Propylene Copolymer Sealing Sheet for Solar Modules
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Solution Overview
Problem
Conventional composite sheets used in solar cell modules face challenges with adhesiveness between ethylene-vinyl acetate (EVA) sealing sheets and polypropylene resin, leading to inadequate moisture barrier properties and reduced production efficiency due to time-consuming crosslinking treatments, which affect the durability and productivity of solar cell modules.
Innovation Solution
A composite sheet comprising a thermoplastic resin composition with specific propylene polymers and copolymers, providing excellent adhesiveness with polypropylene resin, improved heat resistance, and reduced permanent compression set, allowing for low-temperature adhesion without compromising transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If EVA is used for sealing sheet to ensure transparency and flexibility, then the sealing sheet can cover wide areas and is simple to use, but the adhesiveness with polypropylene resin is insufficient and moisture barrier property is inadequate
Solution Approach 1:
The patent changes the chemical composition parameters of the sealing sheet from conventional EVA to a specific copolymer composition (polymer A with 70-90 mol% propylene and 10-30 mol% α-olefin). This parameter change enables the sealing sheet to achieve both good adhesiveness with polypropylene resin and sufficient moisture barrier property, while maintaining transparency and flexibility for easy manufacturing.
2Temperature
If crosslinking treatment is performed on EVA sealing sheet to provide heat resistance, then heat resistance is improved, but production time increases to 1-2 hours reducing productivity
Solution Approach 1:
The patent extracts the crosslinking treatment step from the manufacturing process by using a copolymer composition that inherently provides sufficient heat resistance without requiring crosslinking. The specific copolymer structure (polymer A with controlled propylene and α-olefin content) achieves the desired heat resistance through its molecular structure alone, eliminating the time-consuming crosslinking step and enabling faster production.
3Temperature
If crosslinking treatment is performed on EVA sealing sheet, then heat resistance is improved, but decomposition products such as acetic acid gas may affect the solar cell device
Solution Approach 1:
The patent replaces the crosslinking process (which generates harmful decomposition products) with a disposable-like approach using pre-formulated copolymer materials that provide heat resistance intrinsically. The copolymer composition (polymer A with specific propylene and α-olefin content) is designed to withstand heat without decomposing into harmful substances, eliminating the need for crosslinking and its associated harmful byproducts.
4Strength
If polyethylene terephthalate resin is used for base sheet to ensure strength and transparency, then mechanical properties are improved, but moisture barrier property is insufficient
Solution Approach 1:
The patent uses polypropylene resin for the base sheet instead of polyethylene terephthalate. Polypropylene resin inherently provides excellent moisture barrier property while maintaining sufficient strength and transparency. This material substitution creates a composite structure where the base sheet itself contributes to moisture protection, eliminating the need for additional barrier layers and simplifying the overall structure.
Data Source
Figure 1
AI summary
[Problems to be solved] The present invention provides a sealing sheet that can be used instead of the sealing sheet made from the conventionally widely used EVA, which has good transparency, heat resistance and adhesiveness with a polypropylene resin, and good productivity. [Means to solve the problems] The sealing sheet (I) is made from a thermoplastic resin composition comprising 0 to 90 parts by weight of a propylene polymer (A) having a melting point, as measured by a differential scanning calorimeter, of 100°C or higher, and 10 to 100 parts by weight of a propylene copolymer (B), wherein the copolymer is formed from propylene, and at least one olefin selected from the group consisting of ethylene and α-olefins having 4 to 10 carbon atoms, and the copolymer has a shore A hardness of 30 to 80 and has a melting point, as measured by a differential scanning calorimeter, of 100°C or lower or has no melting point to be observed (with the total of (A) and (B) being 100 parts by weight), wherein the thermoplastic resin composition has a permanent compression set, as measured at 23°C, of 5 to 35%, and a permanent compression set, as measured at 70°C, of 50 to 70%.