Greencoat: Atmospheric Plasma Deposited Coatings as Primer on Metal Substrates

Transcription

1 Greencoat: Atmospheric Plasma Deposited Coatings as Primer on Metal Substrates A. Kakaroglou 1, B. Nisol 3,G. Scheltjens 2, M Wadekar 5,I. De Graeve 1, G. Da Ponte 4. Van Assche 2, B. Van Mele 2, S.Paulussen 4, F. Reniers 3, H. Terryn 1 1-Research Group of Electrochemical and Surface Engineering (SURF), 2- Research Group Physical Chemistry and Polymer Science (FYSC), 3- Analytical and Interfacial Chemistry, Université Libre de Bruxelles, Faculty of Sciences - Brussels, Belgium 4-Vito, Belgium, 5-Cori Belgium

2 Aim of Research Paint Primer Conversion layer Cleaned-etched surf Metal project Paint GREENCOAT Metal Replace the metal pretreatment, the conversion layer and the primer with one environmental friendly coating. Why? Atmospheric plasma deposition: Low production cost, no use of vacuum, no need for solvents, no water

3 Greencoat Project Supported by Brussels Institute of Research and Innovation. Expertise in plasma Production of the coatings FYSC Expertise in surface characterization Chemical characterization Expertise in electrochemistry Electrochemical properties Expertise in polymers Thermomechanical properties Industrial Partners: Performance Tests Up-scaling of the production

4 What is plasma? Plasma is 4 th state of matter in which certain portion of the particles is ionized.

5 Surface Modification using Plasma Process recombination etching Substrate depositition Activation grafting Coating deposition NH OH F COOH 2 AtmosphericPressurePlasma Technology: a StraightforwardDepositionof AntibacterialCoatings, Plasma Processesand Polymers, Volume: 8, pp: 59-69, 2011, Sarghini S., PaulussenS., Terryn H. Impact factor

6 Plasma polymerisation Ar* H. Biederman, Plasma Polymer Films, Imperial College Press, London, UK, Electric glow discharge: Free electrons get energy from the electric field but they lose it when collide with molecules. Formation of free radicals. Free radicals interact with each other and with the substrate. Formation of a organic coating on the substrate.

7 Hybrid Systems 1 Silanes+nanoparticles oxid e Organic layer Native oxide Metal System 1 Organic layer Oxide Metal System 2 Metal System 3 System 2: layered system with tailored metal oxide layer System 3: hybrid system of mixed organic / metal oxide nanoparticle coating

8 Variables Substrate and pre-treatment: Aluminium: Al 99.99% or AA2024-T3 Alkaline treated with 25g/l NaOH at 70 o C: dipping for 6 sec. Organic medium: silanes bis-1,2-(triethoxysilyl)ethane (BTSE), for Systems 1 and 3 hexamethyldisiloxane (HMDSO), for System 2 (plasma deposition) Coating deposition methods Dip-coating from aqueous solutions (water-based) followed by curing Solvent-free plasma deposition: vacuum and atmospheric Metal oxide: CeO 2 nanoparticles Organic layer Native oxide Metal Organic layer Oxide Metal Metal oxid e System 1 System 2 System 3

9 Experimental setup Substrat e Coating solution Al 99.99% or AA2024-T3alkaline treated, to obtain a higher hydroxyl fraction for better bonding with silane Molecular structure of BTSE (1, 2-BIS (TRIETHOXYSILYL) ETHANE: (CH 2 ) 2 Si 2 (OC 2 H5) 6. NaOH solution 25g/L temperature 70 C immersion time 6 s Dipcoating (precursor: BTSE 5 wt% water based) Plasma deposition (precursor: BTSE 98 wt%) Schematic representation of the aluminium substrate cleaning + coating solution

