Common Defects in UV Wood Coatings (Part 2)


While UV wood coatings enhance the aesthetic appeal and protective performance of wooden furniture, process deviations during the coating application often lead to various surface defects. Orange peel is one such common issue: it creates regular, undulating ripples on the otherwise smooth paint film, undermining the intended silky texture of the finish. Particularly in high-gloss products, this orange‑peel–like texture causes light reflections to scatter haphazardly, replacing the anticipated mirror-like effect with distorted, muddled reflections. The pronounced unevenness felt upon touch further diminishes the product’s tactile quality. Behind the phenomenon of orange peel lie numerous technical nuances—ranging from the rheological properties of the coating to precise control of the application environment—each deserving thorough investigation.

I. Description of the Phenomenon

The surface of the paint film exhibits regular, undulating ripples resembling the texture of an orange peel. When illuminated by light, these ripples produce uneven reflections, causing the painted surface to lose its mirror‑like clarity. The higher the gloss of the paint film, the more pronounced the orange‑peel effect becomes. When touched with the fingertips, the unevenness of the surface can be clearly felt. If you hold the workpiece up to a fluorescent light tube and observe, the reflection of the tube on the paint film appears distorted and wavy, rather than forming straight lines. Under a microscope, the orange‑peel effect manifests as a regular alternating pattern of wave crests and troughs: the paint film is thicker at the crests and thinner at the troughs.

II. In-depth Analysis of the Underlying Causes

1. Rheological Imbalance

(1) Excessive Viscosity: The viscosity of UV paint during application is a core factor affecting leveling. When the viscosity is too high, internal friction within the paint film becomes immense, and molecular movement slows down. Within the limited leveling time, the paint lacks the ability to rely on surface tension to smooth out the marks left during coating, and it enters the curing stage, at which point the ripples become permanently set.

(2) Thixotropic Interference: Some UV coatings exhibit thixotropy to prevent sagging—meaning they are thick when stationary but become thinner under shear stress. If the thixotropy is too strong, the coating viscosity will recover too quickly after the paint leaves the applicator roller or spray gun, which can likewise inhibit leveling.

2. Environmental and Energy Impacts

(1) Improper Flow-Flatting Temperature: The temperature during the flow‑flatting stage affects the fluidity of the paint. If the temperature is too low, the paint’s viscosity will be relatively high, resulting in slow leveling. Conversely, if the temperature is too high, solvent may evaporate from the paint film surface too quickly, causing the surface viscosity to spike and form a thin skin that traps internal ripples instead.

(2) Too Rapid Surface Drying: In certain cases, stray light during the leveling stage or excessively high temperatures can trigger premature pre‑curing of the paint film’s surface, forming an extremely thin semi‑cured skin that prevents the underlying paint from flowing and leveling out.

3. Coating marks are too deep.

Whether it’s the roller pattern on a roll coater or the microscopic irregularities caused by the accumulation of atomized particles during spraying, if the height difference between the wave crests and troughs of these initial imperfections is too great—exceeding the limit that the paint’s surface tension can compensate for—orange peel is unavoidable.

III. Conclusion

The formation of orange-peel defects stems from the intricate interplay of multiple factors during the leveling and curing processes of paint. When the coating viscosity is too high, thixotropy recovers too quickly, or the ambient temperature during leveling is unsuitable, or the surface-drying rate is excessively rapid, the paint loses its ability to smooth out application marks within the available time. The microscopic irregularities left behind by the coating equipment become permanently embedded in the paint film, giving rise to a structural characteristic marked by alternating peaks and troughs. This defect serves as a reminder that every stage—rheological design of the coating formulation, precise adjustment of application parameters, and proper optimization of curing conditions—significantly influences the final smoothness of the paint film. A deeper understanding of the mechanisms underlying orange-peel formation helps accurately identify the root causes of problems in production practice, enabling the attainment of coated surfaces that excel in both appearance and tactile quality.

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Boxing Recommended Products – UV Wood Coatings

Putty primer

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-520

Polyester acrylate

Low viscosity, high gloss, excellent wettability, and cost-effective.

B-522

Polyester acrylate

Low shrinkage, excellent flexibility, strong adhesion, and high cost performance.

Sanding Primer

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-163

Modified epoxy acrylate

Good flexibility, excellent pigment wetting, and strong adhesion.

B-520

Polyester acrylate

Low viscosity, high gloss, excellent wettability, and cost-effective.

