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Influence of Molecular Weight on the Mechanical Performance of a Thermoplastic Glassy PolyimideMechanical Testing of an advanced thermoplastic polyimide (LaRC-TM-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength were all determined as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. A critical molecular weight (Mc) was observed to occur at a weight-average molecular weight (Mw) of approx. 22000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Furthermore, inelastic analysis showed that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microstructural images supported these findings.
Document ID
19990115891
Acquisition Source
Langley Research Center
Document Type
Technical Memorandum (TM)
Authors
Nicholson, Lee M. (National Academy of Sciences - National Research Council Hampton, VA United States)
Whitley, Karen S. (NASA Langley Research Center Hampton, VA United States)
Gates, Thomas S. (NASA Langley Research Center Hampton, VA United States)
Hinkley, Jeffrey A. (NASA Langley Research Center Hampton, VA United States)
Date Acquired
September 6, 2013
Publication Date
November 1, 1999
Subject Category
Nonmetallic Materials
Report/Patent Number
L-17907
NASA/TM-1999-209720
NAS 1.15:209720
Funding Number(s)
PROJECT: RTOP 522-32-11-01
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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