Working with Sintra®
A different kind of PVC -- 14 July, 2002

The basics
Finishing & Conclusions

Finishing and Conclusions

Sintra® color choices
In many cases, you can easily accomodate your aesthetic desires by just buying pre-colored Sintra® (the color is uniform through the thickness of the material). If your creation will spend much time outdoors or under bright lights, however, you're probably best off sticking with white material. Colored Sintra® is not UV stable -- the colors will fade over time, and the material itself will get brittle. Contrast this to white Sintra®, which is relatively resistant to UV light; I've read that it will last 2-4 years outdoors. You should also consider sticking to white material (or at least light colors), if your 'bot will be involved in BEAM competition under Halogen lights. Due to Sintra®'s low softening temperature, your 'bot will warp fairly readily if lights are sufficiently near and / or bright.

Marking on Sintra®
You'll eventualy scribble on your material, if not as part of your 'bot's final look, at least while you're laying out lines to cut along. I've found in my tinkering that "permanent" markers work very well with Sintra®; pencils mark the material reasonably well (well enough for layout work); water-based markers are a complete waste of your time (water-based ink "beads" on the material). I wouldn't recommend attempting any sort of iron-on transfer (Sintra® softens at 150° F, while copier / printer toner won't generally melt below about 250° F). Adhesive stickers and tape seem to stick well to the material.

Painting Sintra®
For the most part, Sintra® takes paint well, with no primer being required. As for chemical compatibility, Sintra will tolerate the majority of paints well. In particular, I have tested out Sintra® with discount store spray enamel, and they get along just fine.

Edge treatment
If you're going to paint Sintra®, how you handle the edges can be a bit problematic (since they're porous). You'll need to do a bit of extra work on the edges of Sintra® if you want them to look as smooth as the face sheets after painting. I tried a number of edge treatments, following up with a quick coat of spray paint.


Top: painted Sintra® edges; from left, untreated, 2 coats of paint (sanded between coats with 220 grit sandpaper), white glue, cyanoacrylate, PVC pipe cleaner.

Bottom: painted Sintra® face sheet

As you can see, if you're going to paint Sintra®, doing nothing to the edges leaves them looking a bit rough compared to the faces. The best match is yielded by giving the edges a quick wipe with PVC pipe cleaner (although this needs to be done with some care, as this cleaner can scar the face sheets if you get too much on them). A simpler approach is to just apply two coats of paint, with a bit of sanding between them. A thin coat of cyanoacrylate or even white glue, followed by a quick sanding with 220 grit sandpaper can also be used as a quick sealant, if you prefer a glossier looking edge.

Sintra® is an affordable and promising BEAMbot building material, so long as you know and work within its limitations. It's easy to cut, easily shaped, fairly stiff for its weight, and is compatible with a number of adhesives and most commercially available paints.

For more information

A very good source of detailed information on Sintra® is the official manual, which I've downloaded (in PDF format) from Alusuise's web site and mirrored here.

As for web sites on Sintra®, the most informative one that I've found is Sintra® Online. It has tables of load capacities, material properties, etc. The site itself is written in Spanish, but the technical information tables are all in English. If you'd like to peruse the Spanish material, but can't read the language, just remember to use the fish...

The basics
Finishing & Conclusions

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