micro ftir5-measuring radiation effects,durometer
TRANSCRIPT
Effects of Radiationand Accelerated Aging
Part 6: Radiation Sterilization Issues
ATR Spectrum
Reflection from smearon aluminum sheet
The bloom visible on this catheterwas analyzed both by contactingits surface with the ATR Objectiveand by smearing the bloom ontoaluminum sheet and analyzingthe smear by Reflectance.The smear shows only the DEHPwhile the ATR sees both theDEHP and the PVC catheter.
Radiation Increases PVC BloomingOf Cytotoxic DEHP Plasticizer
Radiation Generates Free Radicals in Polypropylene
Free Radicals Generate Carbonyl Groups in Polymers
Test Method DevelopmentDecreased Ductility Can Cause Devices To Break During Use.
Radiation may increase the force to strain the device, but the strainat break decreases. Devices seldom fail because they’re too stiff.
They fail because they break.
A Syringe barrel wall may be unbreakable during use despite receiving the highest radiation dose allowed. Syringe tips may be much more fragile. Customer complaint history and product history may indicate what areas of a product are areas of concern; what are the products’ weakest links. It is these modes of failure that must be tested.
Testing must mimic the mode of failure expected during customer use. Breakage tests must be performed at a speed of deformation similar to that experienced by the product during customer use.
Testing samples subjected to Accelerated Aging will provide data quickly that predicts the future behavior of products. The Test Protocols will define the Accelerated Aging to be used.
Measuring Radiation Damage using Micro-FTIRMounting Aluminum Sheet On 3X2 Glass Slide
Shavings off Polypropylene Barrel’s Surface Analyzed Herein:Shavings Obtained with Razor Blade
Close-ups of Polypropylene Shavings Analyzed Herein
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Same Polypropylene Film Before and After 40 kGYs of Cobalt RadiationBlue is after
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Same Polypropylene Film Before and After 40 kGYs of Cobalt RadiationBlue is after
Hydroperoxides Carbonyls
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Same Polypropylene Film Before and After 40 kGYs of Cobalt RadiationBlue is after
Scissioned Polymer Chains Oxidize
IR Spectrum Shows Radiation Induced Oxidation of Polypropylene
as per J. Donohue MDDI
Polypropylene Oxidation from 20 and 40 kGYs of Cobalt Radiation
The “Dark Reaction” of Irradiated PolypropyleneOxidative Degradation Continues Long After Irradiation Has Ceased
This is the Reaction that is Accelerated by Accelerated Aging
Dr. Apostolou and I “wrote the book” on Accelerated Aging Methods that work
Oxygen Can More Easily Penetrate and Reactwith the Polymer in a Thin Film
This Post Rad Oxidation is Not Just Peroxide Scissions. Ambient Oxygen Continues to React with the Polymer.
This is Proven by this Vacuum Oven Aging.
Polyethylene Undergoes Similar Oxidationwhen Irradiated with 20 and 40 kGYs
A Carbonyl Index Can be Defined to Measure this Oxidation
Statistical Results for Micro-FTIR Dosimetry of Gamma vs ControlThe Micro-FTIR Method is Accurate, Precise, and Robust
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X = Thickness of slice (area of 1304 cm-1 Absorbance)
Area of C=OAbsorbancedivided by X
(Carbonyl Index)
Radiation Damage (= Dose) Measured for Thin Surface Shavings of Sterilized Polypropylene Medical Devices
Shavings of samples with 0 Mrads
Shavings of samples with 3.5 Mrads
Shavings of sterile product
Shavings of underdosed product
FTIR Microscopy can determine a competitor’s dose or detect underdosed non-sterile devices.
Stability of Fina Syndiotactic and IsotacticPolypropylenes to Cobalt Radiation
and Accelerated Aging
Ziegler-Natta and Metallocene Catalysts
Controlled Orientation of Monomer Approach To Active Site Yields Controlled Stereoregularity of Polymer Chain Formed.For Z-Ns, Solid Catalysts Control Approach to Active Site.For Metallocenes, Molecular Structure Controls Approach.
