Polyurethane-based powder coating is widely used in automotive, home appliances, construction, metal furniture, industrial equipment, and many other fields due to its excellent overall performance, including high decorative performance, outstanding physical and mechanical properties, and comprehensive chemical resistance.
It features low yellowing tendency, excellent weather resistance and light resistance, while combining the advantages of epoxy and acrylic coatings. Compared with TGIC-cured pure polyester powder coating systems, it is also more environmentally friendly and non-toxic.
This article systematically introduces the concept, types, characteristics, functions, application fields, selection considerations, and solutions to common problems of polyurethane-based powder coating. It focuses particularly on the functions of polyurethane-based powder coating, helping readers better understand what polyurethane-based powder coating is, its characteristics, and its applications.
What Is Polyurethane-Based Powder Coating?
Polyurethane-based powder coating is a thermosetting powder coating mainly based on hydroxyl-containing polyester resin and blocked isocyanate curing agents.
After electrostatic spraying and heating, when the temperature reaches the curing condition, the blocked isocyanate is released and participates in the cross-linking reaction, forming a coating film with excellent performance.
Types of Polyurethane-Based Powder Coating
Polyurethane-based powder coating mainly includes two types:
1. Thermosetting polyurethane powder coating
This is the most common type.
It undergoes chemical cross-linking curing after heating.
The main varieties include:
Polyester-polyurethane type
Excellent overall performance
Good cost performance
Widely used
Acrylic-polyurethane type
Better appearance
Higher weather resistance
Suitable for high-end decorative applications
Higher cost
2. UV-curable polyurethane powder coating
It is cured by ultraviolet light irradiation without high-temperature baking.
It is suitable for heat-sensitive substrates such as:
Plastics
Wood
Other temperature-sensitive materials
Features of Polyurethane-Based Powder Coating
The main features of polyurethane-based powder coating include:
1. Excellent balanced performance
It combines:
The adhesion of epoxy coatings
The appearance advantages of acrylic coatings
It provides:
Excellent leveling
High gloss
Good flexibility
Outstanding impact resistance
2. Excellent weather resistance and gloss retention
It has low yellowing tendency during long-term outdoor use.
It is resistant to:
Loss of gloss
Powdering
Color fading
It is one of the powder coating systems with the best weather resistance.
3. Good chemical resistance
It provides excellent resistance against:
Oil contamination
Solvents
Acids
Alkalis
Other chemical media
4. Environmentally friendly and efficient
Features include:
Nearly zero VOC emissions
Powder recycling capability
One-coat coating formation
It can also be developed into low-temperature curing products to meet energy-saving requirements or applications involving heat-sensitive substrates.
Functions of Polyurethane-Based Powder Coating
The main functions of polyurethane-based powder coating include:
1. High-end decorative performance
It provides smooth leveling and high-gloss coating surfaces.
It meets the high appearance requirements of products such as:
Automobiles
Home appliances
2. Long-term outdoor protection
With excellent weather resistance and gloss retention, it can withstand long-term exposure to:
Sunlight
Rain
Outdoor environments
It is resistant to:
Yellowing
Powdering
Suitable for:
Outdoor facilities
Architectural aluminum profiles
3. Comprehensive protection
It combines:
Flexibility
Impact resistance
Chemical resistance
Protecting substrates from:
Mechanical damage
Chemical corrosion
Application Fields of Polyurethane-Based Powder Coating
Polyurethane-based powder coating is mainly applied in the following fields:
1. Automotive and transportation
Applications include:
Automotive wheels
Vehicle frames
Body decorative parts
Truck components
These applications require coatings with excellent appearance and long-term weather resistance.
2. Construction and building materials
Applications include:
Aluminum alloy doors and windows
Curtain walls
Guardrails
Outdoor furniture
These products require excellent color retention and gloss retention under long-term outdoor exposure.
3. Home appliances
Applications include:
Refrigerators
Washing machines
Air conditioner panels
These products require:
Good leveling
High gloss
Excellent yellowing resistance
4. Industrial equipment and machinery
Applications include:
Agricultural machinery
Construction machinery
Mechanical and electrical equipment
They require both protective performance and good appearance quality.
5. Metal furniture and daily products
Applications include:
Outdoor metal tables and chairs
Shelves
Fitness equipment
These applications require both decorative appearance and durability.
How to Select Polyurethane-Based Powder Coating
When selecting polyurethane-based powder coating, many users may not know how to choose the right product.
Based on our industry experience, we recommend focusing on the following aspects:
1. Consider the application environment
Outdoor applications
Examples:
Building curtain walls
Automotive wheels
Choose weather-resistant formulations.
