Guizhou Xinzihong Pharmaceutic Adjuvant Co. Ltd.,
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Advantages of thickeners

Date of issue:2021/05/05Posted by: ZIHONG BIOTECH

Cellulose thickener has high thickening efficiency, especially for thickening aqueous phase. There are few restrictions on coatings and coatings, and they are widely used. And the available pH range is wide. However, there are some disadvantages such as poor leveling, more spatter during roll coating, poor stability and sensitivity to microbial degradation.

Advantages of thickeners

Because of its low viscosity under high shear and high viscosity under static and low shear, the viscosity of the coating increases rapidly after completion, which can prevent sagging, but on the other hand, it will cause poor leveling. The results show that with the increase of relative molecular weight of thickener, the spatter of latex coating increases. Cellulose thickener is easy to splash because of its large molecular weight.

The thickener achieves thickening effect by "fixing water" and hardly absorbs pigment and latex particles. The volume expansion of the thickener fills the whole aqueous phase and squeezes the suspended pigment and latex particles to one side, which easily leads to flocculation and poor stability. Because it is a natural polymer, it is easily attacked by microorganisms.

Polyacrylic acid thickener polyacrylic acid thickener has strong thickening performance, good leveling performance, good biological stability, but it is sensitive to pH and poor water resistance. Under the action of shear force, the association structure of the associated polyurethane thickener is destroyed and the viscosity is reduced. When the shear force disappears, the viscosity can be restored, which can prevent sagging during construction.

And the viscosity recovery has a certain lag, which is conducive to the film leveling. The relative molecular weight of polyurethane thickener (thousands to tens of thousands) is much lower than that of the former two thickeners (hundreds to millions), and it does not promote splashing. The high water solubility of cellulose thickener will affect the water resistance of the film, but the molecule of polyurethane thickener has hydrophilic group and hydrophobic group, and the hydrophobic group has a strong affinity with the substrate of the film.

The thickener can enhance the water resistance of the film. When the latex particles participate in the association, flocculation will not occur, which can make the film smooth and have a higher gloss. Many properties of associative polyurethane thickener are better than other thickeners. However, due to its unique micelle thickening mechanism, the coating formulation components that affect micelles will inevitably affect the thickening. When using this thickener, the influence of various factors on thickening performance should be fully considered. The emulsion, defoamer, dispersant and film builder used in the coating should not be changed easily.

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