FTIR Microscopy can do a lot morethan the simple chemical

identification of contaminants.

> It can determine the physical morphology of polymers.

> It can measure the oxidative degradation caused by radiation sterilization (dosimetry).

> It can measure the hardness of PVCs, Polyurethanes, and numerous other Thermoplastic Elastomers

> It can measure the Butadiene or Styrene content of Styrenics

Part 5: Radiation Effects, Crystallinity, Durometer, Styrenics ESCR

Measuring Changes in Crystallinity:PET Tube Turned Opaque White

Customer complained that PET catheter was opaque white instead of clearBUT

Had the customer accidently left this catheter in a hot Autoclave overnight?

Polyethylene Terephthalate Crystal Structure

The Mettler Hotstage

Remove the glass window and insert a strip of aluminum sheet or a thin, “homemade” KBr “poker chip”.Then you can obtain spectra while heating the sample.

Spectral Differences Between Clear And Hazy PET TubesCrystallinity Peaks marked in Hazy Return

FullSpectrum

zoom in

The hazy (opaque white)catheter had spectraldifferences whencompared to the clearcatheter (crystallinity peaksare shown at right)

When the clear tube was quenched from the melt by Boiling it in Water, it crystallized, turning white like the Customer’s Hazy returned tube.

Proof that Spectral Differences Between Clear and Hazy Tubesare due to Crystallinity

Crystallized in Boiling Water

Crystallized in Boiling Water

The Spectra of the clear tube whenit is molten at 260C is the same aswhen it is quenched from the meltby Liquid Nitrogen.BUT when it is quenched from themelt by Boiling it in Water, itanneals and grows crystals.

Crystallized by Customer’sUnknown Method

Proof that White catheter has hydrolyzed to Lower Molecular WeightWhen the Clear tube, a PET controlsample, and the Hazy PET weremelted and then instantly quenchedfrom the melt in Liquid Nitrogen, theHazy sample has already Crystallized.and the Clear tube sample has not.

The Hazy PET crystallizes much morereadily because it has Hydrolyzed toa Lower Molecular Weight.

When the clear tube is melted andkept (quenched) in ambient air for4 seconds or 10 seconds before beingquenched in Liquid Nitrogen, NO crystallization begins after the 4seconds in air and only a tiny amountafter the 10 seconds in air.

The Hazy PET crystallizes much more readily because it has Hydrolyzed to a Lower Molecular Weight.The Customer probably left the catheter in a hot Autoclave overnight.