10 Experimental setup Plasma source Chemical bubbler Process Gas Inlet Ar (30 L/min) Home made Shower ring Grounded Electrode Showerhead Powered Electrode Sample support Plasma Gas Inlet Plasma Zone Thermostated Baths, 100 C Showerhead 25 mm of diameter Precursor Inlet Home made Shower ring Substrate Holder Atmospheric plasma deposition tool Sample 5 mm Schematic of the atmospheric plasma deposition device

11 SEM analysis Wet deposition (water-based BTSE 5%) Dipcoating Plasma deposition (BTSE 98%) Vacuum plasma Atmospheric plasma SEM micrograph of the cross-section of BTSE films deposited on Al

12 Wet deposition (water-based BTSE 5%) Dipcoating Plasma deposition (BTSE 98%) Vacuum plasma Atmospheric plasma Adhesion property of the silane on aluminium depends on chemical bonding at the interface SEM micrograph of the cross-section of BTSE films deposited on Aluminium

13 Wet deposition (water-based BTSE 5%) Dipcoating hydrolysis condensation formation of hydrogen bonds interfacial bond formation SEM micrograph of the crosssection of BTSE films deposited on Al (*) E. P. Plueddemann, Silane Coupling Agents, Plenum Press, New York, 1991.

14 Wet deposition (water-based BTSE 5%) Dipcoating Plasma deposition (BTSE 98%) Vacuum plasma Atmospheric plasma Is there a covalent AlOSibond at the Plasma polymer-aluminium interface? SEM micrograph of the cross-section of BTSE films deposited on Aluminium

15 ToF-SIMS analysis Atmospheric plasma Vacuum plasma AlOSi + AlOSi Intensity Intensity Atmospheric plasma AlOSi+ 400 vacuum plasma AlOSi mass/u mass/u High-resolutionpositive ToF-SIMS measurementof AlOSi + nearnominal mass m/z equalto 71 (1) AlOSi + :theoreticalmass= amu (2) AlOSi + :experimentalmass= amu (2)-(1) = amu>> 0.01 amu Al 2 SiH 4 + Al 2 OH +

16 ToF-SIMS analysis Atmospheric plasma Vacuum plasma Plasma polymer BTSE film bulk Plasma polymer BTSE film bulk 2500 Al Interface Al Interface Al Intensity Si 2 O Intensity 1500 Al 2 O AlOSi Si 2 O AlOSi + Al 2 O + C C Time (s) Time (s) ToF-SIMS depth profile from plasma polymer BTSE film on Al (99.99%)

17 ToF-SIMS analysis C + Si 2 O + AlOSi + Al 2 O + Al 2 + Atmospheric plasma Z XZ C + Si 2 O + AlOSi + Al 2 O + Al 2 + Vacuum plasma Z XZ ToF-SIMS images from plasma polymer BTSE film on Al(99.99%) Evidence of covalent bond formation at the silane-metal interface during plasma polymerization of bis-1,2-(triethoxysilyl)ethane(btse) on aluminium, Chemical PhysiscsLetters, Volume: 493, N in volume: 1-3, pp: , 2010, BATAN A., PIREAUX J., ReniersF., Mine N., DouhardB., BrusciottiF., De Graeve I., VereeckenJ., Wenkin M., PIENS M., Terryn H.

18 System 1 - Summary EIS Minor differences between deposition methods in terms of barrier properties No self-healing as a function of time The small thickness of the sample affects corrosion properties more than their chemistry Comparisonbetweenwet depositionand plasma depositionof silanecoatingsonaluminium, Progressin OrganicCoatings, Volume: 69, pp: , 2010, BATAN A., BrusciottiF., De Graeve I., VereeckenJ., Wenkin M., PIENS M., PIREAUX J., ReniersF., Terryn H.

