loading page

Combination of NIR and UV-LEDs Enables Physical and Chemical Drying of Aqueous Coating Dispersions as New Green Technology
  • +2
  • Bernd Strehmel,
  • Lukas Appelhoff,
  • Nicolas Hornemann,
  • Jochen Schmidt,
  • Anita Krautz
Bernd Strehmel
Hochschule Niederrhein - Campus Krefeld West

Corresponding Author:[email protected]

Author Profile
Lukas Appelhoff
Hochschule Niederrhein - Campus Krefeld West
Author Profile
Nicolas Hornemann
Actega GmBH
Author Profile
Jochen Schmidt
Actega GmBH
Author Profile
Anita Krautz
Actega GmBH
Author Profile

Abstract

Heptamethine based cyanines, namely 1,3,-trimethyl-2-(2-2[2-phenylsulfanyl-3-[2-(1,3,3-trimethyl-1,3,3-trithyl-1,3-dihydro-indol-2-ylidene)-ethylidene]cyclohex-1-enyl]vinyl)-3H-indolium chloride ( S1) and 2-[2-(2-chloro-[2-[1,1-dimethyl-7-sulfo-3-(4-sulfobutyl)-1,3-dihydro-benzo[e]indol-2-ylidene]-ethylidene]cyclopent-1-enyl]vinyl]-1,1-dimethyl-7-sulfo-3-(4-sulfobutyl)-1Hbenzo[e]indolium hydroxide, inner salt, triethylammonium salt ( S2), efficiently result in physical drying of an aqueous dispersion comprising a polyurethane binder. S2 possesses a water solubility of 40 g/L. A high-intensity NIR-LED emitting at 820 nm with an intensity of 1 W/cm 2 served as light source. The cyanine converted the light absorbed into heat by internal conversion needing less drying time compared to conventional drying. Water content after film formation showed less then 1%. In the second step, UV exposure with a LED emitting at 395 nm resulted in formation of semi-interpenetrating polymer networks by crosslinking of the multifunctional (meth)acrylate operating as reactive diluent. TPO-L served as effective UV-photoinitiator. Furthermore, the UV-exposure together with Norrish Type I and Type II photoinitator systems results in a very efficient bleaching of the green physical dried film. This contribution shows for the first time a new photonic hybrid technique describing successful replacement of an oven-based process by a photonic based step that generates heat needed for drying.
29 Jan 2024Submitted to Applied Research
21 Feb 2024Reviewer(s) Assigned
07 Apr 2024Editorial Decision: Revise Minor
25 Apr 20241st Revision Received
26 Apr 2024Reviewer(s) Assigned
01 May 2024Review(s) Completed, Editorial Evaluation Pending