Effect of EVA crosslinking degree on its mechanical properties
Effect of EVA Cross-Linking Degree on Its Mechanical Properties (1)
Abstract: This paper investigates the impact of cross-linking degree on the mechanical properties of EVA, a commonly used material in the photovoltaic industry. By adjusting lamination process parameters, EVA samples with different cross-linking degrees were prepared and tested for various mechanical properties. After statistical analysis, it was found that an optimal cross-linking degree of around 85% provides the best mechanical performance, including tensile strength, elongation at break, and bonding strength between EVA and glass or backsheet materials.
1. Introduction
Ethylene-vinyl acetate (EVA) is a copolymer composed of ethylene and vinyl acetate units. The presence of polar vinyl acetate groups reduces the crystallization tendency of EVA, resulting in good toughness, softness, and impact resistance. However, as a linear polymer, EVA has limited heat resistance and cohesive strength, which restricts its application. In the solar photovoltaic industry, EVA is typically modified with coupling agents, initiators, and antioxidants to form a thermoset adhesive film. During the lamination process, EVA undergoes cross-linking, forming a three-dimensional network structure. The degree of cross-linking significantly influences the final properties of the cured EVA.
If the cross-linking degree is too low, the three-dimensional network is not fully developed, leading to a loose structure. This results in poor adhesion, reduced tensile strength, and lower bond strength between EVA and the glass or backsheet. On the other hand, if the cross-linking degree is too high, the EVA becomes rigid, losing flexibility and reducing its ability to bond effectively with surrounding materials. Excessive cross-linking can even cause cracking between EVA and the glass or backsheet, negatively affecting the aging resistance of the material.
The cross-linking degree of EVA directly affects its physicochemical properties, which in turn influence the overall performance and lifespan of photovoltaic modules. Due to the variety of EVA suppliers in the domestic photovoltaic industry, the composition and ratios of EVA vary among manufacturers and models, leading to differences in performance. Therefore, there is no unified standard for the optimal cross-linking degree of EVA in the industry. This study aims to analyze the mechanical properties of EVA with different cross-linking degrees using three representative EVA samples from the market. The findings will provide valuable insights for optimizing the packaging process in photovoltaic module production.
2. Experimental Part
2.1 Main Raw Materials
In this study, three representative EVA films commonly used in the industry were selected as research samples. Additional materials such as backsheet, tempered glass, and high-temperature cloth were also used. Table 1 outlines the main performance characteristics of the test materials.
Table 1: Test Raw Materials and Their Performance Description
By conducting comprehensive mechanical tests, this research provides a detailed comparison of EVA samples with varying cross-linking degrees, helping to identify the optimal range for mechanical performance in photovoltaic module applications.
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