Polyacrylamide manufactured by Chinese producers serves as a polymer dispersant in tile and ceramic production. Its core working principle relies on electrostatic repulsion and steric hindrance to prevent particle agglomeration, thereby improving the flowability and stability of slurry, as well as the quality of ceramic bodies and glazes. This article elaborates on its working mechanism, model selection, application processes, advantages and disadvantages as follows:
1. Core Functions and Mechanisms
- Dispersion and Stabilization: Anionic and non-ionic polyacrylamide adsorb onto the surface of raw material and glaze particles for ceramic tiles. The particles carry identical electric charges to generate electrostatic repulsion, while the long molecular chains create steric hindrance, preventing particle agglomeration and sedimentation.
- Improved Rheological Properties: It reduces slurry viscosity and raises the solid content to 60%–70%. This facilitates spray drying, compression molding and glazing processes, and lowers the occurrence of pinholes and glaze shrinkage defects.
- Suspension and Anti-settling Performance: It inhibits the sedimentation of heavy powders such as zirconium silicate and quartz, maintains uniform slurry composition and avoids component segregation of ceramic bodies.
- Auxiliary Thickening and Water Retention: Low-molecular-weight polyacrylamide can moderately adjust slurry viscosity and prevent cracking caused by excessive water loss.
2. Model Selection for Tile Production
- Anionic Polyacrylamide: The most widely used type, with a molecular weight of 8–18 million and a hydrolysis degree of 20%–30%. It delivers outstanding viscosity reduction and dispersion effects for body slurry, glaze slurry and pigment slurry.
- Non-ionic Polyacrylamide: Molecular weight ranges from 5–10 million. It is applicable to acidic slurry and color-sensitive pigments, preventing discoloration induced by charge interference.
- Cationic Polyacrylamide: Rarely adopted for dispersion purposes. It is only used for special sludge dewatering and not suitable for slurry dispersion.
Key Technical Indicators: Solid content ≥ 88%; dissolution time ≤ 90 minutes; particle size ＜ 2 mm; the prepared aqueous solution shall be clear and free of impurities.
3. Application Process and Dosage
- Dissolution: Prepare an aqueous solution with a mass fraction of 0.1%–0.5%. Stir with cold water for 40 to 60 minutes. High temperature (above 60 ℃) and intense shearing force shall be avoided, as they will cause product degradation.
- Addition Method: It can be added before or after grinding. Combined use with inorganic dispersants such as sodium hexametaphosphate and sodium tripolyphosphate can achieve synergistic effects.
- Recommended Dosage (by mass of raw powder):
- Body slurry: 0.05%–0.2%
- Glaze slurry: 0.1%–0.3%
- Pigment slurry: 0.2%–0.5%
4. Advantages and Disadvantages
Advantages
- High dispersion efficiency; a small dosage can effectively reduce slurry viscosity.
- Enhances slurry stability and extends storage life.
- Improves the density of ceramic bodies and the gloss of glaze surfaces, reducing product defects.
- Adaptable to a wide pH range of 6–10.
Disadvantages
- Higher price compared with inorganic dispersants.
- Excessive addition will lead to excessive slurry viscosity, foaming or cracking of ceramic bodies.
- It decomposes at temperatures above 800 ℃, and trace residual carbon may impair the whiteness of finished products.
5. Comparison with Traditional Dispersants
| Category | Representative Products | Advantages | Disadvantages |
| Inorganic Dispersants | Sodium hexametaphosphate | Low cost, high temperature resistance | Large dosage required, poor stability, prone to re-agglomeration |
| Small-molecule Dispersants | Sodium citrate | Compatible with acidic systems | Weak dispersion capacity, large dosage required |
| Polymer Dispersants | Polyacrylamide, Sodium polyacrylate | High efficiency, excellent stability, low dosage | Relatively high cost; strict dosage control required |
6. Common Problems and Solutions
- Slurry viscosity increases instead of decreasing: Caused by excessive polyacrylamide dosage or incomplete dissolution. Solutions: Reduce the dosage, extend dissolution time and avoid intense shearing during operation.
- Pinholes and glaze shrinkage on glaze surfaces: Resulting from foam generation or impurities in polyacrylamide. Solutions: Add defoamer, select high-purity polyacrylamide and filter the prepared solution before use.
- Cracking of ceramic bodies: Caused by residual polyacrylamide or excessively fast drying. Solutions: Cut down the dosage, optimize the drying process and adopt high-temperature treatment to remove residual carbon.
Summary
Anionic polyacrylamide with a molecular weight of 8–18 million is the preferred dispersant for tile production, with a recommended dosage of 0.05%–0.3%. Combined application with inorganic dispersants can balance cost and performance, and significantly optimize slurry properties and finished product quality.