Preface
On December 9, 2022, the world's first domestically produced C919 large passenger aircraft was officially delivered to the first user, China Eastern Airlines. The C919 large passenger aircraft is a large jet civil aircraft developed by the mainland and with independent intellectual property rights, with a single-aisle narrow-body layout, 158 to 168 seats, and a range of 4075 to 5555 kilometers, which is the same level as the most common Airbus 320 and Boeing 737 models in the international aviation market.
Due to the high industry barriers in the field of commercial large aircraft, only a few countries were able to independently undertake the development and production of large aircraft, forming a duopoly pattern of Boeing and Airbus. At present, the global civil aviation large aircraft market that can carry more than 100 people is monopolized by Airbus and Boeing, and the supporting coatings of these large aircraft are all supplied by foreign companies, such as PPG, AkzoNobel, Sherwin-Williams, Meikaiwiqi and other companies have monopolized the global large aircraft coating market.
However, with the Chinese large aircraft C919 about to be put into commercial operation, this also means that the market monopoly of international large passenger aircraft will be broken. At the same time, the continental large aircraft C919 also used the domestic large aircraft coatings, at present, CNOOC Changzhou Coating Chemical Research Institute, Marine Chemical Research Institute two companies independently developed aviation coating products selected into the Commercial Aircraft Corporation of China qualified product catalog, and has been applied in the C919 aircraft, which means to break the PPG, AkzoNobel, Meikaiwich and other foreign brands of market monopoly, with the C919 take-off, as well as its related industrial chain.
Part 1
The development status of China's aviation manufacturing industry
According to the purpose of the aircraft, Continental Airlines aircraft can be divided into civil aviation aircraft and national aviation aircraft. National aviation aircraft refers to the aircraft used by the military, police and customs and other state departments, and civil aircraft mainly include civil aircraft and civil helicopters, including passenger aircraft, cargo aircraft, and passenger and cargo aircraft.
1.1 Large aircraft projects open up a broad civil aircraft market
China will become the main force in the global aviation industry market in the future. According to COMAC statistics, in 2020, China's passenger aircraft fleet size was 3,642 aircraft, accounting for 20.1% of the world's total passenger aircraft fleet, and it is expected that by 2040, China's passenger aircraft fleet will increase to 21.9% to 9,957 aircraft, surpassing North America and Europe to become the largest region in the world's passenger aircraft fleet.
1.1.1 Domestic passenger aircraft market demand forecast
Judging from the forecast of domestic passenger aircraft market demand, in the next 20 years, narrow-body trunk airliners represented by C919 aircraft will still be the main model of mainland civil aviation. Considering the "COMAC Market Forecast Annual Report 2022-2041" released by COMAC, the "2022-2041 Civil Aircraft China Market Forecast Annual Report" released by AVIC, and the "Commercial Market Outlook 2022-2041" released by Boeing, the demand for China's civil airliners in the next 20 years is estimated.
According to the delivery value in the COMAC Market Forecast Annual Report 2022-2041, the average unit prices of turbofan regional airliners, single-aisle jets and wide-body dual-aisle jets are estimated to be US$50 million, US$120 million and US$330 million, respectively. It is estimated that the total value of China's new machine delivery market in the next 20 years will be about 1.3 trillion US dollars, equivalent to about 8.9 trillion yuan (calculated at 6.89 onshore yuan to US dollar).
2022-2041 China civil airliner demand volume forecast
1.1.2 Large aircraft delivery market forecast
Based on COMAC's three main models, ARJ21, C919 and CR929, the delivery volume and value of domestic passenger aircraft in the next 20 years are estimated. The assumptions in the calculation process are as follows: it is assumed that the C919 passenger aircraft will be delivered from 2022 and then steadily increase its market share in the mainland. Refer to the current delivery of the ARJ21 at 25 aircraft per year. Referring to the pace of deliveries of the C919 project launched in 2008 and expected in 2022, it is assumed that the CR929 will be delivered from 2030 (the CR929 wide-body airliner project will be launched in 2014).
Referring to the list price in the COMAC Market Forecast Annual Report 2022-2041, it is assumed that turbofan regional aircraft are US$50 million per aircraft, single-aisle jetliners are US$120 million, and dual-aisle jetliners are US$330 million. Referring to the forecast released by the International Air Transport Association (IATA), it is assumed that the passenger volume of the aviation industry and the delivery volume of China's passenger aircraft market will return to 94% of the pre-epidemic level in 2023 and rise to 103% in 2024. According to this estimate, in the next 20 years, ARJ21/C919/CR929 is expected to deliver 703, 1,526 and 259 respectively, and the delivery of domestic passenger aircraft will be 2,488, worth about 2.09 trillion yuan, with a compound growth rate of about 14.85%. From the perspective of delivery value, the domestic passenger aircraft market in the next 20 years can be divided into a period of rapid growth and a stage of stable development. Rapid growth period (2022-2033): ARJ21 deliveries remain stable, C919 starts to be delivered and gradually increased, and the scale of the domestic passenger aircraft market grows rapidly. Stable development stage (2034 and beyond): ARJ21 continues to be produced, the annual output of C919 aircraft is close to 100 units, CR929 has begun to be delivered, domestic passenger aircraft have achieved full series mass production, and the market size of domestic civil aircraft has climbed to more than 100 billion.
In the next 20 years, the scale of the domestic passenger aircraft market will increase
1.2 Military aircraft are just in demand for multiple services, and the future growth trend is considerable
Military spending is the basis for the expansion of the prosperity of the national defense science and technology industry, and is the fundamental source of demand for the military industry, which intuitively reflects the allocation of national defense policy in the economy and resources, and also directly determines the progress of weapons and equipment construction, and is the core driving factor for the performance of military enterprises.
Judging from the current situation in the field of military aviation, the localization of the Continental Army's domestic aviation has gone through four processes: introduction, imitation, improvement and innovation, and after more than 60 years of development, it has the ability to develop fighters, transport aircraft, armed helicopters/transport helicopters, trainers and other multi-aircraft series aircraft. However, compared with the United States, Russia, and other military powers, the mainland's military aviation still has a lot of room for development. Judging by the size of the continental air force's fleet, the number of aircraft used by the Continental Army has been increasing in recent years. By the end of 2022, the continental air force fleet size reached 3,284 aircraft. In terms of the distribution of types, as of 2022, the fleet size of the Continental Army is 3,284 aircraft, including 1,570 fighters, 913 armed helicopters, 397 trainers, 288 transport aircraft, 4 air tankers and 112 special aircraft.
