Self-Healing polymer coating. NGUYEN Thi Thanh Tam

Transcription

1 Self-Healing polymer coating NGUYEN Thi Thanh Tam

2 Professor Paul V Braun: BS degree, with distinction, at Cornell University PhD in Materials Science and Engineering from UIUC in 1998 One year postdoctoral appointment at Bell Labs, Lucent Technologies, Assistant professor of Materials Science and Engineering at UIUC in 1999 Part-time faculty member of the Beckman Institute. Named a University Scholar by the University of Illinois (2006). from UIUC Many Awards: Beckman Young Investigator Award (2001) 3M Nontenured Faculty Award (2001); The Robert Lansing Hardy Award from TMS (2002) Willett Faculty Scholar Award (2002) The Xerox Award for Faculty Research (2004), The Burnett Teaching Award from the Department of Materials Science and Engineering (2005), Research interest: a wide range of materials science disciplines, chemistry conducting polymers, nanostructured ceramics, semiconductors, biomaterials, liquid crystals, nanoreactor, drug delivery, microelectronics, optical material.

3 Topic Polymeric coatings: Highly stable to species present in the environment Protect a substrate from environmental exposure, When they fail, corrosion of the substrate is greatly accelerated WHY?

4 Microcracking in polymeric composites Microcracking Significant compromise of the integrity of structure Mechanical degradation of fibrereinforced polymer composites Electrical failure in microelectronic polymeric components Worldwide cost of corrosion: nearly y$ 300 billions/ /year Self-preparation of polymeric component is important

5 Self-healing coating What is it? Self-healing coating = Automatically repair and prevent corrosion of the underlying substrate Respond without external intervention to environmental stimuli in a Respond, without external intervention, to environmental stimuli in a productive fashion.

6 Various approaches for achieving healing functionality Encapsulation Monomer phase separation Reversible chemistry Nanoparticle phase separation, Polyionomers, Hollow fiber Microvascular networks.

7 Encapsulation approach First work kdiscribed dby White and al.: autonomic healing of polymer composites Cracks form in the matrix wherever damage occurs Ruptures the mucrocapsules, releasing the healing agent into the crack plane through capilary action Contact of healing agent & catalyst, triggering polymerization that bonds the crack faces closed SR S.R. White and al., Nature. 2001, 409,

8 Chemistry of this self-healing system ROMP: living ring-opening methathesis polymerization Long self-life, low monomer viscosity and volatility, rapid polymerization at RT, low shrinkage upon polymerization G bb t l t hi h t th i ti it t l t f id f Grubbs catalyst: high metathesis activity, tolerant of a wide range of functional groups

9 Mechanism of ROMP Initiation by a carbene transition metal (Ru, W, Mo)

10 NMR studies in an epoxy matrix Rubbs catalyst Solid state 31 P-NMR and 1 H-NMR of self-assembling composite: characteristic signals of PCy 3 and of liquid DCPD monomer, respectively Stability of Rubbs Catalyst and DCPD monomer within the polymer matrix

11 Rupture & release of the microencapsulated agents A time sequence of video (optical) images describing a rupture of a filled microcapsule with a red dye and release of healing agent.the elapsed time from the left to right image is 1/15 s Fracture plane of a self-healing material with a ruptured ureaformaldehyde microcapsule in a thermosetting matrix by SEM

12 ESEM and IR: evidence of polymerization induced by damage Neat DCPD Authentic Poly(DCPD) Poly(DCPD) film formed at the healed interface ESEM micrograph and IR analyses Highlighted peak at 965cm -1 : Trans double bonds of ring-opened poly (DCPD)

13 Limitations Crack-healing kinetics Instability of the catalyst to environmental conditions Poor dispersion i of Grubbs catalyst t in epoxy matrix Attack of epoxy s curing agent (DETA) on Grubbs catalyst: reduction of catalyst amount Encapsulation of Grubbs catalyst needed

14 Encapsulation: wax-protected catalyst microspheres for efficient Self-healing Materials S. R. White and al., Adv. Mater. 2005, 17,

15 Results: Much lower destruction of catalyst by DETA Much lower overall catalyst loading Much better dispersion of catalyst particles

16 Healing efficiency Only 0.75 wt % catalyst t loading, healing efficiency i is 93 % Much better healing efficiency compared to the cas of unprotected catalyst

