The application of whitening agents in plastic products

Whitening agents (mainly fluorescent whitening agents) are key additives for optimizing the appearance of plastic products. They absorb ultraviolet light and convert it into blue purple visible light, neutralizing the yellowing of the plastic itself, while improving whiteness and glossiness. They can also assist in improving weather resistance and avoiding yellowing in the later stage. It is suitable for almost all plastic categories such as PE, PP, PVC, PET, ABS, etc., and is widely used in food packaging, home appliance shells, recycled plastics, outdoor building materials and other scenarios. The addition amount only needs to be 0.01% -0.3% to achieve significant effects. Currently, it is developing towards low migration, safety and environmental protection, and weather resistance, which is an important support for improving the appearance and market competitiveness of plastic products.

1、 The core function of whitening agents: multiple values beyond "white"

1. Brightening and whitening, optimizing appearance

This is the core function, which aims to address the yellowing of plastic raw materials themselves (such as oxidation yellowing of PE and PP resins) or the yellow tone generated during processing. Through the principle of fluorescence complementarity, the plastic presents pure whiteness and transparent luster:

The whiteness value of PP basin without added whitening agent is about 75. After adding 0.05% OB type whitening agent, the whiteness value can be increased to over 90;

After adding OB-1 whitening agent to transparent PVC film, not only does the whiteness improve, but the transmittance can also be retained by more than 90%, avoiding "whitening and loss of transparency".

2. Covering up flaws and improving quality

Whitening agents can effectively mask color differences, residual impurities, or appearance defects caused by trace impurities in recycled plastics, making the product look similar to new materials

After adding 0.1% KCB whitening agent to recycled PE particles, it can mask the yellowing and black spots generated during the recycling process, and can be used to produce products such as shopping bags and trash cans;

The trace metal impurities in the raw materials of ABS household appliance shells, after modification with whitening agents, have no obvious defects on the surface, improving the product qualification rate.

3. Assist in anti yellowing and extend the appearance life

Some weather resistant whitening agents (such as UV-1130) also have the function of absorbing ultraviolet rays, which can inhibit plastic yellowing and aging caused by ultraviolet rays while whitening:

After adding weather resistant whitening agents to PVC door and window profiles for outdoor use, the yellowing index (Δ E) is less than 2 after 2 years of outdoor exposure, which is much better than products without additives (Δ E>5);

After adding whitening agents to PE agricultural film, it not only brightens and benefits crop lighting, but also delays the aging and yellowing of the film, extending its service life.

2、 Mainstream whitening agent types and compatible plastics: precise matching of scene requirements

Different whitening agents have significant differences in heat resistance, compatibility, and safety, and should be selected based on the type of plastic, processing technology, and application scenario

1. Styrene bis (triazine) derivatives (such as OB, OB-1): universal and efficient

Core advantages: high whitening efficiency, good compatibility, heat-resistant temperature of 180-300 ℃, suitable for most plastics;

Compatible plastics: PE, PP, PVC, PET, ABS;

Typical applications: PP microwave lunch boxes, PET beverage bottle preforms, ABS TV housings, in compliance with food contact safety standards (migration<0.01mg/kg).

2. Coumarins (such as KCB, KSN): high weather resistance type

Core advantages: Outstanding UV resistance, long-lasting whitening effect, and not easily faded due to sun exposure;

Compatible plastics: PE, PP, PVC, EVA;

Typical applications: Outdoor PVC tables and chairs, PE agricultural film, EVA yoga mats, maintain stable whiteness even after one year of outdoor use.

3. Benzoxazoles (such as UV-1130): Transparent specialized type

Core advantages: High light transmittance, no impact on plastic transparency after whitening, excellent temperature resistance (≤ 320 ℃);

Compatible plastics: PET, PC, transparent ABS;

Typical applications: PC lamp cover, PET transparent packaging film, transparent PS toys, with a light transmittance of over 90% after whitening and no fog shadow.

4. Special functional type (such as B-3T): food grade dedicated

Core advantages: extremely low toxicity, compliant with EU No.10/2011 and Chinese GB 9685 standards, with almost zero migration volume;

Compatible plastics: PE, PP, PET;

Typical applications: baby PP bottles, food grade PE cling film, PET food packaging bottles, balancing safety and appearance.

3、 Application practice of whitening agents in key plastic products: scenario based formula design

1. General plastic products: balancing cost and effectiveness

PP plastic tableware (food contact):

Formula: PP resin+0.03% OB whitening agent+0.1% antioxidant 1010;

Process: Injection molding temperature 180-200 ℃;

Effect: Whiteness value ≥ 90, no odor, migration amount<0.005mg/kg, in compliance with food grade standards.

