from:
http://www.backcountrytalk.earnyourturns.com/vb/showthread.php?3665-Bolt-on-Duckbutts&p=52658&viewfull=1#post52658
Originally posted by jasonq View Post
Pebax is an copolymer (alloy) of polyamide (nylon) and polyether. I believe several grades of nylon are used for different types of pebax, PA12 and PA11 are most used, ditto with the polyether side. and different ratios are used to control stiffness. Pebax is considered a TPE, thermoplastic elastomer, so isn't used when rigidity is the most important thing, but instead where flex is important.

SLS nylon, aka shapeways versatile plastic, is usually PA12 in powder form. When laser sintered, it generally ends up more brittle than if it was injection modeled, but is by no means weak or delicate. it will do fine, but if you were hiking and jumped off of a boulder and landed on a rock on the duckbutt, it would likely crack. Just walking around, no problem. And the nylon powder is usually white, and the resulting part also white. It is dyed after the fact, so the color is only skin deep, hence the white showing thru where the part was modified after dying.

HP MJF is also usually PA12, but the process is different from SLS, and can result in a less brittle final part. So you might have to jump off a slightly higher boulder to crack it. The nylon powder used is also white, however the monochrome MJF process uses a black fusing agent which results in a part the is black all the way thru.

both can also just be cut by sharp stuff, but that should be no worse than any other nylon.

for 3D printing duckbutts there really isn't anything better that those two options. unless going with a 3d printed metal, which is much more expensive.