Ultra-fine Polypropylene Multifilaments via Nucleating Agent and Drawing
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Solution Overview
Problem
Current methods for producing ultra-fine, high tenacity and high toughness multifilaments from semi-crystalline melt-extrudable/spinnable thermoplastic polymers, such as polypropylene, fail to achieve diameters of 10 μm or less with sufficient tensile strength and toughness, and are not scalable to industrial levels.
Innovation Solution
A composition comprising semi-crystalline thermoplastic polymers like isotactic polypropylene with high molecular weight and a sorbitol-based nucleating agent, combined with antioxidants, is melt-spun and subjected to multiple drawing and annealing cycles under controlled temperatures and winding ratios to produce multifilaments with diameters of 4 to 10 μm, tensile strength greater than 1 GPa, and toughness of over 100 MJ/m3.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional melt-extrusion methods are used to produce ultra-fine multifilaments, then the filament diameter can be reduced, but the tensile strength and toughness become insufficient
Solution Approach 1:
The patent applies parameter changes by carefully controlling the molecular weight of the polypropylene (300-800 kDa), the concentration of nucleating agent (0.1-1.0 wt%), and the processing temperatures during extrusion and drawing. These parameter optimizations enable the production of ultra-fine filaments (≤10 μm) while maintaining high tensile strength (>1 GPa) and toughness (>100 MJ/m³) by achieving the right balance between filament fineness and mechanical properties
Solution Approach 2:
The patent creates a composite system by combining high molecular weight polypropylene with sorbitol-based nucleating agents and antioxidants in specific ratios. This composite composition enhances both the processability and mechanical properties of the ultra-fine multifilaments, resolving the contradiction between reducing diameter and maintaining strength through synergistic material combinations
2Strength
If hand drawing at slow speed is used to improve monofilament tenacity, then the tensile strength increases, but the productivity decreases and the method is not scalable to industrial level
Solution Approach 1:
The patent replaces the manual hand drawing process with an automated extrusion and drawing system that uses controlled mechanical drawing ratios (1.5-3.0) and optimized drawing speeds. This substitution maintains high tenacity through proper mechanical drawing while enabling industrial-scale production with significantly improved productivity and consistency
Solution Approach 2:
The patent optimizes processing parameters including extrusion temperature (180-220°C), drawing temperature, and drawing ratio to achieve high tenacity through automated processing. These parameter changes enable the transition from slow hand drawing to fast automated drawing while maintaining or improving mechanical properties
3Strength
If storage at glass transition temperature for several days is performed, then the monofilament tenacity improves, but the production time increases and the process complexity increases
Solution Approach 1:
The patent incorporates nucleating agents and antioxidants into the polymer composition before extrusion, performing preliminary actions that enable direct production of high-performance ultra-fine multifilaments without requiring extended storage or post-processing treatment. This preliminary formulation allows the material to achieve optimal properties immediately after processing
4Strength
If sorbitol-based nucleating agent is added to improve modulus and tenacity, then the mechanical properties increase, but the elongation decreases and the filament diameter remains above 20 μm
Solution Approach 1:
The patent optimizes the nucleating agent concentration (0.1-1.0 wt%) and selects appropriate types (sorbitol-based, phosphoric acid-based, or carboxylic acid-based) to achieve fine filament diameter (≤10 μm) while maintaining high mechanical properties. The controlled nucleation density and crystal growth are key to resolving the contradiction between diameter reduction and property maintenance
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 achieves multifilaments with enhanced tensile strength and toughness, meeting industrial scalability requirements while maintaining a small diameter, through the controlled processing of semi-crystalline polymers, specifically achieving tensile strength greater than 1 GPa and toughness of at least 100 MJ/m3.
Implementation Method 1
at least one polymer which is not amorphous but preferably semi-crystalline for forming multifilaments
Implementation Method 2
a sorbitol-based nucleating agent
Implementation Method 3
subjected to multiple drawing and annealing cycles
Data Source
AI summary
The present invention provides a composition and method for forming polymeric multifilaments having a filament diameter of no more than 10 μm with a high tensile strength and toughness. The composition includes at least one semi-crystalline thermoplastic polymer and a nucleating agent to stabilize the multifilaments during melt-spinning and facilitate phase transformation of the thermoplastic polymer in subsequent drawing and annealing cycles. The method includes a quenching step for the melt-spun filaments immediately after the melt-spinning and collection of the quenched filaments with a specific winding speed to decrease the filament diameter. The subsequent drawing and annealing cycles further enhance the mechanical properties of the filaments after the quenching.