Workability/Ease of Application
Film build / brushability
Covering power results from the combination of the coating's inherent opacity depending mostly on fillers, pigments and pigment volume concentration (PVC) and the thickness transferable onto the support.
Rheology should therefore help produce sufficient thickness deposited at every application (the film build), while maintaining ease of application (brushability). These properties can be quantified by measuring viscosity at high velocity gradient.
In this area, polyurethane type newtonian thickeners (HEUR) prove entirely suitable.
The most newtonian acrylic thickeners (HASE) are also capable of imparting excellent control of the film build effect, which helps mask the support's blemishes more effectively whereas cellulose type thickeners (HEC) often present major shortcomings.
Excellent covering power is not only given by the type and amount of fillers present in the formulation, but also thanks to a specific rheology.
A good control of the rheology during application (corresponding to high shear rate) contributes to a good film build and a good brushability.
With conventional
cellulosic thickeners |
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With Coapur™ 3025 |
Coatex rheology modifiers are specifically designed to provide higher film build in architectural paints and wood stains formulations.
Compared to cellulosic thickeners, as shown in the pictures, high hiding power can be obtained by using newtonian Coapur™ thickeners, such as Coapur™ 3025.
Hiding surface imperfections with excellent coverage even in coatings is also possible with newtonian Rheotech™ thickeners, such as Rheotech™ 2800.
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Adaptability to application tool
Coatex thickener Thixol™ 53 L is adapted to brush and spray applications..
For spray application, the paint needs to be free-flowing and easy to
manipulate while being sprayed and then to recover its initial viscosity within
a short time when it is allowed to remain at rest. Thanks to these qualities,
a thixotropic paint can be sprayed-applied in thicker films without running or
sagging.
The shear rate nozzle is approximately at 10-5 and 10-1 on the substrate.
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 Figure 1:Coatex thickener Thixol™ 53 L can be applied in various ways thanks to their very large thixotropic character
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Dilution resistance
Below is a test composition of an interior coating formulation based on styrene acrylic binder:
Figure 2: Rheotech™ 4800 demonstrates better water-dilution resistance and storage stability
