PC-7

[jqavins]

I had a thing to fix (re-attaching the top end of the handle to a mug before the bottom end broke too) and thought

• JBW is a little too runny and would drip out of the joint, but
• Various epoxy clays and putties are too stiff and won't mush into place easily enough.

Looking at products in the hardware store I spied PC-7, which I hadn't used in so long I'd forgotten about it, but realized immediately that it's just the right thing for this application. It's intermediate in consistency between JBW and clay - a paste that mushes easily, and sags very little but doesn't run.

So, does anybody use PC-7 in rocketry? I should think it might be good for a few things like surface gluing conformal rail guides and large HP fillets, and that's surely not an exhaustive list. Is there some reason not to use it?

 

[caveduck]

I've seen this stuff on the shelves before and was curious. Found the tech specs on the website...from a strength perspective it is extremely poor. The primary filler is talc (and a lot of it), see the MSDS. This compromises the tensile and flexural strength a lot Here are the PC-7 values.


For reference, here's the tech data for good ol' West System 105/205. Note the tensile and flexural strengths are VASTLY higher. IIRC JBWeld is somewhere in between.

 

[jqavins]

Hmm, so not in physically demanding locations. But then a resin like WS 105/205 has even more of the fluidity that put JBW out of the running in my recent fix.

As an aside, it seems, from your data and memory combined, that WS → JBW → PC-7 have both decreasing fluidity and decreasing strength. If that holds, then the various clays and putties should be even weaker. I'll check on that later.