Stabilized Polypropylene PV Backsheet Without Flame Retardants
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Solution Overview
Problem
There is a need for photovoltaic (PV) modules with long-term UV/light stability, long-term heat aging, and flame resistance without the use of flame retardant additives, specifically requiring a low-cost PV backsheet that maintains low flame spread, tensile property retention, and color stability in Xenon Arc exposure.
Innovation Solution
A polyolefin PV backsheet comprising a polypropylene layer stabilized with hindered amines, thioesters, and hindered hydroxybenzoates, optionally combined with ortho hydroxyl triazine compounds, which provides low flame spread and good weatherability without the need for flame retardant additives, achieved through a multilayer structure or co-extrusion/lamination methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If flame retardant additives are used to achieve flame resistance, then flame spread is reduced, but UV stability and color retention deteriorate
Solution Approach 1:
The invention extracts and removes flame retardant additives from the polyolefin backsheet composition entirely. Instead of adding flame retardants, the patent uses a stabilizer package comprising HALS and antioxidants that provides both UV stability and flame resistance inherently, eliminating the need for separate flame retardant components that would compromise UV stability.
Solution Approach 2:
The stabilizer package (HALS and antioxidants) performs multiple functions simultaneously: it provides UV stabilization, prevents oxidation during heat aging, and imparts flame resistance. This multi-functional approach eliminates the need for separate flame retardant additives, resolving the contradiction between flame resistance and UV stability.
2Stability of the object's composition
If HALS and antioxidants are used for UV and heat stabilization, then weatherability is improved, but flame resistance deteriorates
Solution Approach 1:
The HALS and antioxidant package serves itself by providing flame resistance as an inherent property without requiring additional flame retardant additives. The stabilizers' chemical structures and mechanisms naturally confer flame resistance while maintaining their primary functions of UV stabilization and oxidation prevention, allowing the same component package to handle multiple protection needs.
3Duration of action of stationary object
If thioester is combined with HALS for heat stabilization, then long-term heat stability is improved, but UV stability deteriorates due to interaction with degradation byproducts
Solution Approach 1:
The invention changes the parameter of antioxidant selection by specifying particular antioxidants (hindered phenols and arylalkyl phosphites) that do not interact negatively with HALS degradation byproducts. This parameter change in chemical composition eliminates the harmful interaction while maintaining heat stabilization effectiveness and preserving UV stability.
4Object-affected harmful factors
If inorganic flame retardants are used to achieve flame retardancy, then flame resistance is improved, but mechanical properties and processability deteriorate due to high loadings required
Solution Approach 1:
The invention extracts and eliminates inorganic flame retardants from the composition. By using a stabilizer package that inherently provides flame resistance, the patent avoids the need for high loadings of inorganic FR additives that would compromise mechanical properties and processability.
Solution Approach 2:
The invention uses a composite stabilizer system combining HALS and antioxidants that collectively provide flame resistance without requiring high loadings. This composite approach achieves flame retardancy through synergistic chemical mechanisms rather than through mass loading of inorganic additives.
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 achieves a low flame spread index, maintains over 70% retention of tensile properties, and exhibits good color retention with a yellowness index less than 5 in Xenon Arc exposure, meeting the requirements for PV module certification.
Implementation Method 1
protection of polyolefins against degradation by UV/visible light, heat and oxidation through the use of various (1) hindered amine light stabilizers (HALS)
Implementation Method 2
hindered amine light stabilizers (HALS) such as ortho-tris-aryl triazine light absorbers
Implementation Method 3
antioxidants such as hindered phenol, hindered arylalkyl phosphite, and trisarylphosphite
Implementation Method 4
imparting flame resistance without the use of flame retardant additives
Data Source
AI summary
Polyolefin photovoltaic (PV) backsheets comprise a polypropylene layer stabilized with (A) at least one hindered amine with 2,2,6,6-tetraalkylpiperdine or 2,2,6,6 -tetraakylpiperazinone, either or both in combination with a triazine moiety, (B) a thioester, and, optionally, (C) at least one hindered hydroxybenzoate, and/or (D) an ortho hydroxyl triazine compound. These PV backsheets exhibit a low flame spread index of <100 without the use of FR agents, and the polypropylene layer exhibits good weatherability while providing the required long term heat aging performance necessary for PV modules.