19 Atmosphericplasma depositionof (BTSE + CeO 2 nanoparticles) SEM analysis CeO 2 particles ~ 40 nm x x40000 x2000 x SEM micrographsof (ppbtse+ceo 2 )/Al (99.99%) in atmosphericplasma, 80 W, 30 min. EDX analysis confirmed the spots are Ce-based Characterization of thin water-based silane pre-treatments on aluminium with the incorporation of nano-dispersed CeO2 particles, Surface & Coatings Technology, Volume: 205, pp: , 2010, Brusciotti F., BATAN A., De Graeve I., Wenkin M., Willem R., PIENS M., Reniers F., PIREAUX J., Vereecken J., Terryn H.

20 Atmosphericplasma depositionof (BTSE + CeO 2 nanoparticles) Zone 2 Auger Point2 Ce a 0.4µm Auger Area2 Auger Area3 SEM image of an area with aggregates of particles Counts Cu O Ce Ce Ce Cu Cu Ce Energy (kev) TEM-EDX spectrum performed on of the Ceparticles in TEM image Auger mapping of the area shown in SEM image (a) of a plasma hybrid (BTSE and CeO 2 ) film Al LMM Ce NOO + Si LMM C KLL O KLL Ce MNN Overlay_02 global pt2 global area2 global area Kinetic Energy (ev) Al KLLSi KLL AES wide scan performed on an Al 99.99% substrate coated with atmospheric plasma (BTSE and CeO 2 )

21 General Conclusions (2/2) Thin films (<100nm) with nanodispersedceo 2 Cured film: possible bond between CeO 2 and BTSE after curing Same Interface than wet chemistry Barrier properties of the film increase with the presence of nanodispersed CeO 2 CeO 2 nanoparticles could be deposited with the BTSE through atmospheric plasma

22 Atmospheric plasma processing - The new DBD reactor set-up - Various deposition conditions for optimal operation - Introduction of monomer: various setups - Two flows to dilute the precursor vapor - Variables: Total flow, ratio Argon/monomer Power, frequency Deposition time

23 Investigation of coating chemistries Straight forward targeting approach: Primer for outdoor application: Based on previous findings on potential for barrier properties >> allylmethacrylate (AMA) Finishing for indoor application: Precursor which can not be deposited conventionally as a coating >> heptamethylnonane (HMN) CH2 C CH3 C O O CH2 CH CH2 Plasma Polymerization of a Saturated Branched Hydrocarbon. The Case of HeptamethylnonaneN. Vandencasteele, A. Kakaroglou, B. Nisol, I. de Graeve, G. Van Assche, B. Van Mele,H. Terryn, F. Reniers, C. De Vos* Plasma Process. Polym. 2012, 9,

24 Detailed investigation of polymerisation Straight forward targeting approach: Precursors to compare with AMA for plasma deposition to study the effect of unsaturated double C=C bonds Propyl isobutyrate (PiB) O C H 2 O CH 3 n- Propyl methacrylate (npma) CH 3 Allyl methacrylate (AMA)

25 Deposits of allylmethacrylate pp-ama versus conventional poly-ama FTIR allyl vinyl >> both reactive C=C are broken during plasma deposition >> potential for higher degree of crosslinking Allyl C=C bond stronger then vinyl C=C bond Allyl C=C decrease by lowering the flow of the AMA CH x /C=O ratio is increasing by lowering the AMA flow >> equivalent to higher energy per molecule in plasma

26 Deposits of allylmethacrylate Degree of crosslinking: conventional p-ama Conclusions from solid state NMR: (1) vinylc=cparthasreacted (2) allyl C=C part has not reacted to full extend >> no or little cross-linking

27 Deposits of allylmethacrylate Degree of crosslinking: pp-ama Conclusions from solid state NMR: (1) broader resonances >> due to non-equivalent environments and/or increased degree of molecular rigidity (2) vinyl C=C part has reacted (3) allylc=c part has reacted (not complete) >> Higher degree of crosslinkingin plasma AMA then in conventional AMA >> Possible presence of free radicals to be confirmed with Electron Spin Resonance