In the next 20 years, China's military aircraft demand will be about 2,900, and the market size will exceed one trillion yuan. According to the statistics of the Aileda prospectus, in the next 20 years, China's military aircraft procurement demand, including fighter jets and transport aircraft, will be about 2,900, and the military aircraft market will reach 229 billion US dollars, equivalent to about 1.4 trillion yuan. We believe that the demand for new models will further boost the prosperity of the aviation industry, and the continental aviation industry is expected to enter a period of rapid development.
Part 2
The development status of China's aviation coatings industry
Aerospace coatings mainly refer to coatings used on aircraft. According to the aircraft architecture, according to the use of parts, the coatings applied to an aircraft cover aircraft skin coatings, aircraft cabin coatings, aircraft engine coatings, aircraft parts coatings (radome coatings/transparent parts protection coatings/aircraft fuel tank inner wall protection coatings, etc.), special coatings (temperature coatings applied to aircraft instruments, etc.).
2.1 Summary of the development of major aviation coating varieties
2.1.1 Aircraft skin coatings
Looking at foreign countries, the countries with more advanced levels of aviation coatings include the United States, the Netherlands, Germany and Russia and other industrially developed countries. In the 60~70s of the 20th century, with the further improvement of aircraft performance, the original alkyd and nitro coatings were gradually replaced by epoxy, acrylic and polyurethane coatings because of their poor heat resistance, poor weather resistance, poor aging resistance and easy pollution. At present, the primer of ordinary skin paint in foreign countries generally adopts epoxy/polyamide system or epoxy/polyurethane system, and scaled primer is also used in special parts. With the progress of technology, fluorosilicon and fluorocarbon coatings with good aging resistance and stain resistance have also been gradually applied to aircraft skin coatings.
Continental aircraft skin coatings began in the 50s of the 20th century, and the alkyd coatings based on C01-7 long-oil alkyd coatings were widely used. In the 70s of the 20th century, the continental aviation coating began to develop, Zhonghao North Paint Institute (formerly the Coating Industry Research Institute of the Ministry of Chemical Industry), Beijing 621 Institute, Tianjin Paint Factory have invested a lot of manpower and material resources in research. Acrylic varnish, acrylic acid modified polyurethane enamel, polyurethane enamel and silicone modified polyurethane coating products have been successfully researched and widely used in the surface coating of new military aircraft. At present, China is still the main product of aircraft skin coatings using epoxy primer and polyurethane (polyester, acrylic and various modified polyester) topcoat systems, and its technical performance has reached GJB and MIL standards.
There are mainly the following types of domestic aircraft skin coatings: (1) two-component acrylic aircraft skin coatings, (2) two-component polyacetate polyurethane coatings, (3) fluorocarbon aircraft skin coatings, (4) modified silicone aircraft skin coatings.
At present, there is still a certain gap between the overall technical level of domestic aircraft skin coating, primer and topcoat compared with similar foreign products, such as insufficient serialization, weak pertinence, narrow application range of products and poor process stability. Although fluorosilicon and fluorocarbon skin coatings are also partially used, their technical maturity is insufficient, and their stain resistance and other properties still cannot meet the daily maintenance requirements of fighters, and cannot be produced and applied on a large scale, and are currently limited to small batch trials. As the speed of the aircraft increases, the aerodynamic heat of the fuselage increases (150°C at Mach number M = 2.2; 220°C at M = 2.5 and 320 °C at M = 3). Therefore, ordinary aircraft skin coatings that can withstand high temperatures above 220°C for a long time are an important development direction.
2.1.2 Aircraft cabin coatings
The cockpit of the aircraft is the main place for pilots to work, and the protective coatings in the cockpit must be paid attention to meet the requirements of the more demanding use environment while allowing the pilot to feel comfortable in terms of vision and touch. At this stage, the national military standard only puts forward specific requirements for the gloss and color of the coating, and the semi-light acrylic / polyurethane coating is widely used in China as the aircraft cockpit coating, this kind of coating is often worn and fallen off after a certain period of use, although it will not cause harm to flight safety, but it will affect The pilot's feelings; the requirements of the semi-gloss coating specified in the national military standard are not reasonable, under the strong light exposure, the semi-gloss coating will still produce a relatively strong reflected light; because the standard was formulated earlier, the texture of the coating is not required, and the coating makes people feel cold and has no affinity.
At this stage, the development of imitation leather coatings and elastic coatings in mainland China has been relatively sufficient, and the product performance can fully meet the technical index requirements of protective coatings in the cockpit; because there are slight concave and convex surfaces of different sizes on the surface of this kind of coatings, it will not produce strong reflected light under the same gloss conditions, which is conducive to flight safety; the touch of this kind of paint is extremely comfortable, and the pilot feels very warm as being in a luxury car.
2.1.3 Aircraft engine coatings
Modern aero engine metal materials mostly use magnesium alloy, aluminum alloy, titanium alloy, etc., foreign research on magnesium alloy, aluminum alloy high temperature resistance, anti-corrosion coatings are more sufficient, such as the United States TELEFLEX company brand SERMETEL product series, temperature resistance and protection performance is very good, is the only engine metal material protective coating designated by Rolls-Royce, Boeing, Airbus and other foreign enterprises; titanium alloy is usually not protected by coatings in addition to marking on its surface.
Zhonghao North Coating Industry Research and Design Institute Co., Ltd. (hereinafter referred to as Zhonghao North Coating Institute) has conducted targeted research on TELEFLEX company's SERMETEL products, and the TW-7 coating developed has met the needs of the continental model task, and has been successfully applied to the metal protection of various types of engines, replacing imported products.
The hexavalent chromium salt used in the traditional aviation aluminum alloy and treatment process is unsafe for the human body, and brings serious harm and unnecessary trouble to the control, treatment and management of toxic materials related to the construction process. Since 1982, the World Environmental Protection Organization has proposed to restrict the use of chromate and other chromate compounds. The development of chromium-free, effective, low-cost, environmentally friendly alternatives to chromate and corrosion inhibitors and environmentally friendly transition layer treatment processes is an urgent problem to be solved in the aviation coatings industry, and it is also a new topic we are facing.
