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