Pourquoi les agents de nivellement que vous choisissez posent-ils toujours des problèmes ?

After years of formulating coatings, I’ve seen countless reworks caused by wrong selection or improper use of Leveling Agents—scenarios like meeting gloss standards for the film layer yet facing wrinkling during recoating; solving cratering only to encounter pinholes; and the most frustrating issue: perfect lab results turning into production failures on a mass scale.

The truth is, the core of choosing a flow agent is not “picking the most expensive”, but “picking the right one for your system”. In this article, I’ll break down my decades of hands-on experience for you: from a comparative analysis of three mainstream flow agent types, to detailed control of addition levels and mixing methods, to the pitfalls I’ve personally fallen into. After reading, you’ll solve 80% of flow-related coating issues.

I. Three Mainstream Leveling Agents: Characteristics, Application Scenarios & Pitfalls

1.1 Mixed Solvent-Based Leveling Agents: Cost-Effective Emergency Fixes—Avoid Overdosing

These were my go-to “emergency solutions” when I first entered the industry. Essentially a blend of high-boiling-point solvents—formulated with aromatic hydrocarbons, ketones, and esters—their core function is to adjust solvent evaporation rates.

I recall a client complaining that nitrocellulose lacquers developed whitening and failed to achieve adequate gloss during construction in southern China’s rainy season. On-site testing revealed the surface skin formed too quickly due to rapid solvent evaporation, trapping internal solvent. We added 5% of a mixed solvent-based flow agent (aromatic hydrocarbons + esters compounded) to the formulation, and the issue was resolved instantly.

Core Characteristics & Usage Guidelines

• Application Scenarios: Only addresses cratering, whitening, and insufficient gloss caused by excessively fast solvent dryingor poor binder solubility.
• Key Controls:

• Evaporation Rate: Too low leads to reduced film hardness (I once saw a 7% addition result in a soft film after 3 days).
• Dosage Range: 2%–7% (based on total paint volume); exceeding 7% severely prolongs drying time.
  • Unique Advantages: For vertical coating (e.g., nitrocellulose lacquer), it improves flow, boosts gloss, and prevents fogging under high temperature and humidity.
  • Pitfall Warnings: Must be used synergistically with other Leveling Agents; standalone use yields limited results and increases sagging risk.

1.2 Acrylic Leveling Agents: High Versatility & Excellent Recoatability

These are the current “workhorses” in the market, and their acrylic copolymer structure grants superior compatibility. In the industrial coating projects I oversee today, 80% use acrylic Leveling Agents.

Their core mechanism lies in functional groups in the molecular structure: −COOH and −OH adjust compatibility, alkyl esters provide surface activity, and molecular weight directly impacts spreading performance—this explains why acrylic Leveling Agents of different models exhibit vastly different flow speeds.

Core Characteristics & Usage GuidelinesStandout Advantages:

• Excellent critical compatibility, suitable for the vast majority of coating systems.
• Built-in foam inhibition and defoaming capabilities, reducing the cost of additional defoamers.
• Superior recoatability: Models with minor −OH/−COOH groups enable recoating up to 5 times without wrinkling (lab-tested).

Key Notes:

• Must match polarity via testing (I once caused edge craters in polyurethane coatings by skipping compatibility checks).
• Molecular weight selection aligns with coating viscosity: high-molecular-weight models for high-viscosity coatings, low-molecular-weight models for low-viscosity systems.

1.3 Silicone-Based Leveling Agents: Dual Flow & Defoaming Effects—Modification Is Critical

Silicone-based Leveling Agents boast a core advantage of low surface tension (polydimethylsiloxane has a surface tension of ~20 mN/m), delivering far stronger flow and defoaming performance than other types. However, compatibility is their Achilles’ heel.

Early in my career, I used unmodified polydimethylsiloxane directly, resulting in severe cratering in an entire batch of coatings and a loss of nearly 100,000 RMB. I later learned that unmodified siloxanes are incompatible with most coating systems and must undergo modification.

Modified Types & Application Scenarios

Modification Method	Core Advantages	Coating Systems
Polyether Modification	Best compatibility, strong defoaming power	Water-based coatings, polyurethane coatings
Alkyl Modification	Enhanced scratch resistance	Solvent-based industrial coatings
Fluorine Modification	Superhydrophobic effect	Special protective coatings

Pitfall Warnings: Even modified products require compatibility testing before use (mix 5% paint sample + 0.3% flow agent; no delamination after 24 hours = qualified).

