Will UV Cure Through Polycarbonate, Glass, or Plastic?
Bonding behind a clear window or lens only works if the light can get through the material to the adhesive. Glass, acrylic, and polycarbonate each pass and block different UV wavelengths, pick the wrong band and the adhesive under a perfectly clear part never sees the light that would cure it.
A substrate can look transparent to your eye and still block UV. Ordinary glass and polycarbonate absorb the shorter, more energetic UV (the UVB/UVC end) and pass the longer UVA and visible. So curing through those materials means using a wavelength the material actually transmits, and matching an adhesive whose initiator responds to that same longer wavelength.
The SkyBeam gives you four LED bands, 365, 385, 395, and 405 nm, so you can pick the longer wavelength that passes through polycarbonate or glass and pair it with a matched adhesive. Where you want maximum flexibility, the SunSpot 2’s broad output includes the longer wavelengths too and cures whatever gets through.
Step by Step
- 1 Identify the substrate. Know what the light must pass through, glass, acrylic (PMMA), or polycarbonate. Each has a different UV cut-off.
- 2 Pick a wavelength the material transmits. Glass and polycarbonate block the short UV and pass the longer UVA/visible. Use a longer band, 395 or 405 nm on the SkyBeam, to get light to the adhesive.
- 3 Match the adhesive to that wavelength. Choose an adhesive whose initiator cures at the wavelength you are using. A 405 nm-cure adhesive behind polycarbonate works; a 365 nm-only adhesive behind polycarbonate will not.
- 4 Cure through the part and verify. Expose through the substrate and check the bond. A radiometer on the far side confirms real intensity is actually reaching the adhesive.
Common Pitfalls
- Assuming "clear to my eye" means "clear to UV", polycarbonate looks transparent but blocks short UV.
- Using a 365 nm-only adhesive behind a UV-blocking plastic, the light never reaches the initiator.
- Ignoring the far-side intensity, verify with a radiometer that enough energy is getting through to cure.
Questions
Does UV light cure adhesive through polycarbonate?
Only at wavelengths polycarbonate transmits. Polycarbonate blocks the shorter UV and passes longer UVA/visible, so use a 395–405 nm source with an adhesive that cures at that wavelength. A 365 nm-only adhesive behind polycarbonate will not cure.
Can UV adhesive cure through glass?
Yes, with a longer-wavelength source. Ordinary glass passes UVA and visible while absorbing short UV, so a 395–405 nm LED band or the longer end of a broad-spectrum arc, matched to a compatible adhesive, cures a bond behind glass.
How do I pick the UV wavelength for curing through a clear part?
Match the wavelength to what the substrate transmits and to what the adhesive’s initiator responds to. The SkyBeam’s 365/385/395/405 nm channels let you select the longer band that passes through glass or polycarbonate; verify the intensity reaching the adhesive with a radiometer.
