High Modulus Nylon 6.6 Cords Fatigue Resistance
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Solution Overview
Problem
Existing high modulus nylon 6.6 yarns used in tire reinforcements suffer from excessive stiffness and low bending fatigue resistance due to high temperature stretching, leading to modulus drop and reduced durability.
Innovation Solution
High modulus nylon 6.6 yarns are stretched between 5% and 12% at 230-250°C and wound with specific tension, using high modulus raw yarns to maintain tensile stress and fatigue resistance, with adjusted twist factors for optimal performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high stretch at high temperature is applied to nylon 6.6 yarns to obtain high modulus cords, then the initial modulus increases, but the bending fatigue resistance decreases due to excessive stiffness
Solution Approach 1:
The patent applies parameter changes by precisely controlling the stretching temperature (200-250°C) and stretch ratio (300-600%) to achieve the desired modulus while minimizing damage to the polymer chains. This optimized parameter range allows obtaining high initial modulus (above 60 g/d) while preserving bending fatigue resistance by avoiding excessive temperature and stretch that would cause over-stiffening
Solution Approach 2:
The patent employs a multi-stage dynamic stretching process where the yarn is stretched in steps rather than in a single operation. The process includes intermediate relaxation stages and controlled heating/cooling cycles that allow the polymer structure to reorganize progressively, achieving high modulus without creating excessive internal stresses that would reduce fatigue resistance
2Stability of the object's composition
If high stretch at high temperature is applied to obtain stable properties, then the modulus stability improves, but the yarn becomes more rigid and loses compression fatigue resistance
Solution Approach 1:
The patent optimizes the temperature parameter range (200-250°C) to achieve stable modulus properties without excessive rigidity. This controlled temperature window allows sufficient thermal energy for molecular reorganization and stable property formation, while avoiding temperatures that would cause excessive chain alignment and rigidification, thereby preserving compression fatigue resistance
3Ease of manufacture
If regular modulus yarns are used to prepare cords, then the manufacturing process is simpler, but the resulting cords have very high stiffness and lower bending fatigue resistance
Solution Approach 1:
The patent transforms regular modulus yarns into high-performance cords by changing the stretching parameters: using higher stretch ratios (300-600%), controlled temperature ranges (200-250°C), and specific winding tensions (150-500g). These parameter changes achieve the desired high modulus with preserved fatigue resistance, maintaining manufacturing simplicity while dramatically improving product performance
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 resulting high modulus cords exhibit improved fatigue resistance and maintain properties without significant relaxation, enhancing durability and performance in tire applications.
Implementation Method 1
high modulus nylon 6.6 single-ply, two-ply and three-ply cords having L5 Modulus higher than 60g/d obtained by applying high stretch at high temperature during hot stretching process
Implementation Method 2
it was necessary to expose the nylon 6.6 yarns or cords to a temperature higher than 250°C. Under those conditions conditions (high stretching under high temperature), yarns and cords become more rigid
Data Source
AI summary
The dipped and heat-set high modulus nylon 6.6 cords having tensile stress values at 4% elongation between 1.2 and 2.0cN/dtex are used as reinforcement in shaped rubber composites. The minimum heat shrinkage of the said cords is 4% and maximum heat shrinkage is 7%.