The pool back film is mainly divided into two categories: fluorine-containing back film and fluorine-free back film. The fluorine-containing back film is divided into two types of fluorine (such as TPT) and single-sided fluorine (such as TPE). At present, the mainstream solar cell backsheets are mostly double-sided fluorine-containing compound backing film and coated back film. The compound type solar cell back film (TPT, KPK, etc.) is mostly formed by bonding a fluorine film such as PVF or PVDF developed by some fluorine chemical companies in Europe and America through an adhesive and a PET substrate. The back film should meet the environmental test of the solar cell module for 25 years in terms of aging resistance, insulation resistance and moisture resistance. In the foreseeable future, the back film material will still be dominated by fluorine-containing back film. Under the background that PV modules are more and more sensitive to cost, foreign manufacturers have a monopoly position on the compound-type fluorine film, and the quality is excellent. The development of coated back film is the only way to achieve localization of the back film.
The coated back film is available late, but the process technology is the fastest growing and the market share is increasing year by year. At the beginning of the development and application of double-coated type back film technology, many people in the industry have doubts about the development of coated back film. After several years of application and practice, the coated back film has physical and mechanical properties, electrical insulation properties and resistance. Wet heat performance, EVA bonding performance, and silicone bonding performance can meet the requirements of various technical indicators of photovoltaic backsheets. Many domestic manufacturers of rubber-coated backsheets have begun to apply coating lines. Covered back film has become an essential technology for back film manufacturers.
At present, the industry's performance test and application research on coated back film is not perfect, including the research on the bonding performance of FEVE coated photovoltaic back film and silicone. Most of the silicone sealants used in the industry are based on the research and development of traditional laminating backsheets. They have mature application experience on traditional structural backsheets and have little application experience on FEVE coated backsheets. Some backsheet and component manufacturers have encountered such problems in their applications, including the poor bonding properties of junction boxes and FEVE backing films.
Development Status of FEVE Coated Photovoltaic Film Technology
The FEVE coated photovoltaic back film is mainly coated by coating with a PET substrate by using a coating material mainly composed of a tetrafluoroethylene copolymer resin (such as Daikin: GK570) or a chlorotrifluoroethylene copolymer resin. Type of back film. Compared with the laminated film, this product does not require the use of an adhesive, and the fluorine material is highly integrated with the PET base film and has a low cost, thereby realizing the weight reduction and thinning of the back film. Fluorine fluorinated with chlorotrifluoroethylene-vinyl ether (such as Dalian Yongrui Co., Ltd.: SRF-350), because of the strict alternation between comonomers, the resin has more excellent aging resistance, and is more suitable as a photovoltaic back. Base resin for film coatings.
The coated back film has developed rapidly in China, but its market share is still not high, and it has not yet become a mainstream application in the market. Based on technological advancement and environmental considerations, the water-based coating film will become the new development hotspot of the next stage of photovoltaic coatings. Existing domestic manufacturers are developing related products and have achieved initial results. Dalian Yongrui Fluorine Material Co., Ltd. developed a two-component water-based FEVE fluorine emulsion SRF-E620, which was used to prepare the coating to meet the main performance requirements of the photovoltaic film. At present, the research on the water-based back film of PV is still in its infancy, and the related performance test, process research and market application are still not perfect, and it is difficult to obtain commercial application in a short time.
Application prospects of coated backboard
Since the application of fluorine coating in the photovoltaic industry is not long enough, the experience of the application of the case is not enough, so it has not become the mainstream type of backplane. However, compared with other types of backplanes, coated backsheets have great development prospects, mainly in:
(1) Localization of raw material supply. Both fluorine film and fluororesin are derived from fluorite. China's fluorite resource reserves, production volume and export volume rank first in the world. It has provided great advantages for the localization of fluororesin synthesis. Domestic enterprises have reached or even surpassed imported products in terms of performance design and quality control of fluororesin. In addition, PET raw materials have also been domestically produced on a large scale, which is very beneficial to the cost control of the coated backsheet and laid the foundation for its higher cost performance. For the fluorine film type backboard, the other two kinds of raw materials fluorine film and adhesive other than PET have high process performance requirements, and domestic production technology has not yet made a big breakthrough, and still relies mainly on imports, which is difficult in cost control.
(2) The controllability of the production process of performance. For the fluorine film type back sheet, the production process is the adhesive bonding process between the fluorine film and the PET, the production process is simple, and the technical barrier is low, so the performance of the back sheet is highly dependent on the quality of the raw materials, and cannot be carried out by the process conditions. control. The coated backsheet is not, and its production process involves a series of complex chemical cross-linking reactions. The rational design and control of the production process plays a decisive role in the performance of the backsheet. As a result, coated backsheet companies are more likely to adjust and improve product performance through formulation and process to ensure better reliability and more functionality.
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