Flash-Spun Plexifilamentary Strands for Barrier Protection
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Solution Overview
Problem
Existing protective apparel materials lack sufficient resilience and low crystallinity to effectively provide barrier protection against liquids and fine particles while maintaining durability and breathability, and to enhance bonding with other layers.
Innovation Solution
Flash-spun plexifilamentary fiber strands with a total crystallinity index of less than or equal to 55%, a BET surface area of less than 12 m^2/g, and a crush value of greater than or equal to 0.9 mm/g, predominantly formed from homopolymers of ethylene, which can be consolidated into sheets and optionally thermally or mechanically bonded.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the material has high crystallinity to provide strength and barrier protection, then strength and barrier protection are improved, but resilience and bonding capability deteriorate
Solution Approach 1:
The patent applies parameter changes by controlling the crystallinity index within a specific range (30-55%) rather than maximizing it. This optimized parameter range achieves a balance where the material has sufficient crystallinity for strength and barrier protection (blocking liquids and fine particles) while maintaining low enough crystallinity to preserve resin flow properties for bonding and provide resilience. The flash spinning process parameters (temperature, pressure, spin agent composition) are also adjusted to achieve this optimal crystallinity range.
2Reliability
If the material has low crystallinity to enhance bonding and resilience, then bonding capability and resilience are improved, but strength and barrier protection deteriorate
Solution Approach 1:
The patent resolves this contradiction by establishing a minimum crystallinity threshold (30-55%) that ensures adequate strength and barrier protection while remaining low enough to maintain bonding capability. The flash spinning process creates a specific crystalline structure with controlled crystal size and distribution that provides mechanical strength without excessive crystallinity. The surface area control (5-50 m²/g) also contributes to maintaining appropriate bonding surfaces.
3Object-affected harmful factors
If the material provides dense barrier protection against liquids and particles, then barrier protection is improved, but breathability and moisture transmission deteriorate
Solution Approach 1:
The patent utilizes porous materials by creating a controlled pore structure through flash spinning that allows moisture vapor transmission while blocking liquid penetration. The fibrillar network formed during flash spinning creates interstices that permit breathability but are too small or poorly connected to allow liquid passage. The crystallinity control (30-55%) influences pore size and distribution, creating a structure that provides barrier protection against liquids and fine particles while maintaining moisture vapor transmission for breathability.
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 solution provides enhanced resilience, improved barrier protection, and effective bonding, allowing the material to recover its shape and maintain integrity under stress, while also transmitting moisture and heat, making it suitable for various protective applications.
Implementation Method 1
flash-spinning the spin fluid to form plexifilamentary film-fibril strands
Data Source
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AI summary
A flash-spun plexifilamentary fiber strand having a BET surface area of less than 12 m2?/g, a crush value of at least 0.9 mm/g wherein said fiber strand comprises predominantly fibers formed from polyethylene, said fibers having a total crystallinity index of less than 55 %, and sheets made thereof.