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Tribochemical reactions on polyimide sliding surfaces evaluated with Raman spectroscopy and atomic force microscopy
Author(s) -
Samyn Pieter,
Schoukens Gustaaf
Publication year - 2008
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.2706
Subject(s) - polyimide , raman spectroscopy , materials science , composite material , atomic force microscopy , monomer , imide , crystallography , chemistry , polymer chemistry , layer (electronics) , polymer , nanotechnology , optics , physics
The friction and wear properties of polyimide at high temperatures are influenced by important tribochemical reactions on the sliding surfaces. Hydrolysis at 100–140 °C causes high friction and low wear whereas imidisation at 180–260 °C causes low friction and high wear. Raman spectroscopy confirms that the imidised structure that forms during sliding is characterised by reorientation of the C‐N‐C imide bonds from transverse into axial conformation. Also, the CO and C‐O‐C groups become more flexible and reorient in the worn imide structure. Depending on the normal loads, reorientation is either concentrated on the CO side groups at low loads or on the C‐N‐C and C‐O‐C backbone structure at high loads. Black spots on the surface represent a degraded fraction of polyamic acid monomers. Different surface morphologies are observed from atomic force microscopy. Hydrolysed structures correspond to an irregular surface pattern with pits and are preferentially worn parallel to the sliding direction. The imidised surface is smoother due to high strength and has a structure oriented along the sliding direction. However, it is more brittle and hence craters are formed that are larger compared to those formed under low‐temperature sliding conditions. Depositions on the sliding surfaces at 220–260 °C represent interaction of debris particles on the polyimide surface. On the nanometer scale, a progressive orientation of polyimide clusters parallel to the sliding direction is detected. Copyright © 2008 John Wiley & Sons, Ltd.