Why is wind turbine blade protection needed?
Wind turbine blade protection is essential to ensure the long-term stable operation of wind turbines. As a key component of wind turbines, blades are often exposed to harsh environments. Blades are constantly eroded by wind and sand, UV radiation, rain and freezing. Manufacturing materials, such as epoxy resin fiberglass, are difficult to remain intact under these conditions. Therefore, applying a protective coating on the surface of the blade can significantly increase the service life of the blade and achieve maintenance-free operation for more than 20 years.
Wind turbine blade coating performance requirements
The coating used for wind turbine blade protection must have excellent weather resistance, wear resistance, excellent adhesion and chemical resistance. Technical indicators generally include adhesion greater than 5MPa, natural drying time less than 8 hours, and weight loss less than 20mg/500g after 500 turns of wear resistance test.
Materials for wind turbine blade protection
This article focuses on the materials used for wind turbine blade protection, including polyurethane, fluoropolymers and acrylic resins, and looks forward to their research directions and development trends.
Wind turbine blade materials
Polyurethane materials
Polyurethane coatings excel in oil, wear, chemical resistance, and adhesion, ideal for wind turbine blade protection. Aliphatic or alicyclic polyisocyanates are preferred over aromatic types due to their superior weather resistance.
Research employed polyester and polytetrahydrofuran diol as polyols, IPDI as diisocyanate, and modified hydroxyl siloxane/fluorosilicone for organic fluorine-silicon elastic polyurethane urea resin development. Aliphatic copolyesters and hydroxyl fluorine resins reacted with IPDI to create highly weather-resistant, wear-resistant EPU curing agents.
Expert Li Huaming used silanol-modified polyester resin with Bayer polyurethane N-75 for a weather-resistant coating. Waterborne polyurethane topcoats, combining acrylic dispersion with modified HDI trimer and polyaspartic acid primer, were developed.
Waterborne polyurethane coatings, aligning with “green energy,” are emerging as the future trend for wind turbine blade protection, being eco-friendly and low-VOC.
Fluoropolymer materials
Advantages of fluoropolymer coatings: They provide excellent chemical stability, weather resistance, high temperature resistance and radiation resistance. Fluoropolymers also have low surface energy, are hydrophobic and oleophobic, have good self-lubricity and low friction, which are very consistent with the requirements of wind turbine blade coatings.
Traditional fluororesin (PVDF) – Applications and limitations: Polyvinylidene fluoride (PVDF) is a traditional fluororesin with good weather resistance, toughness and anti-powdering properties, and an outdoor service life of more than 20 years. However, PVDF coatings require high-temperature baking, which makes the process complicated.
Soluble Room Temperature Curing Fluororesin (FEVE): Asahi Glass’s Lumiflon (FEVE) is a soluble room temperature curing fluororesin that simplifies construction and allows direct spraying. FEVE transforms fluororesins from thermoplastic to thermosetting, expanding their application range. NEC and PPG use FEVE for the outermost layer of wind turbine blades. Different groups in Lumiflon’s molecular structure contribute to its solubility, room temperature curing, flexibility, weatherability and durability.
Alois significantly improved the performance of polyurethane coatings by modifying them with a small amount of fluorine. The development of high-performance, low-cost, room temperature curing fluorinated coatings is an important future direction that will promote the development of wind turbine blade protection and the wind power industry.
Acrylic resin materials
Acrylic resin coatings have excellent weatherability, light resistance, corrosion resistance and strong adhesion. However, their water resistance, solvent resistance and abrasion resistance are relatively poor, so they are usually used as primers for wind turbine blade protection.
Fluorine-modified acrylic resins: Modifying acrylic resins with fluorine can improve weatherability and stain resistance. Fluorinated acrylic polymers have been successfully used in bridge, building and automotive coatings. Their use in wind turbine blade coatings is a promising research area.
Other high-performance coatings and modification technologies
Polyaspartic acid coatings: New high-performance two-component coatings that are resistant to yellowing and have stable performance. Bayer uses it for wind turbine blade topcoats or single anti-corrosion coatings, with fast surface drying (3 hours) and excellent anti-corrosion and wear resistance.
Silicone coatings: Excellent weather resistance, high and low temperature resistance, water resistance, and stain resistance. Dow Corning’s silicone resin coating can be applied directly to the blade to provide excellent protection.
Epoxy resin coatings: High adhesion, strong weather resistance, and excellent anti-corrosion performance. Lee’s research shows that Ni-P films with high P content (>7%) and small microvoids can improve the corrosion and wear resistance of GFRP substrates. Film thickness and polishing conditions also affect the coating performance.
Conclusion:
The research and development of blade protective coating materials should not be limited to a single material. The reasonable combination of polymers such as polyurethane, organic fluorine, acrylic acid, polyaspartic acid, silicone, epoxy resin, etc., or the matching use and modification of several resins (such as adding nanomaterials to prepare inorganic films), etc., can make the coating performance more excellent and better enhance the protection of wind turbine blades and extend their life.
