There are some other ways of finding Tg, the following are non
destructive
allowing sample to be retained for reference if required.

One is a "Penetrometer". In this you press a sharp point against the
sample whilst it is being heated. When the material softens at Tg the
needle moves into the sample and the temperature at which this happens
is recorded.
Another [related] method is to listen to the sample as it is being
heated. The change in mechanical properties results in a difference to
its acoustic properties and these can similarly be recorded against
temperature.

Mike


----- Original Message -----
From: "Yves.Dupuis" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, August 14, 2000 3:17 PM
Subject: Re: [TN] Procedure for Tg measuring


> A common (but destructive) test for determining the Tg of a material
is
> Differential Scanning Calorimetry (DSC). You subject a small sample
(mg
> scale) to a (usually linear) temperature scan covering the range you
suspect
> Tg to be in. The slope of the absorbed-energy curve is related to
the heat
> capacity of the substance. At Tg, there will be a heat capacity
change.
> Depending on the thermal history of the substance, there may also be
a
> "bump" in the curve at Tg cause by enthalpic relaxation. DSCs are
common lab
> equipment in materials science and other fields. It may be possible
to have
> such tests done by a contact lab if you just want Tg of a given
substance
> (say an epoxy). This will likely prove too troublesome if you want
to, say,
> check the Tg of each new batch of PCBs you get.
>
> Yves Dupuis
> Leitch Technology
>
> > -----Original Message-----
> > From: Le Dai Tri [SMTP:[log in to unmask]]
> > Sent: Monday, August 14, 2000 5:40 AM
> > To:   [log in to unmask]
> > Subject:      [TN] Procedure for Tg measuring
> >
> > TechNeter,
> >
> > We purchase Prepreg in roll then cut into suitable worksize,
before
> > sending prepreg to Laminating process we have IR heating process:
> > Maximum heating temperature was 115 deg.C (FR-4).
> >
> > 1. Can anyone have any experiences about this treament ? it is
effect
> >     or not ? Does it effect Tg of Prepreg material?
> >
> > 2. Can I measure Tg by ourselves ? I want to confirm Tg before and
> >     after IR treatment. If posible please show me where I can get
> >     procedure.
> >
> > Any help would be appreciated.
> >
> > Best regards,
> > Tri'.
> > _______________________________________
> > E-Mail    : [log in to unmask]
> > <mailto:[log in to unmask]>
> >
> >
>
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