On 25/10/2020 12:19:55, jkn wrote:
On Sunday, October 25, 2020 at 12:03:30 PM UTC, The Natural
Philosopher wrote:
On 25/10/2020 11:19, jkn wrote:
Hi all - slightly stupid question perhaps...

I see plenty of reference here re. the use of 'PVA' as a sealer.
I have some myself, a 5L container of 'Contractors PVA' bought
from Toolstation or similar and used for a few general projects
around the house.

Until recently I thought that this PVA was just an industrial
version of the same "PVA glue" you can buy in stationers,
supermarkets etc, as a paper glue, and in DIY shops as a wood
glue.

But I now realise that they have (or tend to have) different
chemical formulations. For a start, you can't use Contractor's
PVA to make children's slime. Disaster!

Looking into this a bit further:

- PVA glue: Poly Vinyl *Acetate* - Contractors PVA sealer: Poly
Vinyl *Alcohol* (I think)
Ni. Its just dilute Poly Vinyl Acetate

Not true, I think. See eg:

https://www.preservationequipment.co...cohol-Adhesive

{{{ Polyvinyl alcohol is extremely soluble in water for
reversibility and remains flexible as it ages.

Also known as PVA, not to be confused with Polyvinyl Acetate
adhesive, Polyvinyl alcohol adhesive is said to be somewhat more
reversible than PVAc (polyvinyl acetate).

Polyvinyl Alcohol (PVA) liquid 15 % in demineralised water. Can be
used for: Modification of dispersion glues, manufacture of paper
glues and glues which can be remoistened. Protective gel for the
emulsion polymerization, raw material for finishing and textile
glaze, binding agent for the surface processing of paper. }}}

Also see my evidence that only 'PVA Glue' can be used to make
children's slime - and it's not just because of any dilution
differences

This is something I have looked into as well and find the subject
confusing. Many recipes mention Elmer's glue which according to:
https://en.wikipedia.org/wiki/Polyvinyl_acetate
is Polyvinyl Acetate. The wiki entry for Elmer's glue isn't helpful.

https://en.wikipedia.org/wiki/Polyvinyl_alcohol
says, "PVA is prepared by hydrolysis of polyvinyl acetate", which if
you look up is generally with Sodium Hydroxide.

Most slime recipes suggest borax, or sodium carbonate or sodium
sesquicarbonate.

I'm therefore wondering if the glue recipes are actually where start off
with PolyVinyl Acetate and end up with PolyVinyl Alcohol.

To confuse things further I believe the PVA from building type merchants
is PolyVinyl Acetate with PolyVinyl Alcohol as a thickener.

BICBW