Methods for preparing polyurethane film and fabrics comprising the same
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Solution Overview
Problem
Existing polyurethane-based fabrics face challenges in achieving high mechanical strength while maintaining excellent moisture permeability and breathability, with conventional methods leading to uncontrolled cross-linking and poor performance in waterproof and moisture-permeability.
Innovation Solution
A method involving solvent vapor welding with additives and optimized process parameters for polyurethane fiber self-adhesion, combined with electrospinning technology, to create a polyurethane film with enhanced mechanical properties and moisture permeability, suitable for both needle-based and needle-free electrospinning devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coating process is used to prepare polyurethane fabrics, then waterproof and wear resistance is improved, but air permeability and moisture permeability deteriorate
Solution Approach 1:
The patent applies porous materials by creating a microporous structure through electrospinning technology. The polyurethane nanofibers form an interconnected porous network that allows air and water vapor to pass through while maintaining waterproofness against liquid water. This resolves the contradiction by enabling both waterproof protection and breathable comfort simultaneously.
Solution Approach 2:
The patent uses composite materials by combining polyurethane nanofibers with fabric substrates through electrospinning. The composite structure integrates the waterproof properties of polyurethane with the breathable characteristics of the fabric base, achieving both waterproof wear resistance and moisture permeability.
2Ease of operation
If electrospinning technology is used to create microporous structure, then moisture permeability and breathability are improved, but mechanical strength deteriorates
Solution Approach 1:
The patent applies parameter changes by optimizing the electrospinning parameters including voltage (15-30 kV), flow rate (0.1-1.0 mL/h), and receiving distance (10-20 cm). These parameter adjustments control the fiber morphology, diameter, and packing density to achieve an optimal balance between porosity for breathability and fiber density for mechanical strength.
Solution Approach 2:
The patent utilizes the curved, random arrangement of nanofibers formed during electrospinning to create a three-dimensional interconnected network. This curved fiber architecture provides structural integrity and mechanical strength while maintaining high porosity for moisture permeability, resolving the contradiction between strength and breathability.
3Strength
If solvent vapor welding is used to cross-link polyurethane fibers, then mechanical strength is improved, but cross-linking control deteriorates leading to poor waterproof and moisture-permeability performance
Solution Approach 1:
The patent applies feedback control by monitoring and adjusting the solvent vapor welding process parameters. The controlled evaporation rate of the solvent and the exposure time are optimized to achieve uniform cross-linking without over-cross-linking, which would compromise moisture permeability. This feedback mechanism ensures both mechanical strength and functional performance.
Solution Approach 2:
The patent uses periodic action by controlling the intermittent exposure of the electrospun membrane to solvent vapor. The controlled cycling of solvent vapor exposure allows gradual and uniform cross-linking of the polyurethane fibers, maintaining manufacturing precision while achieving the desired mechanical strength and waterproof-moisture permeable properties.
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 method produces a polyurethane film with high comfort and performance in waterproofing and moisture-permeability, suitable for outdoor clothing, by controlling fiber cross-linking and adjusting fiber shape, and enabling efficient transition from laboratory-scale to industrial-scale production.
Implementation Method 1
electrospinning technology enables polyurethane, in fiber form, to be coated on fabrics
Implementation Method 2
based on polyurethane fibers self-adhesion by optimized solvent vapor welding by addition of additives and optimization on process parameters
Implementation Method 3
providing interconnected channels for water vapor transmission, making the fabric breathable, moisture-permeable
Data Source
AI summary
The present invention discloses a method for preparing a polyurethane film, comprising the steps of: i) dissolving polyurethane into a first solvent to form a first solution; ii) dissolving salt into a second solvent to form a second solution; iii) preparing a spinning stock solution by mixing said first solution and said second solution; iv) spinning said spinning stock solution in an electrospinning device to obtain a polyurethane film; v) providing a container to which a third solvent is sprayed; and vi) arranging said polyurethane film in said container for a period of time.