Polyimide Fiber Production via Coagulation Alleviation
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Solution Overview
Problem
Existing methods for producing polyimide fibers are limited to using soluble polyimides, restricting the range of polyimide components and resulting in fibers with suboptimal physical properties, such as strength and thermal expansion.
Innovation Solution
A method involving a polyimide precursor solution with a compound having specific acid dissociation and octanol-water partition coefficients, which acts as both a coagulation alleviating agent and an imidization promoter, allowing the production of polyimide fibers with improved physical properties by using an aqueous coagulation bath and heat drawing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If soluble polyimide is used as fiber material, then wet spinning can be performed, but the type of polyimide component is limited and desired physical properties cannot be obtained
Solution Approach 1:
The invention changes the chemical structure parameters of polyimide by introducing specific moieties (biphenyltetracarboxylic acid dianhydride and toluene diisocyanate or diaminotoluene) to achieve both insolubility and enhanced physical properties. This allows using a wider range of polyimide components while maintaining fiber strength.
Solution Approach 2:
The invention creates a composite polyimide structure by combining different chemical components (aromatic tetracarboxylic acid dianhydride with diamine or diamino compound) to achieve synergistic effects that provide both processability and superior physical properties including strength and heat resistance.
2Strength
If soluble polyimide is used, then fiber production is feasible, but physical properties such as strength and thermal expansion are suboptimal
Solution Approach 1:
The invention modifies the chemical parameters of polyimide by introducing specific rigid moieties that enhance strength and thermal stability while maintaining processability through controlled synthesis methods, thereby improving physical properties without sacrificing manufacturing feasibility.
3Temperature
If conventional polyimide structure is used, then production is straightforward, but heat resistance is insufficient
Solution Approach 1:
The invention changes the thermal parameters of polyimide by incorporating aromatic rings and rigid molecular structures (biphenyltetracarboxylic acid dianhydride with toluene diisocyanate or diaminotoluene) that significantly raise the glass transition temperature and decomposition temperature, achieving superior heat 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 method enables the production of polyimide fibers with desirable properties like thermal stability, strength, and reduced moisture regain, suitable for applications like fiber-reinforced plastics, while expanding the range of usable polyimide components.
Implementation Method 1
a coagulation step of forming a polyimide precursor fiber by extruding a polyimide precursor solution containing a polyimide precursor and a compound having an acid dissociation constant (pKa) of a conjugate acid in water at 25°C in the range of 6.0 to 10 inclusive and an octanol-water partition coefficient (Log P) at 25°C in the range of -0.55 to 0.24 inclusive into a nonsolvent for the polyimide precursor
Implementation Method 2
Subsequent heat treatment is carried out at temperature not higher than 360°C
Data Source
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AI summary
The method for producing a polyimide fiber includes a coagulation step of forming a polyimide precursor fiber by extruding a polyimide precursor solution containing a polyimide precursor and a compound having an acid dissociation constant (pKa) of a conjugate acid in water at 25°C of 6.0 to 10 inclusive and an octanol-water partition coefficient (Log P) at 25°C of -0.75 to 0.75 inclusive into a poor solvent or nonsolvent for the polyimide precursor; and a heat drawing step of forming the polyimide fiber by drawing the polyimide precursor fiber while heating same. The polyimide fiber of the present disclosure has a physical property such that the coefficient of thermal expansion thereof is in the range of -15 ppm/K to 0 ppm/K inclusive.