the surface analysis laboratory flame treatment of polypropylene… · 2018. 3. 7. · the surface...

The Surface Analysis Laboratory

Flame Treatment of Polypropylene:

A Study by Electron and Ion Spectroscopies

David F Williams, Marie-Laure Abel, Eddie Grant*, John F Watts

Department of Mechanical Engineering Sciences

Faculty of Engineering & Physical Sciences

Cagliari, Sardinia Italy

13th – 18th October 2013

*


Flame Treatment Used for

Many Years


Seminal Publications


Automotive Flame Treatment


Outline of Presentation

• Flame Treatment

• Industrial Examples

• Methods and Materials

• XPS Surface Composition as Function of

Treatment Parameters and Sample Type

• Valence Band Studies

• Treatment Layer Thickness

• ToF-SIMS: Oxygen Functionalisation

• ToF-SIMS: Additives

• Conclusions


Flame treatment

• Increases the surface energy

• Ablative cleaning

• Improved adhesion

Active region

Main reaction zone

The Aerogen Company (2013)


Industrial Examples of

Flame Treatment


Flame treatment


Polypropylene

Polymer All Filled with carbon Black

Designation

A homopolymer with no

additional filler A

A homopolymer with 40% talc

B

A copolymer with 20% talc C

A polymer with 20% long glass

fibre D

1 dyn cm-1 = 1 mN m-1

NB Plus unknown processing aids

Automotive Grade PP


Flame Treatment Conditions

• Equivalence ratio 0.93 (stoichiometric amounts =1,

so slightly oxygen rich)

• Natural gas and filtered compressed air mixed in a

venturi 5 m up stream of burner

• Burner PP gap 18 -200 mm (Optimum 100 mm)

• Conveyor speed = 1 ms-1 (double pass)

• Dwell time in flame = 0.02 s

• Multiple passes; 90 s recovery allowed between

passes

• PP injection moulded plaques 3 mm thick

• Dyne pens immediately after flaming then wrapped

in Al foil


Instrumentation Used


XPS/Cluster Profiling

X-ray photoelectron spectroscopy performed

using the Thermo Scientific K-Alpha system

• Monochromated X-ray source

• Fully automated acquisition

MAGCIS (monatomic and gas cluster ion source)

used to produce craters

• Ar Cluster size up to 2000 atoms

• Ion energy = 2 - 8 keV

• Monatomic Ar ion beam


Parameters Investigated

Parameters

• Burner to substrate distance

• Equivalence ratio = Ø

• Dwell time

mfuel/moxidiser

(mfuel/moxidiser)stoich

Effects

• Depth of treatment

• Ablation of surface material

• Ageing

• Chemical changes

• Topography changes

• Surface energy changes

Ø =


Example XPS Spectra

XPS spectra for Sample A untreated

(lower) and treated (upper).


As Received PP Samples

Sample B

Sample C

Sample A

Sample D


Surface Composition vs

Contact Angle

Specimen

Surface Composition

Atomic %

Carbon Oxygen Sulphur O/C

ratio

Water Contact

Angle (°)

Dyne Ink

(mN m-1)

A 100.0 0 0.00 98 30

B 96.8 2.9 0.3 0.03 104


Influence of Dwell Time


Effect of Multiple

Passes on Surface

Properties Specimen C O S N

O/C

ratio

Contact

angle

Dyne

ink level

Sample A

Untreated 100.0 0.0 0.0 0.0 0.0 98 30

1 pass 89.6 10.0 0.4 0.0 0.11 70 52

2 passes 89.3 10.7 0.0 0.0 0.12 66 56

3 passes 85.1 14.9 0.0 0.0 0.18 62 56

5 passes 83.9 16.1 0.0 0.0 0.19 N/A N/A

7 passes 83.1 16.9 0.0 0.0 0.20 N/A N/A

Sample B

Untreated 96.8 2.9 0.3 0.0 0.03 104


Dwell Time

(Passes Through

Flame) • Increased by using more passes 1,2 and 3 passes used (0.02, 0.04 and 0.06s respectively)

