Homebrew PCBs

Short version: More information on Poly Vinyl Alcohol.

Hi Stefan,

Thanks again for chasing up the MDSS of this glue.  You wrote:

> I haven't dealt with PVOH before, only with PV-Acetate, which this
> obviously is not.
> 
> PVOH is readily available and cheap, so it would not be difficult to
> try if someone just can't find the right glue.

I initially wrote that the Helmar "Acid Free" glue:

http://www.helmarusa.com/index.php?page=shop.product_details&flypage=vmj_naru.tp\
l&product_id=8&category_id=1&option=com_virtuemart&Itemid=7

might be similar to the Craft Smart Paper Gum I am using:

. http://www.miyartcrafts.com.au/Craft-Smart-Paper-Gum.html

However, in this Australian MSDS for the Helmar glue:

. http://arbee.com.au/images/DL_312_.pdf

it appears that the Helmar glue is a Poly Vinyl Acetate (PVA, lie common
woodworking glue) because it has a trace quantity of Vinyl Acetate
Monomer and because it is a "White to off-white viscous fluid with a
mild specific odor".  I guess it is PVA in a hydrocarbon solvent with
droplets of this emulsified in water, since they mention fumes.

The glue I am using has no smell.  Its drying is consistent with the
only solvent being water.

Here is some information about Poly Vinyl Alcohol (PVOH):

. http://www.wanwei-pva.com/polyvinyl-alcohol-PVA.htm
. http://www.wanwei-pva.com/PVA-Usage.htm
. https://biopak.com.au/products.php?id=28

There are multiple grades of it.  Here is some on eBay - "DuPont Elvanol
Type 51-05":

. http://www.ebay.com/itm/370629221979

"Water solubility increases as the molecular weight decreases."

. http://www2.dupont.com/Elvanol/en_US/products/index.html
. http://www2.dupont.com/Elvanol/en_US/assets/downloads/elvanol_51_05.pdf

This is a "partially hydrolized general purpose grade".  Viscosity 5.0
to 6.0 cps.  "Elvanol\ufffd 51-05 is suggested for evaluatin in temporary
protective coatings and pigmented coating of paper.  It has additional
applications in remoisturizing adhesives, temporary binder for
ceramics, paper adhesives, cold-water-soluble film, photosensitive
coatings, binder for joint compounds and texture coatings and as a
soil anti-redeposition agent."  The graph in the datasheet goes up to
16% concentration in water.

Here is some more:

. http://www.ebay.com/itm/320941262472

"Celvol Polyvinyl Alcohol Grade 540. This a partially hydrolysed grade
of PVA/PVOH used to make adhesives and to coated papers and textiles. It
is 87-89% hydrolyzed with a viscosity of 45 cps.  Make your own wood
glue! Just add it to hot water."

Celvol information:

. http://www.sekisui-sc.com/products/selvol/index.html
. http://www.sekisui-sc.com/products/selvol/properties.html
. http://www.sekisui-sc.com/products/selvol/applicationandenduse.html
. http://www.sekisui-sc.com/products/selvol/productline.html
. http://www.sekisui-sc.com/products/selvol/solutionpreparation.html

The last page recommends no more than 7% Celvol 540 for dissolving in
hot water at 85C.  Its viscosity is 45.0 to 55.0.

The lower viscosity grades such as 513 (13.0 to 15.0) can be dissolved
at a higher concentration, such as 15%, which matches the 10 to 15%
range specified in the Craft Smart Paper Gum MSDS.

My initial impression is that the Elvanol 51-05 would be a better choice.

 - Robin  http://www.firstpr.com.au/pcb-diy/