Choosing an optical brightener for plastics is not simply a matter of selecting the product with the strongest whitening effect.
Different plastics have different processing temperatures, chemical structures, additive systems and appearance requirements. An optical brightener that performs well in one polymer may not provide the same result in another.
The right selection should therefore consider the polymer, processing temperature, required white shade, compatibility, dispersion and final application conditions.
1. Start with the Polymer Type
The first step is to identify the plastic being processed.
Common materials include:
PE
PP
PVC
PS
ABS
EVA
PET
PBT
PC
PA
PMMA
TPU
Different optical brighteners have different application ranges.
For example, Optical Brightener OB is widely used in thermoplastics including PVC, polyethylene, polypropylene, polystyrene, polycarbonate, acrylics, polyurethane, polyester and polyamide. This broad compatibility makes it a practical starting point for many general plastic applications.
Optical Brightener OB-1, on the other hand, is particularly suitable for polyester, polyamide and high-temperature engineering plastics such as polycarbonate and polyester.
Optical Brightener FP-127 is commonly considered for PVC, PS, HIPS, ABS, TPU, polycarbonate and PMMA applications.
Therefore, product selection should begin with the actual resin rather than simply choosing a familiar optical brightener grade.
2. Consider the Processing Temperature
Processing temperature is one of the most important factors in optical brightener selection.
During extrusion, injection molding or compounding, the optical brightener must remain stable enough to withstand the processing conditions.
For polymers processed at relatively high temperatures, a grade with strong thermal stability should be considered.
OB-1 is particularly known for its high heat resistance and low volatility, which makes it suitable for high-temperature engineering plastics and fiber applications.
However, choosing the product with the highest heat resistance is not always the best solution.
A very high-melting optical brightener may require greater attention to dispersion when used in lower-temperature polymers. For example, technical guidance for OB-1 specifically notes the need to ensure complete dispersion when it is used in lower-temperature systems such as styrenics and acrylics.
The better question is therefore:
Can the optical brightener remain stable and disperse effectively under my actual processing conditions?
3. Determine the Required White Shade
Whiteness is not only about brightness.
Different optical brighteners can produce different fluorescent shades, and the preferred appearance may vary depending on the finished product.
Some customers prefer:
Neutral white
Bluish white
Bluish-violet white
This difference can be important in white plastics, transparent products, films, consumer goods and products where color consistency is critical.
For example, Archroma's technical information identifies KCB with a bluish shade and KSN with a bluish-violet shade.
Therefore, the right grade should not only reduce the visual yellow tone but also produce the desired final white shade.
4. Pay Attention to Dispersion
Optical brighteners are normally used at relatively low addition levels, so good dispersion is important.
If the additive is not distributed uniformly throughout the polymer, the expected whitening effect may not be achieved consistently.
Dispersion can be influenced by:
Particle size
Polymer type
Processing temperature
Mixing conditions
Masterbatch preparation
Other additives in the formulation
This is particularly important when using high-melting optical brighteners in polymers processed at lower temperatures.
A product may have excellent thermal stability on paper but still perform poorly if it cannot disperse properly in the actual production process.
5. Consider the Final Use Environment
The finished product's use environment should also be considered.
For indoor plastic products, a wider range of optical brighteners may be suitable.
For applications exposed to strong sunlight or long-term outdoor conditions, light stability becomes more important.
For example, technical guidance for FP-127 states that because optical brighteners inherently have limitations in light fastness, this particular grade is generally recommended for indoor applications.
This also highlights an important point:
An optical brightener is not a substitute for a UV stabilizer or antioxidant.
If the polymer itself is degrading because of heat, oxidation or UV exposure, the complete stabilization system should be evaluated rather than simply increasing the optical brightener dosage.
6. Check the Other Additives in the Formulation
An optical brightener does not work independently of the rest of the formulation.
The final result may also be influenced by:
Titanium dioxide
Pigments
Fillers
Antioxidants
UV absorbers
Light stabilizers
Processing aids
Other colorants
Supplier technical information for OB, OB-1 and FP-127 specifically notes that the actual formulation and recommended use level depend on the substrate, performance requirements and other formulation factors. It also notes that the presence of a UV absorber can affect the required optical brightener loading.
This is why two factories using the same plastic and the same optical brightener can still obtain different whitening results.
7. More Optical Brightener Does Not Always Mean Better Whiteness
A common mistake is to increase the dosage whenever the whiteness is not sufficient.
The better approach is to find the optimum dosage.
The required amount depends on factors such as:
Original color of the resin
Polymer transparency
Pigment concentration
Product thickness
Required white shade
Other additives
Optical brightener efficiency
Commercial technical recommendations also show that optical brighteners are typically used within specific concentration ranges and that the final dosage should be determined through testing under actual processing conditions.
Therefore, the goal should not be:
Maximum dosage
but rather:
Required whiteness at the most effective dosage.
This can also help control the overall formulation cost.
8. A Practical Selection Guide
When choosing an optical brightener, consider the application in the following order:
Step 1 — Identify the Polymer
Determine whether the material is PE, PP, PVC, ABS, PET, PC, PA, PMMA, TPU or another polymer.
Step 2 — Confirm the Processing Temperature
Higher-temperature engineering plastics require greater thermal stability.
Step 3 — Define the Required White Shade
Decide whether the target appearance is neutral, bluish or bluish-violet.
Step 4 — Evaluate Compatibility and Dispersion
Make sure the product can disperse effectively in the actual resin and processing system.
Step 5 — Consider the End-Use Environment
Determine whether the finished product is intended mainly for indoor use or will experience significant UV exposure.
Step 6 — Review the Complete Formulation
Consider pigments, fillers, antioxidants, UV absorbers and other additives.
Step 7 — Optimize the Dosage
Test several appropriate dosage levels rather than assuming that more optical brightener will provide a better result.
Which Optical Brightener Should You Test First?
There is no single optical brightener that is best for every plastic.
As a general starting point:
For broad thermoplastic applications:
A versatile grade such as Optical Brightener OB may be considered.
For high-temperature engineering plastics:
A high-thermal-stability grade such as Optical Brightener OB-1 may be more suitable.
For PVC, styrenic polymers, TPU, PC or PMMA:
Optical Brightener FP-127 may be one of the grades worth evaluating, particularly for suitable indoor applications.
When a specific fluorescent shade is required:
Grades such as KCB and KSN can be compared according to the polymer and required white shade. Archroma's application data, for example, shows both grades being used across multiple plastic systems while producing different shade directions.
These are starting points rather than universal formulation rules. The final choice should always be confirmed through actual application testing.
How to Compare Different Optical Brighteners
When testing two or more grades, keep the main processing conditions consistent:
Same resin batch
Same pigment and filler levels
Same processing temperature
Same processing time
Comparable optical brightener dosage
Then evaluate:
Whiteness
Yellow tone reduction
Final shade
Dispersion
Surface appearance
Processing stability
Required dosage
Overall formulation cost
This provides a much more reliable basis for selection than comparing product specifications alone.
Need Help Choosing an Optical Brightener for Plastics?
Different polymers and processing conditions require different optical brightener solutions.
Tell us your plastic material, processing temperature, current whitening problem and target appearance.
Blue Dolphin can help you evaluate suitable optical brightener grades and optimize product selection and dosage according to your application requirements.
Post time: Aug-09-2022