B-522

Polyester acrylate

Low shrinkage, excellent flexibility, strong adhesion, and high cost performance.

Primer

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-02

Phosphate ester acrylate

Enhance adhesion to substrates such as metal, glass, and plastic.

B-05

Phosphate ester acrylate

Enhance adhesion to substrates such as metal, glass, and plastic.

B-113

Bisphenol A epoxy acrylate

High hardness, high gloss, high fullness, containing 20% TPGDA.

B-165

Modified epoxy acrylate

Good flexibility and strong adhesion.

B-522

Polyester acrylate

Low shrinkage, excellent flexibility, strong adhesion, and high cost performance.

B-535

Polyester acrylate

Good adhesion, fast curing, excellent flexibility, and yellowing resistance.

B-546

Polyester acrylate

Good adhesion, fast curing, and excellent flexibility.

White primer

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-520

Polyester acrylate

Low viscosity, high gloss, excellent wettability, and cost-effective.

B-522

Polyester acrylate

Low shrinkage, excellent flexibility, strong adhesion, and high cost performance.

B-529

Polyester acrylate

Good adhesion, low shrinkage, and excellent resin compatibility.

B-560

Polyester acrylate

Fast curing and excellent pigment wetting.

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 photoinitiator

Low color, antioxidant and polymerization inhibitor, enhanced curing rate

B-301

Aromatic Polyurethane Acrylate

Fast curing, good toughness, and excellent grindability.

B-302

Aromatic Polyurethane Acrylate

Fast curing, high strength, good toughness, and excellent grindability.

B-574C

Polyester acrylate

Low viscosity, low odor, good wettability, suitable for LED UV.

B-601

Aromatic Polyurethane Acrylate

High hardness, scratch resistance, chemical resistance, and excellent value for money.

B-609

Aliphatic polyurethane acrylate

Fast curing, high hardness, scratch resistance, and chemical resistance.

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.

B-910A2

Aliphatic polyurethane acrylate

Low viscosity, yellowing resistance, chemical resistance, and steel wool resistance.

B-912

Aliphatic polyurethane acrylate

Fast curing, high hardness, good toughness, and excellent chemical and abrasion resistance.

Matte finish paint

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 photoinitiator

Low color, antioxidant and polymerization inhibitor, enhanced curing rate

B-328M

Aliphatic polyurethane acrylate

Low gloss, low viscosity, good wettability, pleasant to the touch.

B-328R

Aliphatic polyurethane acrylate

Low gloss, excellent matting effect, good wetting properties, and a fine, smooth hand feel.

B-333

Aliphatic polyurethane acrylate

Low viscosity, good matting effect, excellent wettability, and good flexibility.

B-572

Polyester acrylate

Low viscosity, low odor, good wettability, suitable for LED UV.

B-650A

Aliphatic polyurethane acrylate

Low viscosity, good matting effect, fast curing, and excellent wettability.

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.

B-910A2

Aliphatic polyurethane acrylate

Low viscosity, yellowing resistance, chemical resistance, and steel wool resistance.

B-912

Aliphatic polyurethane acrylate

Fast curing, high hardness, good toughness, and excellent chemical and abrasion resistance.

Bright white paint

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, good toughness, and excellent 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, good wettability, suitable for LED UV.

B-601

Aromatic Polyurethane Acrylate

High hardness, scratch resistance, chemical resistance, and excellent value for money.

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.

B-912

Aliphatic polyurethane acrylate

Fast curing, high hardness, good toughness, and excellent chemical and abrasion resistance.

Adherent

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-05

Phosphate ester acrylate

Enhance adhesion to substrates such as metal, glass, and plastic.

B-509B

Polyester acrylate

Good adhesion, excellent flexibility, and excellent pigment wetting.

B-531

Polyester acrylate

Good adhesion, impact resistance, excellent flexibility, and yellowing resistance.

B-535

Polyester acrylate

Good adhesion, fast curing, excellent flexibility, and yellowing resistance.

B-546

Polyester acrylate

Good adhesion, fast curing, and excellent flexibility.

B-590

Polyester acrylate

Good adhesion, fast curing, and excellent pigment wetting.

Filler type

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-520

Polyester acrylate

Low viscosity, high gloss, excellent wettability, and cost-effective.

B-522

Polyester acrylate

Low shrinkage, excellent flexibility, strong adhesion, and high cost performance.

B-529

Polyester acrylate

Good adhesion, low shrinkage, and excellent resin compatibility.