Stereostructure of Isotactic Polypropylene
Hydroperoxide Formation by “Backbiting” Oxidation
Strings of Close, Unstable, Pendant Hydroperoxides
Free Radical Degradation of Isotactic Polypropylene
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Isotactic Polypropylene Before and After 38 kGy & 17 Days @ 70 C
Hydroperoxides Carbonyls
The Isotactic Polymer is extensively Oxidized by Irradiation. It sizzles like bacon when it is melted.
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Syndiotactic Polypropylene Before and After 38 kGy & 17 Days @ 70 C
The Syndiotactic Polymer exhibits very little Rad-induced Oxidation
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IPP & SPP: 38 kGy & 70 C Aging StudyAccelerated Aging Increases IPP Oxidation
but has Very Little Effect on SPPIPP @ 70 C: 17 Days 88 Hrs 16 Hrs 0 Hrs
IPP 0 Dose
SPP 0 Dose
SPP @ 70 C:0 to 17 Days
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IPP & SPP: 38 kGy & 40 C Aging Study
IPP @ 40 C: 17 Days 88 Hrs 16 Hrs 0 Hrs
IPP 0 Dose
SPP 0 Dose
SPP @ 40 C:0 to 17 Days
Accelerated Aging Increases IPP Oxidationbut has Very Little Effect on SPP
Carrier Gas Flowpath to Mass Spec Detector
Pure He flowing throughglass lined steel tubethat contains sample.
Tube is injected intoGC Inlet and heated.
Volatiles separate oncolumn and are analyzedby the MS.
Radiation SterilizedSyndiotactic PolypropyleneGenerates an Order ofMagnitude Less Volatilesthan an Equal Mass ofIrradiated Isotactic Polypropylene
THDSB/GC/MS Analysesof Post-Rad Volatiles
The Close, Unstable, Pendant Hydroperoxides Explode Like a String of Firecrackers
CO2acetaldehyde
acetoneacetic acid
4-hydroxy4-methylpentanone
2,4-dimethylfuran
cyclopropylacetone
allylacetone
acetic anhydride
3,5,5-trimethylfuranone
acetoacetone
THDSB/GC/MS IDENTIFICATION OF IPP POST-RAD VOLATILES
Heated Irradiated Isotactic Polypropylene Degrades into Volatiles Based on C-C-O Units that Reveal the Chemical Mechanisms of its Oxidation
Thermally Degraded Post Rad Isotactic PolypropyleneEmits Low Mass Scission Products Based on C-C-O Units …
Air & WaterDesorbed OutOf Tube
Acetone
Acetic Acid
… Because Similar Oxidized Structures Degrade into Similar Volatiles
THDSB/GC/IR Analyses of Post-Rad Volatiles
Thermally Degraded Post Rad Syndiotactic PolypropyleneEmits a Far More Random Mix of Scission Products …
Air & WaterDesorbed OutOf Tube
2-Hydroxy-Propionic Acid
3-Methyl-2,4-Pentanediol
4-Butyl-Gamma-Octanolactone
… Because a More Random Dispersion of Oxidized Structures Yieldsa More Random Mix of Volatile Degradation Products
THDSB/GC/FTIR Analyses of Post-Rad Volatiles
Phenolic Antioxidants Protect Against Radiation Damage by Scavenging the Free Radicals Formed in the Polymer by Radiation
Part 7: Additives; their Analysis and Issues
But Phenolic Antioxidants Turn Plastic Yellow When Irradiated
Hindered Amine Light Stabilizers Form Cytotoxic Hydroxylaminesas they Protect the Polymer from Radiation Damage
Without Discoloration
Millad 3988 Clarifies PolypropyleneMolding Heat Causes Hydrolysis, Releasing Benzaldehyde Derivatives
This Causes the Polymer to Emit a “Cherry Candy” SmellMillad makes Polypropylene more brittle
Clarified Polypropylene Crystallized at 130 C from the MeltNucleation Determines Morphology
ClarifiedNot Clarified
Sublimation depletes Boundary of MilladPolypropylene Spherulites grow
Millad preventsSpherulite growth
Millad Forms Thermally Unstable Precipitate if it is Overheated DuringInjection Molding. Precipitate’s Sizzling Decomposition into Gaseous,
Superheated Aldehyde Strips Char out of Molding Press and Into Molded Parts. Heated excised precipitate chunks undergoing thermal decomposition on Hotplate
Sizzling Decomposition into Aldehyde and Arylate
>Tiny orange spots were scattered across the Polypropylene matrix
>Any attempt to get the spectrum of more than one orange spot at a time yielded only a spectrum of the Polypropylene matrix
>But the IR-Plan can can zoom in on a single tiny orange spot to yield the Arylate spectrum shown …
… and Thermal Desorption of the degrading material into the GC/MS can show the formation of the Aldehydes and Alcohol Intermediates.
