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S. Dahle, T. Waters, W. Maus-Friedrichs

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Presentation on theme: "S. Dahle, T. Waters, W. Maus-Friedrichs"— Presentation transcript:

1 Dielectric barrier discharges prevent cracking in hard latex dispersion coatings
S. Dahle, T. Waters, W. Maus-Friedrichs Clausthal University of Technology Friday, November 10, 2017

2 Latex dispersions Miniemulsion polymerization: Insoluble monomer(s)
Surfactant in water Dispersion by ultrasound Radical polymerization aqueous polymer dispersion “Latex is a stable dispersion (emulsion) of polymer microparticles in an aqueous medium.” Wikipedia (11/06/2017) e.g. natural rubber latex (caoutchouc) Synthetic latexes usually emulsified using surfactants T. Waters

3 Film formation Tg and Young‘s modulus  adjusted by copolymerization of different monomers Keddie, J. L.; Routh, A. F., Fundamentals of Latex Film Formation: Processes and Properties. Springer: 2010.

4 Cracking and Delamination
(MMA/BA 60/40; Tg = 21°C) Cracking + Delamination (MMA/BA 70/30; Tg = 38°C) Softer films: no cracks, but tacky and less sturdy Film-formation dilemma

5 Dielectric Barrier Discharge – Setup
T. Waters

6 Effect of DBD plasma Untreated 15 min DBD 70%/30% MMA/BA – Tg = 38°C

7 Temperature influence
Room temperature 15min DBD

8 Temperature influence

9 Fourier-Transform Infrared Spectroscopy
C=C bond found in MMA but not PMMA C=C bond seen after DBD treatment Chain scission Isopropanol removes MMA Effects of SDS, HD and AIBN excluded

10 Atomic Force Microscopy
Untreated latex, no diffusion and so resulted in a cracked film 5 – 20 Minute treatment shows particles swelling Monomer absorption into particles Isopropanol removes these large particles (monomer)

11 Conclusions Cracks prevented via DBD treatment Monomer content
Depolymerization Swelling of particles Monomer as plasticizer Monomer content Easy removal by washing in isopropanol Only present in upper part of the film

12 Acknowledgements Thomas Waters Prof. Wolfgang Maus-Friedrichs
Prof. Diethelm Johannsmann Prof. Joseph Keddie Lisa Wurlitzer Heike Römermann


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