2.1.4 Coatings for aircraft parts
2.1.4.1 Radome coatings
All aircraft need to be protected, because the aircraft flies at high speed in the air, and the aerodynamic heating is very serious: At the same time, the aircraft may also be eroded by rain, sand and gravel, etc., in order to protect the radome and the internal instrumentation, the surface of the antenna cover must be protected.
Due to the different aircraft and application environments, radome protective coatings can be divided into several categories according to the temperature range: (1) elastic polyurethane protective coatings with a normal temperature of 250 °C, (2) high temperature resistant protective coatings with a temperature of 250 °C-400 °C, and (3) high temperature protective coatings with a temperature of more than 400 °C.
Due to the early development of elastic polyurethane protective coatings, aromatic polyurethane is used as the main ingredient, and the aging resistance of the coating is poor, and the use of MOKO curing agent has a potential carcinogenic risk. In recent years, domestic research units have adopted aliphatic polyurethane to replace aromatic polyurethane in response to the above problems, which has improved the aging resistance of the coating. However, due to the further improvement of the dielectric performance requirements of radar and antenna for protective coatings, reducing the dielectric loss of the coating has become the development direction of this layer.
Because the resin inevitably occurs carbonization and other phenomena above 250 °C, and when the temperature reaches 400 °C, it is basically close to the temperature resistance limit of the resin material, and the radome can only provide protection for a short time, and can not achieve long-term protection; fluorine-containing materials appear thermal decomposition above 385 °C, which may volatilize toxic atmosphere; polyimide resin is sensitive to moisture, which seriously affects the storage stability of the product and the consistency of the coating. Therefore, although there are many resin systems that can be used for radome protective coatings at 250°C-400°C, there are not many product varieties that are really used for model tasks, and they are mainly concentrated in the coating varieties of silicone resin series.
The radome that has been subjected to high temperatures above 400 °C for a long time is mostly made of fiber-reinforced molten silicon materials, which have high compactness. In addition to the water permeability resistance and flexibility of a slight deficiency, other properties do not need to be supplemented by coatings, so the market demand is not urgent, so far, the protective coating that can withstand this temperature and meet the aerodynamic requirements is almost blank in China, although the use of silicone resin system can withstand this high temperature, but the cavitation resistance is limited. In recent years, there are foreign phosphate resin system protective coatings, and their temperature resistance can reach more than 1100 °C.
2.1.4.2 Protective coatings for transparent parts
In the modern military industry, transparent plastics have been widely used in aircraft cockpits, ship portholes, pilots' helmets and other fields, and at present, polymethyl methacrylate glass is widely used in aircraft cockpit cover materials (mainly using aviation directional organic glass PMMA), which will eventually be completely replaced by polycarbonate vinegar (PC) plastic with better performance from the perspective of performance requirements and development trends. However, these materials have problems such as insufficient surface hardness and easy scratches, so they need to be protected and meet the requirements of good light transmittance and haze of transparent parts.
In the 60s of the 20th century, foreign countries began to study the protective coating of plexiglass surface, mainly acrylic coatings, polyurethane resin coatings, polysiloxane coatings, etc. In recent years, nano-modified coatings and organic-inorganic hybrid coatings have been developed. After several years of development, foreign companies have launched mature products for PC surface protection and have been applied in industry.
The mainland high-specification optical grade plexiglass (PMMA) industry started late, the research on protective coatings is not sufficient, the surface protective coating of the model aircraft transparent parts is mainly used in the TU series acrylic/polyurethane protective coating developed by Zhonghao North Coating Industry Research and Design Institute Co., Ltd., and the TU series aircraft cockpit transparent parts protective coating are polyurethane/acrylic resin system, which has good adhesion and toughness, but compared with foreign products, the product variety is single and the selectivity is not strong.
In the development of PC surface protective coatings in China, mature products are almost blank. Different protective coatings should be used for transparent parts with different needs, and the existing products in China are single, and can not fully realize the requirements of anti-fogging and hardening; in Japan, the more mature sol-gel in-situ polymerization method is still limited to the laboratory research stage in China, and cannot be used for transparent parts protection due to the limitation of polymerization temperature.
2.1.4.3 Protective coating for the inner wall of aircraft fuel tank
The overall fuel tank of the aircraft is the structural fuel tank, and the corrosion of the fuel tank is the corrosion of the load-bearing structural parts, that is to say, the corrosion of the fuel tank directly threatens the integrity and reliability of the aircraft. Oil-resistant coatings are used for oil-resistant and anti-corrosion protection of the inner wall and surrounding areas of the overall fuel tank of the aircraft, which can be used in the fuel for a long time to avoid the corrosion of the fuel tank material by the complex corrosive environment in the fuel.
In the early days, foreign fuel tank protective coatings mainly used epoxy-rubber, epoxy, urethane and polyurethane coatings, and the representative products were Boeing's BMS10-39 epoxy coatings. In addition, AkzoNobel's overall fuel tank protection coatings, due to their excellent performance, also occupy a considerable share of the domestic market.
Foreign testing standards for aircraft overall fuel tank protective coatings mainly include AMS-C-27725B, MIL-C-27725B and BMS10-20D, etc., these standards do not mention the detection of coating resistance to anti-icing agents; Some accelerated test methods and evaluation criteria that are in line with the actual environment.
The early domestic fuel tank protection coating is basically a polyamide curing epoxy coating, which can basically meet the requirements of the current national military standard GJB 1390-1992 (not mentioning the detection of the tear of the coating on the anti-icing agent), but compared with the foreign advanced level, there is still a gap in the performance of domestic products, especially in the actual use of the coating shows insufficient resistance to anti-icing agents, can not fully meet the actual use needs. Zhonghao North Institute is the earliest research institute engaged in the research and development of oil-resistant coatings in mainland China, and it is also one of the few units in China that can carry out the research and industrial production of oil-resistant protective coatings for aircraft overall fuel tanks, and successfully apply the products.
2.1.5 Special special coatings
2.1.5.1 Temperature indicator paint
It should be used for the measurement of the temperature distribution of aircraft instruments and skins, and the heating monitoring of electrical equipment. Multi-color irreversible temperature indication coating has the function of large-area field temperature measurement, remembering the maximum temperature without destroying the surface shape of the object. It is widely used in the temperature measurement of engine combustion chambers, turbine outer ring guide vanes, afterburner diffusers and other components, and the monochromic irreversible temperature test patch is now widely used in the temperature measurement of the inner surface of the re-return satellite stabilized skirt and skirt bottom structure, the sidewall of the spacecraft and the outsole, as well as the temperature rise state of electrical equipment and the temperature monitoring of mechanical components.
