What Went Wrong – Polymer Failure Analysis · PDF fileWhat Went Wrong – Polymer...

What Went Wrong – Polymer Failure Analysis

Jeffrey A. Jansen ANTEC 2014

Polymer Failure Analysis Using FT-IR and Other Techniques

FTIR Applications to Failure Analysis

• Material identification of failed part • Qualitative assessment of polymer

copolymers and blends • Identification and verification of resin

formulation ingredients • Identification of material contaminants • Determination of molecular degradation • Identification of chemical agents in contact

with failed part

FTIR in Failure Analysis The Madison Group 608-231-1907

Jeffrey A. Jansen [email protected]


The goal of the failure analysis is to identify

the Mechanism and Cause

of the failure Visual Techniques Analytical Techniques

FTIR Applications to Failure Analysis


Plastic Seal • Plastic seal in high-

temperature chemical application specified to be produced from Vespel SCP 5000 Polyimide – specialty grade



Chemical Seal



• QC FTIR testing used to verify received lots

• Internal library established



Vespel SCP 5000 Polyimide

Exemplar Seal



• QC FTIR testing used to verify received lots

• Internal library established • Nonconformance detected • Field issues avoided • Appearance and MP: no

differences



Failed Seal

0.0

0.2

0.4

0.6

Abs

Exemplar Seal

-0.00

0.02

0.04

0.06

0.08

0.10

Abs

Vespel SP-1 Polyimide

0.02

0.04

0.06

0.08

0.10

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

Exemplar Seal

Latest Lot

Vespel SP-1 Polyimide


• Scientific instruments were not performing well – interference associated with light and UV radiation ingress

• Traced to production batch of covers

• Unreinforced pigmented grade of polycarbonate / poly(acrylonitrile:butadiene:styrene) (PC+ABS) blend

Instrumentation Cover



• Exemplar and failed covers produced results characteristic of PC+ABS

• Spectral variation in baseline below 800 cm-1 suggested formulation differences



Exemplar Cover

Failed Cover

PC+ABS


• Exemplar and failed covers produced results characteristic of PC+ABS


• More about this later…….



Exemplar Cover

Failed Cover

PC+ABS

Polyethylene Tubing • Polyethylene tubing used in

an ice maker supply line failed in service resulting in substantial water damage



Polyethylene Tubing • Analysis of new tubing of

same brand produced results characteristic of polyethylene

• Failed tubing produced from polyethylene

• Failed tubing outer diameter – good match with new

• Failed tubing inner diameter - spectral bands associated with oxidation

• Tubing degraded from contact with chlorinated potable water

• More about this later…… FTIR in Failure Analysis The Madison Group

608-231-1907


Failed Tubing - Outer Diameter

0.0

0.1

0.2

0.3

0.4

Abs

Failed Tubing - Inner Diameter

0.1

0.2

0.3

0.4

Abs

New Tubing

0.0

0.1

0.2

0.3

0.4

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

New Tubing

Failed - ID

Failed - OD

1740

1712

Motor Housing • Motor housing produced

from polycarbonate / poly(acrylonitrile:butadiene:styrene) (PC+ABS) blend failed in service

• Produced off-shore • Failed during outdoor

service at low temperature



Motor Housing • FTIR analysis showed

difference between parts used for first article submission and field failure – resin substitution

• Both materials PC+ABS • Field failure – lower ABS

content resin



Failed Housing

-0.00

0.05

0.10

0.15

0.20

Abs

First Article Submission

-0.0

0.1

0.2

0.3

Abs

PC+ABS

-0.0

0.1

0.2

0.3

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

Failed Housing

First Article Housing

PC+ABS

ACN

BUT

Feeder Screw • A plastic feeder screw

cracked during use causing service interruption

• Material specified as poly(butlyene terephthalate) PBT with polytetrafluoroethylene (PTFE) additive

• It was suspected that molder had substituted a cheaper material



Retaining Clip

• Inserted components failed during assembly

• Cracking within snap fit retention arm

• Assembly with pneumatic equipment, but not automated

• Unfilled PBT



Retaining Clip

• Crack initiation at inclusion – distinctly different morphology

• Inclusion acted as discontinuity concentrating stress applied during snap insertion

• Brittle fracture



Retaining Clip

• Inclusion identified as PPS

• More about this later….

