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Published April 2004 | public
Journal Article

Lubricant pyrolysis during sintering of powder metallurgy compacts

Abstract

The chemistry surrounding the pyrolysis of N,N′-ethylenebisstearimide (EBS) compacted with iron powder is described for the first time. Heat treatment is carried out in a 5 vol pct hydrogen atmosphere (balance nitrogen) over the 100 °C to 850 °C range. The exhaust from the furnace is monitored by Fourier transform infrared and dispersive ultraviolet absorption spectroscopy; condensable materials are analyzed by gas chromatography/mass spectrometry (GC/MS). A wide range of analytes emitted from the preceding process were characterized. The aliphatic CH stretch in the 3000 to 2700 cm⁻¹ range and the asymmetric CO stretch in gaseous CO₂ at 2350 cm⁻¹ are excellent indicators of the extent of delubrication. A bimodal CO emission phase is observed in the temperature window between delubrication and sintering. Three major large molecule reaction products, along with five minor compounds, are identified by GC/MS. A preliminary reaction mechanism is inferred based on product analysis and known organic chemistry. It appears that hydrolysis of EBS competes with γ-H abstraction yielding an N-vinyl amide and stearamide, which undergoes further reaction. Hydrolysis affords stearic acid, which decarboxylates to heptadecane, and 2-heptadecyl-4,5-dihydroimidazole via ring closure of the corresponding amino-amide.

Additional Information

© 2004 Springer Verlag. Manuscript submitted September 9, 2003. This paper is dedicated to Robert M. Becker. Bob died tragically in an automobile accident in December 2003. He was a good friend and valued colleague who will be greatly missed. The authors are grateful to the PMRC members for their support and thank Mr. Fred Semel (Hogaenaes Corp.) for providing compacted samples during the course of this study. The authors also thank Dr. Nathan F. Dalleska, Division of Environmental Science and Engineering, California Institute of Technology (Pasadena, CA), for helpful discussions regarding the interpretation of GC/MS data.

Additional details

Created:
August 22, 2023
Modified:
October 18, 2023