Application of Silicone Adhesive Sealant in Solar Photovoltaic Modules
With the global energy situation tightening, solar photovoltaic power generation as a sustainable alternative to energy has developed rapidly in recent years, and has been widely promoted and applied in countries rich in solar energy resources, such as Germany and Japan. After nearly ten years of rapid development, China's photovoltaic industry has also entered the forefront of world development. Driven by the international market and domestic policies, a large number of outstanding photovoltaic enterprises have emerged, such as Wuxi Sunde, Changzhou Tianhe and Tianwei Yingli, which have promoted the development of upstream and downstream enterprises, and China's photovoltaic power industry chain is taking shape.


The solar photovoltaic cell is an important component of solar photovoltaic power generation. It is composed of single solar cell with high conversion efficiency, EVA film, low iron toughened glass, fluoroplastics and polyester composite back film. These components are heated and laminated under vacuum to form a whole, and finally anti-corrosion aluminium alloy frame is installed. And junction boxes, become photovoltaic module products. In order to prevent water and oxygen from entering the solar photovoltaic module in the air and to oxidize the silicon cells in the module, resulting in the reduction of the conversion rate of the silicon cells, it is necessary to adopt bonding sealing and good weather aging resistance to the gap between the edge frame of the photovoltaic module (i.e., the panel to the positive glass plate, the reverse TPT plate and the aluminum frame). Sealant is used for sealing, and sealant must be used for bonding and fixing around the shell of power transfer box (i.e. junction box) to protect circuit boards and prolong service life.


Compared with other types of sealants, the durability of silicone sealants under harsh conditions is particularly prominent. It also has excellent resistance to ultraviolet light and atmospheric aging. It can keep cracks, brittleness and deterioration for more than 30 years in harsh environments such as sunshine, rain, snow and seasonal climate change. It has the ability to resist deformation and displacement in a wide temperature range of (+50%). Photovoltaic cell modules should be used outdoors without any protection. They need to withstand low temperature in winter (130 C), high temperature in summer (up to 80 C in sunlight), rain and snow erosion, and ultraviolet aging. Building practice has proved that silicone sealant can withstand the test, so it is the most suitable sealant for solar photovoltaic modules.


The common silicone sealants on the market are condensated room temperature vulcanized silicone rubber, which will emit small molecular by-products when vulcanized. According to the types of by-products, condensation room temperature vulcanized silicone rubber can be divided into dealcoholization, deketoxime, deacetic acid, deamidation, deacetone and other types.


Deacetic acid silicone sealant is the most popular sealant on the market. Because acetic acid is the by-product of vulcanization, and acetic acid is corrosive to metals, it is mainly used for sealing glass and ceramics, commonly known as glass sealant, but less used in industry. Amides removed during vulcanization of deamidated silicone sealant The boiling point of small molecule by-products at atmospheric pressure is about 200 oC, and it is difficult to volatilize to form clean rubber materials, so its application is limited and commercialized products are few. The neutral and non-corrosive small molecule by-products released during vulcanization of deacetone silicone sealants are most suitable for application in the field of electronic appliances, but due to the interchange of deacetone silicone rubber. The combination agent is difficult to synthesize and its cost is relatively high, which limits the application of deacetone sealant, and the low molecular alcohol is removed when the deacetate silicone sealant is vulcanized.  Substances (methanol and ethanol) have little toxicity, especially no corrosion to metals. Therefore, they have been widely used in construction field (especially curtain wall) and industry. The deoxime silicone sealant removes ketoxime (methyl ethyl ketone oxime) when vulcanizing, which is an alkaline substance with certain toxicity and corrosive effect on metals. However, due to its fast vulcanization speed and good performance, it is also widely used in the construction and industrial fields.


The cost and performance advantages of dealcoholic and deoxime type make them the most common silicone sealant used in photovoltaic modules on the market.