The United Kingdom, Russia, Germany, France, the United States, Japan and China and other countries around the world have attached great importance to the development and development of temperature indicator coatings. Germany (such as Rols-Royceplc) has the most outstanding performance level of temperature indication coatings, and has been successfully applied to the temperature measurement of engine hot end parts, with a temperature measurement area of 240~1300 °C, and some temperature measurement points have as many as 10 varieties with an interval of 50~70 °C. At present, the temperature indicator coating is developing in the direction of multiple temperature measurement points, wide temperature range, high temperature area and rapid response.
Since the 60s of the 20th century, Zhonghao North Coating Institute began the research of temperature coatings, and is the only institute specializing in the research of temperature coatings in China, with product varieties covering the temperature measurement range from 37 °C to 1150 °C, and is currently developing more than 1150 °C temperature coating varieties.
At present, the research direction of this kind of coating is to assist the research on the thermal properties of fillers and the material varieties of base resins through the development of heat-sensitive pigments. The research on temperature resistance and matching with pigments and fillers overcomes the shortcomings of high temperature and multi-color irreversible temperature indication coatings, such as large temperature interval, large error, insensitive color change, insignificant color difference, long response time, and low upper limit of high temperature, and meets the temperature measurement requirements of dynamic large-area field in model development; We have strengthened our dedicated testing and testing equipment to conduct research on the temperature indication performance, mechanical properties, environmental adaptability and temperature discrimination methods of coatings.
2.1.5.2 Water-based paints
With the increasing requirements of environmental protection and low-carbon economy, in order to ensure the health of construction personnel, improve the construction environment, and meet the requirements of environmental protection, the water-based technology of aviation and aerospace coatings has been paid more and more attention.
Developed countries have realized the water-based primer and pigment for aircraft, such as Boeing, Airbus, etc., taking Germany as an example, as early as 20 years ago, water-based materials have been used for the coating of the inner surface of military vehicles and ships, and now in addition to a layer of overlay coating on the surface of the equipment, the rest of the anti-corrosion coating has basically achieved water-based.
Continental waterborne technology has experienced more than 20 years of development, water-based epoxy, water-based polyurethane coating technology is basically mature, but there is still a big difference in performance compared with solvent-based coatings, it is difficult to meet the requirements of high-performance use, key technologies and key raw materials are generally in the hands of foreign enterprises, due to technology monopoly and other reasons, it is difficult for domestic enterprises to obtain high-quality waterborne coatings.
2.1.5.3 Chemical milling protective coatings and process protective coatings
Chemical milling (referred to as chemical milling) is a processing technology that relies on chemical solutions to dissolve the surface of metal workpieces, that is, the workpiece is processed by chemical dissolution. Chemical milling protective coating, also known as peelable coating, is a temporary protective coating in the process of chemical milling, which plays a temporary protective role in the processing process, and the protective layer is removed after the chemical milling process is completed.
Turco and Purex companies in the United States are engaged in the research and production of chemical milling protection and its supporting products, MaS31k537 and AC-850 chemical milling protective coatings are its representative products. Due to the shortcomings of the first generation of neoprene in China, such as "leakage", high solvent toxicity and poor storage stability, it has been Taoci: although the second generation of styrene-butadiene rubber of protective coatings reduces the toxicity of the solvent, the process is complex, and the problem of "leakage" still exists, and it is gradually eliminated in aviation enterprises. At present, the chemical milling protective coatings used by domestic aviation enterprises are mainly imported products such as AC-850, which are expensive and have a long supply cycle. The performance of the third-generation protective coating (SBS thermoplastic elastomer milling protective coating) developed by Zhonghao North Coating Institute has reached the technical level of AC-850 in the United States and has been applied in many enterprises.
2.2 Applications
2.2.1 Foreign application
2.2.1.1 Application of foreign civil aircraft
At present, most of the civil airliners used in the world are manufactured by Boeing (Boeing) and Airbus (Airbus) of France, and the "three-proof" coating products used in their aircraft are mainly monopolized by several famous foreign paint companies, such as PPG, AkzoNobel, Deft, DeSoto and other companies.
Among them, the most representative are AkzoNobel and PPG. These companies produce a wide range of aircraft skin coatings with consistent performance. A large number of international aviation coating products have been commercialized, and have been widely used by major aircraft manufacturers and airlines for many years. A comprehensive investigation of the related products of major aviation coating manufacturers can clearly find that its performance is mainly reflected in the high-performance coating system, the thin-film and quantification of the coating system, and the green and environmentally friendly coating.
In terms of high-performance aviation coatings, internationally renowned aviation coating manufacturers have carried out research and development and application work in the 80s of the 20th century, mainly analyzing and investigating the corrosion resistance and service life of the coating system of the aircraft during the flight, and the complex diversity of the aircraft flight environment to improve the performance of the aircraft skin coating under extreme conditions, such as suspension resistance, oil resistance, wiping resistance, recoating, impact resistance, etc.: in the 90s, related products were launched and obtained the month, the high and low temperature resistance of the coating film, Excellent impact resistance, excellent initial performance, excellent adhesion and vibration resistance with metal substrates, which can ensure that in the process of intense flight, the skin coating and the substrate will not crack due to stress changes In order to reduce the overall quality of the aircraft and increase the sailing distance, the film and lightweight of the aviation coating system are becoming more and more important, and the coating thickness is required to be reduced by 20%~30% under the premise of meeting the protective performance of the current aviation coating system.
PPG's newly developed base coat clearcoat system reduces the quality of the coating to a significant extent compared to conventional coating systems without sacrificing the protective properties of the coating. In today's rising international fuel prices, the promotion and successful application of this technology will greatly reduce the fuel usage fee of aircraft and create considerable economic benefits for airlines.
