Solution for Yellowing and Aging Resistance in the Paint Industry

Model parameter table of yellowing resistance test chamber SPECIFICATION

Applicable Standards:

The testing of yellowing and aging resistance of exterior wall coatings generally follows recognized industry standards:

1. ISO 4892-3: This international standard outlines the method for accelerated weathering testing of plastics and coatings, which includes UV exposure, and is used to evaluate the aging and yellowing resistance of exterior coatings.

2. ASTM G154: This standard from the American Society for Testing and Materials specifies procedures for accelerated exposure to UV light and is often used to evaluate coatings, paints, and other materials.

3. GB/T 16422.1: This Chinese national standard provides a methodology for accelerated weathering testing on coatings and materials exposed to UV light, ensuring that coatings can withstand outdoor conditions.

4. EN 927-6: This European standard applies to the weathering testing of exterior wood coatings and is used to assess the durability and yellowing resistance of such coatings, though it may also be relevant for other coatings on exterior surfaces.

Yellowing and aging resistance in the coatings industry is an important quality control issue, especially in outdoor environments or during prolonged periods of use, when the color, gloss and physical properties of coatings may change. Yellowing is usually associated with the long-term effects of UV light, moisture, oxygen and other environmental factors, and is particularly noticeable in white, light-colored and clear coatings. For this reason, the coatings industry needs to target yellowing-resistant aging solutions to ensure that products maintain a consistent appearance and performance during use.

Below are some of the solutions that the coatings industry has developed to address yellowing resistance:

1. Optimize coating formulations

Choosing the right raw materials and additives is the key to improving the yellowing resistance of coatings. The selection of components such as base resin, pigment, solvent and additives has a direct impact on the yellowing resistance and aging performance of the coating. Specific measures include:

- The use of light and heat resistant resins: such as acrylic resin, polyurethane resin and epoxy resin, etc., can effectively improve the coating's aging resistance and yellowing resistance.

- Selection of UV Absorbers and Light Stabilizers: UV Absorbers and Hindered Amine Light Stabilizers (HALS) are able to absorb and scatter UV rays and reduce the damage caused by UV rays to the coating, thus preventing yellowing.

- Improve the choice of pigment: For light-colored coatings, choose inorganic pigments with high light resistance, such as titanium dioxide (TiO2) and zinc oxide (ZnO), which have better weathering resistance and can delay yellowing.

- Add antioxidant: Adding appropriate amount of antioxidant in the coating can reduce the oxidizing effect of oxygen on the resin and avoid aging and yellowing.

2. Improve the curing process of the coating

The curing process of the coating directly affects its yellowing resistance. By optimizing the curing process and improving the cross-linking degree of the coating, the weathering resistance of the coating can be enhanced and the yellowing can be reduced.

- Adopt UV curing technology: UV curing coatings are rapidly cured by UV irradiation, resulting in a highly cross-linked coating with greater resistance to yellowing.

- Increase the curing temperature and time: Curing the coating at high temperature can improve the degree of crosslinking of molecular chains and enhance the durability and yellowing resistance of the coating.

3. External protective measures

The coating itself may not be able to completely avoid the influence of environmental factors, so it is necessary to enhance the yellowing resistance of the coating through external protection means.

- Coating the surface of the coating with a transparent protective layer: Coating the surface of the coating with a transparent protective layer (e.g. transparent protective coating or polyurethane varnish) can increase the weathering resistance of the coating and delay the occurrence of yellowing.

- Use of surface light stabilizers: Adding light stabilizers (e.g. light stabilizing resins) to the coating can prevent ultraviolet rays from penetrating into the coating and reduce aging and yellowing.

4. Choose suitable construction environment

During the construction of the coating, the environmental conditions will also affect the yellowing resistance of the coating. It is necessary to pay attention to the following points:

- Painting temperature and humidity control: High temperature or high humidity may accelerate the aging process of the coating, therefore, it is necessary to control the temperature and humidity of the painting environment during the construction, avoiding the construction under high temperature or humidity conditions.

- Avoid pollutant interference: External pollutants (such as smoke, acid rain, etc.) may accelerate the aging process of the coating, so it should be ensured that the construction environment is clean to avoid pollutants affecting the coating.

5. Aging test and quality control

Conduct regular aging test and weathering test to verify the yellowing resistance of the coating. By simulating the aging process under different environmental conditions, problems can be found and adjusted in advance.

- UV Aging Test: Use UV aging test chamber to simulate the aging process of coatings under long-term UV irradiation to detect yellowing.

- Xenon lamp aging test: Xenon lamp test can simulate the long-term exposure to sunlight to test the weathering and yellowing of coatings.

- Temperature and humidity aging test: High temperature and high humidity environment can accelerate the aging process of coatings, so temperature and humidity aging test is conducted to check the performance of coatings under extreme conditions.