Polyurethane Levelling Agent

Rheology is a discipline that studies the deformation and flow laws of material molecules under the action of external forces.

Rheology includes Newtonian fluids and non-Newtonian fluids.

1. Newtonian fluids

Under laminar flow conditions, the shear stress is proportional to the shear rate of pure liquids or low molecular weight substances. However, the rheological properties of water-based paints do not conform to the characteristics of Newtonian fluids.

2. Non-Newtonian fluids

Water-based paints have typical rheological properties of non-Newtonian fluids

Mixtures and most liquids containing polymers or polymers do not follow Newton's viscosity law. The flow shear velocity and shear stress of such substances are not linearly related. It is achieved through the successive transitions of molecular segments, that is, the displacement of the entire macromolecular chain is completed through the gradual displacement of the segments.

3. Definition of viscosity, yield value, and thixotropy

Viscosity is the internal friction resistance of the fluid against flow, which is related to the entanglement and intermolecular forces between molecules. The unit is Pa.s. It is not a specific data value, but a deformation curve corresponding to the shear rate.

Yield value: refers to the minimum moving stress required for a liquid to start flowing. It is related to the strength of the gel network structure inside the liquid. If the yield value is too large, the fluidity will deteriorate. If the yield value is too small, it is easy to sag.

Thixotropy: refers to the phenomenon that a liquid changes from thick to thin when stirred by an external force. It is related to the double electric layer effect and flocculation formed by the liquid.

Shear-thinning non-Newtonian fluid: refers to the viscosity decreasing nonlinearly with the increase of shear force. For example: water-based paint

Shear-expansion non-Newtonian fluid: refers to the viscosity increasing nonlinearly with the increase of shear force. For example: polyvinyl chloride suspension.

Water-based paint will produce different shear and rheological requirements during production, storage, transportation and construction, which requires the adjustment of different shear viscosities of the water-based paint system according to application requirements.

Paints have different viscosity requirements according to their different working conditions. Commonly used test viscosities can be roughly divided into the following three types:

1. Viscosity in storage state (Brookfield viscosity is tested by Brookfield viscometer)

The size of the paint viscosity will involve the length of its shelf life. Paint is actually a solid-liquid mixture. Solid particles such as titanium dioxide and kaolin are evenly distributed in the main resin solution. Under the action of gravity, the solid particles will settle to the bottom layer and stratify and agglomerate, causing quality degradation. For this reason, the paint is required to maintain a high viscosity during storage to prevent sedimentation.

2. Viscosity of the paint when stirred (KU viscosity is tested by Stormer viscometer)

The viscosity of the paint will be related to its performance and directly reflect the difficulty of the user stirring the paint

3. Viscosity of the paint when applied (ICI viscosity is tested by high shear cone and plate viscometer)

The viscosity of the paint directly reflects the performance of the paint under the conditions of application, such as painting, brushing, spraying, and rolling. The lower the viscosity, the better the performance.

Polyurethane leveling thickener YT-825 a non-ionic associative polyether polyurethane leveling thickener, which is especially good for water-based architectural coatings, inks and adhesives. The product is similar to Rohm and Haas RM-825.

1. Significantly improve the in-can state and construction leveling performance of coating products;
2. Excellent leveling performance for various water-based coatings and adhesives;
3. Excellent film fullness, hiding rate and water resistance;
4. Usually used in combination with other types of thickeners.

1. Recommended dosage: 0.5-2.0% (total amount of the system);
2. Can be added directly or diluted with appropriate amount of water or propylene glycol;
3. Add slowly while stirring until the appropriate leveling effect is achieved;
4. Can be used under acidic (or alkaline) conditions, but strong alkaline conditions will cause product degradation

The recommended addition amount is 0.5%-2.0%; it can also be used in combination with other types of thickeners according to different requirements in production, storage, construction and film formation to achieve the rheological performance requirements of the formula design.

 

Packing:

50kg, 120kg PE drum

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