Aramid Yarn Two-Step Heating for Higher Tenacity
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Solution Overview
Problem
Conventional two-step heating processes for producing high-tenacity aramid yarns with higher DAPBI content or lower Cl-PPD content result in unfavorable yarn properties due to uncontrolled tension and temperature variations, leading to suboptimal tenacity levels.
Innovation Solution
A method involving two distinct heating steps with controlled tension and temperature, where the yarn is first heated at 200-360°C at a tension of at least 0.2 cN/dtex, followed by a second heating at 370-500°C at a tension of less than 1 cN/dtex, without intermediate winding or unwinding, to achieve consistent and high tenacity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single heating step at high temperature (450°C) is used, then the process is simple and fast, but the tenacity of the yarn is insufficient
Solution Approach 1:
The heating process is divided into two distinct steps: a first heating step at 200-360°C to set the yarn structure, followed by a second heating step at 370-500°C to achieve high tenacity. This segmentation allows each step to perform its specific function optimally, resulting in yarn with tenacity of at least 2500 mN/tex while maintaining process efficiency
2Ease of manufacture
If a two-step heating process with intermediate winding is used, then the yarn can be processed, but uncontrolled tension and temperature variations occur leading to suboptimal tenacity
Solution Approach 1:
The yarn is heated in two steps without intermediate winding or unwinding, maintaining continuous processing. The first heating step at 200-360°C is followed directly by the second heating step at 370-500°C, eliminating tension variations and temperature fluctuations that would occur with intermediate handling, thereby achieving consistent high tenacity
Solution Approach 2:
The process uses controlled parameter changes with specific temperature ranges (200-360°C then 370-500°C) and tension control (at least 0.2 cN/dtex then less than 1 cN/dtex) for each heating step, optimizing the thermal and mechanical conditions to achieve tenacity of at least 2500 mN/tex without intermediate processing disruptions
3Strength
If higher DAPBI content is used to improve yarn properties, then better performance is achieved, but conventional heating processes result in unfavorable yarn properties
Solution Approach 1:
The first heating step at 200-360°C performs a preliminary heating action that sets the yarn structure before the final high-temperature treatment. This preliminary action prepares the yarn with higher DAPBI content for the subsequent heating at 370-500°C, ensuring favorable and consistent yarn properties with tenacity of at least 2500 mN/tex
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 method significantly increases the tenacity of aramid yarns by up to 200 mN/tex compared to conventional one-step processes, achieving tenacities of at least 2500 mN/tex with optimal DAPBI and PPD content, and maintaining high sulfur content and low hydrogen chloride levels.
Implementation Method 1
the running yarn is heated in at least two process steps, characterized in that in a first step the yarn is heated at a temperature of 200 to 360° C.
Implementation Method 2
followed by a second step wherein the yarn is heated at a temperature of 370 to 500° C.
Implementation Method 3
at a tension of at least 0.2 cN/dtex, followed by a second step wherein the yarn is heated at a temperature of 370 to 500° C. at a tension of less than 1 cN/dtex
Data Source
AI summary
The invention relates to a method for obtaining high-tenacity aramid yarn, wherein the yarn is made of a copolymer obtained from a mixture of monomers comprising DAPBI, an aromatic para-diamine, and an aromatic para-diacid, wherein the yarn is heated in at least two process steps, characterized in that in a first step the yarn is heated at a temperature of 200 to 360° C. at a tension of at least 0.2 cN/dtex, followed by a second step wherein the yarn is heated at a temperature of 370 to 500° C. at a tension of less than 1 cN/dtex. The invention further pertains to a multifilament aramid yarn spun from a sulfuric acid spin dope and having a tenacity of at least 2500 mN/tex.