Polyimide Fiber Hydrogen Bonding Strength
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Solution Overview
Problem
Existing methods for producing polyimide fibers by the two-step method face challenges in enhancing the strength and modulus of the fibers, limiting their high-temperature applications and industrial suitability.
Innovation Solution
A polyimide fiber production method involving a polymerization reaction between a dianhydride compound and a diamine compound, followed by spinning and sequential imidization and thermal drawing, incorporating a hydroxybenzoxazole or hydroxybenzothiazole structure to introduce hydrogen bonding and improve molecular chain arrangement, resulting in higher rigidity and crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the two-step method is used to prepare polyimide fibers, then processability and industrial suitability are improved, but the strength and modulus of the fibers are insufficient
Solution Approach 1:
The patent introduces specific structural parameters (hydroxybenzoxazole or hydroxybenzothiazole groups) into the polyimide molecular chain, which changes the chemical composition and enables hydrogen bonding. This parameter change resolves the contradiction by maintaining the two-step method's processability while significantly enhancing fiber strength and modulus through improved molecular interactions
Solution Approach 2:
The patent creates a composite molecular structure by incorporating hydroxybenzoxazole or hydroxybenzothiazole units into the polyimide backbone. This composite approach combines the processability benefits of conventional two-step polyimide synthesis with the enhanced mechanical properties provided by the specialized heterocyclic structures and their hydrogen bonding capabilities
2Productivity
If the two-step method is used to prepare polyimide fibers, then industrial production suitability is improved, but the modulus of the fibers is insufficient
Solution Approach 1:
By modifying the molecular structure to include hydroxybenzoxazole or hydroxybenzothiazole groups with specific hydrogen bonding capabilities, the patent achieves both high industrial production suitability through the two-step method and enhanced fiber modulus. The structural parameter change enables stronger intermolecular forces without compromising manufacturing processability
3Ease of operation
If conventional polyimide structures are used, then processing is easier, but high-temperature application performance is limited
Solution Approach 1:
The patent combines conventional polyimide processing characteristics with heterocyclic hydroxybenzoxazole or hydroxybenzothiazole structures that provide superior thermal stability. The composite molecular architecture maintains ease of processing through standard two-step methods while the specialized structures confer enhanced high-temperature performance through strong hydrogen bonding networks
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 method produces polyimide fibers with enhanced mechanical properties, including a highest strength of 4.5 GPa and modulus of up to 212 GPa, suitable for high-temperature applications in aerospace, defense, and other demanding fields, with improved process stability.
Implementation Method 1
subjecting a dianhydride compound and a diamine compound to a polymerization reaction in a solvent to obtain a polyamic acid solution
Implementation Method 2
subjecting the polyamic acid fiber to imidization and thermal drawing to obtain a polyimide fiber
Implementation Method 3
incorporating a hydroxybenzoxazole or hydroxybenzothiazole structure to introduce hydrogen bonding and improve molecular chain arrangement
Implementation Method 4
subjecting the polyamic acid fiber to imidization and thermal drawing to obtain a polyimide fiber
Data Source
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AI summary
This application provides a polyimide fiber and a preparation method thereof. This method comprises first subjecting a dianhydride compound and a diamine compound to a polymerization reaction in a solvent to obtain a polyamic acid solution, wherein said diamine compound comprises a diamine having a structure of Formula 12 or Formula 13, wherein A is S or O; said dianhydride compound comprises one or more of dianhydrides having structures of Formula 14 and Formula 15; and t is 0 or 1; then subjecting said polyamic acid solution to spinning to obtain a polyamic acid fiber; and sequentially subjecting said polyamic acid fiber to imidization and thermal drawing to obtain a polyimide fiber. The polyimide fiber having the above structure has a higher rigidity and can introduce a hydrogen bond to provide an interaction between molecular chains so as to influence the arrangement of the molecular chain in the polymer and the crystallinity, which imparts more excellent mechanical properties to the polyimide fiber. The polyimide fiber obtained has a higher glass transition temperature (Tg) and a better heat resistance.