White Particle in Fracture Surface, Bowles Fluidics, TMG 13-11230-00, JN

0.000

0.005

0.010

0.015

0.020

0.025

Abs

White Particle in Fracture Surface - try 2, Bowles Fluidics, TMG 13-11230-00, JN

0.00

0.01

0.02

0.03

Abs

PPS, TMG Internal Library, JN

0.1

0.2

0.3

0.4

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

Poly(phenylene sulfide)

Inclusion 2

Inclusion 1



Pump Body

• Pump bodies failed while in service

• Injection molded from poly(phenyl sulfone) (PPSU)

• Powdered metal retainer – resin impregnated to seal

• Cracking within the bosses securing metal retainer to the body

• Residue within cracking



Pump Body

• Pump bodies failed while in service

• Injection molded from poly(phenyl sulfone) (PPSU)

• Cracking within the bosses securing metal retainer to the body

• Cracking initiating along interface with the metal retainer.

• Failure mode identified as environmental stress cracking (ESC) FTIR in Failure Analysis The Madison Group

608-231-1907 Jeffrey A. Jansen

[email protected]

Pump Body

• FTIR results showed pump body to be produced from PPSU

• No evidence of contamination or degradation



Failed Part - Base Material, GEA Farm Technologies, TMG 13-12596-00, JAJ

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Abs

Poly(phenyl sulfone) (PPSU)

0.05

0.10

0.15

0.20

0.25

0.30

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

PPSU

Failed Part – Base Material

As-Received Plate, GEA Farm Technologies, TMG 13-12596-00, JAJ

0.000

0.005

0.010

0.015

0.020

Abs

As-Received Plate - Transferred Residue, GEA Farm Technologies, TMG 13-12596-00, JAJ

0.000

0.005

0.010

0.015

Abs

Tetraethylene Glycol Dimethacrylate

0.2

0.4

0.6

0.8

1.0

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

Pump Body

• FTIR on fracture surface residue matched the results obtained on the metal retainer

• Identified as a gylycol diemthacrylate compound



Tetraethylene glycol dimethacrylate

Residue on Fracture Surface

Metal Surface

Plate - Properly Cured, GEA Farm Technologies, TMG 13-12596-00, JAJ

0.000

0.005

0.010

Abs

Poly(ethyl methacrylate)

0.5

1.0

Abs

As-Received Plate, GEA Farm Technologies, TMG 13-12596-00, JAJ

-0.00

0.01

0.02

Abs

Tetraethylene Glycol Dimethacrylate

0.5

1.0

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

Pump Body

• FTIR on fracture surface residue matched the results obtained on the metal retainer

• Identified as a gylycol diemthacrylate compound

• Properly cured retainers show a thermoset acrylic resin



Tetraethylene glycol dimethacrylate

Properly Cured Retainer

Poly(ethyl methacrylate)

Metal Surface – Failed Part

SUPPLEMENTING FTIR WITH OTHER TECHNIQUES



FTIR Limitations

• Materials with similar structures produce similar spectral results

• Cannot detect atoms or monoatomic ions • Complex mixtures can be difficult • Highly dependent on libraries • Detection limits generally 1% to 5% • Quantitative analysis difficult • Absorption bands are additive – confounds

interpretation



221.31°C

211.71°C50.60J/g

260.90°C

250.85°C59.92J/g

-1.2

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

Heat

Flow (

W/g)

25 75 125 175 225 275 325Temperature (°C)

Nylon 6––––––– Nylon 6/6–––––––

Exo Up Universal V4.7A TA Instruments

Similar FTIR spectra

Different melting points

FTIR Limitations


• Scientific instruments were not performing well – interference associated with light and UV radiation ingress

