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How to Test the Performance of UV Wood Coatings (Part 2)

Release time:

2026-04-03 23:48

How to Test the Performance of UV Wood Coatings (Part 2)

In addition to excellent curing performance and physical strength, UV wood topcoats must also exhibit superior chemical resistance, optical properties, and ease of application. Chemical performance determines the coating’s ability to withstand everyday chemical exposure; optical performance dictates the decorative appearance; and application performance impacts production efficiency and yield. Understanding the testing methods for these properties is essential for a comprehensive evaluation of the topcoat’s overall quality.

I. Chemical Performance Testing

Chemical performance testing evaluates the topcoat’s resistance to corrosion by various chemical substances, which in turn determines the product’s resistance to soiling and corrosion during everyday use.

1. Water Resistance

Immerse the coating test panel in room-temperature distilled water, remove it after the specified immersion time, and inspect the coating for signs of blistering, whitening, softening, or reduced adhesion. For products with more stringent requirements, a boiling-water immersion test may be conducted, in which the test panel is immersed in boiling water for a specified duration to evaluate the coating’s water resistance under more severe conditions.

2. Chemical Resistance

The spot-test method or the immersion method is employed. In the spot-test method, filter paper or cotton cloth impregnated with the test solution is placed over the coated surface and sealed with a petri dish to prevent volatilization. After a specified exposure time, the covering material is removed, and the coating’s condition—such as discoloration, blistering, softening, loss of gloss, or residual staining—is evaluated to determine the rating.

3. Yellowing Resistance

Place the coating test panels in a UV aging chamber and subject them to accelerated aging under specified UV irradiance levels and temperature–humidity conditions. Periodically remove the panels and measure the color difference of the coating using a spectrophotometer. At the same time, visually inspect the coating for signs of yellowing, chalking, cracking, and other degradation phenomena. For light-colored and transparent coatings, yellowing resistance is one of the key performance indicators for quality assessment.

4. Solvent Resistance

The solvent wipe test is conducted by repeatedly wiping the coating surface with a cotton swab soaked in a specific solvent, and observing whether the coating dissolves or softens. This test provides valuable reference for evaluating the crosslink density and degree of cure of the coating.

5. Environmental Performance

Gas chromatography is used to determine the total volatile organic compound content in coatings. Residual monomer analysis is employed to measure the amount of unreacted monomers remaining in the cured coating, which is particularly critical for products with stringent safety requirements, such as children’s toys. Heavy metal analysis is applicable to paint products and involves determining the levels of heavy metals—including lead, cadmium, and mercury—in the coating to ensure compliance with relevant safety standards.

II. Optical Performance Testing

Optical performance directly determines the decorative effect of the topcoat and is the quality attribute that users perceive first.

1. Glossiness

This is performed using a gloss meter. The instrument is placed on the coated surface, and the reflectance of the coating is measured at a standard angle. High-gloss topcoats exhibit high gloss levels and produce mirror-like reflections, whereas matte topcoats have lower gloss levels and deliver a soft, understated visual effect. In addition to measuring the gloss value, it is also necessary to assess gloss variations across different areas of the coating to ensure overall uniformity and consistency.

2. Color difference

Color difference measurement is performed using a colorimeter. The instrument’s measurement aperture is aligned with the coating surface to measure the coating’s color parameters, which are then compared with the color parameters of a standard color chart or a customer-supplied reference sample to calculate the color difference value. The smaller the color difference value, the smaller the color variation. Color difference testing is of great importance for solid-color coatings and for maintaining color consistency across batches.

3. Transparency

This applies to clear topcoats. Visual inspection can be used: apply the clear coat to black-and-white opacity test paper and assess the coating’s transparency by determining whether the black-and-white boundary remains clearly discernible. Alternatively, a haze meter can be employed for quantitative measurement; the lower the haze value, the higher the transparency. Clear coats with poor transparency will obscure the wood’s natural grain, thereby reducing the product’s decorative appeal.

III. Construction Performance Testing

Construction performance testing and evaluation assess the ease of application and quality stability of topcoats during actual coating operations, as these properties directly impact production efficiency and first-pass yield.

1. Leveling

Apply the coating to the substrate and observe whether, before curing, the coating can spread out on its own to form a smooth, even surface, with no obvious brush marks, roller marks, or orange-peel defects. Coatings with good leveling properties can eliminate application marks and produce a smooth, uniform film. For high-gloss topcoats, the requirement for leveling is particularly stringent.

2. Defoaming Performance

After applying the coating in accordance with the specified method, observe whether the air bubbles within the coating film rupture and escape promptly. Coatings with poor defoaming performance may leave pinholes or bubble defects on the coating surface, compromising both appearance and protective performance.

