Co-extruded Monofilament String with Polyamide Core and Sheath
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Solution Overview
Problem
Monofilament strings for rackets face challenges in achieving a balance between power, control, comfort, and durability, with existing materials either compromising on power for control or degrading quickly, and existing solutions like composite materials increasing durability at the expense of power.
Innovation Solution
A monofilament string design featuring a core made of polyamide 6 and a copolymer of polyamide 6 and 6.6, with a sheath of the same copolymer, where the core has a higher tensile modulus than the sheath, and the string is manufactured through co-extrusion and stretching processes to enhance mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If monofilament strings are made of polyethylene or polyester to achieve high stiffness and good control, then control properties are improved, but power properties worsen as players need high physical strength to accelerate the ball
Solution Approach 1:
The string is segmented into a core and a sheath with different material compositions. The core uses polyethylene or polyester for stiffness and control, while the sheath uses a softer material to provide power and comfort, allowing both properties to coexist without compromise
Solution Approach 2:
The invention uses composite materials by combining polyethylene or polyester core with a polyamide-based sheath containing elastomeric copolymer. This composite structure integrates the high stiffness of polyethylene/polyester with the high elasticity and vibration-dissipating properties of polyamide, achieving both control and power
2Ease of operation
If monofilament strings are made of polyamide to achieve good vibration dissipation and comfort, then comfort properties are improved, but durability properties worsen as strings degrade and lose tension fast
Solution Approach 1:
The string structure is segmented into a durable core and a comfort-providing sheath. The core uses polyethylene or polyester for durability and tension retention, while the sheath uses soft polyamide material for comfort and vibration dissipation
Solution Approach 2:
The composite structure combines the durability of polyethylene/polyester core with the comfort properties of polyamide sheath, allowing the string to maintain tension over time while providing excellent vibration dissipation and player comfort
3Reliability
If intermediate reinforcing layer is added to increase rigidity and durability, then durability properties are improved, but power properties worsen as the ability to bend at impact is reduced
Solution Approach 1:
Instead of uniformly increasing rigidity throughout the string, the invention applies local quality by using a softer sheath material surrounding the core. This allows the core to provide structural durability while the sheath maintains local flexibility and bending ability at impact points for power
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 string achieves a balance between power and control, maintains tension over time, and reduces vibrations, providing improved comfort and durability while allowing for efficient ball acceleration and control.
Implementation Method 1
the first material having a greater tensile modulus than the second material
Implementation Method 2
a sheath extending around the core and in contact with the core, wherein the core is made of a first material comprising polyamide 6 and a first copolymer of polyamide 6 and polyamide 6.6, the sheath is made of a second material comprising a second copolymer of polyamide 6 and polyamide 6.6
Data Source
AI summary
The present invention relates to a monofilament string for a racket, comprising a core consisting of a single filament and a sheath extending around the core and in contact with the core, the monofilament string being characterized in that:the core (2) is made of a first material comprising polyamide 6 and a first copolymer of polyamide 6 and polyamide 6.6,the sheath (3) is made of a second material comprising a second copolymer of polyamide 6 and polyamide 6.6,the first material having a greater tensile modulus than the second material.The present invention also related to a process for manufacturing such a filament string, by co-extrusion of the core and the sheath and stretching of the co-extruded string.