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September 2001

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Subject:
From:
Andrew Hoggan <[log in to unmask]>
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Date:
Fri, 21 Sep 2001 20:37:28 +0100
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DSC Differential Scanning Calorimetry:

measures the differential energy between a standard and a sample, energy is
applied to both and the endothermic or exothermic response of the sample is
measured. This is the difference in energy seen between the standard
(possibly an empty cell or a blank sample) and the sample hence the term
differential. Any extraneous materials present or absent will significantly
effect the results measured hence the difference in expected results between
samples with and without copper. The presence or absence of copper will more
likely effect the heat sink and hence the overall results.

DMA Dynamic Mechanical Analysis

measures the mechanical response, expansion, contraction, physical
structural changes that take place as energy is applied e.g. as the Tg is
exceeded. The measurement is that of a physical movement. There is no
differential comparison as in DSC so although the presence or absence of
copper, if that is the material incorporated, can potentially effect the DMA
results, the effect is significantly reduced.

Note energy applied can be isothermal or dynamic (positive or negative).

Andrew Hoggan
BBA Associates Ltd
www.bba-associates.com

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Timothy Reeves
Sent: 21 September 2001 17:51
To: [log in to unmask]
Subject: Re: [TN] Tg measurements by DMA


DSC (Differential Scanning Calorimetry) measures the temperature of the
material as known quantities of heat are added to it. This behavior depends
on absorbed moisture content which in turn is affected by whether or not the
material is copper clad or not. DMA measures mechanical properties as the
material's temperature is raised which do not so much depend on moisture
content.

Tim Reeves
ECD

-----Original Message-----
From: Gerard O'Brien [mailto:[log in to unmask]]
Sent: Thursday, September 20, 2001 8:23 AM
Subject: Tg measurements by DMA


When testing Tg with DSC, the TM-650 test method calls out for the test to
be run with the copper clad still attached and that if removed to expect an
8 to 15 degree reduction in values. For DMA it does not reference testing
with copper clad or removed. Can anyone give me the reason why?

Regards

Gerard O'Brien

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