J-B Weld "Steel Reinforced Epoxy" resin

Images made through a microscope. All subject types.

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rjlittlefield
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J-B Weld "Steel Reinforced Epoxy" resin

Post by rjlittlefield »

Image

Image

This is the "STEEL" resin component of "J-B Weld(TM) Original Cold-Weld(TM) Formula Steel Reinforced Epoxy", squeezed as thin as possible between slide and cover slip, and illuminated from below with an ordinary brightfield condenser.

I don't know about anybody else, but I'm having a little trouble believing that there's anything resembling metallic ferrous alloy in this stuff. It does work well, though. It also produces an interesting surface texture when the cured epoxy is fractured. That's what prompted me to look at the uncured resin in the first place.

Top image is cropped from a single frame, showing an area about 0.7 x 0.56 mm. Bottom image is an entire frame of a short stack, subject area about 2.2 x 1.5 mm.

As it turned out, the main value of the stack was only to correct for some curvature of field in the objective. This goo is so inhomogeneous that only the stuff near the cover slip is seen sharply anyway. It's like trying to look through stippled glass.

Shot with a Edmund Optics Nikon Finite Conjugate 10X NA 0.25, direct projection onto a Canon T1i (15 megapixels, APS-C format).

Here's what the package looked like. See, the black tube is even labeled "STEEL", despite that it's full of brown crystals. The slide with squeezed-thin STEEL component is sitting between the two tubes.

Image

--Rik

Jacek
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Post by Jacek »

very interesting

JL
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Post by JL »

Those red "crystals" look like Hematite (Fe2O3), a natural occurring iron oxide. I do not know if this mineral is added to the epoxy and then considered as steel. Anyway it really look interesting.

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Post by carlos.uruguay »

interesting

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Post by rjlittlefield »

Thanks, guys.

JL, thanks for the suggestion of hematite. That would make great sense, and I can certainly understand the company's choice of how to spin their labeling. After all, who would buy an epoxy labeled "Reinforced With Rust" . . . even if it works really well for the job. :)

--Rik

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Post by Chris S. »

Hematite doesn't work for me--the fracture angles seem much too sharp. The hematite I've hammered on crumbles, rather than shatters, pretty much the way one would expect for rust. Also, the color looks wrong to my eye. (It's been a long time since minerology lab back in college. But breaking rocks with hammers, then closely examining the freshly-exposed surface was a big part of what we did, and hematite is pretty common stuff.)

However, the MSDS sheet, section three, for the product lists "crystalline silica" as an ingredient. I could easily see crystalline silica shattering like that. And quartz (silicon dioxide) comes in just about every color of the rainbow, depending on what other elements are in there with it.

It's also interesting that carbon black is in there. I suspect it's there as a coloring agent.

If engineers ran the marketing department: "JB-Weld--a reasonably strong epoxy with black coloring and sand added for a look and feel similar to metal."

Or perhaps the silica is there as a filler, to reduce the level of homogeneity in the hardened mixture material. A nascent crack would have a hard time getting started in a straight line, with all those randomly-oriented fracture planes to go through. A bit like coarse and fine aggregate in concrete.

Interesting thread!

--Chris

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Post by rjlittlefield »

I didn't think to check the MSDS. Good idea!

Now that I do read the MSDS, I think I'm more confused than ever.

The ingredients in Section 3 only total up to 10.2 - 32% by weight, with "crystalline silica non-respirable" quoted at 0.1 - 1%.

Just visually, there seems to be a lot more red stuff than 1% in the squeezed sample, but appearance could be misleading if those are mostly very thin flat crystals that are layered with resin.

In any case, I'm now wondering what the other 68 - 89.8% by weight is, and why it's not listed in the MSDS.

--Rik

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Post by Chris S. »

rjlittlefield wrote:The ingredients in Section 3 only total up to 10.2 - 32% by weight, with "crystalline silica non-respirable" quoted at 0.1 - 1%.

