Nanofiber Sheet Bonding for Strength and Surface Area
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Solution Overview
Problem
Existing nanofiber sheets have low mechanical strength and specific surface area due to physical entanglement, and previous methods for improving strength, such as partial bonding treatments, face challenges in temperature control and result in large pore diameters unsuitable for filtering fine substances.
Innovation Solution
A nanofiber sheet with a bulk portion formed by bonding of nanofibers, where 7×10−3 portion/μm2 or more of the bulk portion satisfies the formula 0.5πX2≤Y≤5 μm2, providing high mechanical strength and specific surface area, achieved through a combination of physical and chemical associations of nanofibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If physical entanglement of nanofibers is used, then the nanofiber sheet can be formed easily, but the mechanical strength is low
Solution Approach 1:
The patent creates a composite structure where nanofibers are bonded together through bulk portions formed by thermal treatment. This combines the ease of nanofiber formation with enhanced mechanical strength through the bonded network, transforming the simple physical entanglement into a composite material system with improved properties.
Solution Approach 2:
The patent applies thermal treatment to change the physical state of nanofibers, transforming them from a loose entangled state to a bonded state with bulk portions. This parameter change (temperature application) resolves the contradiction by maintaining ease of formation while significantly improving mechanical strength through controlled thermal bonding.
2Strength
If partial bonding treatment is applied to improve mechanical strength, then the nanofiber structural body gains strength, but the temperature control is difficult and nanofibers may melt or fail to bond
Solution Approach 1:
The patent defines a specific temperature range (50°C to 100°C below the melting point) for thermal treatment, transforming the uncertain bonding process into a controlled parameter change. This resolves the temperature control difficulty by providing precise guidance that prevents both failure to bond and excessive melting.
Solution Approach 2:
The patent applies partial bonding treatment but controls it to create bulk portions of specific size (0.5πX² ≤ Y ≤ 5 μm²) rather than complete fusion. This partial action approach improves strength while preventing excessive melting that would occur with uncontrolled thermal treatment.
3Strength
If nanofibers are thermally bonded to improve strength, then mechanical strength increases, but the specific surface area decreases due to large pore diameters
Solution Approach 1:
The patent creates localized bulk portions at specific locations where nanofibers intersect, rather than uniform bonding throughout. This local quality approach bonds nanofibers only where necessary to improve strength while preserving the high specific surface area in the remaining regions, resolving the contradiction between strength and surface area.
Solution Approach 2:
The patent applies partial bonding to create bulk portions of controlled size (0.5πX² ≤ Y ≤ 5 μm²) rather than complete thermal fusion. This partial action provides sufficient mechanical strength while maintaining the porous structure and high specific surface area necessary for filtration applications.
4Productivity
If melt electrospinning is used to form extra-fine composite fibers, then fiber production is achieved, but large pore diameters result and fine substance leakage occurs
Solution Approach 1:
The patent applies thermal treatment at controlled temperatures to change the physical state of nanofibers and create bulk portions that reduce pore diameters. This parameter change transforms the production process to maintain high productivity while improving reliability by preventing fine substance leakage through the bonded structure.
Solution Approach 2:
The patent creates a composite structure with bulk portions formed by bonding nanofibers together. This composite approach maintains the productivity of fiber production while creating a more reliable structure with reduced pore diameters that prevents fine substance leakage.
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 nanofiber sheet exhibits enhanced mechanical strength, durability, and specific surface area, suitable for long-term use and applications like dust collection filters, with improved wind pressure durability and air permeability.
Implementation Method 1
a bulk portion produced by bonding of the nanofibers
Data Source
AI summary
Provided is a nanofiber sheet that has a high mechanical strength, is excellent in durability, and has a high specific surface area. The nanofiber sheet includes: a plurality of nanofibers; and a bulk portion produced by bonding of the nanofibers, in which 7×10−3 portion/μm2 or more of the bulk portion satisfying the following formula is contained:0.5πX2≤Y≤5 μm2 (1)where X represents a diameter (μm) of each of the nanofibers and Y represents an area (μm2) of an inscribed circle of the bulk portion when viewed from a surface.