The Axson F40 (now marketed as Sika Biresin F40) is a low-viscosity, odourless rigid polyurethane resin with minimal shrinkage. It reaches a Shore Hardness of 83 D with demoulding in just one hour, making it one of the most efficient options on the market for manufacturing rigid two-part moulds and high-precision structural parts.
Technical specifications
Parameter
Value
Material type
Rigid polyurethane resin (two-component)
Cured colour
Blue
Shore Hardness
83 D
Mix ratio (by weight)
100 A : 20 B
Working time
6 minutes
Demould time
1 hour
Maximum depth per layer (casting)
Up to 10 cm
Kit contents
1.2 Kg
What it is used for
The F40 excels particularly in the fabrication of rigid two-part moulds, where a resistant, precise and fast-curing shell is required. Its low viscosity allows complex geometries to be filled without leaving bubbles or voids, and its odourless formulation makes working in indoor spaces more comfortable. It also works as a backup layer over first coats of epoxy resin in composite lamination processes.
Fabrication of rigid two-part moulds for casting silicone
Production of high-precision workshop tools and jigs
Functional parts requiring hardness and mechanical resistance
Cost-effective large-volume castings with the addition of Polvo de Aluminio or other fillers
How to use it
Prepare the mould or surface and apply a suitable release agent for polyurethane to all contact surfaces.
Weigh the components in the correct ratio: 100 parts of component A to 20 parts of component B (by weight). The working time is only 6 minutes, so have everything ready before mixing.
Mix both components vigorously for at least 60 seconds, scraping the sides and bottom of the container thoroughly to ensure a homogeneous cure.
If you need to thicken the mix for brush application on vertical surfaces, incorporate Gel de Sílice AT2 gradually until the desired viscosity is reached.
For block castings, pour the mix continuously. The maximum depth per layer is 10 cm.
Allow to cure at room temperature. Demoulding can be carried out in 1 hour.
If using the F40 as a backup layer over an epoxy coat, create a mechanical bond (for example, by embedding fibreglass strands in the epoxy layer before it fully cures), as both materials do not bond chemically to each other.
Once demoulded, the part can be machined, sanded or painted according to the final application.
Warning: Axson F40 is an isocyanate polyurethane resin. Component B contains isocyanates, which can be irritating to skin, eyes and respiratory tract. Always work with nitrile gloves, safety glasses and in a well-ventilated space. Avoid contact with excessive ambient moisture, as it can cause bubble formation in the mix and affect curing. Consult the safety data sheets before using the product.
Usage tips
Reduce costs with fillers
The F40 accepts the incorporation of fillers to increase volume without losing flowability. Polvo de Aluminio is an excellent option: you can load it up to 100% by volume and the resin continues to flow normally, making block castings much more cost-effective without sacrificing strength or detail.
Working time rules: organise before you mix
With only 6 minutes of pot life, any hesitation after starting the mix can ruin the casting. Prepare the mould with release agent applied, weighing containers ready and workspace clear before opening the components. If working in large batches, divide production into smaller runs rather than increasing the volume of each mix.
Mechanical bond when using as a backup over epoxy
When using the F40 as a backup layer over an epoxy laminate, bear in mind that the two materials do not create a chemical bond with each other. To ensure the cohesion of the assembly, embed fibreglass strands or create a rough texture on the epoxy surface before applying the F40. This mechanical bond is key to the structural integrity of the mould or part.
Frequently asked questions
Is it necessary to use a release agent with rigid polyurethane resins?
Yes, always. Polyurethane resins like Axson F40 tend to adhere to many surfaces, especially wood, porous plaster and some plastics. Applying a suitable release agent to all surfaces in contact with the resin is essential to be able to demould without damaging the part or the mould.
Can I use this resin to cast directly into a silicone mould?
Yes. Axson F40 works very well cast into silicone moulds, which by their nature do not require a release agent. It is precisely for that use (rigid mould housing silicone, or backup shell) that it is optimised. The short working time means you must have the mould ready before mixing.
How many layers can be poured and what is the maximum thickness?
You can pour Axson F40 in layers of up to 10 cm depth. If you need greater thickness, wait for the first layer to cure before pouring the next one. For very large blocks, the ability to batch and stack layers makes this product particularly economical and practical.
Can it be applied with a brush instead of casting?
Yes. If you thicken the mix with Gel de Sílice AT2, you can apply the F40 with a brush or spatula on vertical or complex surfaces. Bear in mind that the working time is 6 minutes, so work quickly and in small quantities.
What is the difference between using this resin and an epoxy casting resin for large moulds?
The main difference is time: a large-block epoxy resin can take many hours or even days to cure completely. Axson F40 is ready to demould in 1 hour, which multiplies workshop productivity. Additionally, in large blocks epoxy generates more exothermic heat, while the F40 manages this better. In terms of strength and precision, the F40 is fully comparable.
Can it be pigmented or coloured?
Yes, although the F40 already cures to a blue colour, which makes visual identification of the material easy. If you need a specific colour, you can add polyurethane-compatible pigments to component A before mixing. Consult Feroca for which pigments are compatible so as not to affect curing.
Is it suitable for outdoor use or contact with water?
Axson F40 is a technical resin designed for the manufacture of moulds and workshop tools, not for applications involving prolonged outdoor exposure or continuous water immersion. For outdoor or water-contact applications, consult Feroca for the most suitable options for your specific case.
What should I do if the resin has cured with bubbles?
Bubbles in the F40 cure are usually the result of moisture in the components, the mould or the working environment, or from overly vigorous mixing without time to degas. Make sure to work in a dry environment, mix with slow and continuous movements, and if possible apply vacuum to the mix before casting. Always store components tightly sealed.
Impalpable aluminium powder, mesh 150 µm and density 2.7 g/cm³. Provides a greyish metallic finish in resins and improves the thermal dissipation of the part.
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