In terms of green and environment-friendly coatings, developed countries such as Europe and the United States have successfully developed a number of high-solids, non-inscription, water-based, and solvent-free varieties due to their policies and regulations, and most of the coating film performance is equivalent to that of traditional solvent-based coatings. Among them, the development of high-solids coatings is the fastest, among which PPG and AkzoNobel's aviation coating products are mainly high-solids coating, the volume solid content of the coating under construction is as high as 70%, and the VOC emission is less than 420g/L, which meets the requirements of environmental protection regulations of the European Union and the United States.
When it comes to chromium-free primers, PPG has successfully developed a number of varieties. In terms of water-based coatings, PPG and AkzoNobel have also developed the Eco Prime series and Aerowava series of water-based aviation coatings in recent years, covering aircraft skin base coats and parts protective materials, etc., which have been successfully applied in Boeing and Airbus aircraft. Bayer and Deft have jointly developed a UV-curable solvent-free aircraft skin coating that is comparable in performance to conventional polyurethane aircraft skin coatings due to its fast curing speed and low VOC content. These green coatings have been successfully applied to many types of aircraft, such as Boeing 737, 747, 757, 767 and Airbus 380, etc., which meet the requirements of the actual flight environment while being based on low-carbon and environmental protection, and meet the requirements of policies and regulations.
2.2.1.2 Application of foreign military aircraft
Due to the involvement of military special coatings, foreign countries have taken strict confidentiality measures for the specific grades and performance of this part of the coatings, and we cannot judge the actual application of military coatings. However, from some literature, we can still learn some from the side. PPG and AkzoNobel both have corresponding military coating products, the specific performance of which is unknown.
Indestructible Paint INC, Inc. is a manufacturer of aircraft paints, many of which are used on different types of aircraft, but most of which cannot be purchased through normal channels.
2.2.2 Competitive landscape and market share of the domestic aviation industry
2.2.2.1 Industrial structure: PGG was the first to enter the Chinese market
According to the progress of competitors in China's aviation coatings industry, the early participation in China's aviation coatings industry enterprises mainly include PPG, Three Gorges Paint and other enterprises, the United States Sherwin-Williams and Henan Aviation Materials to enter the market time is relatively late, 1995-2005 is a more intensive period of time for competitors to enter the aviation coatings industry.
*Note: The horizontal axis is the time of enterprise registration and the time when the international enterprise first entered China, and the vertical axis and the size of the bubble are the scale of the registered capital of the enterprise.
2.2.2.2 Market competition: It is mainly divided into two major factions: domestic and foreign
The competition pattern of China's aviation coatings industry can be divided into two major factions, one is the competitive faction formed in China by PPG, AkzoNobel, Sherwin-Williams and other national aviation coating leaders, and the other is the competitive faction formed by China's aviation coating enterprises represented by Haohua Technology.
The competitive landscape of enterprises in China's aviation coatings industry
By analyzing the industry layout and business objectives of the existing competitors in China's aviation coatings industry, the overall strategic layout of domestic and foreign enterprises is analyzed. From the perspective of the development goals of aviation coating enterprises, international enterprises focus on commercial purposes, and domestic enterprises focus on achieving political goals, which leads to certain differences between the two types of enterprises in the process of determining the development path of enterprises, and the relevant comparisons are as follows:
The strategic layout of competitors in China's aviation coatings industry
2.2.2.3 Industrial distribution: International enterprises are concentrated in the eastern coastal area, and domestic enterprises are concentrated in central China
From the perspective of industrial distribution, the production layout of aviation coatings related to international enterprises in China is mainly concentrated in Tianjin, Jiangsu, Shanghai and other eastern coastal areas with a high degree of foreign exchange.
Domestic aviation coating production related enterprises are concentrated in Shaanxi, Henan, Hubei, Sichuan, Chongqing and other central China.
2.2.2.4 Market concentration: The overall market concentration of the industry is relatively high
Limited by high market access barriers, China's aviation coatings industry market suppliers are relatively fixed, in the field of commercial aviation equipment production, represented by PPG European and American companies accounted for more than 85% of the domestic market share.
In the field of military aviation equipment production, the "national team" enterprises represented by Haohua Technology occupy the main market. Although with the production of China's large aircraft, domestic aviation coatings have a certain space for development, but the overall market concentration is still at a high level.
2.2.3 Domestic application
2.2.3.1 Application of domestic civil aircraft
Due to the high industry barriers in the field of commercial large aircraft, only a few countries were able to independently undertake the development and production of large aircraft, forming a duopoly pattern of Boeing and Airbus. At present, the global civil aviation large aircraft market that can carry more than 100 people is monopolized by Airbus and Boeing, and the supporting coatings of these large aircraft are all supplied by foreign companies, such as PPG, AkzoNobel, Sherwin-Williams, Meikaiwiqi and other companies have monopolized the global large aircraft coating market.
But with the advent of COMAC's self-labeled C919 large airliner, the situation has changed. This shows that China has finally been given the opportunity to enter and compete in this market. At present, the aviation coating products independently developed by CNOOC Changzhou Coating Chemical Research Institute and Marine Chemical Research Institute have been selected into the qualified product catalog of Commercial Aircraft Corporation of China, which means that the foreign monopoly of PPG, AkzoNobel, Meikaiwiqi and other enterprises has been broken.
The Coating Industry Research Center noted that the results of the formal review of the 2022 Jiangsu Provincial Science and Technology Award announced by the Jiangsu Provincial Department of Science and Technology on July 18, 2022 showed that CNOOC Changzhou Coating Chemical Research Institute Co., Ltd., Commercial Aircraft Corporation of China Shanghai Aircraft Design and Research Institute, Changzhou Nanjing University High-tech Research Institute, Aviation Industry First Aircraft Design and Research Institute, and CNOOC Changzhou Environmental Protection Coatings Co., Ltd. jointly completed the "R&D and Application of Key Technologies for High-performance Coating Materials for Domestic Large Aircraft" The project was shortlisted.
The intellectual property rights of the technical invention of the project include: a coating for aircraft with low VOC and preparation method thereof, a polyester polyurethane coating for helicopter rotor and preparation method thereof, an environmentally friendly coating for simulating the hyperspectral of green vegetation and its preparation method, an environmentally friendly coating with colorful infrared low emissivity, a coating composition for quickly repairing the damaged skin coating of an aviation aircraft, a coating system for aviation aircraft, a general primer for non-ferrous metals and a preparation method thereof, a coating system for the outer skin of an aviation aircraft and its preparation method, and a covering light coating for the outer skin of an aviation aircraft and a preparation method thereof, a simple synthesis method of N-butyl-2,2,6,6-tetramethyl-4-piperidinamine.