Pay attention to:
Gloss retention rate
QUV aging test results
Indoor applications
Examples:
Home appliances
Furniture
Mainly consider:
Leveling
Gloss
Chemical exposure environments
Confirm acid, alkali, and solvent resistance data.
2. Consider decorative requirements
For high-gloss appearance:
Choose high-gloss formulations with gloss ≥90%.
For:
Matte effects
Textured finishes
Choose matte additives or texture powder coatings.
Colors should be selected according to color samples.
Polyurethane coatings have good color retention, but bright colors should still be confirmed.
3. Consider performance requirements
For bending and impact requirements:
Confirm flexibility data.
For:
High hardness
Wear resistance
Choose high-hardness formulations.
For corrosion protection:
Confirm salt spray test data.
Primer may be required in some applications.
4. Consider curing and coating process
Normal curing:
180-200℃
For aluminum materials or thin sheets:
Choose low-temperature curing types (160℃ or lower).
Control recycled powder/new powder mixing ratio carefully to avoid affecting appearance.
Common Problems and Solutions of Polyurethane-Based Powder Coating
During the application of polyurethane-based powder coating, the most common problems include the following.
Based on our industry experience, we provide targeted solutions to help effectively solve powder coating issues.
1. Low Gloss or Loss of Gloss Problem
Problem:
Coating gloss does not meet requirements or becomes dull.
Causes:
Excessive curing temperature or baking time causing coating aging
Powder absorbing moisture or exceeding shelf life
Excessive recycled powder ratio
Solutions:
Strictly control curing temperature and time according to curing curve
Store powder in a cool and dry environment
Control recycled powder/new powder ratio at 1:3 to 1:5
Avoid using recycled powder alone
2. Orange Peel or Poor Leveling Problem
Problem:
The coating surface is uneven like orange peel.
Causes:
Film thickness too high or too low
Insufficient atomizing air pressure
Powder particle size too coarse
Poor formulation leveling performance
Solutions:
Control film thickness within a reasonable range (usually 60-80μm)
Adjust spray gun air pressure for better atomization
Use formulations with better leveling performance or finer powder particles
3. Poor Adhesion and Coating Peeling Problem
Problem:
Coating peels off or fails cross-cut adhesion test.
Causes:
Incomplete pretreatment:
Oil contamination
Rust
Oxide scale
Workpiece not sufficiently preheated
Incomplete curing
Solutions:
Improve pretreatment:
Degreasing
Sand blasting
Phosphating
Ensure sufficient preheating
Check curing oven temperature curve to ensure complete curing
4. Fading and Powdering Problem
Problem:
After outdoor exposure, coating color becomes lighter, gloss decreases, or powder appears on the surface.
Causes:
Non-weather-resistant formulation selected
Excessive curing causing resin degradation
Poor weather resistance of pigments
Solutions:
Use weather-resistant polyurethane formulations for outdoor applications
Avoid over-curing
Use weather-resistant pigments such as rutile titanium dioxide
5. Pinholes and Bubble Problems
Problem:
Small holes appear on the coating surface.
Causes:
Residual moisture or volatile substances after pretreatment
Oil and water contamination in compressed air
Excessive film thickness preventing gas release
Solutions:
Improve pretreatment drying
Install oil-water separators and check compressed air quality daily
Avoid excessive thickness and use multiple thin coating layers
6. Color Difference Problem
Problem:
Actual color differs from the standard color sample.
Causes:
Film thickness variation affecting color depth
Different curing temperatures causing color shift
Large batch-to-batch color variation
Solutions:
Strictly control film thickness uniformity
Maintain stable curing temperature according to process requirements
Require suppliers to control batch color difference (ΔE<1.0)
Conduct trial spraying inspection for each batch
7. Powder Caking During Storage
Problem:
Powder sticks together and forms lumps in packaging or hopper.
Causes:
High storage temperature
Moisture absorption
Excessive storage time
Solutions:
Keep storage temperature below 30℃
Store in a dry and ventilated environment
Use the FIFO (first in, first out) principle
Avoid long-term storage
If you encounter difficult problems during the application of polyurethane-based powder coating, please feel free to contact us for professional technical support.
We are happy to discuss solutions together, promote the development of the powder coating industry, and help customers achieve better coating results.
We hope this article provides a professional and reliable reference for the powder coating industry.
We sincerely welcome your inquiries regarding powder coating product performance, industry standards, application methods, precautions, or any related questions.
Please feel free to leave a message or contact us directly. We can provide detailed product information, demonstration videos, and customized solutions to help you fully understand product features and advantages.
