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

Transcription

1 David F Williams, Marie-Laure Abel, Eddie Grant*, John F Watts Department of Mechanical Engineering Sciences 24 February 2015

2 Flame Treatment Used for Many Years

3 Seminal Publications

4 Flame Treatment of PVC

5 Automotive Flame Treatment

6 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

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

8 Industrial Examples of 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 Polypropylene Grades Investigated DESIGNATION POLYMER DESCRIPTION TYPICAL USE Sample A: Super high impact polypropylene copolymer Bumpers Sample B: 40 % talc-filled polypropylene homopolymer Under the hood (fan shrouds) Sample C: 20 % talc-filled polypropylene homopolymer Under the hood (fan shrouds) Sample D: 20 % long glass filled polypropylene copolymer Various (e.g. panel carriers) instrument

11 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 upstream of burner Burner PP gap = 100 mm ( mm range) Conveyor speed = 1 ms -1 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

12 Instrumentation Used

13 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

14 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

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

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

17 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

18 Influence of Dwell Time Sample A

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

20 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

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

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

23 Atomic percent (%) Depth Profiling: MAGCIS/XPS Etch Depth (nm) C1s O1s (5x) Analysis on a Thermo Scientific K-Alpha using large cluster ions to etch (Ar 1000 ). Depth calculation using estimate from data of Cumpson et al (in press).

24 ToF-SIMS Identification of Oxygenation: Sample C C 3 H 5 O C 4 H 9 Treated Untreated

25 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 pass 4 x Untreated: Sample A mass / u

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

27 Ablation of Additives: Sample A Ethylene Bis-steramide Irganox 1010 Treated C 18 H 36 NO C 20 H 40 NO C 15 H 23 O Untreated C 17 H 23 O

28 Conclusions Flame treatment can bring about three possible processes: Removal of low molecular weight hydrocarbon Removal of surface segregated processing aids etc Oxygenation of PP Increase of surface energy Level of treatment is most sensitive to equivalence ratio Depth of treatment 15 nm Oxygenation of the methyl pendant group.