Siloxane-based additives are crucial in coating applications because their structures can be varied in order to provide a broad range of performance benefits in many types of formulations and chemistries. Surfactants and defoamers are some of the more commonly recognized additive classes, but many other functionalities can be derived from siloxane chemistries, particularly attributes related to surface control such as flow and leveling, slip, scratch resistance, and haptic properties. This extensive range of performance is achievable due to the broad flexibility inherent in siloxane chemistry, allowing a fine-tuned balance of compatibility, and surface activity.
Evonik has a long-standing history as a supplier of surface additives combined with a good understanding of the general structure-property relationships that drive the performance attributes of siloxane additives. Through comparison with commercial benchmark additives and molecular design, Evonik has developed a novel recoatable surface additive called TEGO® Glide 496 to meet the desire for advanced solutions.
The main attribute of TEGO® Glide 496 is that it allows formulators to adjust slip and anti-blocking properties (Figure 1) combined with improved scratch resistance. In addition, this novel recoatable surface additive also provides excellent recoatability in various coating systems.
This is illustrated in Figure 2 below showing the results of the cross-hatch adhesion test in a 2K solvent based polyester clear wood lacquer spray applied onto black PMMA panels. The applied coating containing TEGO® Glide 496 (right) shows very good recoatability properties compared with the one containing a market standard surface additive (left).
Similar adhesion tests were performed in a different coating, spray applied on beech wood in two layers of 150 microns wet. The cross-hatch test was performed 7 days after the coating was applied and showed excellent recoatability. This adhesion test was repeated when increasing the use level of the Novel Recoatable Surface Additive from 0.1 wt% to 0.5 wt% on total formulation, confirming that there was no impact on recoatability, even with the highest surface additive loading.
Further application tests have shown that TEGO® Glide 496 is suitable for both solvent- and water-based formulations, has excellent compatibility and demonstrated scratch resistance improvement in various systems. Besides wood lacquers and plastic coatings, this new product is also suitable for automotive and transportation coatings, as well as printing inks. Furthermore, the additive is globally registered, not considered a Substance of Very High Concern (SVHC) and complies with various food contact regulations.
Comparison of anti-blocking properties between two wood coating samples, one containing TEGO® Glide 496 (right) and one containing a market standard surface additive (left). Test conditions: Two panels were placed face-to-face under 1.6 kg/cm2 for 20h at room temperature.
Comparison of the effect of surface additives on recoatability properties in a 2K solvent-based polyester clear wood lacquer.