[Herbie72]

Hi everyone,

For some experiments I'm looking for a 2-component casting resin with approximately the same stiffness, toughness and strength as polypropylene.
Does anyone know which casting resin comes closest to polypropylene?

Kind regards,

Bert.

[Corribus]

What kind of casting? Why can't you just use polypropylene?

[Herbie72]

We are developing a product which will be made with polypropylene injection molding in the future.
But before we make an expensive mold for injection molding, we want to make some prototypes.
Making a mold for casting is a lot easier for us than making a mold for injection molding.

[Enthalpy]

Resins tend to be stiffer than polypropylene. Special formulations, for instance mixes with an elastomer, could mimic polypropylene, but I suppose you want a resin available commercially.

Did you consider other paths?
- 3D printing. Polypropylene is possible, though not the most common. The parts are a bit more fragile than if injected.
- Milling. Polypropylene is possible too, if the parts are not too thin.

Besides companies, you can find individuals and clubs of amateurs that make parts by 3D printing.

[Herbie72]

Milling might be possible.

Thanks for reply!

[Enthalpy]

I just remember the EC2216. It's a glue rather than a resin, but it shows that an epoxy can have a low modulus, like 340MPa shear @+24°C
https://multimedia.3m.com/mws/media/594118O/3m-scotch-weld-epoxy-adhesive-ec-2216-b-a.pdf
So maybe some mix with an stiffer epoxy will mimic the modulus of polypropylene.

This would need several trials and measurements, as one formulation with the proper modulus is unlikely available commercially. The chances to mimic the strength in addition to the stiffness aren't good neither. I'd definitely go the route of milling the prototype from massive polypropylene, as this seems possible.