Watching CA glue dry...

[Scotts]

Originally Posted by arizonian

So the obvious question is, how or why does it stay liquid in a sealed container? That question applies to Loktite as well.

If I understand it correctly the sealed container has a bit of air in it so the contents will not harden. That is why the Loktite bottles are never full to the top.

Scott

[Lew Hartswick]

I've read that the plastic bottle is permeable to air. This always bothered me, as a water molecule is smaller that an Oxygen or Nitrogen so it seems the stuff would get "wet". :-)
...lew...

[dubby]

If that fella was around in '95 when I was in the process of failing college chemistry for the first time, I might not've failed as badly. Or maybe my mental state is just better prepared for it now. Nah... he didn't do math. Just explained it.


Anyhow, while he never really answered the "why doesn't it harden in the bottle" question, I think he sort of hit on it with the little penny test. Adding a big drop of the stuff takes longer to cure and the surface tension on top takes a while before it starts breaking down to allow other stuff in to accelerate the process. In a bottle, you have a barrier on the sides/bottom, and surface tension on the top with very little air inside. Just like in a soda bottle, the chemical reaction is gonna stop when the 'space' reaches eqilibrium by releasing the CO2 from the liquid. This is the other way around--the air only has so much of the free hydroxide to react with the glue. The reaction is still going on, but it can only go as far as the air will allow.

The hardener works the other way around, whatever it's made of is supplying more of the necessary hydroxide to get the job done quicker.

I may be wrong, but that's sorta what I'm getting.


For my project/experiment with the stuff I've still got a jig and a tool to make. I have some CA products in my amazon cart, we'll give it a test!

[Shade Tree Welder]

Originally Posted by Lew Hartswick

I've read that the plastic bottle is permeable to air. This always bothered me, as a water molecule is smaller that an Oxygen or Nitrogen so it seems the stuff would get "wet". :-)
...lew...

Is it... also polarity matters...

Oh and the bottle is not permeable.

[yooper]

Found this on youtube tonight , never seen anything like it
https://www.youtube.com/watch?v=ImLAmfM_AgA

[dubby]

Originally Posted by yooper

Found this on youtube tonight , never seen anything like it
https://www.youtube.com/watch?v=ImLAmfM_AgA

I ran across this when I was searching the subject originally. Part of the "home brew" hardener mix is the baking soda. You dissolve it in alcohol to make it sprayable. I would imagine the extra poured on powder is overkill, but also appears to add bulk to the glue joint kinda like a body filler.


I have still not attempted the project I need the CA for, but have made some strides towards it. A buddy and I spent a couple evenings cleaning off his wood carving CNC machine and getting it back into action. I haven't done my part to actually design the part or done the tool path. I really need to go test it and see how it cuts the kydex plastic before I get too ambitious. It may not have enough speed to keep the plastic from gumming up.