Just visually, there seems to be a lot more red stuff than 1% in the squeezed sample, but appearance could be misleading if those are mostly very thin flat crystals that are layered with resin.
One silicate that makes thin, flat crystals is mica. I think of mica as being light-weight (and it is, for a rock). But on looking just now, I see that epoxy weighs only about a third as much. (The specific gravity of mica is about 3; epoxy is slightly over 1.)
In any case, I'm now wondering what the other 68 - 89.8% by weight is, and why it's not listed in the MSDS.
"OSHA requires MSDS's ONLY for materials that a) meet OSHA's definition of hazardous. . . ." Much more detail available at the link.

Probably, OSHA is striking a balance between worker safety and trade secrecy. But I, too, wonder what the greater portion of this mix is.

Lest anyone wonder why the silica on this MSDS is labeled "non-respirable"--inhaled silica (for example, from road-construction dust) can lead to silicosis, a chronic and deadly disease. One presumes that the silica filler in this epoxy is trapped in the resin and not likely to become airborne. (Unless, perhaps, one sands the hardened joint?)

--Chris

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Post by ralfwagner »

Interesting stuff. Is the material magnetic? If not, there could still be (non-magnetic) stainless steel in it. If yes, there is for sure some magnetic iron in it.

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Post by ChrisR »

"Red" Haematite and "Black" Magnetite iron oxides are both ferromagnetic. They both dissolve much faster than unoxidised iron in hydrochloric, sulphuric, phosphoric or acetic acids. All those are used to remove oxides from iron, in fact, because the rate difference is so large.
You would get characteristically yellow or green solutions, but
I'm not sure how much that helps with analysis, with so many other unknowns around.
"Non" magnetic stainless steel is likely to have filings somewhat attracted to a magnet because of the working of the filings, which changes their phase.

It doesn't look amorphous enough or brown enough to match the Fe2O3 I've seen, but I haven't looked much ;)

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Post by rjlittlefield »

OK, I took a deeper look.

It turns out that the STEEL component of J-B Weld comes apart nicely in acetone. I use those words carefully -- "comes apart" -- because most of the material doesn't actually dissolve. Instead, what I think happens is that the uncured resin component does dissolve, revealing that the bulk of the material is already solid crystals of something or other.

In any case, after three washings in acetone followed by a thorough drying, what's left over is a substantial pile of fine powder. When completely dry, the color of the pile is light gray, but when wetted, it goes very dark gray. Scattered throughout the pile of light gray powder are larger flakes of dark stuff that are just barely visible to the naked eye in diffused light but obviously sparkle in directional light.

I transferred a small pile of this stuff to a microscope slide and slid it around over a 1/4" cube rare earth magnet to see if anything moved. Nothing did, in any component of the powder.

Then I put on a drop of acetone, stirred to mix, dropped on a cover slip, and slid that around while pressing it down. I waited for the acetone to dry, and photographed through the cover slip using a 40X NA 0.65 objective with the diaphragm stopped slightly for maximum contrast. Shown here are the results.

Direct projection onto Canon T1i (APS-C), most of the whole frame, ZS PMax stacked at 1.25 microns.

Image

Crop:

Image

Now I understand why my first impression of the squeezed-thin resin was "like trying to look through stippled glass". I was actually trying to look through a bunch of these clear crystals suspended in resin. By the way, there's no reason to think that this sample is representative of the size distributions. Certainly there was a lot of separation by size as the stuff was settling out of suspension.

It remains an open question what this stuff is. I haven't tried dissolving the crystals in anything. In any case, my guess is that we're looking at that large percentage of the STEEL component that is not covered by the MSDS for J-B Weld.

