Flame Treatment of Polypropylene: A Study by Electron and Ion Spectroscopies

Transcription

1 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 13 th 18 th October 2013

2 Flame Treatment Used for Many Years

3 Seminal Publications

4 Automotive Flame Treatment

5 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

6 Flame treatment Increases the surface energy Ablative cleaning Improved adhesion Active region Main reaction zone The Aerogen Company (2013)

7 Industrial Examples of Flame Treatment

8 Flame treatment

9 Polypropylene Automotive Grade PP Polymer All Filled with carbon Black A homopolymer with no additional filler A homopolymer with 40% talc Designation A B A copolymer with 20% talc A polymer with 20% long glass fibre C D NB Plus unknown processing aids 1 dyn cm -1 = 1 mn m -1

10 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 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

11 Instrumentation Used

12 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

13 Parameters Investigated Parameters Burner to substrate distance Equivalence ratio = Ø Dwell time m fuel /m oxidiser Ø = (m fuel /m oxidiser ) stoich Effects Depth of treatment Ablation of surface material Ageing Chemical changes Topography changes Surface energy changes

14 Example XPS Spectra XPS spectra for Sample A untreated (lower) and treated (upper).

15 As Received PP Samples Sample B Sample C Sample A Sample D

16 Surface Composition vs Contact Angle Specimen Surface Composition Atomic % Carbon Oxygen Sulphur O/C ratio Water Contact Angle ( ) Dyne Ink (mn m -1 ) A B <30 C <30 D

17 Influence of Dwell Time

18 Effect of Multiple Passes on Surface Properties Specimen C O S N O/C Contact Dyne ratio angle ink level Sample A Untreated pass passes passes passes N/A N/A 7 passes N/A N/A Sample B Untreated < Sample C Untreated <30 1 pass passes passes Sample D Untreated pass passes

19 O/C ratio Contact angle (Degrees) Dwell Time (Passes Through Increased by using more passes Flame) 1,2 and 3 passes used (0.02, 0.04 and 0.06s respectively) O/C Ratio Contact Angle Number of passes Sample A X Sample B Sample C Sample D Number of passes

20 Water contact angle (degrees) O/C ratio Burner Gap Burner gap (mm) Sample C X Sample D Sample A Sample B Burner gap (mm)

21 O/C Ratio Water Contact Angle (degrees) Equivalence Ratio Equivalence Ratio Equivalance Ratio Sample A X Sample C Sample B Sample D

22 O/C Ratio Water Contact angle (Degrees) Ageing Test Untreated 0 Days 7 Days 14 Days 21 Days 26 Days 42 Days 49 Days Untreated 0 Days 7 Days 14 Days 21 Days 26 Days 42 Days 49 Days Sample C X Sample B Sample A Sample D

23 Valence Band polyethylene Valence band spectra for Sample B polypropylene untreated treated with 1 pass Briggs (1979) treated with 2 passes treated with 3 passes

24 Mono XPS Valence Band Untreated 1 Pass 3 Passes 7 Passes

25 O/C Ratio Depth of Treatment Angle Resolved XPS Mg-Al Source Comparison Depth profiling with cluster ions MF treated 19T treated STAMAX Treated Electron Take Off Angle (ETOA) (Degrees from the normal)

26 Atomic percent (%) Depth Profiling Etch Depth (nm) C1s O1s (5x) Analysis on a K-Alpha using large cluster ions to etch (Ar 1000 ) Depth calculation using estimate from Irganox reference.

27 ToF-SIMS Identification of Oxygenation C 4 H 9 C 3 H 5 O

28 Intensity Intensity Intensity Intensity Intensity Intensity 4 x C 3 HO 2 C 4 H 5 O C 5 H 9 8 passes 4 x passes 4 x passes 4 x passes 4 x x pass mass / u Untreated

29 Variation with Treatment

30 Additives: ToF-SIMS Spectra Additive Chemical structure Characteristic peaks Ethylene Bis-steramide 282, 310 Irganox , 203, 219, 259

31 Ablation of Additives Ethylene Bis-steramide Irganox 1010 C 20 H 40 NO C 15 H 23 O C 18 H 36 NO C 17 H 23 O

32 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.