Liaoning Xinda Talc Group Co., LTD. - Zheng Yi

I. The Importance of the Suspension Property of Coatings

The suspension property of coatings, also known as storage stability, refers to the ability of coatings to resist the sedimentation and stratification of pigments and fillers during storage. Its significance is reflected in the following aspects, which are directly related to the product quality, user experience and economic benefits of the coating.

Ensure the consistency of product performance

Uniform performance: Coatings are multiphase mixtures, including resins, pigments, fillers, additives, etc. If the suspension is poor, heavy components (such as titanium dioxide and barite) will settle at the bottom of the tank, while light components (such as resin and solvent) will float to the top. This results in the paint on the upper part being thin and distorted in color after opening the can, while the lower part forms lumps and hardens. When in use, no matter how well it is stirred, it is difficult to restore it to the initial uniform state, resulting in the key properties of the coating film such as covering power, adhesion, durability and color being unable to be guaranteed.

2. Enhance the convenience of construction and the coating effect

Easy to apply: Coatings with good suspension properties are uniform upon opening the can and can be used after a little stirring, greatly reducing the preparatory labor before application.

Uniform effect: The uniform system ensures that the composition of each application is consistent, thereby achieving a coating film with uniform color, gloss and thickness. If the suspension property is poor and the composition of the paint applied first and later is different, it is very likely to cause problems such as color difference and uneven gloss of the paint film.

3. Avoid sedimentation and caking to reduce waste

Prevent hard sedimentation: Severe sedimentation can form hard bottom lumps that cannot be dispersed even with vigorous stirring. These hard lumps not only clog the spray gun and brush, but also form particles on the surface of the paint film, affecting the appearance and protective effect. Ultimately, a large amount of sediment at the bottom of the tank had to be discarded, causing direct economic losses.

4. Maintain chemical stability

Suspension property is not only physical stability but also indirectly reflects the chemical stability of the formula. Severe stratification and sedimentation are sometimes signs of incompatibility among the components in the formula, flocculation or reactions.

5. Affect brand reputation and market acceptance

For consumers and industrial users, when they open the can and see the paint with layers and water seepage, the first impression is that "the product quality is poor". Good suspension stability is the basic external manifestation of high-quality coatings and is directly related to the professional image and market competitiveness of the brand.

Ii. The Influence of Talcum Powder on the Suspension Property of Coatings

Talcum powder, as an important functional filler, has a complex and dual impact on the suspension property of coatings. However, under correct usage conditions, its positive effects are dominant.

(1) Positive impact: Enhance suspension stability

Talcum powder mainly enhances its suspension property through the following two physical mechanisms:

The "stuck house effect" of sheet-like structures and network support

Mechanism: High-quality talcum powder has a typical flaky or plate-like structure. These tiny flaky particles can interweave and overlap with each other in a liquid medium, forming a weakened, three-dimensional network structure.

Function: This network structure acts like a rack, capable of "lifting" and "trapping" other heavier and more easily settling pigment particles in the coating (such as titanium dioxide and calcium carbonate), greatly hindering their downward movement path due to gravity, thereby effectively preventing the formation of hard sediment.

2. Increase the viscosity and thixotropy of the system

Mechanism: The irregularly shaped particles of talcum powder will increase the physical entanglement and internal friction of the coating system, thereby significantly raising the viscosity of the system, especially the low shear viscosity (i.e., the viscosity of the coating at rest).

Function: According to Stokes' law, the settling velocity of particles is inversely proportional to the viscosity of the system. The higher the viscosity, the greater the resistance to particle sedimentation and the better the suspension property. Meanwhile, this structure helps to endow the coating with thixotropy - it forms a high-viscosity gel-like state when standing still, preventing sedimentation. During construction, under the action of shear force (brushing, roller coating), the viscosity drops rapidly, facilitating leveling. This feature perfectly meets the dual requirements of storage and application for coatings.

(II) Potential Risks and Negative Impacts

If used improperly, talcum powder may also have an adverse effect on suspension.

The risks brought by high oil absorption

Mechanism: Talcum powder has a large specific surface area, so its oil absorption is usually high. This means that it will adsorb more resin (film-forming substances) and wetting dispersants.

Consequence: If the amount of talcum powder added to the formula is too high, or if the amount of resin and additives is not increased accordingly, it will lead to insufficient "free liquid" in the system. This will make the coating overly thick and have poor fluidity. It may even disrupt the stability of the emulsion or additives, causing pigment flocculation and leading to the collapse of the suspension system, resulting in problems such as water separation and thickening.

2. Differences in talcum powder quality

Low-quality talcum powder: If talcum powder contains a large amount of non-flaky impurities (such as calcium carbonate, quartz), or its flaky structure is damaged (due to grinding being too coarse or too fine), its "stuck house effect" and thickening effect will be greatly reduced, and the suspension effect will be weakened.

3. Compatibility with other components

Talcum powder is hydrophilic. In some resin systems with strong hydrophobicity, if the wetting and dispersion are not sufficient, it may cause the talcum powder to agglomerate by itself or interact with other pigments, thus disrupting the uniformity of the system.

Application in Coating Formula Design

As an auxiliary anti-settling agent: Talcum powder is often used in combination with main anti-settling agents (such as organic bentonite, fumed silica, and polyamide wax). The physical support it provides can enhance the entire anti-settling network and sometimes even reduce the dosage of the main anti-settling agent, lowering costs.

Control the optimal addition amount: It is necessary to determine the optimal addition range of talcum powder through experiments to balance the risk brought by its suspension contribution and oil absorption.

Select the appropriate category: Prioritize high-quality talcum powder with a high aspect ratio and well-developed flaky structure to achieve the best suspension effect.

Comprehensive formula balance: When using talcum powder, it is necessary to comprehensively consider its impact on suspension, viscosity, gloss, water resistance, cost and other aspects, and optimize the overall formula.

Conclusion

The suspension property of coatings is a core indicator related to their product quality and user experience. Talcum powder, with its unique flaky structure, is a highly effective and economical choice for improving the suspension stability of coatings. However, formulators must have a profound understanding of its "double-edged sword" characteristics. Only through meticulous formula design and category selection can they leverage its strengths and avoid its weaknesses, and prepare coating products that are stable in storage and have excellent performance.