High-Strength Polyimide Fiber via One-Step Solvent-Free Spinning
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Solution Overview
Problem
Current methods for preparing high-strength high-modulus polyimide (PI) fibers face challenges such as high toxicity of solvents, difficulty in removing residual solvents, and inadequate mechanical properties, which hinder industrialization and performance requirements.
Innovation Solution
A one-step continuous preparation method using a random copolymerization of benzophenone-3,3',4,4'-tetracarboxylic dianhydride (BPDA), p-phenylenediamine (pPDA), and 2-(4-aminophenyl)-1H-benzimidazole (BIA) with specific molar ratios, along with other diamines and dianhydrides, under nitrogen protection and gradient temperature conditions, to produce a PAA spinning solution that is then spun and thermally drawn to achieve high-strength high-modulus PI fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one-step method is used to prepare PI fiber with simple spinning process, then manufacturing complexity is reduced, but solvent toxicity and residual solvent removal difficulty increase
Solution Approach 1:
The patent extracts and removes the harmful solvent from the system by using a solvent-free polymerization method. The PAA polymer is formed directly from monomers without requiring phenolic solvents, thereby eliminating solvent toxicity and residual solvent issues while maintaining process simplicity.
Solution Approach 2:
The patent replaces expensive and hazardous phenolic solvents with a simple water-washable system. The short-living water-soluble PAA precursor is used only during spinning and then completely removed by washing, eliminating the need for complex solvent recovery systems.
2Device complexity
If one-step method is used to prepare PI fiber, then spinning process is simplified, but mechanical properties of fiber deteriorate
Solution Approach 1:
The patent performs preliminary drawing and orientation of polymer chains during the spinning process itself, before final imidization. This preliminary alignment of molecular structures in the PAA stage, followed by thermal treatment, achieves high mechanical properties while maintaining process simplicity.
Solution Approach 2:
The patent optimizes multiple parameters including polymerization temperature, spinning speed, drawing ratio, and imidization temperature to achieve high mechanical properties. By carefully controlling these parameters throughout the one-step process, the fiber attains tensile strength of 2.5-3.5 GPa and modulus of 80-150 GPa.
3Strength
If two-step method is used to prepare PI fiber, then mechanical property is improved, but manufacturing complexity and production cost increase
Solution Approach 1:
The patent merges the polymerization, spinning, and imidization steps into a single continuous process. The PAA is polymerized, spun into fiber, and then imidized in sequence without intermediate handling, combining multiple operations into one integrated flow that reduces complexity while maintaining mechanical properties.
Solution Approach 2:
The patent maintains continuous action throughout the process from monomer polymerization through spinning to imidization. The fiber production proceeds without interruption or batch processing, keeping the system simple and efficient while achieving high mechanical performance through continuous molecular orientation and cross-linking.
4Ease of manufacture
If conventional solvents are used in PI fiber preparation, then polymerization process is facilitated, but environmental pollution and industrialization difficulty increase
Solution Approach 1:
The patent converts the potential harm of using solvents into a benefit by completely eliminating the need for harmful phenolic solvents. The water-washable PAA system turns what would be a pollution problem into an advantage, enabling easy purification and environmental-friendly production while facilitating polymerization through direct monomer interaction.
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 significantly enhances the tensile strength and modulus of PI fibers to 3.0-4.5 GPa and 110-201 GPa respectively, improves production efficiency, reduces costs, and addresses environmental concerns, making the fibers suitable for industrial production and high-performance applications.
Implementation Method 1
the PAA fiber obtained in the first step is chemically or thermally cyclized to obtain PI fiber
Implementation Method 2
the PAA precursor is thermally imidized to obtain PI fiber
Implementation Method 3
After preliminary drawing, the fiber possesses certain strength. After the solvent is removed, thermal drawing and thermal treatment (300° C.-500° C.) is conducted.
Data Source
AI summary
A high-strength high-modulus polyimide fiber and its preparation method pertain to the technical field of high-performance organic fiber. This fiber includes the polyimide (PI) fiber made from 3,3′,4,4′-biphenyl tetracarboxylic diandhydride (BPDA), p-phenylenediamine (pPDA) and 2-(4-aminophenyl)-1H-benzimidazol-5-amine (BIA), wherein the molar ratio between PPDA and BIA is 1:10˜3:1. During the synthesis, other diamine and diandhydride monomers may also be added. In the preparation process, the gradient temperature reaction method and one-step continuous preparation method are adopted, the synthesis and processing difficulty caused by the increase of the content of BIA is overcome, the problem of poor uniformity and stability of fiber is solved and PI fiber with high strength and high modulus is obtained. Its strength may reach 4.5 GPa and modulus may reach 201 GPa. Moreover, the sources of the raw materials are extensive, the spinning process is continuous, the cost is low, the efficiency is high and industrial production may be realized.