Effect of EVA cross-linking degree on its mechanical properties (1)

Abstract: This paper takes the EVA model commonly used in the photovoltaic industry as a sample to study the influence of the change of cross-linking degree on the mechanical properties of various aspects of EVA. EVA research samples with different cross-linking degrees were prepared by adjusting the lamination process parameters, and various mechanical properties of the samples were tested. After statistical processing of the data, it was concluded that the EVA of the PV module package has a cross-linking degree of about 85%. At the same time, the mechanical properties of all aspects, namely the tensile strength of EVA, the elongation at break, and the bonding strength of EVA and glass and back sheet are the best.

1 Introduction

Due to the presence of polar vinyl acetate units in ethylene and vinyl acetate copolymer (EVA), this polar unit reduces the crystallization ability of EVA, which is reflected in its mechanical properties, which shows that EVA has good toughness, softness and impact resistance. strength. However, since EVA is a linear polymer copolymer, its heat resistance and cohesive strength are poor, which limits its application range. The EVA used in the solar photovoltaic industry is a hot-melt and thermosetting adhesive film modified by adding a coupling agent, an initiator, an antioxidant, etc., and the EVA film is formed into a crosslinked three-dimensional network after hot-melting and thermosetting. Structure, the degree of cross-linking directly affects the physicochemical properties of EVA after curing.

If the cross-linking degree is too low, the three-dimensional network structure of EVA is not completely formed, and its material is loose, which is difficult to form a dense packaging effect, which is characterized by loose EVA material, poor toughness and tensile strength, and back sheet and glass. The bond strength is also relatively low. However, if the cross-linking degree of EVA is too high, the EVA material will be hardened, the flexibility will be lowered, and the bond strength with the back sheet and the glass will be decreased, and even the EVA and the back sheet or glass may be cracked, and the aging resistance of the EVA is improved. Will also decrease. It can be seen that the degree of cross-linking of EVA will directly affect the physicochemical properties of EVA after curing, which will have a great impact on the packaging effect of components and the service life of components.

Due to the large number of EVA manufacturers in the domestic solar industry, the composition and ratio of different manufacturers and different models of EVA are also different, reflecting the difference in the performance of EVA. Therefore, in the photovoltaic industry, the degree of cross-linking of EVA is the best, (ie, the best combination of the cured EVA and the backsheet, glass bond strength and self-toughness, tensile strength) has not been unified, A clear understanding. In this paper, by selecting three representative EVA models in the industry as research samples, a comprehensive and detailed comparative analysis of the mechanical properties of EVA with different cross-linking degrees is made, and then the optimal range of EVA mechanical properties is found. The packaging process for photovoltaic module production has certain reference value.

2 experimental part

2.1 main raw materials

Three representative EVA films in the industry were selected as research samples, and other auxiliary materials (such as back sheet, tempered glass, high temperature cloth, etc.) were selected. The main performance descriptions are shown in Table 1.

Table 1 Test raw materials and their performance description

7.5 Inch Rubber Roller

7.5 Inch Rubber Roller,Paint Rubber Roller Brush,Small Rubber Paint Roller,Rubber Pattern Paint Roller

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