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How to Address Defects in UV 3C Coatings (Part 12)

Release time:

2026-07-06 06:50

How to Address Defects in UV 3C Coatings (Part 12)

In the practical production of UV 3C coatings, whitening is one of the common defects that adversely affect coating appearance. It manifests as a lighter, paler shade than expected, with a milky‑white haze, reduced transparency, and diminished color saturation—effects that are particularly pronounced in light‑colored finishes and clear coats. Whitening is closely linked to moisture and is influenced by multiple factors, including substrate condition, environmental conditions, and coating formulation. Addressing this defect requires targeted measures covering substrate drying management, control of the application environment, and careful selection of thinners. This paper outlines approaches to mitigating whitening, focusing on controlling substrate moisture content, managing ambient humidity during application, and choosing appropriate diluents.

I. Control of Substrate Moisture Content

Excessive moisture content in the substrate is a major cause of whitening. During treatment, the substrate must be properly dried to maintain its moisture level within an appropriate range. Substrates with high hygroscopicity should be stored in a dry environment; prior to use, they can be dried in an oven or with a dehumidifying dryer to remove moisture adsorbed within the material.

Drying temperature and duration should be set according to the substrate’s heat resistance to prevent deformation caused by excessive heat. After drying, the substrate should be stored in a dry environment and removed only prior to use. For substrates that have been stored for an extended period, their moisture content should be re‑tested before application; proceed with coating only if the moisture level is within an acceptable range.

II. Control of Construction Environment Humidity

Excessively high humidity in the construction environment is a common external cause of whitening. When addressing this issue, the relative humidity in the work area should be maintained within an appropriate range. Spray booths should be equipped with humidity‑control devices; during seasons or in regions with high humidity, dehumidifiers or air-conditioning systems should be used to reduce ambient humidity.

Monitoring of ambient humidity should be integrated into routine operations. When humidity exceeds the process‑specified limits, coating operations should be suspended or dehumidification measures implemented. For production environments where humidity cannot be controlled, process parameters may be adjusted under high‑humidity conditions, such as appropriately extending the leveling time to reduce the rate of solvent evaporation.

III. Control of Moisture on the Substrate Surface and in the Coating

Moisture on the substrate surface and moisture entrained in the coating are both sources of whitening. During processing, ensure that the substrate is thoroughly dried after cleaning, and apply the coating within the specified time to prevent residual surface moisture. The quality of the cleaning water should also be carefully controlled, avoiding the use of water containing impurities.

During storage and application, coatings should be protected from moisture ingress. Coating containers must remain tightly sealed to prevent atmospheric moisture from entering. Tools and containers used for mixing coatings should be kept dry and clean to avoid introducing moisture. When selecting thinners, pay close attention to their water content; use only thinners that meet the specified requirements.

IV. Adjustment of the Diluent’s Volatilization Rate

One of the factors causing whitening is the rapid evaporation of the thinner. When applying the coating, select a thinner with an appropriate evaporation rate based on the application environment. In higher‑temperature conditions, opt for a thinner with a slightly slower evaporation rate to prevent the surface from cooling too quickly and causing moisture to condense.

The evaporation rate of the thinner should strike a balance between leveling performance and the risk of whitening. An excessively slow evaporation rate may result in poor leveling, while an overly rapid evaporation rate increases the likelihood of whitening. Through experimentation, select the appropriate type and formulation of thinner for the current application conditions, achieving an optimal trade-off between leveling quality and whitening control.

V. Integrated Process Control

Addressing whitening defects requires comprehensive control across multiple stages, including substrate drying, environmental management, and the selection of thinners. For the substrate, maintain low moisture content and ensure proper drying; for the environment, keep the application area’s humidity within an appropriate range; and for the coating, prevent water contamination and choose a suitable thinner.

The control of each process step is interrelated, and adjustments should be made with a holistic approach. In actual production, the primary source of whitening can be identified based on its distribution pattern: uniform whitening is typically associated with ambient humidity or the overall moisture content of the substrate, whereas localized whitening may be linked to localized contamination or abnormal moisture levels in specific areas.

VI. Conclusion

Addressing whitening defects involves multiple steps, including proper substrate drying management, control of ambient humidity during application, and the judicious selection of thinners. By maintaining appropriate substrate moisture levels, keeping the application environment within an optimal humidity range, preventing moisture ingress on the substrate surface and in the coating system, and choosing thinners with suitable evaporation rates based on application conditions, the occurrence of whitening can be effectively minimized. Optimizing each of these stages requires coordinated efforts and a comprehensive consideration of material properties, environmental factors, and process requirements to achieve a desirable coating appearance.

Disclaimer: The above content has been compiled from publicly available sources and is provided for reference only. If any infringement occurs, please contact us, and we will address it promptly.

