Wang Shuzhong: About the performance and application of fluorocarbon resin and its coatings

Wang Shuzhong
Ph.D., Engineering, Tokyo University of Technology, has been engaged in research and development work at asahi Nitro Central Research Institute since 1992 and has been based in Shanghai since 2012, serving as Minister of Marketing and Technology Development of Asahi Nitro Chemical Trade (Shanghai) Co., Ltd., during which time he has participated in the development or revision of coating-related standards in the transportation and chemical industries.
--- Forum Platform / Coatings and Protection magazine, E Zhongmin
Coatings and Protection: What are the main varieties of fluorocarbon resins? What have more market potential?
: The term fluorocarbon resin is more common in the paint industry and can be thought of as a generic term for fluorine-containing resins used in coatings. In this sense, the main fluorocarbon resins are now FEVE and PVDF two categories, FEVE is a co-polymer containing fluoroethylene and vinyl ether, in recent years, there have been some fluoroethylene and vinyl esters co-polymer fluorocarbon resin FEVEs appear, these can be regarded as sub-FEVE Class, it is worth noting that the latest version of the international standard ISO12944 clearly states that FEVE is a co-polymer containing fluoroethylene and vinyl ether, so strictly speaking, the use of vinyl esters made of fluorocarbon resin is not called FEVE

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FEVE from the content of the official energy group is polyols, in the formation of the coating film, there is a reaction with the curing agent to produce urethane bonds to form a cross-linking network structure process, so in the ISO12944 standard FEVE is expressed as a special polyurethane, belongs to the thermostered resin. PVDF is polyfluoroethylene, belongs to thermoplastic resin, the formation of coating film needs high temperature baking.
From the point of view of material development, when adjusting the structure or function group of individual units can make changes to FEVE, so it has a higher degree of freedom and a larger improvement space, in addition to the conditions of coating construction, FEVE can be both temperature curing and high temperature baking, so higher than PVDF selectivity.
In addition to the above two types of fluorocarbon resins, the building exterior is also coated with some fluoroacrylic acid resin, such products are far less weather resistant than the above two categories, and the biggest reason for the use of fluorocarbon resins is often the need for good weather resistance, so I personally think that fluoroacrylic acid and the above two types of resin should be distinguished, can not be referred to as fluorocarbon resin in general.
Pingtan Bridge
Coatings and Protection: Is FEVE fluorocarbon resin the best resin variety in terms of weather resistance?
Wang Shuzhong: In the field of heavy corrosion protection, FEVE is a well-deserved best weather-resistant resin, precisely because FEVE in the steel structure of the protective coating has more than 30 years of actual performance, ISO12944 will be FEVE as a high weather resistance material. In the construction sector, long-term weather-resistant aluminum curtain walls are coated with solvent-based PVDF, while some of the most high-end landmarks are decorated with FAVE composite panels. In recent years, due to the national environmental protection policy on VOC emission requirements more and more stringent, powder coating is increasingly used in aluminum profile coating, FEVE type of powder coating has the same weather resistance as PVDF, but also to reduce VOC emissions, so that outdoor aluminum profiles have a greener choice.
Coatings and Protection: Graphene is "playing tricks" everywhere, and how effective is graphene in terms of performance improvements in fluorocarbon resins and their coatings?
: There are some preliminary test results showing the excellent performance of graphene in coatings, including the mix of graphene and fluorocarbon resin, which is of concern. When FEVE came out, the impact on the anti-corrosion coating field at that time was considerable. From the development process of FEVE, any new material in the field of long-term anti-corrosion to occupy a place, first of all, to clarify the characteristics and properties of the material itself, the second need to be able to ensure stable production and use, and ultimately need a long time of experimental practical use to prove.
Coatings and Protection: Why are 3F resins better than 4F resins in terms of coating weather resistance? How to evaluate the relationship between fluorine content and weather resistance scientifically?
Wang Shuzhong: Before talking about 3F and 4F resins, it is first necessary to make clear the use of vinyl ether as a monomer with fluoroethylene-containing monomers to achieve good weather resistance, because vinyl ether and fluoroethylene-containing co-gathering produces a completely alternating co-polymer structure, which is critical to the material's UV resistance. Asahi nitro's early results prove that TEF or Teflon and vinyl ether co-polymer can get a completely alternating structure, so 3F resin and 4F resin if both use vinyl ether to co-polymer, as a resin, its own weather resistance is very good.
But after making these two resins into coatings, it is found that 4F resin and pigment compatibness is not good, in other words, the use of 4F resin as paint when the pigment dispersion is not good, such a coating, its coating film will have many gaps, water, oxygen, chloride and other corrosion factors can easily invade such coatings and through the coating system, which affects the durability of the entire coating system. The fluorine content of fluorocarbon resin should have been reflected in its structure, so fluorine content and weather resistance is not a positive relationship, which can be easily seen from the PVDF (nearly 50% fluorine content) and FEVE (3F resin fluorine content of about 27%).