Retouch color

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-560

Polyester acrylate

Fast curing and excellent pigment wetting.

Hardened

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-301

Aromatic Polyurethane Acrylate

Fast curing, good toughness, and excellent 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, good wettability, suitable for LED UV.

B-601

Aromatic Polyurethane Acrylate

High hardness, scratch resistance, chemical resistance, and excellent value for money.

B-912

Aliphatic polyurethane acrylate

Fast curing, high hardness, good toughness, and excellent chemical and abrasion resistance.

Matte

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-328M

Aliphatic polyurethane acrylate

Low gloss, low viscosity, good wettability, pleasant to the touch.

B-328R

Aliphatic polyurethane acrylate

Low gloss, excellent matting effect, good wetting properties, and a fine, smooth hand feel.

B-329D

Aliphatic polyurethane acrylate

Low irritation, low viscosity, excellent wettability, and a pleasant hand feel.

B-333

Aliphatic polyurethane acrylate

Low viscosity, good matting effect, excellent wettability, and good flexibility.

B-650A

Aliphatic polyurethane acrylate

Low viscosity, good matting effect, fast curing, and excellent wettability.

Solid-color paint

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-519

Self‑Curing Polyester Acrylate

Self‑initiated Photocuring Performance

B-530

Polyester acrylate

Low viscosity, excellent hydrophobicity, thixotropy, and improved ink mist.

B-560

Polyester acrylate

Fast curing and excellent pigment wetting.

Yellowing resistance

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-160D

Modified epoxy acrylate

Good flexibility, yellowing resistance, and strong adhesion.

B-431

Alicyclic Specialty Acrylates

Yellowing resistance, excellent wettability, low viscosity, fast curing.

Coating by spraying

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-160D

Modified epoxy acrylate

Good flexibility, yellowing resistance, and strong adhesion.

Roller Coating

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-100

Bisphenol A epoxy acrylate

High hardness, high gloss, excellent chemical resistance, and rich body.

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-163

Modified epoxy acrylate

Good flexibility, excellent pigment wetting, and strong adhesion.

B-165

Modified epoxy acrylate

Good flexibility and strong adhesion.

B-520

Polyester acrylate

Low viscosity, high gloss, excellent wettability, and cost-effective.

B-522

Polyester acrylate

Low shrinkage, excellent flexibility, strong adhesion, and high cost performance.

Solvent-free spraying

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-251

Aromatic Polyurethane Acrylate

Fast curing, excellent flexibility, and good wetting performance with black ink pigments.

B-520

Polyester acrylate

Low viscosity, high gloss, excellent wettability, and cost-effective.

B-574C

Polyester acrylate

Low viscosity, low odor, good wettability, suitable for LED UV.

LED-UV

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-21C

Active amine photoinitiator

Low color, antioxidant and polymerization inhibitor, enhanced curing rate

B-241

Aliphatic polyurethane acrylate

Fast matting speed, excellent skin feel, and yellowing resistance.

B-27

Active amine photoinitiator

Low color, benzene-free, low odor, antioxidant and anti‑polymerization.

B-570

Polyester acrylate

Low viscosity, benzene‑free, low odor, suitable for LED UV.

B-574

Polyester acrylate

Benzene-free, low odor, and VOCs meet cigarette pack standards.

B-574C

Polyester acrylate

Low viscosity, low odor, good wettability, suitable for LED UV.

Excimer lamp

Product Model/English Abbreviation

Product Name/Product Type

Product Features

B-241

Aliphatic polyurethane acrylate

Fast matting speed, excellent skin feel, and yellowing resistance.

Skin feel

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-165

Modified epoxy acrylate

Good flexibility and strong adhesion.

B-241

Aliphatic polyurethane acrylate

Fast matting speed, excellent skin feel, and yellowing resistance.

B-328M

Aliphatic polyurethane acrylate

Low gloss, low viscosity, good wettability, pleasant to the touch.

B-328R

Aliphatic polyurethane acrylate

Low gloss, excellent matting effect, good wetting properties, and a fine, smooth hand feel.

B-574C

Polyester acrylate

Low viscosity, low odor, good wettability, suitable for LED UV.

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.

Single-Component 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

Ethoxylated 1,6-hexanediol diacrylate

Good adhesion to plastics, excellent 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 abrasion resistance, and water resistance.

BM6263/DPHA-90

Dipentaerythritol hexaacrylate

High crosslink density, high hardness, chemical and abrasion resistance, and water resistance.

 

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