28 13 C Nuclear Magnetic Resonance Poly(AMA) Plasma deposited In plasma deposition: Extra peak 8 Peaks 2&3 lower Indication for polymerisation of the allylic moiety. Broader peaks Due to the random structure of the plasma polymerisation A. Kakaroglou, G. Scheltjens, B. Nisol, I. De Graeve, G. Van Assche, B. Van Mele, R. Willem, M. Biesemans, F. Reniers, H. Terryn, Plasma Processes and Polymers 2012, 9,

29 Deposits of allylmethacrylate Electron paragmagnetic resonance spectroscopy of pp-ama Aim: Detection of temporarily stable trapped radicals inside the polymer (a)80w, 2 slm, stored at low T (liquid N2) >> signal indicating trapped radicals (b) 30W, 1 slm, stored at RT >> no signal (c) 30W, 2 slm, stored at RT >> weak signal (d) 80W, 1 slmstored at RT >> weak signal >>> Trapped radicals are short lived Signal Intensity Signal Intensity c a H pp g-factor Magnetic Field (G) Magnetic Field (G) Signal Intensity Signal Intensity d b Magnetic Field (G) Magnetic Field (G) >>> confirms that peak broadening in NMR is due to higher degree of crosslinking and not due to trapped radicals

30 Deposits of allylmethacrylate In-depth thermal analysis of pp-ama: DSC General observations for all AMA coatings: Temperature ( C) st hc 2 nd hc 3 rd hc Time (min) 30 W_11.8 khz_2'_0.5 L/min DSC analysis Temperature profile: rate = ±20 C/min. cooling to -90 C + heating cycle (hc) to 200 C 3 heating cycles -Exothermic reaction peak observed in the first heating st heating C 232.0mJ >> not fully reacted system -Initial Tgin broad range of C for plasma AMA compared to 50 C for conventional poly-ama Heat Flow (mw) nd heating 3rd heating C >> lower Tgcompared to full network type polymeric coating Exo Down Temperature ( C) Universal V4.5A TA Instruments

31 Barrier properties of pp-ama EIS Coatings with increasing thickness Power (W) Vis-SE Thickness (µm) C/O ratio (from XPS) Z Frequency (Hz) 30W 30W-2 40W 50W 70W 90W Blank >> evidence of barrier behaviour confirms degree of crosslinking, even as the coating has a relatively low Tg >> higher thickness =better barrier properties pag. 31 theta Frequency (Hz)

32 Property testing Adherence testing by CoRI Set-up: Plasma coatings have been applied on 5005-H24 commercial aluminium alloy. As these coatings will be used as primers in the industry, a commercial topcoat has been applied on them. Three paint systems are being evaluated: Paint 1 is waterborne adhesion primer Paint 2 is an anticorrosive paint for steel and zinc protection based on zinc phosphate Paint 3 is powder paint (polyester based) Adherence testing cross-cut tape test and pull-off test on AMA coatings

33 Samples Paints Pull off Rupture test S (MPa) Paint 1 9,37 1% adhesive substrate/paint + 99% cohesive Paint 1 7,42 cohesive cross-cut ISO AMA NX 90-30w -17,1 khz - 2min AMA NX 90-30w - 17,1 khz - 2min AMA NX 90-30w - 17,1 khz - Paint 1 8,49 cohesive 2min AMA NX 90-30w - 17,1 khz - Paint 1 7,92 cohesive 2min AMA NX 90-30w - 17,1 khz - Paint 1 8,3+0,83 0 2min blanc Paint 1 10,99 100% cohesive blanc Paint 1 12,37 100% cohesive blanc Paint 1 11,23 100% cohesive blanc Paint 1 blanc Paint 1 11,53+0, 74 AMA NX 90-30w - 17,1 khz - 2min AMA NX 90-30w - 17,1 khz - 2min AMA NX 90-30w - 17,1 khz - 2min AMA NX 90-30w - 17,1 khz - 2min Paint 2 8,69 2% adhesive substrate/paint + 50% adhesive paint/plot + 48 % cohesive Paint 2 10,72 2% adhesive substrate/paint + 2% adhesive paint/plot + 96 % cohesive Paint 2 7,78 10% adhesive substrate/paint + 80 % cohesive Paint 2 6,27 8% adhesive substrate/paint + 3% adhesive paint/plot + 89 % cohesive AMA NX 90-30w - 17,1 khz - 2min Paint 2 8,4+1,9 0 blanc Paint 2 9,37 100% cohesive blanc Paint 2 11,83 100% cohesive blanc Paint 2 9,48 100% cohesive blanc Paint 2 9,71 100% cohesive blanc Paint 2 10,09+1, WP 4: Property testing Adherence testing on pp-ama >> High Adherence Rupture between glue and coating >> The high adhesion values, 8 MPa -10 MPa show that this kind of primer is certainly a very promising pretreatment prior to the application of top coatings.