17 Limitations: The self-healing system based on poly(dcpd): - Air and water, high h temperature t unstable - High cost of catalyst An other self-healing composite needed

18 Self-healing by monomer phase separation: P. V. Braun,S. R. White, Adv. Mater. 2006, 18, PDMS-based self-healing materials Polydimethylsiloxane: PDMS

19 Advantages over the previous methodologies Chemically stable in humid or wet environments Stable in the air and high temperature (>100 C) Widely available and comparatively low in cost Simplicity of procedure Organotin catalyst: limit side reaction

20 Schematic of self-healing process a. Self-healing composite consisting of: -Microencapsulated catalyst t - Phase-separated healing-agent droplets - Green matrix b. Crack propagating into the matrix releasing catalyst t into the crack plane c. Crack healed by polymerization of healing agent PDMS d. Empty microcapsule of a fracture surface and phase-separated healing agent

21 Polycondensation of HOPDMS with PDMS DBTL, 50 C, Air or water media DBTL = Di-n-butyltin dilaurate

22 Self-healing efficiency under real-world conditions RH: relative humidity High RH: >90 % Low RH: <10 % The fracture load of the sample healed under water decrease only 25 % with respect to the other samples

23 Aim Obtain a self-healing polymer, effective for both model and industrially important coating systems Respond to rigorous demands: chemical stability, p g y, passivating ability and any external stimuli excluded

24 Choice of self-healing system Catalyst: Rubbs catalyst: costly, air and water unstable Organotin catalyst: cheap, widely available, air, water and temperature stable Healing agent: DCPD: catalyzed by Rubbs catalyst, good mechanical properties of crosslinking materials Mixture HOPDMS + PDES: catalyzed by Organotin catalyst, performance of chemicalstability and passivating ability but not exceptional mechanical strength th of the healed matrix Siloxane-based materials system:best choice

25 Two Strategies Two self-healing coating approaches: 1.Microencapsulation of the catalyst and phase-separated droplets of healing agents within an epoxy vinyl ester matrix 2. Encapsulation of both catalyst and healing agents Encapsulation of both phases is advantageous in cases capsu at o o bot p ases s ad a tageous cases where the matrix can react with the healing agent

26 Optimal percentages of components in the self-healing matrix The maximum efficiency of healing for samples containing 12 wt % PDMS, 4wt % adhesion promoter and 3.6 wt % microcapsules

27 First strategy:only catalyst encapsulated This model system consists of: Epoxy vinyl ester matrix 12 wt % phase-separated healing agent: mixture HOPDMS + PDES 3 wt % catalyst DMDNT in microencapsule polyurethane (PU)) 3 wt% adhesion promoter (methylacryloxy propyl triethoxy silane)

28 DMDNT/ chlorobenzene-filled PU Capsules Optical microscopy Size histogram Average 90 µm in diameter DMDNT: dimethyldineodecanoate tin (catalyst)

29 Microcapsule Synthesis DBTL containing microcapsule

30 Interfacial Polymerization: chlorobenzene/h 2 O 70 C, 2 h Stirring: 1000 rpm

31 Thermogravimetric Analysis (TGA) Primary weight loss: 131 C near the boiling point of chorobenzene Primary weight loss: 131 C, near the boiling point of chorobenzene Secondary weight loss : 225 C, decomposition of PU shell

32 Procedure of corrosion test Healed coated steel or control sample Hand scribing 100 µm by razor blade 1. Healing, 50 o C, 24 h 2. Immersed in 5 wt % NaCl solution, 24 h Rapidily corrosion Extensive rust formation within the groove of the scribed and extending across the substrate surface Self-healing simple Control simple No visuel evidence of corrosion, osion even en 120 h after exposure e

33 Necessary presence of both healing agents and catalyst Coating without catalyst Coating without PDMS Removal of either phase: rapid corrosion of coating

34 SEM images of the scribed region Control simple Self-healing sample In the self-healing coating:40 % of damage filled In the control simple: scribe with 15 µm of extension into the metal substrate

