What is the compatability of HDU used with PVC. I have an HDU sign that will have some dimensional trim elements on it. The pieces will run the entire length of the sign - approximately 10 ft. At Home Depot I found some trim pieces that are exterior, paintable cellular vinyl PVC and they would work great for what I need, saving me the hassle of cutting and routering them by hand (don't have a computer driven router). I would glue or silicone them to the HDU. I guess what I'm wondering is if there is a big difference in expansion/contraction. The HDU and PVC would both be painted a dark charcoal grey. It is going to be a fascia sign on a north face so not much problem with heat absorbtion from the sun. Any experience, caution or tips?
[ October 25, 2003, 08:52 PM: Message edited by: Dan Seese ]
Posted by Joe Cieslowski (Member # 2429) on :
Dan,
Good question.....I Dunno
Sign Foam and Prescision Board are merchants here and you can ask them this sort of question through their web sites.
Sorry I can't be of more help.
Joe, Makin Chips and Havin Fun!
Posted by Joe Rees (Member # 211) on :
That's a dang good suggestion Joe. for what it's worth Dan, I've been doing what you mentioned, along with pushing the envelope with all kinds of other wacky combinations, successfully for some time. It never really occured to me to ask the manufacturer for their input. (even if they said no, I'd try to find some how to do it anyway, just to prove them wrong).
Posted by Ray Rheaume (Member # 3794) on :
Dan,
Maybe a mechanical fastening system might be the way to go. Not quite sure what difficulties it would pose in your specific situation, but I often find when a chemical concern arises, eliminate the chemicals. Sometimes some predrilled holes, a few well placed wood pegs, screws or even a with a minimal amount of adhesives can be effective. They can bridge the expansion differences that a direct adhesion may not.
Just a few thoughts in another direction... Rapid
Posted by Ian Stewart-Koster (Member # 3500) on :
Danthonia Designs (see Signcraft from last year)laminate PVC to HDU 'all the time' more or less. But they have a big roller press, and maybe have worked out a special glue to accommodate thermal expansion differentials. I'm just guessing that. Could be worth a query to them.
Posted by Dave Sherby (Member # 698) on :
I would research this first with the various manufacturers. HDU manufacturers boast about the stability of HDU, which makes me think it does not expand and contract much. On the other hand I've read the suggestions on installing PVC from the manufacturers, and they recommend oversize holes to allow for expansion & contraction.
HDU has a shearing strength only equal to the strength of the bond from one HDU cell or bubble to the next. Whenever I have had any glue failure between HDU and whatever, there has always been a very thin layer of HDU still attached to the glue. This tells me that if enough force is applied, the cells of HDU will seperate from each other.
If a length of PVC is glued to HDU, and if there is enough difference between the expansion of the HDU and PVC, and if the thermal expansion of one of the products is strong enough, there will be a failure of one of the products at the glue line and in my opinion it would be the HDU.
If this is the case, a loose mechanical connection would probably be in order.
Posted by Dave Utter (Member # 634) on :
I did some trim pieces a few years ago that were 10 foot long strips of closed cell foam, 2" thick, with strips of dark blue SG acrylic laminated to them with Sonaborn construction adhesive. WARNING! don't try this at home! The expansion of the acrylic literally ripped big chunks of the foam out and looked like a roller coaster. It wasn't pretty! hehe. In your situation, I would imagine, the foam would have very little expansion, and the PVC would have more, to some degree, resulting in a similar situation. I'm by no means an expert at this, but I can say that by trial and error, I know what NOT to do! hahaha Oh well, live and learn.
Posted by Dan Seese (Member # 3705) on :
Thanks for the suggestions & insight. I'll call Sign Arts or Costal Enterprises today and get their input. I may just go on the safe side and form the trim pieces myself out of HDU. I hate going back and fixing a sign because of short cuts at the front end. Really appreciate your help.
Posted by Glenn S. Harris (Member # 2190) on :
I saw an HDU sign with PVC elements today. The PVC was attached with some kind of little nails or rivets or something. Didn't look great up-close. There's ana excellent article on PVC in the new SignCraft. Aparently, PVC expands & contracts quite a bit.
Posted by Kent Smith (Member # 251) on :
The expansion/contraction coefficient of PVC should roughly be 7-10 times that of HDU, depending upon the plasticizer content.
![[Dunno]](graemlins/dunno.gif)
![[Eek!]](eek.gif)
Oh well, live and learn.