It is particularly important to note that if a certain fluorine content is rigidly specified, some resins with higher fluorine content of the structure itself will provide a great deal of room in the formulation to mix other resins, resulting in a decrease in weather resistance.
Previously, the test of fluorine content has been using oxygen cans burning method, the error of this method is relatively large, if there is not enough combustion phenomenon, the resulting fluorine content will be low, the chemical industry standard HG/T3792-2014 gave the use of standard fluorine-containing compounds as a sample synchronous test to make corrections to the test results, This method reduces the error of fluorine content testing, which plays an important role in regulating some of the chaos in the fluorocarbon coating industry, but this method is not effective for mixing other substances with high fluorine content, such as perfluorocarbons, to fake the fluorine content, and may be considered in the future with reference to the 19F MRI spectrometry to determine the effective fluorine content from the structure.
Many of the standards involving fluorocarbon resins or fluorocarbon coatings now have fluorine content indicators, because it makes sense to make it clear that a certain fluorine content is meaningful for verifying the quality of fluorocarbon resins and coatings, but it is important to understand that the higher the fluorine content, the better the weather resistance.
Bridge
Coatings and Protection: What role does hydration technology play in the field of fluorocarbon coatings under the two-wheel drive of environmental regulations and standards revisions? What are the problems?
Wang Shuzhong: Water-based fluorocarbon coatings have been used for a long time, especially in the concrete structures that require flexible coating, there are more water-based fluorocarbon coatings, and the Three Gorges Dam and Shanghai Oriental Pearl are some cases of water-based fluorocarbon coatings coated with asahi nitros. The benefits of hydration are obvious, and the use of water-based coatings not only reduces VOC emissions, but also reduces odors on the construction site, especially in relatively closed environments, which can reduce the risk of fire.
But the current water-based series of coating, especially the steel structure of the coating system using water-based fluorocarbon paint is not many, the reasons are many, most of which are water-based coating this way of its own problems, such as in order to prevent resin freezing, whether it is transportation storage or construction coating need to control the temperature, which will increase energy consumption costs. And the water-based coating itself is a highly technical work, if the operator to paint similar to the feeling of the paint, often a big problem. There is data to prove that water-based fluorocarbon coatings can be and solvent-based fluorocarbon coatings have considerable weather resistance, so the potential of water-based fluorocarbon coatings is great, provided that it needs to be done well.
coating and protection: fluorocarbon powder coating is also an environmental protection concept in recent years, an environmentally friendly coating varieties, its development prospects? Is it covered with water-based fluorocarbon coatings?
Wang Shuzhong: Fluorocarbon powder coatings have been used in the construction industry aluminum curtain wall, almost became China's tallest landmark building Shenzhen Ping An Building is the use of FEVE powder resin aluminum curtain wall. With the reduction of solvent-based PVDF use, more and more fluorocarbon powder coatings will be used in this field. The way the powder is applied determines that the coating needs to be implemented at a certain high temperature, so the powder coating is not suitable for the giant structure and cannot be applied on site, but it is particularly suitable for coating on the factory floor. From an environmental point of view, powder is a greener product than water, but the application areas of the two are very different, there is no simple question of who replaces whom.
Shenzhen Ping An
Coatings and Protection: Fluorocarbon coatings have excellent comprehensive performance, mainly reflected in what aspects? What are the main application areas?
Wang Shuzhong: The biggest advantage of fluorocarbon coating is the excellent anti-UV performance of fluorocarbon resin to bring weather resistance, at the same time, as a coating, in order to achieve good weather resistance, pigment dispersion is also very important, so good weather resistance coating film often color is also very good to see. Good weather resistance means a long recoat cycle, which means a low cost for the full life cycle, which means saving resources and reducing emissions, so it can also be said that the greatest advantage of fluorocarbon coatings is its green environment. Fluorocarbon coating applications are very wide, the main applications are bridges and wind power and offshore platforms and other steel structure heavy anti-corrosion coating, decorative coating of building facades, high-speed rail and other rail transportation and large passenger aircraft and other means of transport coating, in recent years, photovoltaic back panels also have a part of the use of fluorocarbon paint for waterproof coating.The Official Hall Reservoir Railway Bridge
Coatings and Protection: In the field of corrosion protection, how can fluorine coatings improve long-term anti-corrosion performance while taking into account environmental protection and economy?
Shuzhong: As mentioned earlier, long-life materials are an environmentally friendly material in themselves and an economical material. Considering the full life cycle, the longer the life span of the material, the lower its cost and less emissions. For example, if graphene can greatly extend the coating life, even if the cost of graphene is very high, it is well worth trying. Nevertheless, there is room for improvement on the basis of existing fluorocarbon coatings. For example, we can try to improve the solid content of the coating to reduce VOC emissions. On the other hand, for relatively small components, powder coating can be used to reduce VOC emissions.