Oxford Advanced Surfaces

Transcription

1 Oxford Advanced Surfaces The Practical Uses of Chemical Adhesion In Interlayer Bonding AIMCAL Europe 2012 Web Coating Conference 1

2 Adhesion is important! In use and in process Adhesion Relates to other factors such as chemical and water resistance Numerous ways of improving adhesion some better then others Many myths and out there

3 VDW Polar Mechanical Adhesion Chemical Diffusion Surface Wetting?

4 Chemical Adhesion Why is chemical adhesion appealing? Figures speak for themselves Bond Type Van der Waals Acid Base Chemical Bond strength 1KJ/mol 50 KJ/mol >200 KJ/mol Also helps with stability to hydrolysis and solvent resistance So why bother with other bonding modes

5 Real Chemical Adhesion Or maybe just Practical Chemical Adhesion Fundamentals of chemical adhesion 3 step plan Substrate Coating Mutual Reactivity

6 Real Chemical Adhesion 1. Need reactive or functional substrate Glass Metals Natural polymers Polyamides Surface prepared materials (e.g. hydrolysed TAC) 2. Need reactive or functional coating Epoxy Rad Cure

7 Real Chemical Adhesion Substrate and Coating must have mutual Reactivity Possible to cheat and stack odds in your favour Surface modification to alter chemical nature Silanes, Thiols, Phosphonates Chemical Pre-Treatments Reactive Intermediates Plasma or Corona

8 Plasma/Corona to introduce a mix of chemistry (and to roughen and break up the surface) Surface Modification Glass fibre to epoxy bonding:- silane treatments Nanoparticle modification for binder compatibility OH 3 R' Si OH + OH OH OH OH Inorganic/Metal Surface O R' R' R' Si O Si O Si Silane Modifed Inorganic/Metal Surface O Basic hydrolysis of TAC to produce cellulose surface

9 Surface Modification Other Factors Density of functionality High for a reactive substrate or a SAM modification Variable for everything else Wetting Rate of Reaction: -Difference between theory and practice c.f. Hydroxyl modification and isocyanate coating Amine modification and isocyanate coating Competitive side reactions vs. premature curing

10 Next Generation Products Adhesion of a Polyester (PEN) to Fluoropolymer coating Critical for the manufacture of next gen flexible OTFT Adhesion critical during processing :- R2R vs. rigid System is:- chemically inert on both sides conformal coating (wetting not an issue) no diffusion or entanglement plannerised PEN Worst combination you could have!

11 Onto Reactive Chemistry Based on highly reactive intermediate chemistry Unique carbene chemical reactivity Solution Processable

12 Onto Reactive Chemistry Onto Cross-linker systems allow chemical bonding between inert interfaces Multiple reactive heads allow bonding in 3-dimensions

13 Process Schematic Coat Teflon-AF Cure Coat Onto-XL Coat Teflon-AF Cure

14 Analysis of the Onto Layer 5.02 nm 5.53 nm 1.0µm 0.00 nm 400nm nm Z[nm] X[µm]

15 Attempted Cross-Hatch Tape Testing Untreated Treated

16 Nano-indentation 40 mn Load

17 Control Film Failure 2 nd Topography (after scratch test) 1 st Topography (before Scratch)

18 Control

19 Control

20 Treated Film Failure No Delamination

21 Treated

22 Nano-indentation pendulum test

23 Control 2mN 3mN 4mN 5mN 10mN 20mN Delamination Treated 2mN 3mN 4mN 5mN 10mN 20mN 80mN No bubbling effect around the impact

24 Solvent Resistance Control Immersion Line Immersion Line Treated

25 Mobility Printing an OTFT

26 Summary Chemical Adhesion is a powerful tool In practice not so easy to achieve Should be used in harmony with other techniques Will become more apparent when dealing with smooth low surface energy materials Or inert coatings

27 Oxford Advanced Surfaces Acknowledgments Dr Remedios H Perni Dr Stuart Hunter Dr David King Dr Gareth Wakefield Dr Jonathan Moghal Oxford University PETEC Prof Mark Moloney Dr Simon Ogier