0.00

0.05

0.10

0.15

0.20

0.25

0 1 2 3 4

O/C

rat

io

Number of passes

O/C Ratio

60.0

62.0

64.0

66.0

68.0

70.0

72.0

74.0

0 1 2 3 4

Co

nta

ct a

ngl

e (

Degr

ees)

Number of passes

Contact Angle

Sample A X Sample B

Sample C

Sample D


Burner Gap

0.00

0.05

0.10

0.15

0.20

0.25

0 20 40 60 80 100 120 140 160

O/C

rati

o

Burner gap (mm)

60.00

65.00

70.00

75.00

80.00

85.00

90.00

0 20 40 60 80 100 120 140 160

Wate

r c

on

tact

an

gle

(d

eg

rees)

Burner gap (mm)

Sample C X Sample D

Sample A

Sample B


Equivalence Ratio

55.00

60.00

65.00

70.00

75.00

80.00

1.07 1.01 0.96 0.92 0.89

Wa

ter

Co

nta

ct

An

gle

(d

eg

rees

)

Equivalence Ratio

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

1.07 1.01 0.96 0.92 0.89

O/C

Rati

o

Equivalance Ratio

Sample A X Sample C

Sample B

Sample D


Ageing Test

60.0

65.0

70.0

75.0

80.0

85.0

90.0

95.0

100.0

105.0

110.0

Untreated 0 Days 7 Days 14 Days 21 Days 26 Days 42 Days 49 DaysWate

r C

on

tact

an

gle

(D

eg

rees)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

Untreated 0 Days 7 Days 14 Days 21 Days 26 Days 42 Days 49 Days

O/C

Rati

o

Sample C X Sample B

Sample A

Sample D


Valence Band

Valence band spectra

for Sample B

untreated

treated with 1 pass

treated with 2 passes

treated with 3 passes Briggs (1979)

polyethylene

polypropylene


Mono XPS Valence Band

Untreated

1 Pass

3 Passes

7 Passes


Depth of Treatment

• Angle Resolved XPS

• Mg-Al Source Comparison

• Depth profiling with cluster ions

0.04

0.06

0.08

0.1

0.12

0.14

0.16

25 29 32 36 40 44 47 51 55 59 62 66 70 74 77 81

O/C

Rati

o

Electron Take Off Angle (ETOA) (Degrees from the normal)

108MF treated

19T treated

STAMAX Treated


Depth Profiling

0

10

20

30

40

50

60

70

80

90

100

0 10 20 30 40 50 60

Ato

mic

perc

en

t (%

)

Etch Depth (nm)

C1s

O1s (5x)

Analysis on a K-Alpha using large cluster ions to etch (Ar1000)

Depth calculation using estimate from Irganox reference.


ToF-SIMS Identification of

Oxygenation

C3H5O

C4H9


mass / u69.00 69.05 69.10

4x10

2.0

4.0

Inte

nsit

y

4x10

1.0

2.0

Inte

nsit

y

4x10

0.5

1.0

1.5

Inte

nsit

y

4x10

1.0

2.0

Inte

nsit

y4x10

1.0

2.0

Inte

nsit

y

4x10

1.0

2.0

Inte

nsit

y

C3HO2

C4H5O C5H9

8 passes

6 passes

3 passes

2 passes

1 pass

Untreated


Variation with Treatment


Additives: ToF-SIMS Spectra

Additive Chemical structure Characteristic peaks

Ethylene Bis-steramide 282, 310

Irganox™ 1010 57, 203, 219, 259


Ablation of Additives

C18H36NO

C20H40NO C15H23O

C17H23O

Ethylene Bis-steramide Irganox™ 1010


Conclusions

• Increase of surface energy

• Level of treatment is most sensitive to

equivalence ratio

• Depth of treatment ≈ 20nm

• Ablation of detected additives

• Reduction of the methyl pendant group.

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