Hi Dale and Greg,
I am not sure, but I think that this is all a confusion over terminology, and that both Weldbond and Aleenes (and probably also Sobo) are all what Schaff and Pianotek call PVC-E. Here's my reasoning and supporting evidence.
In "The Glue Book," by William Tandy Young (Taunton Press), there is a section titled "EVA: A PVA Relative" (all of page 38). Young lists the attributes of Ethelyne Vinyl Acetate Glue, which sound identical to what we call PVC-E: "It has high initial tack and adheres well to a variety of materials, but dries to a soft, flexible film that you can jam your thumbnail into long after it has cured." The rest of the page sounds exactly like he is talking about what we call PVC-E, as well, as do other suggested uses for this adhesive throughout the rest of the book. So, I believe that what we call PVC-E can also be called EVA, or ethylene vinyl acetate. I think Ethylene is what the "E" stands for at the end of PVC-E.
Now, as for Weldbond and Sobo being referred to as PVA glues in their MSDS's, if you look up ethelyne vinyl acetate on Wikipedia, you will find a section that reads:
"EVA emulsions are
polyvinyl acetate (PVAc) copolymers based on vinyl acetate (VAM) internally plastized with vinyl acetate ethylene (VAE). PVAc copolymer are adhesives used in packaging, textile, bookbinding for bonding plastic films, metal surfaces, coated paper, as redispersible powder in
plasters and
cement renders...."
Maybe PVC-E stand for PolyVinyl Copolymer-Ethylene?
I believe that EVA glues are basically a subcategory of PVA glues with Etheylene. Young makes it clear that the PVA designation encompasses a wide range of chemicals; it is a family of chemicals, not one specific one. He does not call EVA a subcategory of PVA, as I am suggesting, but calls it a relative. The Wikipedia article, on the other hand, does say explicitly that EVA emulsions are PVA copolymers. And, the Young book does suggest mixing together EVA and PVA glues for certain glue applications, which implies that they extremely compatible.
From all of these clues put together, I feel fairly comfortable concluding that that what we call PVC-E is really a PVA with ethelyne vinyl acetate as one ingredient (the one that makes it rubbery), and that Weldbond and the others in question can be called EVA and/or PVA and/or PVC-E. That would explain these glues having exactly the properties we associate with what Schaff and Pianotek call PVC-E, while still being called PVA glues on their respective MSDS's.
None of the above is truly conclusive, and if there is a chemist out there who would like to weigh in, that would be great. But it is what I currently believe, based on the best evidence I have been able to gather thus far.
Joe DeFazio
Pittsburgh
P.S. - remember in all of this that the PVC-E glue sold in the plumbing aisle at Home Depot or Lowe's is a totally different adhesive (an adhesive for joining together PVC piping), and is not used in our field. That's nasty stuff!
Original Message:
Sent: 03-14-2011 02:36
From: Dale Probst
Here's a link to the MSDS for Sobo Glue which is a Poly Vinyl Acetate Copolymer Emulsio Weldbond the glue I was thinking was a PVC-E is actually a PVA.
As you found, Aleene's doesn't disclose.