I still think the key is "inadequately supported", rather than " laminated".
Contributor
I still think the key is "inadequately supported", rather than " laminated".
Member
Who is "they"? PVA wood glues are typically used for cold pressing HPLs onto sheet materials.Originally Posted by Peter Quinn
Member
Yes, I agree. However, if you laminate both sides of a piece of plywood or MDF rather than one side, it will be much more resistant to warping if not adequately supported. There are two reasons that I can think of for this. First of all, the plastic laminate acts like the skins of a "torsion box" if you are familiar with that type of construction. The second reason is that both sides will absorb and release moisture at the same rate during radical and sustained changes in relative humidity which prevents differential absorption and expansion/contraction rates. The same is true as if you paint or varnish one side or both.
The warped router table top I mentioned in my first post was constructed of 2 layers of 3/4" MDF glued together with the top of my table saw as the reference surface during gluing. When I was done, the top was flat +/- 3 or 4 thousandths over the whole top as verified by a precision straight edge and feeler gauge. After a year in my non climate controlled shop, the top had cupped so that there was in excess of 1/4" of gap between a straight edge and the table surface when it was placed across the table in the long (32") direction. A replacement top built in exactly the same manner, mounted in the same place, and used in the same environment but laminated on both sides has been in service for maybe 10 years and hasn't warped enough to measure.
Single thickness plywood is quite flexible and can be forced to remain flat if the right support and fasteners are used, regardless of changes in humidity and temperature.
Member
By who? I don't do a lot of laminate work, but enough that I buy 30 lb canisters of contact cement for it. I've never heard of anyone using PVA on laminate? To my knowledge PVA is used for veneers and contact for laminates. I'm not saying someone somewhere doesn't do it, but I would think it's the exception and certainly not typical around me anyway?
JeffD
Member
I have been around a lot of cabinet shops, done business with multiple counter top fabricators and done a fair amount of laminating myself and I have never heard of anyone using PVA glue to attach plastic laminates. The only adhesive I have seen used commercially is solvent based contact cement. PVA might work but I'm not willing to try it.
Member
Wood glue is actually a much better adhesive for HPL. In fact, Titebond manufactures a PVA adhesive specifically for cold pressing HPLs http://www.titebond.com/product.aspx...3-ec9e5af5fca4
Contact cement is fine for counter tops and irregular shapes. Cold-pressed PVA is preferrable for doors and flat work.
Member
That's an interesting looking product, but it's not your typical wood glue…not even totally sure it's a PVA? Also looks like one may need either a pinch roller or a vac press to utilize it correctly? Not sure a J-roller will get you to the higher end of the PSI spec'd out? Having said that it does look interesting enough to research a bit more. Certainly a LOT more effort involved than spraying contact, but could be good in the right situation.
JeffD
Member
I tried a water based adhesive once that was supposed to be especially made for gluing plastic laminates onto plywood and MDF. It was not Titebond brand. I think it was Weldwood. I found it to be completely unsatisfactory. The stuff simply wouldn't hold. I have always had good luck with solvent based contact cement and have no reason to stop using it. Apparently, neither does the counter top manufacturer with which I have done business.
Last edited by Art Mann; 09-17-2014 at 11:53 PM.
Contributor
It's possible your Weldwood UF had gone bad. It is a good " permanent" laminate glue compared to contact cement which
is usually rated at 8 to 10 years of holding by its manufacturers.
Member
Titebond HPL is PVA. The main difference is the tack speed being a bit slower for cold-pressing rather than the fast tack kind for pinch rolling. Any PVA will work for laminating HPL, it just depends on how much open time you need to get everything in the press or roller.
Also no VOCs!
Member
I don't get a lot of demand for doors with HpL of the cabinet size. I've seen it in large panel format in commercial situations, hotels, hospitals, etc. How do you deal with the squeeze out on edges using PvA in a press? Franklin directions say wipe with wet rag...kind of hard to do through a bag or piles of clamps on a traditional press. Or "sand off with abrasives when dry....great for hardwood edges....not so much for HpL edges. I don't care for sanding scratches on my door edges. Or they have those really sexy plastic edges you can route in a kerf and stuff them on....doctors office type stuff? Interesting that it holds the HPL, but how do you actually work with it ? I'd normally do edges then faces, how to keep it clean? The they on the no contact cement for veneer is almost everybody I've ever worked with and every thing I've ever read, just doesn't hold the veneer. Interesting that pva holds HPL, but then you sort of have to cover both sides no?
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