35 Profilometry and EDS. Good agreement with SEM mesurements

36 Further evidence by electrochemical testing System consists of: An electrochemical cell: coated metal substrate A platinum electrode held 3 V An aqueous electrolyte (1M NaCl) Current versus time Before scribing, current passing: -Nearly identical: ~ 0.34 µa cm -2 through both control and self-healing coating After scribing and healing, current passing : ma cm -2 through control simple and 12.9 µa cm ma cm -2 through self-healing samples Dramatically reduced current for the self-healing coating

37 Limitation & solution Systems consisting of phase-separated PDMS healing agent: PDMS healing agent in direct contact with the coating matrix, susceptible to matrix initiated reactions Strategy: Protect also healing agent PDMS by encapsulation Dual capsule self-healing coating system

38 Second strategy: Dual capsule coating system PDMS Microcapsules TGA Optical microscopy image Average diameter of PDMS capsules is 60 µm Slow So Weight eg loss ossat 150 CC Overall small weight loss at 500 C High thermal stability of PDMS

39 Dual capsule self-healing coating system Preliminary corrosion Testing Inadequate adhesion of this epoxy-based coating and the substate Application of 50 µm thick epoxy-based primer layer to the substrateand cured prior to coating application Corrosion-test for 100 µm thick control and dual capsule self-healing coating simples All control simples: extensive corrosion after only 24 h of salt water exposure Self-healed simples (healed 24 h at 50 C), no evidence of rust formation, even after 120 of exposure

40 Dual capsule self-healing coating system Control experiments All images 75 mm x 150 mm. a, Matrix + adhesion promoter. b, Matrix + adhesion promoter + PDMS healing agent. c, Matrix + adhesion promoter + catalyst containing microcapsules. d, Matrix + adhesion promoter + catalyst containing microcapsules + PDMS healing agent (self-healing sample) Removal catalyst and/or healing agent resulted in rapid corrosion No evidence of rust formation for self-healed samples

41 Summary of corrosion testing of control and self-healing simples a, Matrix + adhesion promoter. b, Matrix + adhesion promoter + PDMS healing agent. c, Matrix + adhesion promoter + catalyst containing microcapsules. d, Matrix + adhesion promoter + catalyst containing microcapsules cocapsues+ PDMS healing agent (self-healing sample). All images 75 mm x 150 mm.

42 Dual capsule self-healing coating system Efficient at RT True self-healing: no external intervention, including heating to temperatures greater than ambient DMDNT: reduced catalytic activity at RT TKAS: a highly effective catalyst for curing PDMS, not require moisture for activation C 4 H 9 C 4 H 9 Successful for preparing a true self-healing coating (at RT) C 4 H 9 C 4 H 9 Sn O H 3 COCO H 3 COCO Sn O C 4 H 9 C 4 H 9 Si Sn OCOCH 3 O C 4 H 9 O Sn C 4 H 9 H 3 CCOO Potential self-healing coating for moisture-free environments: aerospace applications; buries interfaces TKAS: Si [OSn(n-C 4 H 9 ) 2 OOCCH 3 ] J. Appl. Polym. Sci. 1998, 70, 2235 Macromol. Chem. 1980, 181, 2541

43 Synthesis of TKAS C 4 H 9 C 4H Sn H 3 CCOO OOCCH 3 Di-n-butyltin diacetate 150 C, anhydrous - AcOEt EtO Si OEt C 4 H 9 C 4 H H 3 COCO Sn C 4 H 9 C 4 H 9 Si Sn O OCOCH 3 O H 3 COCO Sn O O Sn C 4 H C 9 4 H 9 H 3 CCOO EtO OEt Si[OSn(n-C 4 H 9 ) 2 OOCCH 3 ] C 4 H 9 C 4 H 9 Tetraethylsilicate TKAS US patent t 4, 137, 249, 1979

44 Corrosion performance in real-world condition Control and self-healing samples of general epoxybased coating system a, b c, d Efficacy of the RT activity for both systems Control and self-healing samples of a commercial marine (epoxy) coating system

45 Conclusion & perspectives Conclusion: Dual-capsule l PDMS healing system: chemical compatibility and stability TKAS catalyst: autonomic corrosion protection under ambient environmental conditions Perspective: Formulation of multilayer coating to provide self-healing functionality while maintaining extreme tolerances on surface finish, specific requirements for engineered primers, or unique surface chemistries (self-cleaning) l Microcapsule motif: a delivery mechanism for multifunctional chemical agent, antimicrobial i agent