PCTFE - Amorphous / Crystalline

[PeterIgg]

Is anyone aware of a test that can be performed to give a reliable indication as to whether the form of the material is in either the crystalline or amorphous state?

We use this material for seals in cryogenic applications and experienced a failure when using the crystalline form of the material as opposed to the amorphous (or 'more amorphous') grade.

Can anyone direct me to any useful information on this product - our suppliers have been as helpful as possible but, obviously, need to protect their proprietary processes.

 

[patprimmer]

Specific gravity can often be used if the material is unfilled, the higher the SG, the greater the crystalinity in most cases. Water and ice being a notable exception.

Regards
pat pprimmer@acay.com.au
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[plasgears]

Testing for strength vs temp should reveal crystalline vs amorphous properties. The crystalline material will exhibit more strength, but the amorphous material will exhibit more energy absorption: the area under the stress-strain curve.

In a gearbox that experienced stall at travel limits in the mechanism, we had trouble with crystalline Acetal gears, but the problem went away when we switched to Nylon 6.

 

[CoryPad]

X-ray diffraction is the method used to determine crystallinity directly . The other methods are indirect, though much less complicated and much less expensive.

Regards,

Cory

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[patprimmer]

Cory

Even some polymer manufacturers do not have in house access to X-ray diffraction, however i agree it is the only "real method".

Regards
pat pprimmer@acay.com.au
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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[PeterIgg]

Guys

Thank you all for your comments - much appreciated.

 

[pierrig]

Differential Scanning Calorimetry is a very simple way to determine if your polymer is crystalline or amorphous.