Hello, I'm new to this forum.

Recently, my lab has seen the correlation between soot by TGA and FT-IR, which has been very good for us for many years, begin to separate to an unnacceptable degree. We have had to employ a correction factor to report data we can rely on. I'm wondering if anyone else has seen this trend, and what your thoughts are if you have. My intial thoughts are either 1) soot particle size is trending upward in general, or 2) new additive chemistries could be interfering with the FT-IR peaks of interest.

Any thoughts would be appreciated.

CDT

Correct determination of soot by TG requires oils that are not oxidatively too much degraded. Oxidation products can contribute to the formation of carbon residue measured by TG. FTIR measures only the soot loading. Difference between TG and FTIR determination can be caused by this factor. May be, oils are oxidatively less stable, engines have another construction, EGR ventils are mounted in engines etc.

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Originally posted by CTaylor:
Hello, I'm new to this forum.

Recently, my lab has seen the correlation between soot by TGA and FT-IR, which has been very good for us for many years, begin to separate to an unnacceptable degree. We have had to employ a correction factor to report data we can rely on. I'm wondering if anyone else has seen this trend, and what your thoughts are if you have. My intial thoughts are either 1) soot particle size is trending upward in general, or 2) new additive chemistries could be interfering with the FT-IR peaks of interest.

Any thoughts would be appreciated.

CDT

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In my opinion, at the most soot test value can be considered as indicative tool as there are many variable factors that contribute soot size and quantity. They are fuel quality, engine combustion design parameters, Exhaust gas recirculation mechanisms, complexity of additive chemistries with regard to dispersant and detergents in the engine oils formulation etc. I wonder how there can be a correlation between two test methods. I am not criticizing test metnods, but only expressing the difficulties involved in the actual engine operating conditions. Due to these reasons OEMs express their own warning limits with regard to soot levels. Any further comments are welcome.

Kumar
kumartr2@yahoo.com