Recommendations for the use of viscosity-reducing dispersants for epoxy coatings

In the production and construction process of epoxy coatings, viscosity-reducing dispersants play an important role as key additives to improve the performance of coatings. However, if used improperly, not only will the expected effect not be achieved, but the quality of the coating and the construction effect may also be affected. In order to give full play to the advantages of viscosity-reducing dispersants for epoxy coatings, practical usage suggestions are given from multiple dimensions such as product selection, addition method, and construction process.

Accurate selection of products based on coating systems and needs

Epoxy coating systems are diverse, including solvent-based, water-based, and solvent-free types, and the requirements for viscosity-reducing dispersants in different systems are significantly different. In solvent-based epoxy coatings, dispersants must have good compatibility with organic solvents to avoid turbidity, stratification, and other phenomena; water-based epoxy coatings require the selection of hydrophilic dispersants to ensure that pigments and fillers can be effectively dispersed in the water phase. For example, in water-based epoxy floor paints, selecting a polymer dispersant with a special hydrophilic group can maintain the stability of the coating while ensuring the viscosity reduction effect.

In addition, it is also crucial to select a dispersant based on the specific application scenarios and performance requirements of the coating. For epoxy coatings used in the field of corrosion protection, dispersants that can promote the dispersion of anti-rust pigments and enhance the corrosion resistance of coatings should be preferred; for epoxy coatings that focus on decoration, such as paints for furniture coatings, dispersants that can improve the uniformity of pigment dispersion and ensure color vividness and glossiness should be selected.

Strictly control the amount of addition

The more viscosity-reducing dispersants are added, the better. Excessive use will not only increase costs, but may also lead to a decrease in coating performance. Generally speaking, the amount of dispersant added needs to be adjusted according to the type and content of pigments and fillers in the coating formula and the expected viscosity of the coating. Usually, the amount added is between 0.5% and 3% of the total amount of coating, but the optimal amount must be determined through a laboratory test before actual use.

During the test, multiple groups of coating samples with different amounts of dispersant added can be prepared to test their viscosity, dispersion stability, fluidity and other indicators. Taking an industrial epoxy anticorrosive coating as an example, by gradually increasing the amount of dispersant, observing the dispersion state of the antirust pigment in the coating and the anticorrosive performance of the coating, the dispersant addition ratio that makes the coating performance reach the optimal level is finally determined to avoid affecting the use effect of the coating due to improper addition.

Optimize the addition method and mixing process

The timing and mixing method of the viscosity-reducing dispersant have a significant impact on its effect. In the coating production process, it is recommended to first mix the dispersant with part of the solvent or water to make a premixed liquid, and then add it to the coating system. This allows the dispersant to be more evenly dispersed in the coating and give full play to its role.

In terms of mixing technology, it is crucial to use appropriate stirring equipment and stirring speed. High-speed dispersers are commonly used mixing equipment. Generally, they are stirred at a higher speed (1000-1500 rpm) in the early stage of dispersion to quickly disperse the dispersant and wrap the pigment and filler particles; after the dispersant is fully effective, the speed is reduced (300-500 rpm) for low-speed stirring to avoid introducing too many bubbles due to high-speed stirring, which affects the quality of the coating. At the same time, attention should be paid to controlling the stirring time. If the time is too short, the dispersion is not sufficient. If the time is too long, the pigment may be over-grinded, affecting the coating performance.

Pay attention to the construction environment and supporting materials

The temperature and humidity of the construction environment have a certain impact on the effect of the epoxy coating viscosity reducing dispersant. Generally speaking, the construction environment temperature should be controlled between 5℃ - 35℃, and the humidity should not exceed 85%. In a low temperature environment, the viscosity of the coating will increase, and the effect of the dispersant may be weakened. At this time, the amount of dispersant can be appropriately increased or heating equipment can be used to increase the temperature of the coating and the construction environment; in a high humidity environment, water-based epoxy coatings may have problems such as slow drying and whitening of the coating. Dehumidification measures need to be taken to ensure the construction quality.

In addition, the compatibility of the viscosity reducing dispersant with other additives in the coating, such as defoamers and leveling agents, should not be ignored. Before use, compatibility testing is required to ensure that there will be no chemical reaction or mutual interference between the additives to avoid coating defects. For example, if the dispersant is incompatible with the defoamer, it may lead to poor defoaming effect of the coating and a large number of bubbles on the surface of the coating.

Good storage and management

Improper storage of viscosity-reducing dispersants may lead to performance degradation or failure. Dispersants should be stored in a cool, dry, ventilated environment, away from direct sunlight and high temperature. At the same time, it should be sealed to prevent moisture and impurities from entering the dispersant and affecting its quality. For unused dispersants, their appearance and performance should be checked before re-use. If abnormal phenomena such as discoloration, turbidity, and precipitation are found, they should be used with caution or stopped.

The rational use of viscosity-reducing dispersants for epoxy coatings is a systematic project involving multiple links such as product selection, addition amount control, and process optimization. Only by strictly following the usage recommendations and fully considering various influencing factors can the viscosity-reducing dispersant be ensured to achieve the best effect, improve the quality and construction performance of epoxy coatings, and meet the application needs of different fields.