Does two part resin go bad in the bottle ?

In a word... Yes.

but it could also be a reaction to oxidation in the tin, age, humidity, the release agent, the moulds, if it's Monday...

or all of the above, have there been any changes since the last time you used the resin?

Jon_a_its

In a word... Yes.

but it could also be a reaction to oxidation in the tin, age, humidity, the release agent, the moulds, if it's Monday...

or all of the above, have there been any changes since the last time you used the resin?

I find it can last quite awhile, but the resin does seperate.  One needs to invert the bottle back and forth to remix it.  It is well known that one needs to stir/mix the resin and catalyst together well. It is not as well known that you have to remix the resin itself before mixing together the resin and catalyst.  Someone on this forum clued me to this several years ago, and I have successfully used quite old resin since.

Was the resin as old as you and I are, Don?

Just kidding, now a new question for this subject:

Why does epoxy give up when solvent-glue don't?

Does the chewing gum lose its flavor, on the bedpost overnight???

T_Terrific

Was the resin as old as you and I are, Don?

Just kidding, now a new question for this subject:

Why does epoxy give up when solvent-glue don't?

 

It is a different kind of bond.  Solvent glue really is akin to welding.  The cement melts the surfaces so the plastic actually fuses together. The solvent can eat through some limited amount of contamination on the surface.

Epoxy relies on a true adhesive bond.  With such surface bonding cleanliness is next to holiness.  Also, I have had a harder time with epoxies lately- it seems something is different in the chemistry of the styrene some kits now use.

Don Stauffer

 

 

T_Terrific

Was the resin as old as you and I are, Don?

Just kidding, now a new question for this subject:

Why does epoxy give up when solvent-glue don't?

 

 

 

 

It is a different kind of bond.  Solvent glue really is akin to welding.  The cement melts the surfaces so the plastic actually fuses together. The solvent can eat through some limited amount of contamination on the surface.

Epoxy relies on a true adhesive bond.  With such surface bonding cleanliness is next to holiness.  Also, I have had a harder time with epoxies lately- it seems something is different in the chemistry of the styrene some kits now use.

 

 

I would say it is both the kit and the epoxy's chemistries have changed.

Kits are typically "soft plastic" as compared with the rock-hard petro-based styrene plastic of the older kits. As I understand, the newer plastic uses a sugar-based product.

I remember when epoxy first came out, one ad showed a full-size car literally suspended in the air by an epoxy bond!

My experience is that for bonding plastic, the newer epoxy is a lot like the old Lindberg model cement sold at the local mom-and-pop store. It didn't bond well, and had a strange amber residue.

The other day, I unboxed a built-up plastic electrical substation structure fora railroad layout, that our big fat cat slept on, caving-in the box-lid, and all the epoxy bonds were broken, and the epoxy residue (which had turned from clear to amber-yellow) was easily scraped-off. Just like the old Lindberg plastic model cement.

Go figure.

Hi folks,

thanks for all the answers........the idea of putting it in the fridge sounds good.....I use it with super-glues and it does work.

thanks....

Urethane resins are so sensitive to moisture that the shelf life is very slim unless real precaution is taken.

The isocyanates in the yellowish component bond immdeiately with the slightest hint of water, that's the crust you get on the container lip and also what happens in your lungs and throat (if you've ever felt the tightness after mixing it).

Refrigeration makes zero difference, keeping it closed as tightly as possible and only opening it for the shortest period you can will prolong it. Smooth-On sells what they call a gas blanket, with is used to get an inert gas into the bottle and drive out the air.

I buy resin in large quantities and have kept it for extended periods be breaking it down from the gallon jugs into smaller units and keeping them in double sealed zip lock bags. 

I measure out the MDI (the clear part), add color, etc. open the iso (yellowish part), measure, close the container, mix, pour, vacuum and while it's getting to 29inches, I seal the bags on the iso. That way there's little exposure and it lasts. After about a dozen pours, the bottom of the inner bag fills with a crust of moisture bonded sand.

I know someone who spilled a gallon the iso in his shop. He thought he cleaned it up, but the next day his aquarium had a plastic crust on the surfae and everything was dead.

The Isocynate is similiar to the one in CA glue, that's why you can accelerate it by exhaling on it. The moisture in your breath sets it up.

See !

   You fellows wonder sometime about us stubborn older modelers not using certain things . Now you you know why I won't use Urethane type glues on anything if I don't have too .

 The stuff is just too dangerous !    T.B.

T_Terrific

The other day, I unboxed a built-up plastic electrical substation structure fora railroad layout, that our big fat cat slept on, caving-in the box-lid, and all the epoxy bonds were broken, and the epoxy residue (which had turned from clear to amber-yellow) was easily scraped-off. Just like the old Lindberg plastic model cement.

I have experienced the same thing. Too often I have seen epoxy joins pop over time, (not even a long time) and yellow. I am very disappointed with epoxy. I am migrating over to using melted sprue as a bonding agent. That stuff holds beautifully. And, if you make it with sprue from the same kit, the color will be a perfect match, if that matters.