25 - Safety Data Sheet EN.pdf

384 KB

SILISIL RTV MF-Flex 25 - Safety Data Sheet FR.pdf

390 KB

Frequently Asked Questions about SILISIL RTV MF-Flex 25

Practical application and design questions — answered by SILITECH.

What is SILISIL RTV MF-Flex 25 suitable for?

SILISIL RTV MF-Flex 25 is a 2K addition-cure silicone (Shore A 24, transparent) for jewelry wax burnout molds and related applications. Transparent 2K flexible silicone, Shore A 24, with high elongation at break of 530%

What are the pot life and demolding time of MF-Flex 25?

At 23 °C, the pot life is approx. 20 minutes and the demolding time approx. 3 hours. Full curing is achieved after 24 hours. Lower temperatures extend these values, higher temperatures shorten them.

Which materials should be avoided with MF-Flex 25?

As an addition-curing system, SILISIL RTV MF-Flex 25 is sensitive to crosslinking inhibitors: sulfur, amine, tin, and phosphorus compounds can locally stop vulcanization. Avoid latex gloves, sulfur-containing modeling compounds, certain adhesive tapes, and PVC plasticizers in the immediate vicinity of the mold. When in doubt, perform a small test pour.

In what mixing ratio is MF-Flex 25 processed?

SILISIL RTV MF-Flex 25 is mixed in a 1:1 ratio by weight (base to catalyst), with a tolerance of maximum ±5%. Homogenize both components separately before mixing, then incorporate thoroughly — including container walls and bottom. A brief vacuum degassing of the mixture is recommended for pore-free molds.

What Shore hardness and mechanical values does MF-Flex 25 have?

SILISIL RTV MF-Flex 25 achieves a Shore A hardness of 24 (ASTM D 2240), a tear strength of >5.5 N/mm² (ASTM D 412), an elongation at break of approx. 530%, and a tear resistance of 15 N/mm (ASTM D 624).

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Product Specifications

Product Information
Container	500 g + 500 g or 1 kg + 1 kg or 5 kg + 5 kg or 10 kg + 10 kg or 25 kg + 25 kg
Brand	SILISIL
Mixing Ratio	1:1
Curing type	Addition (Platinum)

Physical Properties
Cured Color	Transparent
Self-leveling	Yes
Density (g/cm³)	1.1
Uncrosslinked viscosity (mPa·s)	4500

Electrical Properties
Electrical Insulation	Yes

Curing values
Pot life (min)	20
Demolding time (min)	3
Full cure (h)	24

Product Approvals
Certificates	RoHS or REACH
Food contact	No
Medical grade	No

Mechanical properties
Shore hardness A (cured)	A 25
Elongation at break (%)	530

Keywords
Keywords	Mold making SILISIL Silicone RTV-2 Swiss stock Addition Platinum Prototyping Shore A 25 Swiss brand 2K Moulding / Mold making

Documents and data sheets

Safety Data Sheets (SDS) and Technical Data Sheets (TDS) for download:

SILISIL RTV MF-Flex 25

Price on request

Documents

Shipping & Delivery

Product data

What sets SILISIL RTV MF-Flex 25 apart

What is SILISIL RTV MF-Flex 25 used for?

Processing

Important Notes

Recommended accessories

Which MF silicone for which application?

Technical data for SILISIL RTV MF-Flex 25

Documents and data sheets

Technical Data Sheets (TDS) 3

Safety Data Sheets (SDS) 3

Frequently Asked Questions about SILISIL RTV MF-Flex 25

Your question not covered?

Product Specifications

Documents and data sheets