"Although the flamewar with MM is over for me, this devoted truther still can serve for me as a source of info what should be again pointed out for other people, who are basically able to admit that Harrit et al. could be wrong with their conclusions. Now, I will concentrate solely on the color of heated red chips. I will suppose that red chips (a) to (d) in Bentham paper were particles of Laclede primer paint, e.g. since their XEDS spectra are in almost perfect match with the simulated spectra of the paint.
Laclede paint contained over 70 % of basically colorless/transparent epoxy binder (this epoxy was cured by some amine). The rest was formed by red (or reddish-brown) iron oxide (55 %), white (or whitish, yellowish) aluminosilicate (41 %) and brightly yellow strontium chromate (4 %). Whereas epoxy is degraded/oxidized/evaporated at high temperatures over ca 350 degrees C, inorganic pigments remain in the paint layer during heating up to very high temperatures and they color do not substantially change (at least in the case of iron oxide and aluminosilicate; strontium chromate – as a strong oxidizing agent – can be consumed by some oxidation reactions with organics).
The basics of the thermal degradation of amine-cured epoxy resins can be found in this fine paper, p. 209-231. The epoxy degradation is followed mostly by thermogravimetric analysis (TGA), which measures the mass decrease during slow heating.
Very typical examples of such TGA curves can be seen in these two figures of measurements on my Laclede paint imitation (composition very similar to the real paint):
http://bobule100.rajce.idnes.cz/epoxides/#TGA-N2.jpg
http://bobule100.rajce.idnes.cz/epoxides/#TGA-air2.jpg
The first Fig shows TGA under nitrogen. We can see that the most of epoxy binder is degraded/evaporated in the temperature range ca 350 – 430 degrees C.
(21 % of inorganic pigments always remain in the samples even after heating.)
The second Fig shows TGA under air (i.e. at conditions of DSC in Bentham paper). We can see that the degradation proceeds basically in two steps here. In the first stage, the similar mass decrease is observed as under nitrogen, but roughly 20 % of organic matter remains in the sample up to ca 430 degrees C. This organic matter is described in the paper linked above (p. 223) as a „carbon char“. In other papers, the same kind of matter is described as „polyaromatics“ or „graphitized“. Regardless of naming, this matter is always dark/black, since it consists of system of highly conjugated polyaromatic moieties.
This carbon char can be further oxidized/evaporated at even higher temperatures. In my Laclede paint imitation, almost no char was present at ca 600 degrees C (see second Fig.). This is again a typical TGA behavior of epoxies, as can be seen in the linked paper (eg. Fig. 10).
Now, finally for colors of paint heated under air.
The fate of the dark char at high temperatures is strongly dependent on the heating conditions.
If the heating is slow and/or high temperatures last for a long time and/or very high temperature is achieved, dark char is eventually (almost) completely burned/vaporized and resulting matter is red because of the color of iron oxide.
If the high temperatures do not last for a long time and/or the access of oxygen to the sample is limited, the char is not completely burned/vaporized and the residue after heating is dark.
The first scenario can be valid for heating in DSC or TGA apparatus. Therefore, chips (a) to (d) in Bentham paper (Fig. 20) or my chip of Laclede imitation (http://bobule100.rajce.idnes.cz/epox...16epi_magn.jpg) remain red.
The second scenario could be valid for the red chip heated on the heating element by Marc Basile. Therefore, this chip was dark after heating/burning (because of char color). Simply spoken: the combustion of organic matter was not perfect in this case."
A few preliminary observations.
It is important to note the time scale applied for those TGA curve.
http://bobule100.rajce.idnes.cz/epoxides/#TGA-air2.jpg
This represents the application of heat from
40C to
800C at a rate of
10C per minute.
Your statement that;
"We can see that the most of epoxy binder is degraded/evaporated in the temperature range ca 350 – 430 degrees C.", translates to a time period of
1 hour and 20 minutes.
You base your
char conclusions on your reference papers, and a strong dependency on heating conditions.
For the purposes of this reply, I will address your reference to the Mark Basile tests which I have already used as visual evidence.
For Mark Basile's observations, you use the criteria;
"If the high temperatures do not last for a long time and/or the access of oxygen to the sample is limited, the char is not completely burned/vaporized and the residue after heating is dark.".
You claim that Mark Basile's red chip test fits this criteria without attempting to justify your conclusion.
Actually, if I interpret your scenario 1 correctly, you believe that had he exposed his red chips to a very long period of high heat, that his red chip would have gone black and then back to red because the final residue would be the reddish iron oxide.
Well Mark Basile's test was certainly not of long duration. What would be expected from an energetic thermitic ignition.
He setup a power supply to deliver 6.8 amps electrical current to a .002 inch thick stainless steel strip .1 inch wide x .25 inch long. The power supply was preset to give this current, the chip was placed onto the strip, video record was activated, and then after approximately 5 seconds, power was applied to the strip.
There is no reason to believe that the test was in an oxygen-restricted environment.
You were notably silent on what constituted a high temperature, and what is too short a time span.
Anyway.
Based on a video reference frame of
75099 (approximately 00:41:40 into his video presentation
911 Dust Analysis Raises Questions); and a final reference frame marked when ignition was extinguished at
75170, some timing information could be determined. Note, each video frame should represent the NTSC standard of 1/30th of a second.
It took 49 frames for the gas to be released (~1 2/3 seconds).
4 frames later the flash of ignition occurred and its total duration was 18 frames or 3/5 of a second.
So compared to those times described by your TGA tests, we are talking damn fast.
Here is how Mark Basile characterizes what was observed in the video of his test;
Chemist said:
"Basically what happened is that the red chip ignited and what you see is that on the left hand side of the chip, you see a sudden bright white-hot flash and you are then going to see a wave front move through the inside of the chip because it is so bright inside that it is actually radiating through the material that is still surrounding it. You basically see a bright flash progressively move through that chip and then extinguish. The chip pretty much puffed up and you can see gas escaping from it. It has basically become porous on the outside with actually some holes that burst through allowing the gas to escape out."
"Inside we find the reaction product of solidified iron metal droplets and thin films of metal on the void walls within the residue."
"From the reaction, they have basically fallen to the bottom of the chip. And then when they cooled, they have solidified. So they are not perfect spheres. Microspheres form when a material is liquid and it falls through air and the only real force acting on it is its own surface tension. And so it tries to minimize that surface area, and hence the surface energy, and goes into a sphere because that is the minimum surface area for a given volume of material.
These don't form into perfect spheres. They are trying to but then they hit something and they flatten out and so you basically wind up with all these metallic iron-based droplets that formed inside the chip. And the other thing. They don't all form into droplets. As these are actually burning down through the chip, or melting their way down through, they actually along the walls leave this very thin film of solidified iron.
Where as if you take these chips, before you ignite them, and I have done it, just like I did where I said I exposed a fresh section. I've cut into these chips, dozens, if not hundreds of times and I have never found an iron microsphere inside. I have never found a film of iron inside. It is not there until the chip reacts. When the chip reacts, it produces molten iron. There is no free iron. There is iron oxide before you ignite it but there is no free iron inside these chips."
Now Ivan, if I understand you correctly, you believe that by further subjecting this residue to high extended heat, we will end up with red residue representing the iron oxide remains of your Laclede paint?
Sorry but I think you fail.
THE RED CHIPS ARE NOT PRIMER PAINT.
MM
I have just put here a quite elaborate post why Basile's chip can be dark after burning (and I stand on this), now you write that it is not really clear that the chip was dark after burning
