Ray,
I’m not surprised you missed the clear masking on the Sintra Sheet. I’ve been fabricating items out of plastic since I started in the business in 1980 and I’ve done the exact same thing! Clear masking on clear acrylic is easy to miss, it is hard to tell which side of the sheet it is on after you remove the masking from one side. At least the clear masking on the Sintra sheet is shinier than the generally matte finish of the unmasked surface. Easier to spot when you know it is there but also easy enough to miss. I glued a bunch of white foamed PVC pieces for a job for GOOGLE and when I picked them up to glue the other side all of the pieces I glued stayed on the table… whoops! The solvent cement just doesn’t work on the clear poly-masking…
As for the concern of using foamed PVC outside… First, the good news is that it is totally impervious to moisture damage and if made correctly will last a very long time. Some members of the Bay Area Garden Railway Society have plastic buildings (both foamed PVC and Acrylic) that have held up for over 15 years that they made themselves after attending one of my clinics. The biggest problem with plastics is they tend to expand and contract quite a bit with temperature variations. And dark colored surfaces tend to absorb more of the sun’s energy and thus heat up more causing the most movement. Now most of our buildings are quite small compared to the large signs that the foamed PVC is used for and where the expansion of the sheet has the most effect. This thermal movement of the sheet is something to always keep in mind when designing a building. I always recommend that interior reinforcements, in the form of floors and roofs, be glued inside of our model structures to help hold the sides flat and combat any heat caused warping. I also recommend that the structure’s walls be made out of 6mm (1/4") thick material at a minimum with the thinner gauges being used only for detail. I am aware of the 3mm (1/8") thick being used for entire buildings up North in Washington where the temperatures are generally cooler and I don’t see a problem as long as the buildings are small. Larger buildings need to use the thicker material and especially if the buildings will be painted a dark color, I would recommend using extra reinforcements to combat the warping caused by heat. As far as the UV degradation issue, the PVC will hold up forever as long as it has a decent exterior grade paint job. What I tell people to do is to prime with a good automotive primer that will etch into the surface and then to paint with good old high grade exterior house paint. You can get color samples mixed at your local hardware store for minimal cost and the paint will last a very long time.
A generic term for this type of plastic is Foamed PVC. It goes by many names with Sintra, Komatex and Celtec being the most common. TAP Plastics stocks Komatex for our thinner sheets because of the wide range of colors. We stock Komacel in the 3/8" and 1/2" thickness only in White… To read more about Komatex visit the manufacture’s website: http://www.kommerlingusa.com and read about Celtec at the Vycom website: http://www.vycomplastics.com/product-families/celtec/
Russ Miller…
2016 NGRC Chairman
Past BAGRS President
Manager TAP Plastics, San Leandro