The Coating Industry Research Center also noted that CNOOC Changzhou Coating Chemical Research Institute Co., Ltd., CNOOC Changzhou Environmental Protection Coating Co., Ltd., Aviation Industry First Aircraft Design and Research Institute, and Aviation Industry Xi'an Aircraft Industry (Group) Co., Ltd. have jointly completed the project of "Development and Industrialization of High-performance and Low-pollution Large (Medium) Aircraft Supporting Coating Materials". According to the requirements of aviation skin coatings, the project carried out the development of water-based anti-corrosion primers, water-based anti-corrosion topcoats and high-solid mask varnishes, so as to achieve a VOC of water-based coatings and high-solids coatings less than 100 g/L, leading the development of mainland aircraft skin coatings in an environmentally friendly direction.
The major science and technology project of large aircraft is a major strategic decision for the mainland to build an innovative country, enhance its independent innovation ability and enhance its core competitiveness. In recent years, the mainland's aviation industry has developed rapidly, and remarkable results have been achieved in the research and development of large and medium-sized aircraft, especially a number of new models such as large military transport aircraft, large commercial passenger aircraft, and amphibious aircraft, which have made their first flights, and some of the aircraft have also been equipped and put into service.
Aircraft supporting coating materials are indispensable auxiliary materials for aircraft, in addition to the role of decoration, more important is to protect the aircraft structural materials, for maintaining flight safety, prolonging the life of the aircraft, has a positive significance. Large (medium) aircraft have the characteristics of large size, high load capacity and long service life that are different from ordinary aircraft, which determine the special requirements of large (medium) aircraft supporting coating materials in terms of performance.
At present, most of the coating materials for domestic large (medium) aircraft are solvent-based products, and some models use high-solid coatings and water-based coatings, and the release of solvents has been reduced. With the increasing environmental protection requirements of the mainland, it is necessary to further reduce the content of volatile organic compounds (VOCs) in aviation coatings, so the project has carried out technical research on aviation water-based coatings and high-solids coatings, and through the research on resin synthesis, coating supporting design and coating component optimization technology, the VOC of water-based coatings and high-solids coatings is less than 100g/L, leading the development of mainland aircraft skin coatings in the direction of environmental friendliness.
The project studies three kinds of coatings, including primer, topcoat and overcoat varnish, and the main research contents are: 1) Research on water-based epoxy primer: focus on the preparation of water-based epoxy emulsifier, the preparation of water-based epoxy emulsion, the preparation of water-based epoxy curing agent, the screening of special pigments and additives, the preparation of water-based epoxy primer and performance evaluation. 2) Research on waterborne polyurethane topcoat: focus on the synthesis of hydroxyl acrylic emulsion, the screening of waterborne polyurethane curing agent, the screening of special pigment fillers and additives, the preparation of waterborne polyurethane topcoat and performance evaluation. 3) Research on overprint paint: focus on the screening of polyaspartic acid resin and supporting curing agent, the preparation of high-solids polyester polyol resin, the screening of solvents and additives, the preparation of high-solid coating and performance evaluation.
Innovation point 1: research on the supporting system of ultra-low VOC aviation coatingsAt present, the international mainstream aircraft skin coatings use a solvent-based high-solids epoxy primer and a high-solids polyurethane topcoat supporting system, the VOC of the primer is not more than 340g/L, and the VOC of the topcoat is not more than 420g/L. The project adopts a supporting system of water-based epoxy primer plus water-based polyurethane topcoat and overlay varnish, which belongs to three layers of matching. Through research, the VOC of the water-based epoxy primer prepared is 44g/L, the VOC of the water-based polyurethane topcoat is 2g/L, the VOC of the overprint paint is 10g/L, and the VOC of the three coatings is less than 50g/L. Therefore, this project has developed a new type of supporting system for aircraft skin coatings (i.e., supporting system for water-based coatings and high-solids coatings), which significantly reduces VOC compared with the existing coating supporting systems.
Innovation point 2: A non-ionic and reactive epoxy emulsifier with block structure was prepared for the preparation of aqueous epoxy emulsion. Using anhydride, polyethylene glycol and liquid epoxy resin as raw materials, a blocked, non-ionic and reactive polymer epoxy emulsifier (resin) was synthesized. The advantages of the technical route of the emulsifier synthesis are: the synthesis process is controllable, which can effectively avoid the problem of severe heat release of the reaction, and no catalyst is added in the synthesis process, which is conducive to improving the comprehensive performance of the coating film. With the above-mentioned emulsifier, non-ionic water-based epoxy emulsion products with good stability can be prepared. Through the test, it was found that when the concentration of emulsifier resin was about 11% (i.e., 1/8 of emulsifier/epoxy resin), the prepared emulsion had excellent stability.
Innovation point 3: A water-based epoxy curing agent with excellent flexibility is synthesized. By introducing flexible non-ionic hydrophilic segments, the flexibility of the curing agent is increased, and the shortcomings of poor impact resistance of the coating film are improved. The synthesis process of water-based epoxy curing agent is divided into two steps: polyamine and epoxy resin chain expansion: polyamine and bisphenol A-type epoxy resin are added to form adducts with primary amine hydrogen at both ends. Hydrophilic groups are introduced-the adducts are then opened and expanded with polyethylene glycol diglycidyl ethers, hydrophilic groups are introduced, and primary amine hydrogen at both ends of the molecular chain is closed by single epoxy compounds to make water-based epoxy curing agents. The advantages of the epoxy curing agent synthesis technology route: no catalyst is required in the reaction process, no acid neutralization is required in the dispersion process, and flexible nonionic hydrophilic segments are introduced to improve the flexibility of the coating film.
Innovation point 4: A hydroxyl emulsion with core-shell structure was prepared for the preparation of waterborne polyurethane topcoat. Water, initiators, emulsifiers, acrylate mixed monomers, functional monomers, etc., are mixed and polymerized into seed emulsions, and then the remaining acrylic monomers, functional monomers and initiators are added and then polymerized to form an emulsion with a core-shell structure. The advantages of the hydroxyl emulsion synthesis technology route: excellent film-forming, almost no film-forming additives, can prepare "zero VOC" coatings, less emulsifier, excellent water resistance of the coating film, most of the hydroxyl functional groups are in the shell, high cross-linking efficiency with curing agent, excellent comprehensive performance of the coating film, and low cost.
