ATIPIC SCIENTIFIC & TECHNICAL SYMPOSIUM

A critical point in the long-term performance of coatings is their compatibility with various substrates and possible adhesive failure in the interface. If the performance of bio-based coatings needs to be improved, we have to look into nature what is the functionality of the different bio-based moieties: how are they expressed and organized in natural environment, what is their chemical composition and what is the mechanism behind. In particular, an impressive system for adhesion is observed in nature in the byssal foot of blue mussels, which is controlled by the presence of decapeptides. Therefore, a bio-mimetic approach for the design of adhesive interlayers has been further explored based on the synthesis of hybrid materials from peptides and lipids. It will particularly be explained what is the role of dopamine in specific adhesion and crosslinking mechanisms in connection with polymers and metallic surfaces. The adhesive interlayer can be synthetically created by the direct polymerization of dopamine into a continuous layer, or can be incorporated into nano-vesicular structures with controlled presentation of the adhesive particles. First, the controlled polymerization of a polydopamine layer deposited by dip-coating or spraying enables the creation of an adhesive interlayer onto glass or metal substrates. The improved adhesion is demonstrated in connection with the application of sprayed nanocellulose coatings. Second, innovative adhesive interlayers are created in combinations of dopamine and hierarchical interface structures. The latter may consists of either (i) the deposition of a polydopamine layer onto laser-structures substrates, or (ii) the organization of dopamine into nanovesicles. The nanovesicles provide smallest possible adhesive points with strong adhesive force, while also presenting intrinsic sensitive properties to stress and load. Experimental data on adhesive strength of the interlayers will be presented. Moreover, the latter may serve as a functional interface for coatings or composites allowing for failure analysis and localization of internal stresses in the adhesive interlayer. Finally, reversibility of the adhesive interlayer can be demonstrated after disintegration under controlled chemical conditions.

Inkjet printing in general has many challenges as a printing technique: limited viscosity range and preferably Newtonian behaviour of the inks, nano-particle dispersions due to the small nozzle sizes, decision to make on a single pass or multiple pass printing process, how to handle colour management to achieve the highest colour gamut, etc. All those in the inkjet business recognise these questions. However, ChemStream will go a step further and will take you into the world of 3D inkjet printing or “Material Jetting”. We will introduce you to the various additional challenges that crop up when you want to use inkjet for Additive Manufacturing purposes. Think of physical properties, optical properties, for mono-or multi-material objects. How does one build an object, layer by layer? How does one then ensure shape and strength are maintained? How does one achieve the desired colour in a 3D object? And finally, how does Material Jetting relate to other existing 3D printing techniques? Does it have a future among those?

UV-curing process typically results in coatings with smooth surfaces and a glossy appearance. To create ultra-low gloss finishes, different solutions exist, the most commonly used one being the incorporation of matting agents into the formulation. However, these additives produce undesirable effects and lead to important modification of the formulation viscosity and reduction of application characteristics.

To overcome those drawbacks, resins for optimum results under Excimer curing conditions are developed. Indeed, excimer curing technology forms a micro-folded structure and can offer a very low gloss level with matting agents-free formulation. It will be shown in this presentation new WB UV resins that have been specially designed to enhance the performance of substrates while giving an aesthetic appeal to the end product.