Isopropyl Alcohol Resistant Paint

Question

Which paint binders are most resilient to IPA?

Background: I'm looking for an IPA-resistant spray paint to coat a 3D printed model composed of a high-performance stereolithography resin MSDS.

"Binder plays the role of an adhesive enabling the paint to stick to the surface and holds other components to itself. The binder dissolves in the solvents used and the thinners reduce the viscosity of the resultant mixture. Binders used in the paints are Alkyd Resins, Acrylic Resins, Poly Vinyl Acetate, Chloro Rubber, Epoxy Resins, Poly Urethane Resins, and so on." Quora

Paints I'm considering:

• Modified Alkyd: Rust-Oleum High Performance Enamel Spray TDS
• Modified Alkyd: Montana MTN94 TDS
• Acrylic Modified Alkyd: Rust-Oleum Painter's Touch TDS
• Epoxy Ester Modified Alkyd: Rust-Oleum Appliance Epoxy TDS
• Polycarbonate: Tamiya Polycarbonate MSDS

Thank you so much for your time and help!

Answer 1

The Hansen Solubility Parameters is a useful tool in the context of solubility of paints, glues and polymers in general. Basically every polymer is represented by a sphere in $\mathbb{R}^3$ where (most) solvents lie inside the sphere and (most) non-solvents lie outside. The polymer you need should have its center far away from IPA coordinates, specifically farther than its radius.

The HSP parameters of 2-Propanol are $(15.8,6.1,16.4)$; to get an idea, PVC and PVAc (mentioned in the polycarbonate paint) spheres are respectively $(18,8.8,2.2,r=8)$ and $(17.6,2.2,4,r=8)$. IPA should be a non-solvent for both.

It's hard to say what would happen with proprietary blends, even if broadly categorized as (modified) alkyds: different alkyds can have wildly different spheres, the modification just adds even more complexity. That said, seeing Toluene and Acetone in the list of solvents for the same polymer makes me worry that its solubility sphere is big, and if the sphere is too big it will include IPA.