Achieving the perfect shade of white in plastic products often involves precise formulation, and Optical Brightener OB-1 (CAS No. 1533-45-5) is a cornerstone additive for this purpose. As a highly effective fluorescent whitening agent, OB-1 enhances brightness by converting UV light into visible blue light, counteracting yellowing. However, its efficacy is closely tied to the correct dosage, which varies depending on the polymer type, processing conditions, and desired outcome. This guide provides insights into optimal dosage levels for various plastics.

The fundamental principle behind dosage is to add enough OB-1 to achieve the desired level of whiteness and brightness without causing adverse effects, such as a greenish hue or reduced lightfastness. Generally, optical brighteners are used in very low concentrations, typically measured in parts per million (ppm) or as a percentage of the total material weight.

For Polyolefins (PE, PP) processed at temperatures between 180–240°C, recommended dosages for OB-1 range from 0.01% to 0.05%. This range is suitable for applications like films, injection molding, and fibers. Higher crystallinity materials might require careful attention to dispersion to ensure uniform whitening. It's advisable to start with a lower concentration and adjust upwards based on visual assessment.

In Polyesters (PET, PBT), which are processed at higher temperatures (250–280°C), the recommended dosage for OB-1 is typically 0.005% to 0.03%. For fibers, the lower end of this spectrum (0.005–0.02%) is often sufficient. Given the high processing temperatures, prolonged exposure can lead to thermal decomposition, so precise control and adequate dispersion are key.

For Polyamides (PA6/PA66), processed between 260–290°C, dosages of 0.01% to 0.04% are commonly used. Controlling humidity and avoiding interaction with metal ions are important considerations for these hygroscopic materials.

Polycarbonate (PC) and other high-temperature engineering plastics processed between 280–320°C typically require very low dosages, around 0.005% to 0.02%. These materials are sensitive to thermal degradation, and excessive OB-1 can sometimes impact mechanical properties. Small-scale trials are crucial to determine the optimal balance.

In ABS, processed at 200–240°C, a dosage of 0.01% to 0.05% is generally recommended for applications like automotive parts and appliance housings. Compatibility with other additives, such as flame retardants, should be tested.

For PVC, processed at 160–200°C, dosages of 0.01% to 0.03% are typical. Careful control of processing temperature is essential to prevent additive migration.

In Polystyrene (PS), processed at 180–220°C, dosages of 0.01% to 0.03% are used. Ensuring good dispersion, especially in high-impact polystyrene (HIPS), is important.

Masterbatches containing OB-1 might have higher concentrations, with recommended addition rates of 3kg to 10kg per ton of the final polymer. This allows for easier handling and more precise dosing in the manufacturing process.

Recycled Plastics: For recycled materials, the dosage can vary more widely, often ranging from 500g to 700g per ton, depending on the degree of degradation and the desired level of whiteness. The goal here is to mask yellowness and improve the visual consistency of the recycled product.

It is always recommended to start with the lower end of the suggested dosage range and conduct small-scale trials to assess the visual outcome and ensure compatibility with the specific polymer matrix and processing equipment. Factors like the intensity of the initial yellowing, the presence of other additives, and the specific end-use requirements will influence the final optimal dosage. Consulting the manufacturer's technical data sheet for Optical Brightener OB-1 is essential for detailed guidance.

NINGBO INNO PHARMCHEM CO.,LTD. provides high-quality Optical Brightener OB-1 and expert advice on dosage optimization to help clients achieve the best possible results in their plastic applications.