Some suggestive guidance might be provided by the MSDS of a competing product, Loctite Weld. According to the MSDS for that product, its ingredients are:

Code: Select all

    3. COMPOSITION / INFORMATION ON INGREDIENTS
Hazardous Component(s)    CAS Number    Percentage*

Epoxy resin               Proprietary      30 - 60
Calcium carbonate         471-34-1         10 - 30
Barium sulfate            7727-43-7        10 - 30
Triiron tetraoxide        1317-61-9        10 - 30
Epoxy resin               Proprietary       1 -  5
Kaolin                    1332-58-7         1 -  5
Titanium dioxide          13463-67-7      0.1 -  1
Quartz (SiO2)             14808-60-7      0.1 -  1

* Exact percentage is a trade secret. 
  Concentration range is provided to assist users in providing appropriate protections.
In reading the Loctite Weld MSDS, I'm struck by what a very different approach it takes from that of J-B Weld.

Here is the J-B Weld MSDS, Section 3:

Code: Select all

                  3. COMPOSITION/INFORMATION ON INGREDIENTS
   Substance/mixture    Mixture
   Ingredient name                                             % by weight CAS number
   reaction product: bisphenol-A-(epichlorhydrin); epoxy resin   10  - 30   25068-38-6
   crystalline silica non-respirable                             0.1 -  1   14808-60-7
   carbon black respirable                                       0.1 -  1   1333-86-4
   
Occupational exposure limits, if available, are listed in Section 8.
I've copied here both Section 3's in their entirety.

In my admittedly naive interpretation, I think what I'm looking at are close to opposite ends of the spectrum of completeness for writing an MSDS. This is speculation of course, but Loctite appears to have listed everything in the stuff, just on the off chance that it might be relevant, while J-B Weld lists only what they think they have to. It's an interesting distinction. (Both suppliers list U.S. addresses, by the way.)

--Rik

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Post by TheLostVertex »

According to THIS PDF it lists the substance as "iron powder", the CAS 65997-19-5 refers specifically to stainless steel.

THIS PAGE also shows it as stainless steel in the resin.

I do notice among other things though, that the specific gravity listed in the sheet I link is 1.8, and the sheet Rik links is 1.927.

Also the MSDS that I linked to is from 2004, while newer MSDS's for the "same" product omit much of the information. I can only guess there has been a change of formula and then a change in the way the MSDS is written?

But the most puzzling thing of all to me, is if there is steel in it... why do they advertise it on the package, but intentionally omit it from the MSDS? It is not like they are keeping a big secret :roll:

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Post by ChrisR »

Too late - but a common solvent used for epoxy resins is methylene chloride, popular in paint strippers.

None of those grains look a lot like stainless steel, which would be opaque, to me. Though once a metallurgist I now have no useful knowledge or memories!
On etching (dissolving) stainless steel, I only dimly recall picric acid and nitric acid, and hydroflouric which was avoided. Some interesting notes about microscopy techniques in the latter parts of :

http://www.google.co.uk/url?sa=t&rct=j& ... 2980,d.ZGU

It worth emphasizing that the etchants only do their job on prepared finely polished specimens.

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Post by TheLostVertex »

ChrisR wrote:None of those grains look a lot like stainless steel, which would be opaque, to me. Though once a metallurgist I now have no useful knowledge or memories!
I thought the same thing. If there was metal in it, then I imagine it was "washed" away between the first images and the post acetone images. As for the translucent red crystal, I haven't any idea. I wonder if maybe we are being fooled a little bit by the illumination used?
Last edited by TheLostVertex on Tue Jul 07, 2015 4:29 pm, edited 1 time in total.

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Post by ChrisR »

I do remember preparing specimens - sometimes in a block of epoxy :). So a piece of the stuff could be taken through finer grades of abrasive (change direction 90º at each grade) and finally polished. It should hold the particles nicely!
In my day, 400 grit wet and dry paper was the finest, then a couple of grades of diamond paste on cloth, 8 and 1 micron I think, then Alumina something like 0.005 micron, though that wasn't always necessary on softer material.
Now I have some 3000 grit, after which domestic metal polish would probably be good enough for the purpose.

A job for epi-polarised light?

A little hydrochloric + sulphuric acid should attack things differentially, though I wouldn't like to predict.
I doubt nitric acid is generally available these days?

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