3. Wettability

This is assessed by observing the spreading behavior of the topcoat on the primer surface. The topcoat is applied to the primer, and it is examined whether the coating spreads uniformly and whether any defects such as craters or fish eyes—indicative of poor wetting—are present. Good wetting is essential for ensuring full contact between the topcoat and the primer and for achieving strong adhesion.

4. Storage Stability Testing

After the topcoat has been stored under the specified conditions for a designated period, its viscosity change, sedimentation behavior, and application performance should be evaluated to determine whether any alterations have occurred. Products with good storage stability will continue to exhibit satisfactory performance even after prolonged storage.

IV. Conclusion

Testing the chemical, optical, and application performance of UV wood coatings is a critical step in comprehensively evaluating product quality. Chemical performance ensures the coating’s resistance to everyday environmental aggressions; optical performance guarantees its decorative appeal; and application performance supports production efficiency. Systematic testing enables a thorough assessment of the coating’s overall quality, providing a scientific basis for product development, process optimization, and quality control.

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Bossin Recommended Products – UV Wood Coatings
Glossy topcoat
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-113	Bisphenol A epoxy acrylate	High hardness, high gloss, high fullness, containing 20% TPGDA.
B-163	Modified epoxy acrylate	Good flexibility, excellent pigment wetting, and strong adhesion.
B-165	Modified epoxy acrylate	Good flexibility and strong adhesion
B-21C	Active amine photosensitizing promoter	Low color number, antioxidant and anti-polymerization, and enhanced curing rate
B-301	Aromatic Polyurethane Acrylate	Fast curing, excellent toughness, and good grindability.
B-302	Aromatic Polyurethane Acrylate	Fast curing, high strength, good toughness, and excellent grindability.
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 performance.
B-609	Aliphatic polyurethane acrylate	Fast curing, high hardness, scratch resistance, and chemical resistance.
B-868	Organosilicon UV-Curable Resin	Excellent leveling, smooth finish, fast curing, and stain resistance.
B-868H	Organosilicon UV-Curable Resin	Excellent leveling, smooth finish, fast curing, and stain resistance.
B-910A2	Aliphatic polyurethane acrylate	Low viscosity, yellowing resistance, chemical resistance, and steel-wool resistance.
B-912	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and outstanding chemical and wear resistance.
Matte topcoat
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-160D	Modified epoxy acrylate	Good flexibility, yellowing resistance, and strong adhesion.
B-163	Modified epoxy acrylate	Good flexibility, excellent pigment wetting, and strong adhesion.
B-21C	Active amine photosensitizing promoter	Low color number, antioxidant and anti-polymerization, and enhanced curing rate
B-328M	Aliphatic polyurethane acrylate	Low gloss, low viscosity, excellent wettability, and a pleasant hand feel.
B-328R	Aliphatic polyurethane acrylate	Low gloss, excellent matting, good wetting, and a fine, smooth, and silky hand feel.
B-333	Aliphatic polyurethane acrylate	Low viscosity, excellent matting effect, good wetting properties, and excellent flexibility.
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.
B-868	Organosilicon UV-Curable Resin	Excellent leveling, smooth finish, fast curing, and stain resistance.
B-868H	Organosilicon UV-Curable Resin	Excellent leveling, smooth finish, fast curing, and stain resistance.
B-910A2	Aliphatic polyurethane acrylate	Low viscosity, yellowing resistance, chemical resistance, and steel-wool resistance.
B-912	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and outstanding chemical and wear resistance.
Bright White Finish
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-113	Bisphenol A epoxy acrylate	High hardness, high gloss, high fullness, containing 20% TPGDA.
B-160D	Modified epoxy acrylate	Good flexibility, yellowing resistance, and strong adhesion.
B-301	Aromatic Polyurethane Acrylate	Fast curing, excellent toughness, and good grindability.
B-302	Aromatic Polyurethane Acrylate	Fast curing, high strength, good toughness, and excellent grindability.
B-560	Polyester acrylate	Fast curing and excellent pigment wetting
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 performance.
B-868	Organosilicon UV-Curable Resin	Excellent leveling, smooth finish, fast curing, and stain resistance.
B-868H	Organosilicon UV-Curable Resin	Excellent leveling, smooth finish, fast curing, and stain resistance.
B-912	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and outstanding chemical and wear resistance.
Single Product Recommendation
Product Model/English Abbreviation	Product Name/Product Type	Product Features
BM2223 (TPGDA)	Di(propylene glycol) diacrylate	Good flexibility and low volatility
BM2224 (EO-HDDA)	Ethoxy-1,6-hexanediol diacrylate	Excellent adhesion to plastics, good dilutability, and low volatility.
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 excellent chemical resistance.
BM3380 (3EO-TMPTA)	Ethoxylated trimethylolpropane triacrylate	More flexible and less irritating than TMPTA.
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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Application Methods for UV Wood Finish Coatings

How to Test the Performance of UV Wood Coatings (Part 1)