News

Knowledge

Company News

Application Mind Map

Test Report

Technical Article

Industry News

Curing Mechanism of Waterborne UV 3C Coatings

Release time:

2026-07-10 07:16

Curing Mechanism of Waterborne UV 3C Coatings

The curing mechanism of waterborne UV coatings for 3C applications differs markedly from that of conventional solvent-based UV coatings. Because water serves as the primary diluent in waterborne systems, their curing process is not a simple exposure to ultraviolet light; rather, it comprises two distinct steps: pre‑drying (evaporation of water) and UV curing. This dual‑stage curing mechanism is a key distinguishing feature of waterborne UV coatings and is essential for understanding their application procedures. Gaining insight into the curing behavior of waterborne UV coatings and the factors that influence it helps in designing optimal coating processes and ensuring superior coating performance.

I. Pre-drying — Evaporation of moisture prior to photopolymerization

Pre‑drying is an essential step that waterborne UV coatings must undergo prior to photopolymerization; this process is a requirement unique to waterborne systems. Since water serves as the diluent in waterborne UV coatings, the applied film contains a significant amount of moisture. If pre‑drying is skipped and UV curing is performed directly, the moisture within the coating will not have sufficient time to evaporate, leading to the formation of bubbles or micro‑voids during curing. This can result in defects such as whitening of the coating and reduced adhesion.

The essence of the pre‑drying process lies in the evaporation of water and the phase transition of the resin. In the production of waterborne UV coatings, water‑based photocurable resins are rendered water‑soluble as carboxylate salts by the addition of amine compounds, enabling them to disperse in water. During the pre‑drying heating stage, the amines volatilize, and the resin reverts to an insoluble state; this transformation prepares the system at the molecular level for subsequent UV curing.

The conditions of pre‑drying directly affect the curing outcome. For waterborne UV coatings, the pre‑baking temperature is typically maintained within an optimal range—usually around 60°C—and the baking time is determined by the coating thickness; thicker coatings require a correspondingly longer dwell time. If drying is insufficient, residual moisture will inhibit the UV curing reaction, so even with extended irradiation, the coating may achieve only surface hardening while remaining incompletely cured internally. Consequently, the precision of control during the pre‑drying stage is critical to realizing the desired coating performance.

II. UV Curing — Free-Radical Polymerization Reaction

After pre-drying is complete and the moisture in the coating has fully evaporated, the coating enters the UV curing stage. The UV curing mechanism of waterborne UV coatings is essentially the same as that of solvent-based UV coatings, both being free-radical photopolymerization reactions.

Under ultraviolet irradiation, the photoinitiator in the coating absorbs UV radiation of a specific wavelength and, upon transitioning from the ground state to an excited state, decomposes to generate free radicals. These highly reactive free radicals rapidly attack the unsaturated double bonds in resin and monomer molecules, initiating a chain‑growth polymerization reaction that converts liquid oligomers and monomers into a solid polymeric network within a relatively short time.

The UV curing process of waterborne UV coatings typically requires precise control of both the curing energy and irradiation time. Insufficient curing energy can result in incomplete cure, inadequate coating hardness, and poor chemical resistance; excessive energy, on the other hand, may lead to yellowing or thermal damage to the substrate. For colored systems containing pigments, since pigments compete with the photoinitiator for absorption of UV light, special photoinitiators must be employed in conjunction with appropriate light sources—such as halogen lamps—to ensure thorough deep‑layer curing.

III. Main Factors Affecting Curing

The curing performance of waterborne UV coatings for 3C products is influenced by multiple factors.

Pre-drying conditions are the primary influencing factor. When pre-drying is inadequate, residual moisture can severely impede UV curing; during the curing process, moisture trapped within the coating escapes, leading to defects. Insufficient pre-baking temperature or insufficient dwell time can both result in residual moisture.

The resin structure influences the curing rate. The higher the content of unsaturated groups in the resin molecules, the faster the crosslinking reaction proceeds. Acryloyl groups exhibit greater reactivity than methacryloyl groups, so resins incorporating acryloyl groups typically cure more rapidly.

The type and amount of pigment influence the curing process. Pigments absorb a portion of the UV‑light energy, competing with the photoinitiator and thereby reducing curing efficiency. Different colors exhibit varying degrees of UV absorption; black pigments have strong absorptivity, making curing more challenging.

The selection and compatibility of photoinitiators are critical to ensuring effective curing. The photoinitiator’s absorption wavelength should match the emission spectrum of the light source, and it must exhibit good compatibility with aqueous systems to prevent volatilization and loss with water vapor during the pre‑drying stage.

UV light sources and curing parameters directly affect the curing outcome. Irradiation distance, curing time, and curing energy must be tailored to the coating formulation, and coatings of different colors may require distinct curing settings.

IV. Conclusion

The curing process of waterborne UV 3C coatings comprises two steps: pre‑drying (evaporation of moisture) and UV curing. This dual‑curing mechanism is a key distinguishing feature that sets these coatings apart from solvent‑based UV systems. During the pre‑drying stage, residual moisture in the coating is thoroughly evaporated, preparing the film for UV curing; in the UV curing stage, free-radical photopolymerization induces crosslinking of the coating. Factors such as pre‑drying conditions, resin architecture, pigment characteristics, photoinitiator selection, and UV‑source parameters collectively determine the overall curing performance. In process design, it is essential to integrate these variables and carefully optimize the conditions of both stages to achieve the desired coating properties.

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 wetting, 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 superior 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 superior 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 superior 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.

Share to:

Various Curing Methods for Waterborne UV 3C Coatings

Types of Waterborne UV Coatings for 3C Products