SPHERILEX® DP-0117 - Enabling high durability matte powder coatings

As powder coatings applications continue to diversify, and grow for both indoor and exterior use, the different chemistries that are being developed may find gloss reduction to be more challenging. Adding to the drivers for consistent matte finish are the trend towards lower temperature cure for greater energy efficiency as well as accommodation of heat sensitive substrates. Currently matted powder coatings account for 25-30% of all powders used [1]. In some of these applications, a greater range of aesthetic appearance is needed while coating performance requirements must be maintained or enhanced. In liquid coatings where film shrinkage occurs during cure, matting effects can be easily accomplished by the addition of matting agents to create the micro-roughness surfaces to readily control gloss levels. However, in powder coatings, since the systems are 100% solids, there is no film shrinkage from the evaporation of solvents, only slight volume shrinkage during cure. As a result, current methods of creating a matte finish in powder coatings have varying effectiveness and limitations.

It is well documented that the unique spherical morphology (Fig. 1) combined with the low oil absorption of SPHERILEX® grades, provide an advantage over conventional  fillers when evaluating performance criteria of powder coatings.

At the same use level, compared to standard fillers, a higher matting efficiency is reached, while providing a linear, predictable, and repeatable gloss reduction. The resulting matted surface appearance shows excellent uniformity and consistency. In addition, the unique morphology of these particles provide improved flexibility while also improving hardness. This novel spherical precipitated silica performs equally well in exterior exposure and corrosion tests as current fillers used. Finally, it allows for greater theoretical coverage and transfer efficiency due to its low specific gravity.

Figure 1

SPHERILEX® offers similar advantages in liquid coating applications and the particle size typically determines the effects and use cases for each coating system. Until now, Evonik’s SPHERILEX® portfolio had ranged from d₅₀ ~4.4 mm to d₅₀ ~15 µm, but new technical advancements allow us to introduce a new, larger grade: SPHERILEX® DP-0117 with a d₅₀ ~18 mm. (Fig.2)

Figure 2: Particle Size

For optimal gloss reduction in powder coatings, combining conventional matting techniques (e.g. waxes, matting agents) with SPHERILEX^® grades, results in highly durable low gloss formulations. SPHERILEX® DP-0115 grade has been first choice for many applications, but the new SPHERILEX^® DP-0117 may open up new opportunities for your powder coatings. Both larger SPHERILEX^® grades are comparable in gloss reduction and show improved matting over Aluminum Trihydrate (ATH) of a similar size (Fig. 3). Furthermore durability and scratch resistance is boosted with improved pencil hardness as shown in Tab.1

Figur 3: Improved Matting

A key performance criteria, especially in super durable resin systems, has always been the positive impact on flexibility the SPHERILEX® grades provide. In Tab.2 / Fig. 4 the DP-0117 has shown even further flexibilization properties over DP-0115 and drastically improved compared to ATH.

Figure. 4 – Reverse impact (30 in-lb) results of reference, DP-0115 and DP-0117

In summary, SPHERILEX® DP-0117 is a versatile and performance enhancing matting specialty filler, for a wide variety of powder coating applications and chemistries.

[1] Cal EzeAgu, “Gloss Control Powder Coating Resin”, Paint & Coatings Industry, August 7, 2020