PAN Fiber Densification via Progressive Wash Bath Heating
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Solution Overview
Problem
The existing carbon fiber manufacturing process often results in a decrease in fiber network density during the spinning stage, leading to potential defects and reduced tensile strength in the final carbon fiber product, as indicated by increasing fiber swelling values in the first wash/draw bath before they decrease in subsequent baths.
Innovation Solution
A progressive densification process is implemented during the spinning stage, where the acrylic fibers are drawn through a series of heated wash baths with increasing temperatures, and the stretching is relaxed in the last bath, maintaining or increasing fiber network density without solvent removal issues or stretching problems, thereby enhancing tensile strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional spinning process with heated wash baths is used, then solvent removal and fiber stretching are achieved, but fiber network density decreases leading to reduced tensile strength
Solution Approach 1:
The patent applies parameter changes by precisely controlling wash bath temperatures and draw ratios at each spinning stage. The temperature is increased progressively through multiple baths (e.g., 60°C, 80°C, 100°C) while adjusting draw ratios to maintain fiber network density. This controlled parameter progression allows solvent removal and stretching without causing excessive density loss that would reduce tensile strength.
Solution Approach 2:
The spinning process is segmented into multiple sequential wash baths rather than a single bath. Each bath performs a specific function with controlled temperature and draw ratio parameters. This segmentation allows progressive solvent removal and controlled stretching while maintaining fiber network density at each stage, ultimately preserving tensile strength.
2Strength
If fiber stretching is increased during spinning, then fiber orientation and strength are improved, but fiber network density decreases causing defects
Solution Approach 1:
The patent applies dynamics by making the draw ratio adjustable and variable across different washing stages rather than applying a fixed stretch. The draw ratio is optimized at each wash bath stage to achieve appropriate fiber orientation without excessive stretching that would compromise network density. This dynamic adjustment maintains both fiber strength and manufacturing precision.
3Productivity
If wash bath temperature is increased, then solvent removal efficiency is improved, but fiber swelling increases reducing network density
Solution Approach 1:
The washing process is divided into multiple sequential baths with progressively increasing temperatures. This segmentation allows efficient solvent removal through cumulative effect of multiple lower-temperature baths rather than a single high-temperature bath, thereby maintaining fiber network density while achieving high productivity in solvent removal.
Solution Approach 2:
The patent applies parameter changes by optimizing both temperature and time parameters across multiple wash baths. The cumulative solvent removal effect of multiple baths at controlled temperatures achieves high efficiency without the adverse effect of excessive fiber swelling that would occur in a single high-temperature bath.
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
This approach results in carbon fibers with higher tensile strength and retained Young's modulus, as demonstrated by increased tensile strength of up to 744 ksi compared to the control method, while maintaining the same Young's modulus, and achieving the same final fiber network density without unnecessary loss of density in intermediate draw baths.
Implementation Method 1
the acrylic fibers are drawn through a series of heated wash baths with increasing temperatures
Implementation Method 2
A progressive densification process is implemented during the spinning stage, where the acrylic fibers are drawn through a series of heated wash baths
Data Source
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AI summary
Provided herewith is a process for improving tensile strength of precursor PAN fiber during the spinning stage in the manufacturing process. According to the process of the present invention, precursor fiber is made denser as it enters each wash bath. This progressive densification approach is useful for all PAN precursor bath draw/wash processes where a need for careful control of fiber network density and structure is required for improved carbon fiber properties.