Thiol-Ene Optical Fiber Coating for High-Temperature Resistance
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Solution Overview
Problem
Current optical fiber coatings lack high-temperature resistance, with existing UV-curable urethane acrylate coatings being insufficient for applications above 200 °C, while polyimide and silicone-based coatings have impractical properties such as low shelf life, slow thermal cure, solvent emission, and limited pot life, making them unsuitable for efficient use in optical fiber coatings.
Innovation Solution
A radiation-curable optical fiber coating composition comprising at least 20 wt% trifunctional ethylenically unsaturated monomers and trifunctional thiol monomers, with a ratio of polymerizable ethylenic unsaturations to thiols of at least 1, and an effective amount of a free radical photoinitiator, which forms a highly crosslinked material upon UV exposure, providing enhanced thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If UV-curable urethane acrylate coatings are used, then mechanical and chemical protection is provided, but high-temperature resistance is insufficient above 200°C
Solution Approach 1:
The patent changes the chemical composition parameters of the UV-curable coating by incorporating thiol-ene monomers with specific functional groups (aromatic rings, heteroatoms) that provide thermal stability. The formulation uses at least 20 wt% thiol monomers and 20 wt% ethylenically unsaturated monomers with a ratio of polymerizable ethylenic unsaturations to thiols of at least 1, creating a highly crosslinked network that maintains integrity at temperatures up to 200°C
Solution Approach 2:
The patent creates a composite coating system combining UV-curable thiol-ene monomers with photoinitiators and optional additives. The cured coating exhibits composite-like properties where the highly crosslinked thiol-ene network provides both UV curability and high-temperature resistance, merging advantages previously found in separate coating systems
2Temperature
If polyimide coatings are used for high-temperature resistance, then thermal stability is improved, but shelf life and curing speed deteriorate
Solution Approach 1:
The patent replaces the thermal curing mechanism of polyimides with UV photopolymerization. The thiol-ene monomers cure via free radical photopolymerization initiated by UV light, eliminating the need for prolonged high-temperature thermal treatment. This substitution reduces curing time from hours to minutes while maintaining high-temperature resistance
Solution Approach 2:
The patent changes the curing mechanism from thermal to photopolymerization, and adjusts monomer selection to achieve rapid cure. The use of photoinitiators and thiol-ene chemistry enables fast UV curing while the aromatic and heteroatom-containing structures provide thermal stability matching polyimide performance
3Temperature
If silicone-based RTV coatings are used for high-temperature resistance, then thermal performance is improved, but pot life and curing speed deteriorate
Solution Approach 1:
The patent replaces heat-cure silicone chemistry with UV-curable thiol-ene photopolymerization. The UV curing mechanism enables rapid coating formation and cure without the slow thermal processing required for silicones, significantly improving draw speeds and manufacturing productivity while maintaining thermal performance
Solution Approach 2:
The patent changes the curing energy source from thermal to UV radiation, and adjusts the chemical composition to use thiol-ene monomers that cure rapidly under UV exposure. This enables fast curing with minimal pot life constraints, allowing higher draw speeds and more efficient coating processes
4Temperature
If polyimide coatings are used for high-temperature resistance, then thermal stability is improved, but solvent emission and environmental impact worsen
Solution Approach 1:
The patent extracts and eliminates the solvent component from the coating formulation. The UV-curable thiol-ene system is inherently solvent-free or contains minimal solvents, curing through photopolymerization of the monomer molecules themselves. This eliminates solvent emission and associated environmental and health hazards while maintaining high-temperature resistance
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 coating composition exhibits minimal weight loss (≤6% at 1000 hours at 200 °C) and maintains mechanical integrity, outperforming industry-standard silicone and acrylate-based coatings, with the ability to cure quickly through thicker layers without tackiness issues.
Implementation Method 1
UV-curable monomers and/or oligomers are cured by the action of a free radical photoinitiator
Implementation Method 2
thiol-ene based coating compositions and polymeric compositions that are resistant to high temperature
Data Source
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AI summary
The present disclosure relates to thiol-ene based coating compositions and polymeric compositions that are resistant to high temperature, as well as optical fibers coated with such polymeric compositions. In one aspect, the disclosure provides a radiation-curable optical fiber coating composition that includes at least 20 wt% of one or more at least trifunctional ethylenically unsaturated monomers, each having three or more free radical polymerizable ethylenic unsaturations; at least 20 wt% of one or more at least trifunctional thiol monomers, each having three or more free radical polymerizable thiols; and an effective amount of a free radical photoinitiator, wherein the ratio of the number of polymerizable ethylenic unsaturations of the curable composition to the number of polymerizable thiols of the curable compositions is at least about 1.