Method for testing crosslinking degree of photovoltaic assembly EVA packaging material

Abstract

The invention discloses a method for testing the crosslinking degree of a photovoltaic assembly EVA packaging material. The method comprises the following steps: (1) taking EVA packaging material samples with the same specification and different crosslinking degrees, and respectively testing the curing degree and the crosslinking degree of every sample; (2) establishing a curve map of the curing degree and the crosslinking degree, and fitting the curve map to obtain a relation between the curing degree and the crosslinking degree, represented by y = ax<2> + bx + c; and (3) testing the curing degree x of an EVA packaging material with the same specification and an arbitrary crosslinking degree, substituting the obtained result to the relationship obtained I step 2, and calculating the crosslinking degree y of the EVA packaging material. The corresponding relationship between two test results is found by combining a DSC test technology with a xylene extraction technology in order to conveniently switch test results obtained through the two test technologies, so the defects of the long test period and low test precision of the xylene extraction technology are overcome, widely received test results are obtained, and disputes are avoided.

Description

technical field [0001] The invention belongs to the field of production and assembly of photovoltaic cells, and in particular relates to a method for testing the crosslinking degree of EVA packaging materials of photovoltaic modules. Background technique [0002] With the increasingly serious problems of environmental pollution and energy shortage, solar energy as a green energy has gradually been paid attention to. Solar cells can directly convert solar energy into electrical energy. Especially with the deepening of research and improvement of technology, some new materials are applied to solar cell components, which greatly improves the photoelectric conversion efficiency of components. [0003] EVA (ethylene-vinyl acetate copolymer) is currently the most commonly used material in the solar cell packaging process. Its main functions are: packaging components; influences. The degree of cross-linking of EVA has an important impact on the performance of the module. In order...

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Problems solved by technology

[0004] However, the xylene extraction method has three fatal shortcomings: 1, xylene is highly toxic; 2, there are many interfering factors (people, instruments and environment, etc.) that affect the test results, and the repeatability is poor (at least 5% deviation)

The EVA crosslinking reaction is related to the free radicals released by the decomposition of the crosslinking agent. At the beginning of the reaction stage, the content of free radicals is high, and the reaction proceeds violently. EVA quickly becomes "viscous", and the activation energy required for crosslinking agent migration increases. Separated in various areas, resulting in poor uniformity of crosslinking agent content in EVA; 2. The previous sampling method was to use scissors to cut a small disc of 3-15mg after the EVA was stripped. Due to the small amount of sampling, this lead to poor representativeness of the sample

[0007] Generally speaking, the result data obtained by the DSC method is lower than that obtained by the xylene extraction method. The reason may come from two aspects: 1. The DSC method uses the curing enthalpy released when the temperature of the uncrosslinked EVA is raised as the 100% uncrosslinked curing enthalpy , but due to the fact that the actual chemical reaction cannot achieve 100% complete reaction, and the half-life of the cross-linking agent and other characteristics, the cross-linking agent has a residual amount

In this way, the 100% uncrosslinked curing enthalpy value is too small, resulting in a small degree of curing that is finally calculated; 2. During xylene extraction, all substances that are insoluble in xylene are used as crosslinked EVA. Some fillers or impurities are insoluble in xylene, and a small amount of uncrosslinked EVA may also be insoluble in xylene, so the overall crosslinking degree measured by the solvent method will be high

[0008] At present, most manufacturers use the xylene extraction method as the main test method, which leads to the fact that although the DSC method has certain advantages, the measured data is difficult to be accepted by everyone.

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