What are PU Sealants?
Sealants are used as a hindrance to the flow of water molecules. They help in removing undesired humidity and helps in keeping the surface dry. Sealants can be said to insulate a surface from the vapour. The major two sealants in use are silicone and polyurethane sealants. Polyurethane sealant or PU sealants are organic compounds made from an addition reaction between isocyanates and polyols. So there are no side-products formed. The organic structure of a PU sealant is to be strictly maintained and any trace of water component can disturb its characteristics. These are available in one and two-component formulations.
Why PU Sealants:
Among the two, the silicone sealants and polyurethane sealants, the latter is said to have higher mechanical strength and adhesion capacity. Also, the hardness and flexibility of this organic compound can be altered to increase the sealing performance. The major advantages of PU sealants include good tear resistance, chemical strength, weather resistance, flexibility, and adhesion compatibility.
Molecular Sieve powder as desiccants:
Molecular sieve is used as an agent to remove water molecules from air or any liquids and gases in general. For better performance, an activated form like Zeolite Molecular Sieve is used. The powder form of such zeolite desiccant is used in the right quantity depending upon the concentration of water molecules. There are different varieties of zeolite desiccants available in the market. According to the diameter of the desiccant pores, these variants can trap different sized molecules in the medium. These are used to remove water from polymers and thus help in forming of CO2 gases as a result of moisture.
Role of molecular sieve powder in drying of PU Sealants:
As we saw, polyurethane is an organic mixture of isocyanates and polyols. Moisture content in this compound will result in producing CO2 gas, as a result of its reaction with the isocyanate component. This CO2 gas will result in foaming and bubbling, thus affecting the insulation property of the sealants.
To avoid these effects, a PU sealant is to be maintained dry. By using the right zeolite sieves, the water content can be removed from the sealants. The working is simple as the water molecules get trapped in the adsorbent sieves used, leaving the medium dry. The adsorbent here is the molecular sieve powder and the medium is the PU sealant.
Adsorption is a surface process and does not alter the initial structure of the components. So the use of molecular sieve powder ensures no chemical change to the PU sealant. Also, the thermal and mechanical strength of the zeolite desiccant helps in the same being used across any conditions.
The use of powdered form helps to maintain the surface finish while ensuring extended shelf life, hardness, and elimination of foaming for the PU sealants. It also ensures proper mixing and superb distribution. The zeolite sieve also possesses high water adsorption capacity and consistency. These work perfectly for both single and multiple component polyurethane compounds. The use of molecular sieve powder leaves no impact on the colour of the surface, and this is an attractive feature that makes it suitable to use on sealants applied on visible or exposed surfaces. Consistent viscosity is another feature of the desiccant which thus imparts aiding the steady pot life. As we already know adsorption is not a chemical reaction, it is clear that no agglomerates will be formed by using this method for drying the PU sealants.
Molecular sieve powder is considered the best drying agent for PU sealants. PU sealants are used for sealing or bonding purposes. Any amount of water and air present in the compound can affect its efficiency and so it is very important to keep them dry. The use of a zeolite desiccant ensures proper removal of water components from a polyurethane sealant.
Sorbead India is one of the best providers of all variants of molecular sieve powder. The powdered form of 3A, 4A, and 5A sieves are available with us and are widely in use in the market as a drying agent for Polyurethane, Polysulfide and silicone systems, Potting compounds, Metallic paints, Industrial and Pipe coating, Flooring, Anti-corrosion applications, Pigment, and solvent drying.