Thermal Decomposition of Precipitate Forms Aldehyde.Cannizzaro Reaction of Aldehydes Forms Acid and Alcohol.
Condensation of Acid and Alcohol Forms Arylate.
Arylate Forms The Orange Spots
Thin Layer Chromatography (TLC) can Separate Chemical Mixtures that theGC/MS can’t: Chemicals that are non-Volatile or Thermally Unstable
Liquid carries chemicals in spot of extract up the plate, separating them
>TLC is done on a Plate Covered with Fluorescent Silica>UV Light makes the Separated Chemicals from the Mixture Visible>The Regions of Silica Containing these Chemicals are scraped off the plate, separated from the Silica, and Identified using the Analytical Instrumentation
Under Visible Light
Under UV Light
After Scraping
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Measuring Durometer of FINISHED (competitive) Devices:FTIR of DEHP Plasticized PVC Device vs Pure PVC
Pure PVCDEHP
Part 8: Tricks of the Trade
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FINISHED Device: Measuring Plasticized PVC Durometer
Hard Endotracheal Tube
Soft Nasogastric Tube
DEHP
PVC
Spectra “normalized” for equal plasticizer (DEHP) content showthat the harder PVC has a higher PVC to Plasticizer RatioSuch a test can tell the Durometer used by a Competitor
HigherPVC
conc.
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Reverse engineering competitive cathetersMicro-FTIR Spectrum of Pellethane
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Micro-FTIR ID: FINISHED Device Pellethane Durometer
80A
90A
75D
>Many catheters have tips made from a softer grade material than the shaft.
>FTIR can measure the Durometer of finished Polyurethane devices quickly and easily
>Multiple runs below show that the method is robust
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Micro-FTIR Spectrum of Tecothane
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Micro-FTIR ID: FINISHED Device Tecothane Durometer
74A
85A
55D
75D
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Micro-FTIR Spectrum of Tecoflex with 20% BaSO4
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Micro-FTIR ID: FINISHED Device Tecoflex Durometer
80 A
85 A
100 A
65 D
60 D
NOTE:This method is more accurate than themanufacturer’s ability to control or measuretheir Durometer. The Hardness Pucks thatwere supplied by the manufacturer (aftermeasuring Durometer with a Hardness Tester)and were supposed to be 60 D were insteadHARDER than the supposed 65 D pucks.
HIGH-GLOSSABS CRACKS
LOW-GLOSS ABSRESISTS CRACKING
FTIR Shows Why High-Gloss ABS Has Less ESCR Than Low-Gloss ABS
More Styrene/Butadiene Rubber dispersed in the Acrylonitrile matrixyields High Gloss ABS with less resistance to Environmental Stress Cracking
Packaging Materials
>There are a lot of “Tricks of the Trade” in Materials Analysis.
>For example, Most packaging films are laminates with outer heat-sealable plies and an inner strength ply.
>The FTIR Microscope requires Liquid Nitrogen (LN2) to operate and this LN2 can be used to cryo-fracture materials.
>Cryo-fractured laminated films can be separated easily into their individual plies for material identification and also for accurate thickness measurements free from thickness artifacts caused by cutting techniques that can decrease the measured thicknesses.
The film contains K-Resin…
…and the stretched Heat Seal Ply is EVA
Device package bottom web wascryo-fractured with liquid N2 andthe heat seal ply was stretched over aluminum sheet.
Device package bottom web wascryo-fractured with liquid N2 andthe protruding and overhangingplys show a Surlyn center plysandwiched in EVA heat seal plys.
Surlyn center plyprotruding fromfractured laminatedfilm
Surlyn ply and EVA heatseal ply together
Device package bottom web wascryofractured with liquid N2 andthis two ply film separated intoa K Resin ply and a more flexibleEVA heat seal ply.
K Resin ply is stiffer
EVA heat seal ply