34 Plasma polymerisation + inhibitor IP protection: ALUMINIUM SUBSTRATE INHIBITOR AMA Multimetal coating as primer for outdoor application Steel, galvanised steel, aluminium All-in-one coating procedure

35 Hybrid coatings AMA+inhibitor Cerium dibutyl phosphate Ce(dbp)3 The Phase-I-concept AES depth profile confirms gradient structure SEM image: Cerium inhibitor particles with uniform distribution, but also some agglomerations XPS confirms presence of active Ce III+ ions XPS expected ratios of C-C:C-O-P, C-O-P:P=O indicate the presence of indeed Ce(dbp) 3

36 Local electrochemical behaviour: Current density mapping by SVET uncoated aluminum AA2024 coated aluminum AA hours a. c. b. d. 24 hours

37 Conclusions for plasma deposited AMA Scientific relevant properties: Plasma deposition radicalizing of AMA from both allyl and vinyl sides Chemistry driven by deposition energy per precursor molecule Higher crosslink density then for conventional poly-ama Not fully reacted films, low Tg values and broad Tg range Further conversion during post-heating results in thinning and densification >> Organic network film but not typical poly-ama Industrial relevant properties: High deposition rates (up to ~10 nm/sec) High adherence with substrate and topcoat > good primer! Stable barrier behavior Add inhibitors

38 Upscaling carrier gas: N2, He, Ar, O2, CO2 (air) frequency range: 250 Hz 250 khz high voltage range: 1 kv 40 kv dissipated power: W/cm2 Reactor VITO

39 Thank you for your attention

40 Experimental setup- Depositions Introduction Plasma deposition Chemistry and Structure Performance Conclusions Q tot =Q p +Q s =4 slm Atmospheric Dielectric Barrier Discharge Plasma Two experimental setups used Monomer introduction from ring Rotation of the bottom electrode. Thickness homogeneity. Minor changes in the chemistry distribution. Fixed power (30 W), Fixed frequency (17.1kHz), Fixed deposition time (120 s), Monomer feed: 4 mg/min, 8.3 mg/min, 15 mg/min, 30 mg/min, 73 mg/min.

41 Deposits of allylmethacrylate In-depth thermal analysis of pp-ama: DSC C(T) J/(g C) C DSC curves of pp-ama samples at 30 W (blue) and 80 W (red) - HPS DSC crucibles. -Heating and cooling rate 5 C/min. (Two successive heating cycles) >> 30 W sample, a large residual reaction exotherm of about -200 J/g Exo Down >> 80 W sample, the residual Temperature ( C) reaction exotherm is smaller = -90 J/g >>>> higher deposition plasma power results in higher degree of conversion, in line with chemical analyses by XPS >>>> no need for trapped radicals to get further conversion; other reactive groups are still present Heat Flow (W/g) New observation: 10% weight loss during DSC measurements using perforated crucibles (for heating up to 250 C) C C C C J/g C J/g Universal V4.1D TA Instruments