High-Modulus Low-Shrinkage PET Yarn via Branched Diol Modification
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Solution Overview
Problem
Current methods for producing PET industrial yarns face challenges in achieving high modulus and low shrinkage due to the rigid molecular structure and high crystallinity of PET, which limits the diffusion of activation molecules and results in high thermal shrinkage and poor adhesion to rubber.
Innovation Solution
The method involves modifying PET through solid state polycondensation with tert-butyl branched heptanediol, followed by processes like viscosity enhancement, extrusion, stretching, heat setting, and relaxation heat-treating, to create a high-modulus-low-shrinkage PET industrial yarn with improved activation efficiency and reduced thermal shrinkage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If PET industrial yarn undergoes activation treatment at high temperature for long time to improve adhesion, then adhesion to rubber is improved, but fiber strength deteriorates due to tension relaxation
Solution Approach 1:
The patent changes the chemical composition parameter of PET by introducing tert-butyl branched heptanediol with specific molecular structure (formula I), which modifies the molecular chain flexibility and intermolecular distance. This chemical parameter change enables effective activation at lower temperatures (160-180°C) and shorter times (10-20 minutes), avoiding the high-temperature long-time treatment that causes fiber strength deterioration.
Solution Approach 2:
The patent creates a composite molecular structure by incorporating tert-butyl branched heptanediol into the PET polymer chain. This composite approach combines the rigidity of benzene rings with the flexibility of branched alkylene chains, optimizing both adhesion properties and mechanical strength retention during activation treatment.
2Stability of the object's composition
If PET undergoes tension heat setting to reduce shrinkage, then thermal shrinkage is reduced, but fiber length becomes fixed and unchangeable which restricts macromolecular chain folding and crystalline grain growth
Solution Approach 1:
The patent changes the molecular structure parameter by introducing tert-butyl branched heptanediol, which increases molecular chain flexibility and free volume. This enables the fiber to achieve low shrinkage (2.5-3.5%) without requiring excessive tension heat setting, as the modified molecular structure can accommodate thermal expansion better while maintaining the ability to fold and crystallize.
3Strength
If PET maintains high crystallinity and high orientation for high strength, then mechanical strength is improved, but diffusion of activation molecules is hindered reducing adhesion
Solution Approach 1:
The patent creates a composite molecular structure combining rigid benzene rings with flexible tert-butyl branched alkylene chains. This composite structure maintains high crystallinity and orientation for mechanical strength while the branched chains create intermolecular distance and free volume that facilitates diffusion of activation molecules, enabling both high strength and good adhesion.
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 approach results in PET industrial yarns with enhanced mechanical properties, reduced thermal shrinkage, and improved adhesion to rubber, achieving high activation efficiency at lower temperatures and shorter times while maintaining fiber strength.
Implementation Method 1
viscosity enhancing by solid state polycondensation
Implementation Method 2
relaxation heat-treating
Implementation Method 3
the diffusion of the activation molecules
Data Source
AI summary
A type of high-modulus-low-shrinkage activated PET industrial yarn and preparing method thereof are disclosed. The preparing method is to manufacture filament from a modified polyester, which is the product of the esterification and the successive polycondensation reactions of evenly mixed terephthalic acid, ethylene glycol and tert-butyl branched heptanediol, through a series of processes composed of viscosity enhancing by solid state polycondensation, melting, metering, extruding, cooling, oiling, stretching, heat setting, relaxation heat-treating, oiling with activation oil, winding and pre-activation treatment. The relaxation heat-treating indicates passing the modified polyester yarns through a space with a certain temperature within 200-220° C. under a proper relaxation state; and the proper relaxation state means a 3.0-5.0% of overfeed for the winding. The improvement of activator efficiency by importing the tert-butyl branched diol into the polyester, together with the synergistic effect of heat setting temperature and high winding overfeed rate, will reduce the fiber thermal shrinkage.