Epoxy cure process

[Figment]

(yeah, this could fall under "Boatbuilding Techniques" or some other category, but the Nerdery has been quiet lately)

I'm much more of a physicist than a chemist. How does epoxy cure?

Is it like concrete, which achieves most of its ultimate strength in the first 7 days, but can take ten times that long to truly fully cure?

Or does it cure as much as it's ever going to cure in the first 24 hours or so?

Or is it entirely about temperature?
Is the epoxy I lay this week in 40 degree temperatures only really mostly cured, to complete the process and really "bake out" on the first 100-degree July day?

Does it matter when a "postcure" bake-out happens?
Does it need to happen in the first 48 hours to have an effect, or can it be weeks or months later?

What's my record for the highest number of loosely-associated questions in one post?
How many M&Ms can you fit in your mouth before you lose your ability to chew them?

[Tim]

Here's a West System paper that covers your questions fairly well.

Cold Temperature Bonding, # 000-915

How many licks does it take to get to the chewy center of a Tootsie Roll pop?

[dasein668]

How many licks does it take to get to the chewy center of a Tootsie Roll pop?

Three.

Doesn't everyone know that?

Sheesh.

[Figment]

For those too lazy to read the West paper (me, usually), some answers in bold below.

Is it like concrete, which achieves most of its ultimate strength in the first 7 days, but can take ten times that long to truly fully cure? not really.

Or does it cure as much as it's ever going to cure in the first 24 hours or so? More like 72 hours, but yeah.

Or is it entirely about temperature? Bingo.
Is the epoxy I lay this week in 40 degree temperatures only really mostly cured, to complete the process and really "bake out" on the first 100-degree July day? no, cured is cured after 72 hours or so.

Does it matter when a "postcure" bake-out happens?
Does it need to happen in the first 48 hours to have an effect, or can it be weeks or months later?
yes. must be within a week or so.
Essentially, temperature during cure (including "post-cure bake") affects strength, but only for the first week or so. After that, temperature has no affect on strength, aside from melting of course.

What's my record for the highest number of loosely-associated questions in one post?
How many M&Ms can you fit in your mouth before you lose your ability to chew them? Still waiting for an answer on this one!

[CharlieJ]

Well- yeah - BUT.

If you lay on a layer of fiberglass during cooler weather, fill it nicely and finish it, and then some months later roll that boat out into the sun, you definitely begin to see some very slight "shrinkage" of the epoxy. It can cause what is known as "Print-through" of the glass weave, showing on the surface.

So while it may totally cure, it may not totally stabilize until after getting hot that first time.

[Tim]

How many M&Ms can you fit in your mouth before you lose your ability to chew them?

I have filed the paperwork to apply for a grant so that I can purchase the M&Ms required for the exhaustive testing that this will require.

Of course, the test must be performed with both regular and peanut M&Ms. And, for the sake of continuity, I suppose all the other variations, even if they're the same size as the regular M&Ms, must also be tested--though we all know those aren't "real" M&Ms.

Obviously, I will have to start with one, then two, and so on until I reach the ultimate number. I'll let you know when I receive my grant money for this important research.

[Tim]

How many licks does it take to get to the chewy center of a Tootsie Roll pop?

Three.

Doesn't everyone know that?

Sheesh.

I heard the owl sold out for a book deal and was subsequently discredited, however.

[dasein668]

I heard the owl sold out for a book deal and was subsequently discredited, however.

You've just ruined my childhood, Tim. ::weep::

hehe