Any boffins here?

[Chrispy]

Any chemistry/physics boffin up for a challenge?

 

[SVB]

Go on, try us...

 

[Chrispy]

Pva glue and squeezy bottles.

 

[Alpha-Dave]

Do you want more than Wikipedia can supply? It’s usually pretty good for chemistry/physics, less so for celebrity or commercial facts.

 

[Chrispy]

Half empty bottles in particular.

 

[Alpha-Dave]

PVA is rarely purely a polymer in water, usually there are all sorts of additives to give stability. How those separate is an issue.

 

[Chrispy]

Lets explain, you pick up a half empty bottle turn it over, wait for glue to run to nozzle and squeeze, so far so good, now here the problem you have sufficient glue so you stop squeezing and stand bottle upright, this is where it starts going wrong, glue carries on pushing out and runs down the side of bottle, how come?

 

[Myfordman]

The warmth of your hand grip has raised the pressure inside slightly.
Buy a glu-bot and wave the problems away. Quite reasonably priced at peter seftons - usual disclaimer

 

[Benchwayze]

Maybe the nozzle is too fine and air can't get back into the bottle?

Maybe, I said! :mrgreen:
I cut the nozzle to about No 8 dia, and use a No. 8 screw as a 'stopper'.

John (homer)

 

[Alpha-Dave]

It shouldn’t happen because the fluid is incompressible and you have stopped applying pressure. Therefore because we observe the effect happening there must be more than the given problem statement. Additional information would be required, including:
Are the external conditions constant: temperature and pressure? Could the squeezing action be initiating something that could cause additional expansion of the fluid or gas in the head-space?
What is the nozzle geometry? Is it a glue-bot or simple nozzle or a closeable nozzle with complex internal geometry?

 

[Droogs]

you have a leak in the seal between the bottle and the nozzle thread

 

[Fitzroy]

And if you’re interested in some rough numbers.

Holding bottle increases temperature by say 0.1degC. In rough terms that will raise pressure by 0.1/293 (Kelvin) or 0.034%. 1atm is c. 10meters of water head of which .034% is 34mm.

So long has the depth of glue in the nozzle is less than 34mm it will push out all the glue in the nozzle.

If you hold it long enough for the temperature to raise 1 degC it’ll be 10 fold greater.

Fitz.

 

[Chrispy]

Just a regular glue bottle.

 

[Trevanion]

Just squeeze the bottle the other way (turn the bottle 90 degrees in hand to squeeze to protruding parts of the bottle) when you put it upright, draws it back in.

 

[lurker]

Practical (free) solution
Buy this

https://www.waitrose.com/ecom/products/ ... lsrc=aw.ds


Use contents
Rinse
Fill with pva

 

[gregmcateer]

Or save yourself even more money and buy this, (which in our family blind trials won the taste test!);
https://www.aldi.co.uk/squeezy-mayonnai ... 2003817200

 

[samhay]

I'm a physical chemist. Even do the bit of research on glue.
This hasn't really equipped me to answer your question. Will go and do a bit of an experiment and get back to you. Suspect the answer will involve surface tension, bubbles and trapped air though.

 

[Chrispy]

And if you’re interested in some rough numbers.

Holding bottle increases temperature by say 0.1degC. In rough terms that will raise pressure by 0.1/293 (Kelvin) or 0.034%. 1atm is c. 10meters of water head of which .034% is 34mm.

So long has the depth of glue in the nozzle is less than 34mm it will push out all the glue in the nozzle.

If you hold it long enough for the temperature to raise 1 degC it’ll be 10 fold greater.

Fitz.

But surely the volume of glue I have squeezed out would counteract any expansion of air and cause a slight vacuum in side when squeezing stops.

 

[memzey]

Could the capillarity of the PVA be playing a part in this?

 

[Rich C]

And if you’re interested in some rough numbers.

Holding bottle increases temperature by say 0.1degC. In rough terms that will raise pressure by 0.1/293 (Kelvin) or 0.034%. 1atm is c. 10meters of water head of which .034% is 34mm.

So long has the depth of glue in the nozzle is less than 34mm it will push out all the glue in the nozzle.

If you hold it long enough for the temperature to raise 1 degC it’ll be 10 fold greater.

Fitz.

But surely the volume of glue I have squeezed out would counteract any expansion of air and cause a slight vacuum in side when squeezing stops.

It should, and does in my glue bottle at least. I stop squeezing and the glue in the nozzle is sucked back into the bottle by the bottle trying to return to its natural shape.