Innovation point 5: the use of polyaspartic ester resin to prepare varnish varnish. Two polyaspartic ester resins with different structures were used for compounding, and Tolonate® HDT-LV2 was selected as the curing agent, and the shelf life of the two-component coating could be extended by adding a reaction modifier.
The industrialization construction of the project relies on CNOOC Changzhou Environmental Protection Coatings Co., Ltd., and has completed the construction of a 2,000 tons/year demonstration production line for high-performance and low-pollution large and medium-sized aircraft coating materials, including the construction of an 800 tons/year demonstration production line for water-based aircraft coating materials and a 1,200 tons/year demonstration production line for high-solid aircraft coating materials, and a production line of 800 tons/year for water-based epoxy resin synthesis and 500 tons/year for aviation special resin synthesis.
The project has carried out the development and industrialization of high-performance and low-pollution large and medium-sized aircraft skin coatings, forming a new type of supporting system for aircraft skin (i.e., water-based primer, water-based topcoat and high-solid mask varnish), which can reduce the VOC of aircraft skin coatings to below 50g/L, which is much lower than the solvent-based coatings currently used, leading the development of the mainland aircraft skin coatings in an environmentally friendly direction.
The project has completed the demonstration coating of typical aviation parts in Aviation Industry Xi'an Aircraft Industry (Group) Co., Ltd., the construction performance of the coating is good, the surface of the typical parts after coating is smooth, the color and gloss appearance are uniform, there are no defects such as smoke and orange peel, and the coating has good hiding power. After being placed at room temperature for 24 hours, it was sanded with No. 240 sandpaper, and there was no obvious sandpaper sandpaper sanding mark in the sanding area, and the sanding performance was good. After 7 days at room temperature, the wet tape adhesion test was carried out, and no paint layer fell off, and the application effect was excellent.
The products developed by the project such as water-based epoxy emulsifier, water-based epoxy emulsion, water-based epoxy curing agent, water-based hydroxyl emulsion, water-based polyurethane coating, high-solids resin and high-solids coating have realized the independent development and industrialization of the core technology of aviation skin coating.
Relying on the research of this project, building a technical platform for water-based coatings will help reduce the use and emission of organic solvents, and play an important role in promoting the development of coating products in the direction of resource conservation and low pollution. The water-based epoxy emulsion and water-based epoxy curing agent products developed by this project have been widely used in many fields such as metal, flooring, cement curing, etc., with sales of more than 1.5 million yuan in the past two years;
The development of the continental aviation industry will bring about the application of environmentally friendly aviation coatings, and with the country's emphasis on environmental protection and the introduction of relevant environmental protection policies, the project developed hydroxy emulsion, water-based epoxy emulsion, water-based epoxy curing agent, water-based anti-corrosion primer and water-based polyurethane topcoat, high-solid coatings, etc., will achieve tremendous development and achieve good economic benefits.
2.2.3.2 Application of domestic military aircraft
The varieties of aircraft coatings for the Continental Army are quite different from those of foreign countries. At present, there are only six types of primer products and corresponding military standards, such as aircraft skin primer, polyurethane primer for composite materials, fluorine polyurethane matte magnetic paint supporting polyurethane primer, zinc-rich anti-rust primer for ships, epoxy silicone heat-resistant primer and aluminum powder asphalt ship.
GJB 5591-2006 "General Specification for Fluorine Polyurethane Coatings for Military Aircraft" is matched with the use of TB 06-9 zinc yellow acrylic polyurethane primer, which was developed during the "Ninth Five-Year Plan" period equivalent to the US military standard MIL-P-23377D-85 "Chemical and Solvent Resistant Epoxy Polyamide Primer Standard", and was popularized and applied to important aviation weapons and equipment during the "Eleventh Five-Year Plan" period, so that the protective coating material on the outer surface of the continental fighter aircraft reached the international advanced level at that time. However, since then, the United States has developed a new high-efficiency anticorrosive primer suitable for military aircraft and weapons and equipment, especially carrier-based aircraft, forming a new standard of MIL-PRF-23377K-2012.
The research on Continental's high-efficiency anti-corrosion coating materials is relatively lagging behind, and the new model still uses TB 06-9 zinc yellow acrylic polyurethane primer. The technical specifications of GJB 5591 and MIL-PRF-23377K are significantly different. MIL-PRF-23377K primer has excellent corrosion resistance, after 1000h filamentous corrosion, the length of filamentous corrosion at the scratch is not more than 3.2mm, and the tear-breaking specimen does not corrode the scratch after 2000h salt spray resistance. The anti-corrosion performance index of TB 06-9 zinc yellow acrylic polyurethane primer has been lower than the corresponding index requirements of MIL-PRF-23377K, and the salt spray resistance is lacking, while the filament corrosion resistance has not been considered. In harsh environments such as high temperature, high humidity and high salt spray, filament corrosion is very easy to occur and is quite serious.
In the future, the mainland's defense spending will maintain sustained and rapid growth, and there will be a sustained high growth demand for military coatings for weapons and equipment. According to the data, the mainland's defense spending exceeded 1 trillion yuan for the first time in 2017, and the defense budget in 2022 is 1,476.081 billion yuan. After 40 years of rapid development, with the increasing size of the economies of China and the United States, the external environment for peaceful and stable development since the reform and opening up is being challenged, China is facing a severe and complex political and economic environment, and the mainland's defense expenditure will continue to maintain a steady growth trend in the future. According to the national strategic plan, a new "three-step" strategy for national defense and military modernization is proposed, which is to achieve the goal of the centenary of the founding of the armed forces by 2027, basically realize the modernization of national defense and the armed forces by 2035, and build a world-class military in an all-round way by the middle of this century. Therefore, in the long run, the mainland's national defense spending will continue to maintain a moderate and steady growth in line with the country's economic development level, and the demand for national defense weapons and equipment and supporting materials will also continue to grow.
