Polyolefin Photovoltaic Backsheet for Heat and Weather Resistance
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Solution Overview
Problem
Photovoltaic module backsheets in the prior art suffer from issues such as cracking, yellowing, and thermal degradation due to high temperatures, particularly from hotspots or long-term exposure, and contain non-recyclable fluorinated polymers that can release harmful compounds.
Innovation Solution
A photovoltaic module backsheet composed of layers with at least 50 wt.% polyolefin, including a functional layer of polyethylene and polyethylene copolymer, a connecting layer, and a weather-resistant layer of polypropylene with UV and thermal stabilizers, antioxidants, and optionally inorganic fillers, produced through coextrusion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fluorinated polymers (PVF, PVDF) are used in backsheets to provide good barrier properties against environmental conditions, then weather resistance is improved, but recyclability deteriorates and harmful fluorinated compounds may be released into the environment
Solution Approach 1:
The patent changes the chemical composition parameters by completely replacing fluorinated polymers with polyolefin-based polymers (polyethylene, polypropylene, polybutylene). This substitution maintains the barrier properties and weather resistance function while eliminating the harmful fluorinated compounds, achieving both improved environmental compatibility and recyclability
Solution Approach 2:
The patent extracts and removes the fluorinated polymer components from the backsheet structure entirely. By eliminating PVF and PVDF layers that traditionally provided weather resistance, the invention replaces them with fluorine-free polyolefin alternatives, thereby removing the source of harmful fluorinated compound release while maintaining protective functionality
2Reliability
If polyamide layers are used to provide good barrier against weathering and UV radiation, then weather resistance is improved, but the backsheet suffers from cracking and yellowing under high temperature conditions
Solution Approach 1:
The patent changes the material composition by replacing polyamide with polyolefin-based polymers (polyethylene, polypropylene, polybutylene). This parameter change eliminates the thermal degradation issues of polyamide while maintaining UV resistance through titanium dioxide additives and weathering protection, achieving both weather resistance and thermal stability
Solution Approach 2:
The patent creates a composite material system using polyolefin base polymers combined with inorganic fillers (titanium dioxide, zinc oxide) and stabilizers. This composite approach provides the weather resistance previously achieved by polyamide while adding thermal stability through the inherent heat resistance of polyolefins and the protective effect of inorganic additives
3Strength
If coextrusion is used to produce multi-layer backsheets to increase interlaminar strength, then delamination resistance is improved, but the complexity of manufacturing increases
Solution Approach 1:
The patent applies homogeneity by using polyolefin-based polymers across all layers of the multi-layer backsheet structure. Since all layers are based on compatible polyolefin materials, they exhibit natural compatibility and strong adhesion without requiring complex bonding processes, thereby maintaining interlaminar strength while simplifying the coextrusion manufacturing process
Solution Approach 2:
The patent applies local quality by assigning specific functions to specific layers while maintaining material compatibility throughout. The functional layer provides adhesion and moisture barrier, the intermediate layer provides structural support, and the outer layer provides weather resistance, with each layer optimized for its specific function while maintaining overall system simplicity through uniform polyolefin chemistry
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 backsheet exhibits improved resistance to cracking and yellowing under high temperatures, maintaining electrical insulation and weather resistance, while being free of fluorinated polymers for environmental sustainability.
Implementation Method 1
coextrusion to produce a multi-layer backsheet
Implementation Method 2
coextrusion requires the polymers in the multiple layers to be sufficiently compatible in terms of bonding and to be processable in coextrusion apparatus
Implementation Method 3
The functional layer comprises polyethylene and a polyethylene copolymer
Implementation Method 4
the weather-resistant layer comprises polypropylene; a UV stabilizer
Implementation Method 5
a primary antioxidant, which primary antioxidant is a phenolic antioxidant or an aromatic amine antioxidant; and secondary antioxidant, which secondary antioxidant is a trivalent phosphorus containing antioxidant or a thioether containing antioxidant
Data Source
AI summary
The present invention relates to a photovoltaic module backsheet, comprising photovoltaic module backsheet comprising, in order: a functional layer; a connecting layer; and a weather-resistant layer, wherein each layer of the backsheet comprises at least 50 wt. % polyolefin and the backsheet is free of fluorinated polymers, characterized in that: i) the functional layer comprises a blend of polyethylene and a polyethylene copolymer; and ii) the weather-resistant layer comprises polypropylene; a UV stabilizer; a primary antioxidant, which primary antioxidant is a phenolic antioxidant or an aromatic amine antioxidant; and secondary antioxidant, which secondary antioxidant is a trivalent phosphorus containing antioxidant or a thioether containing antioxidant. The present invention also relates to a process for producing the backsheet and a photovoltaic module comprising the backsheet according to the present invention.