Frequently asked questions for
Here are some of the most frequently asked questions with their answers from Adhesives and Sealants.
RHEOBYK-R 606 is increasing the hydrogen bondings between the fumed silica particles. This is giving a much stronger rheology effect which allows to reduce the overall amount of fumed silica. It also avoids the viscosity drift over time by a more complete wetting of the silica. The recommended dosage is 10% based on the amount of fumed silica. The RHEOBYK-R 606 should be added before the fumed silica.
We recommend to test 0,5 % of BYK-W 969 calculated on the amount of filler. This will significantly reduce the viscosity.
Our rheology additive RHEOBYK-430 is creating a pseudoplastic flow behaviour. The higher viscosity at low shear stress will prevent the settling of the particles.
First recommendation for this application is BYK-016. It is a polymer defoamer which complies with FDA §175.300 and PIM 10/2011 regulation without restrictions. Recommended dosage is 0.3 -0.5 %.
You can use HORDAMER PE 02 which is added into the cooling water system at a dosage of 1 to 4 % based on the amount of water in your system. HORDAMER PE 02 is a stable dispersion of a primary polyethylene in water. Even at low dosages it will remain stable and not separate and float on the water surface. On the pellets it creates a very thin layer of product to avoid the blocking. The product complies with FDA §175.300. In most of the water cooling systems the HORDAMER PE 02 will tend to stabilize foam. We recommend to add 0.05 to 0.2 % of a defoamer such as the polymer defoamer BYK-014 or the modified silicone defoamer BYK-022.
Main reasons for these difficulties are the differences in surface tension of your acrylic adhesive and the surface tension of the polyester film. Adding 0.3 % of BYK-349 will significantly reduce the surface tension of the adhesive to achieve a homogeneous wetting of the polyester film. BYK-349 is a modified silicone surfactant and according to our knowledge does not have a negative impact on adhesion properties. A silicone-free alternative would be 0.5 to 1 % of BYK-3410 to achieve a good substrate wetting. This product tends to stabilize foam. When you have already got a defoamer in your system, this is often enough. If not, we recommend to add 0.2% BYK-014.
We have seen an improved adhesion in this application when adding HORDAMER PE 02 into the water based adhesive. HORDAMER PE 02 is more seen as a part of the binder and therefore dosages of 20 to 40 % are necessary. HORDAMER PE 02 is a very polar primary polyethylene dispersion in water.