• Traced to production batch of covers

• Unreinforced pigmented grade of polycarbonate / poly(acrylonitrile:butadiene:styrene) (PC+ABS) blend




Exemplar Cover

Failed Cover

PC+ABS


• Thermogravimetric analysis (TGA) conducted on exemplar and failed covers



77.06% Loss in N2(12.79mg)

17.59% Loss in Air(2.92mg)

Residue:5.35%(0.89mg)

445°C

529°C

Heat to 650°C @ 20°C/min. in N2Cool to 500°CHeat to 1000°C @ 20°C/min. in Air

0.0

0.5

1.0

1.5

Deriv

. Wei

ght (

%/°C

)

0

20

40

60

80

100

Wei

ght (

%)

0 200 400 600 800 1000Temperature (°C)

Sample: Sample G1Size: 16.6020 mgMethod: Ramp

TGA Run Date: 18-Mar-2014 10:05Instrument: TGA Q500 V20.13 Build 39

Universal V4.7A TA Instruments



• TGA determined difference in the level of non-combusted residue associated with pigment



0

20

40

60

80

100

Wei

ght (

%)

0 200 400 600 800 1000Temperature (°C)

Sample B1––––––– Sample G1–––––––

Weight Loss Profile Comparison




• TGA determined difference in the level of non-combusted residue associated with pigment

• Pigment identified as TiO2 – an excellent light and UV absorber

• Field failure has less pigment and lower relative TiO2 content



Polyethylene Tubing • Polyethylene tubing used in

an ice maker supply line failed in service resulting in substantial water damage

• Failed tubing produced from polyethylene

• Failed tubing outer diameter – good match with new

• Failed tubing inner diameter - spectral bands associated with oxidation

• Tubing degraded from contact with chlorinated potable water



Failed Tubing - Outer Diameter

0.0

0.1

0.2

0.3

0.4

Abs

Failed Tubing - Inner Diameter

0.1

0.2

0.3

0.4

Abs

New Tubing

0.0

0.1

0.2

0.3

0.4

Abs

800 1000 1000 1500 2000 3000 4000 Wavenumbers (cm-1)

New Tubing

Failed - ID

Failed - OD

1740

1712

Polyethylene Tubing • Differential scanning

calorimetry (DSC) was used to determine resistance to oxidation – Oxidative Induction Time (OIT)

• Control tubing shows moderate resistance

• Failed tubing inner diameter shows no resistance – antioxidant fully consumed



Feeder Screw • A plastic feeder screw

cracked during use causing service interruption

• It was suspected that molder had substituted a cheaper material

• Analysis of failed and exemplar slides produce comparable results

• Spectra characteristic of a thermoplastic polyester containing PTFE



Failed Screw

Exemplar Screw

PBT

PET

PTFE

Feeder Screw • DSC showed melting peaks

associated with PBT and PTFE

• Similar results for both exemplar and failed



Feeder Screw • TGA analysis showed PTFE

content of 14% to 15% for both failed and exemplar

• Consistent with 15% specified



0.1% Volatiles(0.0mg)

50.6% PBT in N2(8.1mg)

14.4% PTFE(2.3mg)

3.1% Char & Carbon Black(0.5mg)

Residue:31.8% Glass(5.1mg)

423°C

587°C

Heat to 650°C @ 20°C/min. in N2Cool to 500°CHeat to 1000°C @ 20°C/min. in Air

0.0

0.5

1.0

1.5

Deriv

. Weig

ht (%

/°C)

0

20

40

60

80

100

Weig

ht (%

)0 200 400 600 800 1000

Temperature (°C)

Sample: Sample 2Size: 16.0230 mg TGA Run Date: 21-Jan-2013 10:45

Instrument: 2950 TGA V5.4A


Feeder Screw • Melt flow rate (MFR) testing

showed big difference • Corresponds to much lower

average molecular weight in failed parts – molecular degradation from molding



Thank You



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