The definition of modulus is clear (stress/strain) however calculation from a typical data set is not clear. There are standards (ISO, ASTM) that define modulus types (such as Young, tangent, secant) however choice of consistent calculation method depends upon the skill and experience of the analyst. I am interested to learn of the recommendations and experience of others in determining the modulus of polymers.
Dear Robert: I suggest you to check literature on this subject by DMA, TAInstruments has a lot of info, however Netsch, Perkin Elmer and other have also a say on the matter.
Though it is usual to correlate the band positions in FTIR spectra of natural fibers with the functional groups, because of the complexity of these fibers, accurate interpretation may not be possible. It is advisable to carryout a complimentary investigation like solid state NMR and couple the data with FTIR to get comprehensive chemical nature of the carbohydrates.
This ASTM standard was very helpful in determining how best to test a polymer:
ASTM E 111-97 Standard Test Method for Young's Modulus, Tangent Modulus and Chord modulus, (1997)
Where there is a curve rather than a straight line ASTM tells you to use a tangent modulus... and usefully it also tells you to measure at 0.25 % strain or less to minimise the need the make adjustments due to deformation.
The discussion in this standard is very useful in understanding which method to use and why.
The one weakness of standards is that they are often trapped behind paywalls... and thus access can be restricted or difficult particularly for some user groups.
Like Bob I'm interested in hearing what others might have to say on the subject.
Johan's response is currently the best one... thanks.
:-)
PS. Thanks to Isaac Martinez who provided a copy of the standard and helped contextualise the information.
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