PBT Polyolefin Back-sheet Acetic Acid Resistance
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Solution Overview
Problem
Photovoltaic module back-sheets face challenges with corrosion resistance, durability, hydrolytic stability, and UV stability, leading to reduced power output over time due to issues like delamination and the formation of corrosive degradation products like acetic acid from existing encapsulation materials.
Innovation Solution
A back-sheet comprising a weatherable layer, a structural layer, and a functional layer, where one layer is impact modified polybutylene terephthalate (PBT) and one or both other layers are polyolefin, enhancing acetic acid permeation resistance and mechanical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If EVA copolymer is used as encapsulation material, then good encapsulation and protection are achieved, but corrosive degradation products like acetic acid are formed leading to corrosion of interconnectors and cell metallization
Solution Approach 1:
The patent extracts and removes the harmful acetic acid degradation products from the encapsulation system by introducing a basic substance (such as magnesium oxide, calcium oxide, or aluminum oxide) that chemically neutralizes and binds the acetic acid, preventing it from corroding metal components. This extraction approach eliminates the harmful effect while preserving the beneficial encapsulation properties of EVA.
Solution Approach 2:
The patent introduces a basic substance as an intermediary between the acetic acid degradation products and the metal components. This intermediary substance acts as a buffer that absorbs and neutralizes the corrosive acetic acid, preventing direct contact and corrosion of the interconnectors and cell metallization while allowing the EVA to continue its encapsulation function.
2Reliability
If back-sheet protects PV module from environmental influences, then durability is improved, but delamination occurs reducing long-term performance
Solution Approach 1:
The patent modifies the chemical and physical parameters of the back-sheet materials and their interfaces. By adjusting the surface energy, chemical composition, and structural properties of the back-sheet layers and adhesive interfaces, the patent enhances adhesion strength and prevents delamination while maintaining the protective function against UV, moisture, and weathering.
3Reliability
If multiple polymeric layers are used in back-sheet, then weather resistance and durability are improved, but complexity of structure increases
Solution Approach 1:
The patent designs back-sheet layers and adhesive compositions that perform multiple functions simultaneously. For example, certain layers provide both mechanical reinforcement and UV protection, while adhesive compositions simultaneously bond different materials and provide corrosion resistance. This multi-functionality reduces the need for separate dedicated layers, simplifying the overall structure while maintaining comprehensive protection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides improved corrosion resistance, durability, and hydrolytic stability, resulting in better power output retention over the lifetime of photovoltaic modules by reducing acetic acid permeation and enhancing thermal stability.
Implementation Method 1
enhancing acetic acid permeation resistance
Implementation Method 2
improved corrosion resistance, durability, and hydrolytic stability
Data Source
AI summary
The present invention relates to a back-sheet comprising a weatherable layer, a structural layer and a functional layer whereby one of the layers comprises polybutylene terephthalate and one or both of the other layers comprises a polyolefin. The layer comprising polybutylene terephthalate preferably further comprises an impact modifier. The impact modifier comprises an elastomer that contains functional groups that bond chemically and/or interact physically with the polybutylene terephthalate and wherein the elastomer constitutes the dispersed phase at a concentration of 1-49 Vol %. Preferably the elastomer contains epoxy functional groups. The polyolefin is selected from the group consisting of polyethylene homo or copolymers, polypropylene homo or (block-)copolymers, cyclic olefin copolymers, polymethylpentene, a thermoplastic polyolefine (TPO), or blends thereof.