Bosheng Related Product Recommendations – 3C Coatings
General-purpose
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-102	Bisphenol A epoxy acrylate	High hardness, high gloss, chemical resistance, contains 15% TMPTA.
B-151	Modified epoxy acrylate	Low halogen, yellowing-resistant, excellent plating performance, and strong adhesion.
B-165	Modified epoxy acrylate	Good flexibility and strong adhesion
B-216	Aliphatic polyurethane acrylate	Fast curing, high fullness, and excellent toughness.
B-368	Aliphatic polyurethane acrylate	Good toughness, excellent leveling, excellent bend resistance, and excellent heat resistance.
B-574C	Polyester acrylate	Low viscosity, low odor, excellent wettability, suitable for LED UV.
B-601	Aromatic polyurethane acrylate	High hardness, scratch resistance, chemical resistance, and excellent cost-effectiveness.
B-6019	Special functional group acrylate	Good leveling, excellent wettability, resistant to boiling water, and superior color dispersion.
B-609	Aliphatic polyurethane acrylate	Fast curing, high hardness, scratch resistance, and chemical resistance.
B-615A	Aliphatic polyurethane acrylate	Fast curing, excellent toughness, wear resistance, and chemical resistance.
B-619W	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, wear resistance, and chemical resistance.
B-6380N	Special functional group acrylate	Excellent adhesion to plastics, strong hiding power, and improved paint film appearance.
B-919B	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and outstanding chemical and wear resistance.
Matte
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-572	Polyester acrylate	Low viscosity, low odor, excellent wettability, suitable for LED UV.
B-650A	Aliphatic polyurethane acrylate	Low viscosity, excellent matting effect, fast curing, and good wettability.
Wearable device
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-6211	Aliphatic polyurethane acrylate	Fast curing, high hardness, scratch-resistant, and free of organotin.
Hand feel
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-328M	Aliphatic polyurethane acrylate	Low gloss, low viscosity, excellent wettability, and a pleasant hand feel.
B-868	Organosilicon photocurable resin	Good leveling, smooth finish, fast curing, and stain resistance.
B-868H	Organosilicon photocurable resin	Good leveling, smooth finish, fast curing, and stain resistance.
Large-area spraying
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-374	Aliphatic polyurethane acrylate	Good flexibility, excellent leveling, resistant to abrasion and chemicals, and yellowing‑resistant.
Car interior
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-6063	Special functional group acrylate	High molecular weight, low curing shrinkage
B-6210	Aliphatic polyurethane acrylate	Low viscosity, chemical resistance, environmental resistance, and dual photocatalytic–thermal curing.
B-6263	Special functional group acrylate	Fast curing, high build, boil‑water resistant, and excellent toughness.
B-916	Aliphatic polyurethane acrylate	Low viscosity, solvent resistance, chemical resistance, and steel-wool resistance.
B-919B	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and outstanding chemical and wear resistance.
Resistant to steel wool
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-910A2	Aliphatic polyurethane acrylate	Low viscosity, yellowing resistance, chemical resistance, and steel-wool resistance.
B-916	Aliphatic polyurethane acrylate	Low viscosity, solvent resistance, chemical resistance, and steel-wool resistance.
B-919B	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and outstanding chemical and wear resistance.
Oil-resistant pen
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-868	Organosilicon photocurable resin	Good leveling, smooth finish, fast curing, and stain resistance.
B-868H	Organosilicon photocurable resin	Good leveling, smooth finish, fast curing, and stain resistance.
Battery casing
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-431	Cycloaliphatic Specialty Acrylate	Yellowing-resistant, excellent wettability, low viscosity, fast curing
B-548	Polyester acrylate	Withstands high temperatures of 250–280°C.
Solid color paint
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-519	Self-curing polyester acrylate	Self-initiated photopolymerization performance
B-560	Polyester acrylate	Fast curing and excellent pigment wetting.
Yellowing resistance
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-151	Modified epoxy acrylate	Low halogen, yellowing-resistant, excellent plating performance, and strong adhesion.
B-160D	Modified epoxy acrylate	Good flexibility, yellowing resistance, and excellent adhesion.
B-216	Aliphatic polyurethane acrylate	Fast curing, high fullness, and excellent toughness.
B-296	Aliphatic polyurethane acrylate	Fast curing, chemical resistance, yellowing resistance, impact resistance
B-431	Cycloaliphatic Specialty Acrylate	Yellowing-resistant, excellent wettability, low viscosity, fast curing
Monomer Recommendation
Product Model/English Abbreviation	Product Name/Product Type	Product Features
BM3231 (TMPTA)	Trimethylolpropane triacrylate	High crosslink density, high hardness, high gloss, and excellent wear resistance.
BM3235 (PET3A)	Pentaerythritol triacrylate	Fast curing, high crosslink density, high hardness, and chemical resistance.
BM3380 (3EO-TMPTA)	Pentaerythritol triacrylate	More flexible and less irritating than TMPTA.
BM4241 (DiTMPTA-80)	Bis(2,3-dihydroxypropyl) tetraacrylate	High crosslink density, high hardness, chemical and wear resistance, and water resistance.
BM4242 (Di-TMPTA)	Bis-trimethylolpropane tetraacrylate	High crosslink density, high hardness, chemical and wear resistance, and water resistance.
BM6261 (DPHA-80)	Dipentaerythritol hexaacrylate	High crosslink density, high hardness, chemical and wear resistance, and water resistance.
BM6263 (DPHA-90)	Dipentaerythritol hexaacrylate	High crosslink density, high hardness, chemical and wear resistance, and water resistance.

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How to Address Defects in UV 3C Coatings (Part 13)

How to Address Defects in UV 3C Coatings (Part 11)