Is There a Durability Difference Between MJF PA12 Black and SLS Dyed-Black Nylon for an Outdoor Bracket?

For an outdoor-use bracket, the color process matters less than you'd think. The bigger durability factor is UV exposure on bare nylon in general. It degrades both MJF and SLS parts over time regardless of how the black got there.

MJF PA12 comes out a natural dark gray-black straight from the build, a result of the fusing agent and process rather than an added dye. SLS nylon is naturally a lighter off-white or gray and gets dyed black afterward in a separate finishing step, soaking color into the surface and near-surface material. That's a surface-level distinction, not a structural one. It doesn't change the bulk mechanical properties underneath.

Where the real durability question is

Unfilled nylon isn't inherently UV-stable, printed by either process. Sunlight breaks down the polymer chain near the surface over months of outdoor exposure. Chalking, surface embrittlement, gradual color fade. On SLS, that fade is more visually obvious because the black is a dye sitting in the surface layer. As that layer degrades and sheds, the lighter base material underneath becomes visible, and the part looks like it's fading unevenly. On MJF, the color comes from deeper in the process, so UV degradation shows up more as surface haze or roughening than a dramatic color shift, even though the underlying material is breaking down at a similar rate.

So SLS dyed black will look worse faster, cosmetically, because the color loss is more visible. MJF black holds its appearance a bit longer but isn't actually more UV-resistant underneath. Both are the same base nylon chemistry exposed to the same sun.

What actually protects an outdoor bracket

If the bracket is genuinely living outside for an extended period, don't rely on either process's as-built black to carry you through years of exposure. A UV-stable clear coat or a true UV-stabilized dye applied after the build holds up better than either process's native finish. That's a step added after the part comes off the printer, not a property of choosing MJF over SLS.

Worth separating from the color question: outdoor brackets see thermal cycling and moisture along with UV. Unfilled nylon picks up ambient moisture over time, which changes its dimensions and stiffness slightly. That's a property of nylon generally, not something tied to which process printed it. If the bracket is load-bearing as well as outdoor, size it with that moisture-driven stiffness drop in mind rather than assuming dry, as-printed properties hold indefinitely.

If color retention over years outdoors is the spec actually driving this, treat it as a coating question, not a process-selection question between MJF and SLS. The process changes how the black looks on day one, not how long it survives a summer on a roof.