It is worth mentioning that the Central Military Commission's emphasis on actual combat training will inevitably increase the demand for procurement of national defense equipment and favor the development of supporting materials for weapons and equipment. In recent years, the Central Military Commission has always emphasized "unswervingly promoting military training in real combat, urging the whole army to persist in placing military training in a strategic position, focusing on promoting actual combat training, and deepening joint combat and joint training." It can be seen that actual combat training will continue to be a measure for the transformation and upgrading of military training on the mainland. Therefore, actual combat training has increased the procurement and maintenance needs of the mainland army in terms of weapons and equipment, and put forward higher requirements for the overall units and supporting enterprises of weapons and equipment at the performance level, which will drive the growth of the national defense equipment industry chain, including coatings and coatings.
In order to meet the needs of national defense and army construction, under the new military requirements of building a strong modern army, navy, air force, rocket force and strategic support forces, military coatings are playing an increasingly important role and playing an increasingly important role in promoting the modernization of weapons and equipment. Benefiting from the continuous development of the mainland's national defense, the economic construction paint, which provides supporting materials for military weapons and equipment, will also benefit from it.
Part 3
Forecast for the future development of China's aviation coatings industry
For the current development status of domestic aviation coatings, the technical hotspots that really need to be solved are the following two aspects: one is the development and industrialization of high-performance resins, and the other is the research and production of new functional pigments.
As the main film-forming substance of the coating film, the resin plays a decisive role in both the mechanical properties and the protective properties of the coating film. At present, most of the domestic aviation coating manufacturers are using commercialized resins, so the performance of the coating products produced is comparable, and at the same time, there are some drawbacks that the performance of the coating film cannot be improved. The structure of the resin is a key factor in the performance of the resin, and the commercialized resin can meet the general industrial needs, but when it comes to special uses, it is not as good as it should be. After investigating the technical resources of many well-known foreign resin manufacturers, it was found that there are many binder resins suitable for aviation coating products, and in the process of applying for samples and procurement, they were told that because these resins are used in special industries, and these resins are prohibited from being sold in China. It can be seen that foreign countries have strictly controlled the supply of raw materials for special coatings, which has seriously restricted the development of domestic aviation coatings for many years. Therefore, the research and development of special resins is the top priority.
Many of the functions of coatings are provided by the added pigments and fillers, such as electrical conductivity, corrosion resistance, reflective properties, wave transmission properties, wave absorption properties, etc. Therefore, the properties of the filler itself determine the functionality of the final coating film. For example, if the conductivity or absorption properties of the filler are good enough, the conductivity or absorption performance of the coating film will be even better under the same amount of additives. For another example, the dielectric constant and dielectric loss of the pigment and filler itself are very low, so the corresponding wave transmission performance of the coating film prepared with this kind of pigment and filler will be better. How to develop functional coatings with better performance is of great significance to the development of special coatings in the future, and efforts should be made in the following four aspects.
3.1 Aerodynamic performance optimization
In the period of high fuel prices, the focus of aircraft design is to improve fuel efficiency, however, fuel prices are low in 2018, so the current hot coating technology is mainly around improving the aerodynamic performance of the aircraft. For example, AkzoNobel is working with universities and OEMs to develop coating technologies that can improve aircraft performance and reduce flight drag, thereby reducing fuel consumption by 1%~2%.
3.2 Primer varnish system
Primer-clearcoat systems not only help to improve gloss and color stability, but also lead to longer coating life, lighter weight and shorter drying time, such as AkzoNobel's Aerodur/ Aerobase products are one such product, which lasts twice as long as conventional aerospace paints: PPG's Aerocronj products are 30% lighter than single-layer paints, which means that the weight of an entire aircraft can be reduced by 453.59kg (1000lb - equivalent to the mass of a piano) when used with this coating. The advantages of primer-clearcoat systems are set to become the technical standard in the coating industry because airlines want to increase brand value through bright airframe colors, etc., and OEMs want to increase production rates by continuously reducing coating drying time.
3.3 Chromium-free trend
As manufacturers and other businesses pay more and more attention to environmental protection, there is a strong demand for reducing chromium content. Chromium, especially hexavalent chromium, has long been used to prevent corrosion, but its carcinogenicity poses a great threat to sprayers and the environment. PPG believes that the development of chrome-free coating products is accelerating, but its corrosion resistance needs to be further evaluated for adhesion, flexibility and protection are key attributes of the coating, and AkzoNobel is investing heavily in chrome-free coatings, which are known to provide better key performance indicators than chromium-containing products. The company believes that the key to product development is to identify a method that can accurately test the performance of the product, which is also the key to the delay in the development and application of chrome-free coating products.
3.4 The coating dries quickly
After technical aircraft have undergone paint stripping, their wings, engines and composite areas need to be covered before blasting. This is followed by electric grinding, followed by a base spray cover, followed by a base color, and finally a spray stripe and logo, repair and emergency notices, registration numbers and door stripes. Turnaround time and price are key factors for spraying companies. In the bidding of spraying projects, it is not uncommon for a contract project to have 5~7 bidders. Since spray turnaround time is greatly affected by paint curing time, coating manufacturers have also done quite a bit of research to accelerate paint curing. For example, primer and varnish systems incorporate a quick-drying topcoat. This technology benefits both aircraft OEMs and maintenance companies. In addition, repair companies use heated hangars to speed up coating curing.
"Thirteenth Five-Year Plan" is the period of high-speed development of various undertakings in the mainland, with the development and accumulation of technology in the continental aviation and aerospace technology over the years, the mainland will launch new models in this period, showing unprecedented activity in terms of technological advancement and covering technology, and at the same time, the supporting coating technology, especially the special coating technology, has developed rapidly and made great progress.
Overall, China will become the world's second largest commercial aircraft market in the next 10 years, second only to the United States, and the market prospect of aviation and aerospace material preparation industry is huge. The demand for coating material technology in the aviation field is also constantly increasing, and higher requirements are put forward for the coating technology level and service capacity, the coating industry is facing a rare historical development opportunity, and the market prospect is broad; "circular economy, sustainable development" is the inevitable requirement for the implementation of the scientific concept of development, the development of the coating material industry in line with this strategic policy is a very good opportunity for development, at the same time, foreign coating material enterprises have entered the domestic market one after another, bringing huge challenges and competitive pressure to domestic enterprises.
Therefore, only by seizing this opportunity to explore new models of scientific research, development and achievement transformation, improve the level of original innovation and engineering of technology, integrate all aspects of resources, and enhance the ability to cooperate, can domestic enterprises promote the rapid development of the surface technology industry and become the leader of the industry while achieving significant economic benefits.