II. 4 Critical Points for Flow Agent Use: From Lab to Mass Production

2.1 Selection Logic: Prioritize Coating Type First, Then Functional Needs

Many users only focus on “flow performance” when selecting Leveling Agents, ignoring the coating’s inherent properties. My 经验 (experience) is:

• Revêtements à base de solvants: Prioritize acrylic (high versatility) or modified silicone (for high flow demands).
• Revêtements à base d'eau: Polyether-modified silicones are the first choice (excellent compatibility, low defoaming risk).
• Room-temperature curing coatings (e.g., nitrocellulose lacquer): Synergistic use of mixed solvent-based + acrylic Leveling Agents.
• High-temperature curing coatings: Prioritize acrylic (good heat resistance, no interference with curing reactions).

2.2 Dosage Control: Less Is More—Gradient Testing

Dosage is the most error-prone step: too little yields no effect; too much triggers cratering, sagging, poor recoatability, and a host of other issues.

Standard Lab Workflow:

1. Conduct small-sample tests at gradients of 0.1%, 0.3%, 0.5%, and 1.0% (based on total paint volume).
2. Inspect the film layer after 48 hours: check flowability, gloss, and presence of cratering.
3. Confirm the optimal dosage, then run a 10x scale-up pilot test to avoid mass production risks.

Data Reference: The optimal dosage for most systems falls between 0.3%–0.8%; exceeding 1.0% increases cratering risk by 300%.

2.3 Coating Application Methods: Adaptation Tips for Different Scenarios

Flow agent performance is directly impacted by application methods—a detail often overlooked:

• Brushing/Rolling: Choose low-molecular-weight acrylic Leveling Agents(fast spreading, reduces brush marks).
• Spraying: Prioritize modified silicone-based Leveling Agents(low surface tension, rapid spreading, minimizes orange peel).
• Vertical Coating: Compound mixed solvent-based + acrylic Leveling Agents(prevents sagging and maintains gloss).

2.4 Mixing Techniques: Uniform Dispersion Is Key

In many cases, Leveling Agents fail not because of poor product quality, but improper mixing. My on-site operational standards:

• Mixing Speed: 300–500 r/min (too fast introduces air bubbles; too slow causes uneven dispersion).
• Mixing Time: Adjust based on flow agent type:

• Mixed solvent-based: 3–5 minutes (easy to disperse).
• Acrylic/silicone-based: 5–8 minutes (full dispersion required for high-molecular-weight products).
  • Note: Let the mixture stand for 10 minutes before construction to release air bubbles generated during mixing.

III. 3 High-Frequency Pain Points & Solutions for Flow Agent Use

3.1 Poor Recoatability: Balancing Flow and Recoatability

This is the most common issue, especially with silicone-based Leveling Agents. My solutions:

• Prioritize acrylic Leveling Agentswith −OH/−COOH groups (optimal recoatability).
• If silicone-based agents are mandatory, choose polyether- or acrylic-modified models and limit dosage to ≤0.5%.
• Validation: Conduct a “coat-dry-recoat” cycle test to check for wrinkling/edge craters in the second coat.

3.2 Cratering: Is the Flow Agent Misselected?

Cratering stems from two core causes: incompatibility between the flow agent and coating or excessive dosage. Follow these steps to resolve:

1. Elimination Method: Apply a small mixture of paint and flow agent to a glass slide; edge craters indicate incompatibility.
2. Adjustment Plan: Switch modified types (e.g., replace silicone with polyether-modified) or reduce dosage (cut by 0.2% each time).

• Case Study: We solved cratering in polyurethane coatings by replacing silicone-based Leveling Agentswith acrylic ones and reducing dosage from 0.8% to 0.4%.

3.3 Compatibility Testing: 3 Rapid Validation Methods

Many users find compatibility testing cumbersome—3 simple methods suffice:

1. Glass Slide Coating Method: Apply the mixture to a glass slide; no edge craters/delamination after 24 hours = qualified.
2. Storage Stability Test: Place in a 50℃ oven for 7 days; no precipitation/floating layer = qualified.
3. Gloss Change Test: Gloss variation before/after addition ≤5% (avoids gloss loss from poor compatibility).

IV. Future Trends: Multifunctional Flow Agent Development

With stricter environmental regulations, single-functional Leveling Agents can no longer meet market demands. I’m currently developing multifunctional Leveling Agents (flow + scratch resistance + stain resistance) via graft copolymerization of acrylates and fluorine-modified silicones. These agents maintain flow performance while boosting film scratch resistance and stain resistance.

Such multifunctional Leveling Agents will become the mainstream, especially for high-end furniture coatings, automotive refinish coatings, and other sectors. If you have relevant needs, feel free to connect with me—we can explore customized solutions together.

Closing: What Flow Agent Issues Have You Encountered?

There are no absolute standards for flow agent selection and use—only the most suitable solutions for your system. All the insights shared here are distilled from years of lab experiments and project practice.

Have you faced unsolvable flow issues in your work? For example, selection for special coating systems, construction challenges in extreme environments, or balancing recoatability with flow performance? Leave a comment below, and let’s discuss solutions together!