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  • Topic: Sintra PVC warning

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    • October 9, 2017 11:05 PM EDT

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      Sintra PVC warning

      I just encountered an unusual problem with some Sintra PVC foam board I bought back in July. I started using some of the 3mm sheets a few days ago, and had a structure partially assembled. Then it started coming apart. The glue I normally use was not adhering to it at all, which is really weird. So I tried sanding the surface, and discovered it had a super thin layer of clear vinyl or something on one side! In all the years I've been using Sintra I've never seen that before. 

       

      I couldn't tell by looking at the sheets that there was any kind of coating, and there was nothing in the ordering or packaging info that mentioned it. But apparently it's supposed to be peeled off. 

       

      I had some 1mm sheets in that same order, and those did not have the peel off coating. 

       

      Anyway, I just thought I should give you guys a heads up on this potential issue. 

    • October 10, 2017 8:52 AM EDT
      • Your Host in Littleton, MA
         
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      That's good to know to look for.  I've never seen that, and I use a ton of PVC board.  Thanks for the heads up!

      ____________________________________

      Bob, your Site Host and Benevolent Dictator.

    • October 10, 2017 10:03 AM EDT
      • Settle Down Boomer ,
         
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      I have seen this before and there are a couple reasons why. Usually I see it on the UV treated board for outdoor use (why I don't know). But sign guys often order the stuff (wrapped) as it protects the side they want to face out. You can also get both sides wrapped but most sign guys only use one side. My guess is either you got the treated stuff or perhaps it was cut from a sheet that was ordered wrapped.

    • October 10, 2017 2:33 PM EDT
      • Marysville, Kansas
         
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      Ray Dunakin said:

       Then it started coming apart. 

       

      So did you work your Ray Voodoo Black Magic and turn it into some amazing collapsing structure?

    • October 10, 2017 2:46 PM EDT
      • Vail, Az
         
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      You probably shouldn't let it get over 112* F ... I was given some (I think)(I know it was given, not sure of what) and it warped ...

      ____________________________________

      John

       

      The older I get, the less I know, please don't make me prove it.

       

       

    • October 10, 2017 3:06 PM EDT
      • Amesbury, Massachusetts
         
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      Ray - Ever Since the addition of direct flat bed printers (3-4 yearsago) the sign business has been complaining about trying to print on PVC (sintra/Komatex) sheets that have dust and oils on them from handling.  They now ship with a masking on one side (Yeah).  Also for those that are planning on using it for outdoor structures there is a difference in Interior and Exterior grade PVC Expanded Foam Board

       

      Komatex - Interior - Weather resistant

      Komacel - Exterior use.

       

      Scott

    • October 10, 2017 7:26 PM EDT
      • Candlewood Valley, Connecticut
         
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      @Scott - You want a good deal on a 10Ft MacDermid flatbed printer?  Come get it out of my shop and you can have it. It sat for several months with ink in the heads while we were waiting for parts. Put well over $5K into it (new CPU & lots more) only to find the heads were shot due to clogged ink.  New heads were about $20K so we pulled the plug and it has been sitting in my shop for over 3 years and in my way. For anyone who has the patience to rebuild the heads it's a steal. Old technology though.

      This post was edited by Jon Radder at October 10, 2017 7:27 PM EDT
      ____________________________________

      www.cvsry.com www.cvsry.com

    • October 11, 2017 1:37 AM EDT
      • Castro Valley, CA
         
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      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

    • October 11, 2017 8:46 AM EDT
      • Burke, Virginia
         
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      Russ,

      I really do thank you for all the help you have provided to me over the years.  Following your advice, my buildings have more than survived the elements.  My first acrylic building was Matheson Textiles, a large (42" x 24" base) building.  It was built in 2007 with acrylic sheets cut by TAP Plastics.   It still looks as good as the day it was put outside.  

      I really liked having the acrylic cut by TAP plastics as it insured that every piece was a LOT more square than if I had done it.   Plus everything was always packed so well; I was even able to use the cardboard that the sheets came in as sides for a quick prototype of a building.

      I have implemented your suggestion of ventilation in every building that I have built since that time.   Most of those buildings have been created using some sort of plastic.   

      Thanks again for all of the assistance.

      ____________________________________

      Bruce

      http://jbrr.com/

       

    • October 11, 2017 9:37 PM EDT

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      Yeah, the clear peel-off stuff is slightly shinier than the Sintra, so if you know what to look for, it is possible to detect. 

      I had emailed the supplier about this yesterday, and received their reply today. They said that sometimes the 3mm sheets come from the mill that way, for whatever reason. 

       

      Anyway, I was able to reassemble the affected structural segments, after removing the coating.

       

       

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