PE shopping bag (recycled material):

Formula: Recycled PE particles+0.08% KCB whitening agent+0.2% antioxidant DLTP;

Process: blown film temperature 150-170 ℃;

Effect: Uniform whiteness, no obvious yellow or black spots, tensile strength retention rate>85%, meeting the appearance standards of new shopping bags.

2. Engineering Plastic Products: Balancing Temperature Resistance and Transparency

PET beverage bottle preform:

Formula: PET resin+0.05% OB-1 whitening agent+0.2% phosphite 168;

Process: drying temperature of 160 ℃, injection molding temperature of 270-280 ℃;

Effect: The whiteness of the bottle blank is pure, the bottle body is transparent after blow molding, there is no yellowing phenomenon, and the appearance is stable within the shelf life.

PC computer shell:

Formula: PC resin+0.04% UV-1130 whitening agent+0.3% light stabilizer UV-327;

Process: Injection molding temperature 280-300 ℃;

Effect: The shell has uniform whiteness, a light transmittance of over 85%, strong weather resistance, and no yellowing after long-term use.

3. Recycled plastic products: the key to turning waste into treasure

Recycled PVC pipes:

Formula: Recycled PVC resin+0.1% OB whitening agent+2% calcium zinc composite heat stabilizer;

Process: Extrusion temperature 150-170 ℃;

Effect: The whiteness of the pipe is uniform, covering up impurities and color differences in the recycled material. The mechanical properties reach over 80% of the standard for new pipe materials, and the cost is reduced by 30%.

Recycled PP woven bag:

Formula: Recycled PP particles+0.06% KSN whitening agent+0.15% antioxidant 1076;

Process: Drawing temperature 160-180 ℃, weaving temperature 140-160 ℃;

Effect: The woven bag has consistent whiteness, no significant color difference, improved weather resistance, and no obvious yellowing after 6 months of outdoor use.

4. Outdoor plastic products: priority given to weather resistance

PVC outdoor flooring:

Formula: PVC resin+0.07% KSN whitening agent+0.3% light stabilizer HALS 944;

Process: Rolling temperature 160-180 ℃;

Effect: The floor has a bright whiteness and a yellowing index of less than 2 after 2 years of outdoor exposure. Its wear resistance and weather resistance meet the requirements for outdoor use.

PE agricultural film:

Formula: PE resin+0.05% OB whitening agent+0.2% light stabilizer UV-327;

Process: blown film temperature 150-180 ℃;

Effect: The whiteness of the film is improved, the light transmittance is greater than 85%, which is beneficial for crop photosynthesis, while delaying aging and extending the service life to 12 months.

4、 Application precautions and development trends

1. Key precautions

Control the amount of addition: Excessive addition can easily cause plastic to turn blue, reduce light transmittance, and even precipitate, usually 0.01% -0.3% is appropriate;

Matching processing temperature: If the PET processing temperature is high (270-280 ℃), OB-1 with a temperature resistance of ≥ 300 ℃ should be selected to avoid the decomposition and failure of whitening agents;

Safety compliance: In scenarios such as food contact and children's toys, food grade whitening agents should be selected to avoid the use of products containing heavy metals or high mobility.

2. Development Trends

Low migration and environmental protection: Developing high molecular weight whitening agents to reduce migration risks and adapt to high-end scenarios such as food and pharmaceutical packaging;

Multi functional integration: Developing "whitening+antioxidant+weather resistant" composite additives, simplifying formulas, and reducing costs, such as whitening anti yellowing composite agents;

Biobased: Developing natural whitening agents using plant extracts as raw materials, in line with the "dual carbon" policy, suitable for environmentally friendly plastic products.

5、 Summary: Whitening agent - the "beauty enabler" of plastic products

From daily PP tableware and PE shopping bags, to high-end PC electronic shells and PET food packaging, and to the resource utilization of recycled plastics, whitening agents significantly enhance the appearance quality and market competitiveness of plastic products by accurately brightening, concealing defects, and assisting in anti yellowing. It is not only an "appearance optimization additive", but also plays a key role in the recycling of recycled plastics, helping to promote environmental protection. In the future, with the development of low migration, multifunctional, and bio based whitening agents, it will further adapt to the high-end and environmentally friendly development needs of the plastic industry, providing continuous support for the upgrading of the appearance and value of plastic products.