Progress in Organic Coatings 55 (2006) 154–159 Two-step curing processes for coating application Barteld de Ruiter a,∗ , Abdelkrim El-ghayoury a,1 , Harald Hofmeier b , Ulrich S. Schubert b , Mircea Manea c a TNO Science and Industry, Materials Technology, P.O. Box 6235, 5600 HE Eindhoven, The Netherlands b Eindhoven University of Technology and Dutch Polymer Institute (DPI), Laboratory of Macromolecular Chemistry and Nanoscience, P.O. Box 513, 5600 MB Eindhoven, The Netherlands c Perstorp Specialty Chemicals, Perstorp, Sweden Received 14 July 2005; accepted 19 September 2005 Abstract Two novel two-stage cure processes will be described, both involving oxetane chemistry. In both processes, the two consecutive cure processes are completely separated from one another. In the first process, two UV-initiated cure steps are combined, which are separated through their different polymerization mechanisms, i.e., free-radical and cationic. Possible application areas include deformable coatings, e.g., abrasion-resistant coatings and coil coatings. The second process refers to the combination of a covalent cationic cross-linking step and a supramolecular, reversible cross-linking step (through metal–ligand interaction). This could lead to a novel class of coatings with unprecedented rheological properties, with potential applications as “self-healing” coatings. Examples of these processes will be described in detail. © 2005 Elsevier B.V. All rights reserved. Keywords: Dual cure; UV curing; Oxetanes; Supramolecular cross-linking 1. Introduction An increasingly important application of photocrosslinkable systems is the mechanical protection of plastic surfaces, i.e., the improvement of properties such as scratch and wear resistance of sensitive polymers like polycarbonate and polyacrylics. The most applied coatings derive their scratch resistance from a very high cross-link density or from the presence of inorganic con- stituents. The coatings are generally hard and brittle. Although the hardness is desired in the final application, the implied resis- tance against deformation represents a major limitation of the use of coatings on 3D substrates. A system, suitable for curing in two consecutive steps, would offer the opportunity to apply the coating conveniently on flat surfaces and cure it in a first step, leaving a tack-free, handable surface with sufficient deformability to resist further shaping. The flat plates are then transported to the customer were the final ∗ Corresponding author. Tel.: +31 40 2650493; fax: +31 40 2650302. E-mail address: barteld.deruiter@tno.nl (B. de Ruiter). 1 Present address: Universit´ e d’Angers, France. product is prepared by a deformation step and after (or during) this deformation step the surface can undergo a second cure step to obtain a hard surface coating with increased chemical and mechanical resistance properties. In this paper, we report on the feasibility of two-step cure processes. These consist of the combination of two consecutive cure steps, based on different polymerization mechanisms. In a first approach, we will present the development of coating formulations that can be cured in two consecutive irreversible UV-cure steps, in a second approach we will present evidence for the feasibility of coatings that can be cured in two consecutive steps, of which one is reversible. 2. Experimental 2.1. Materials Trimethylolpropane oxetane (TMPO) was a gift from Per- storp Specialty Chemicals and was used as received. The syn- theses of the acrylate of TMPO (I) and of the extended-chain acrylated oxetane (II) have been described elsewhere [1]. 0300-9440/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.porgcoat.2005.09.011