The powder is clumped and the powder is not good, how to improve it?

Introduction

With the advent of summer, powder agglomeration is a headache for the majority of manufacturers, in addition to the process problems in the production process, storage and transportation are also factors that affect the final spraying effect. In summer, the temperature is high and the humidity is high, and the temperature and humidity can directly affect the final coating quality of the powder coating.

Many customers have high requirements for the utilization rate of powder, and the powder loading rate is the most specific manifestation of the utilization rate. There are many factors that affect the powder loading rate, such as resin content, particle size, fluidity, resin type and so on.One of the most important factors affecting the powder loading rate is the electrification of powder coatings.

 This kind of problem is a system engineering integrating materials, formula design, and application, and each manufacturer also has different ways to solve it, so we will not discuss it for the time being. Today, I would like to recommend an additive for you, which can greatly improve this kind of problem.

【Hydrophobic type】fumed nano alumina Alu C-S

Alu C-S is a nano-alumina that has been hydrophobically modified on the surface. It has finer particles, better flowability, and better compatibility with resins. When applied to medium and high-grade powder coatings, it can achieve a comprehensive improvement of fluidity and electrostatic spraying performance, and play a role in preventing agglomeration.

The role of fumed alumina in powder coatings

1. Anti-caking: nano-level (13 nanometer native particle size) powder and unique structure and chargeability can prevent caking.

2. Improve fluidity: due to the unique positive charge characteristics and unique structure, it plays a good role in fluidity.

3. Improve wear resistance: Alumina has a high hardness and can play a good wear resistance effect.

4. Improve the powder loading rate: the positive charge of fumed alumina makes it an effective additive for the formulation of frictional charged powder coatings. Whether it's epoxy polyester blends, polyester-TGIC or other resin systems, fumed alumina offers an excellent combination of fluidity and electrical charge in friction coating applications;

5. Improve the compactness of the coating.

 The fluidity of the positive charge of fumed alumina in powder coatings and the mechanism of improving the upper fraction

Powder aggregation is the result of the internal structural forces of the material competing with the gravitational forces on the particles in a variety of ways, depending on particle size, humidity and particle composition.

In general, when the size of the dry particles is greater than 75um, the gravity force is greater than the structure or the inter-particle force, the gravitational force between the particles is small, the powder can be fluidized, and only a small amount of energy is needed to flow, and the particles can move independently of each other. However, when the particles are large, the appearance quality of the coating film decreases, and the orange peel is also more serious, and the quality of the sprayed surface is reduced.

When the powder particles are less than 75um, the gravitational force between the particles is often greater than the gravity of the particles, and the powder is easy to agglomerate, resulting in a decrease in fluidity.

At present, the powder coating particles are basically about 35um, and the future development trend is to further control the size of the powder particles between 10~20um to obtain a thinner coating by reducing the size of the matrix particles.

In order to overcome the agglomeration between powders, it is necessary to add nanomaterials such as fumed alumina to play a role in promoting fluidity. An appropriate amount of alumina powder is added to the powder coating, and through sufficient mechanical stirring, the alumina nanoparticles can be orderly combined on the surface of the matrix particles to form a layer of "coating".

In this way, a "shell core" structure is formed, and the whole movement can effectively reduce the electrostatic attraction between the particles, and avoid powder adhesion due to van der Waals force, moisture absorption, particle friction, etc.

Fluidization requires less energy, less sedimentation occurs during transport, powder fluidity is better, and powder fluffiness density increases.

If too much or too little alumina is added or due to insufficient stirring, then the nano alumina particles can not be evenly combined on the surface of the matrix particles, but randomly distributed between the matrix particles, and can not form an effective "coating" on the surface of the matrix particles, then the powder coating particles will also agglomerate, resulting in reduced fluidity, the matrix particles tend to agglomerate, fluidization requires more energy, and it is not convenient for construction spraying.

It is precisely because of the unique structure of fumed alumina and the appropriate size of the "agglomerate" particles and the electropositivity of the surface that it can form a coated "shell core" structure with the matrix particles of the powder coating, thereby effectively improving the fluidity of the powder coating, and also providing the possibility for further refinement of powder coating particles in the future, especially the ultra-fine powder coating currently appearing in the market, and the particle size of the product is even controlled to 0.1~0.2um.

The smaller the powder coating particles, the lower its heat capacity, and the less time required for melting, so that it can coalesce quickly to form a film and then level, the coating is dense, adhesion, impact strength and toughness are good, the corner coverage is high, and it has excellent chemical corrosion resistance and electrical insulation performance.

Generally, the amount of fumed alumina is 0.1%~0.3% of the total mass of powder coating, which can be mixed before and after crushing. If the addition amount is too much, the appearance and mechanical properties of the coating film will be affected, and the fluidization effect will not be obvious if the addition amount is too small. In addition, it is necessary to mix well when adding.

Special advantages of hydrophobic fumed alumina

1. It has all the advantages of hydrophilic alumina;

2. Due to hydrophobic treatment, the fluidity is greatly improved, and the anti-caking ability is greatly improved;

3. The charge is more stable, and its hydrophobic characteristics make it difficult for moisture in the air to enter and take away the charge;

4. It reduces the agglomeration of gas and aluminum itself, and greatly reduces the probability of white spots.