EVA film for Solar Panels

1.1 EVA film for Solar Panels
Among solar cell encapsulation materials, EVA is the most important material. Improper use of EVA will have fatal flaws in solar panels.
 
1.1.1 Composition and Characteristics of EVA
EVA is a resin product of ethylene-vinyl acetate copolymer. The product has good softness, impact strength, environmental stress crack resistance and good optical properties, low temperature resistance and non-toxic properties in a wide temperature range. EVA film, as shown in Figure 5-3, is a thermosetting film-like hot melt adhesive that does not stick at room temperature, but is heated to the required temperature and melt-bonded and cross-linking curing under certain conditions.

EVA film has cross-linking curing effect, EVA film is heated to a certain temperature, in the molten state, the cross-linking agent decomposes to generate free radicals, triggers the bonding between EVA molecules, and makes it and crystalline silicon solar cell, glass, TPT Bonding and curing, the three-layer material is integrated into one body. After curing, the EVA no longer flows in the sunlight, and the solar cell no longer moves. Because solar cells work in the open air for a long time, EVA films must withstand the erosion of different geographical environments and different climates. Therefore, the cross-linking index of EVA plays an important role in the quality and longevity of solar modules;
 
The bonding strength of EVA determines the near-term quality of solar modules. EVA is not sticky at room temperature, easy to handle, but heated to the required temperature, under the action of the laminator, physical and chemical changes occur, bonding the solar cell, glass and TPT. If the bonding is not strong, degumming can occur in a short period of time;
The heat resistance, low temperature resistance, and ultraviolet aging resistance of EVA play a decisive role in the power attenuation of solar cell modules.
  
The difference between various EVA materials
1. Appearance difference:
1) thickness - according to different needs, can use 0.35, 0.45, 0.60 and 0.80 thickness of EVA;
    Suede or plane
2) soft and hard - softer EVA has a lower melting point, and vice versa.
 
2. Inner difference:
1) cross-linking agent - cross-linking agent added, high degree of cross-linking, but easy to age, easy to yellow; conversely, the degree of cross-linking is low, not easy to yellow.
2) vinyl acetate (melt flow rate is constant)
High vinyl acetate content, EVA elasticity, flexibility, impact resistance, stress crack resistance, weather resistance, adhesion, compatibility and transparency, and improved gloss. On the contrary, the strength, hardness, melting point, flexural and extension stress, and thermal deformation are lowered.
3) melt flow rate (vinyl acetate must)
The melt flow rate is high, the meltability of the melt, the viscosity of the melt, the toughness, the tensile strength, and the stress crack resistance increase; on the contrary, the elongation at break, strength, and hardness decrease; but the flexural and tensile stress is not affected.
 
1.1.2 The Role of EVA
a. Encapsulate the solar cell sheet to prevent the external environment from affecting the electrical performance of the solar cell sheet.
b. Enhancing the light transmission of the solar cell module: an advantageous combination of EVA and glass can increase the transparency of the light source and increase the power of the solar cell module.
 c. Bonding the solar cell sheet, tempered glass, and TPT together to have a certain bonding strength.
Note: Although EVA can function as a encapsulation component, EVA has water absorption.
 
1.1.3 EVA Storage Environment
a. EVA film should be protected from light, heat, and moisture, and stacked.
b. The best storage conditions for EVA film: placed in a constant temperature, constant humidity warehouse, the temperature is between 0-30 ° C, the relative humidity is less than 60%. Avoid direct sunlight and should not be near places with heating equipment or dust, and should pay attention to fire prevention. The warranty period is half a year.

GWELL provide the turnkey solution for EVA film production, welcome to contact us.