VDF Polymer Dispersion With Iodine-Controlled Low Gel Formation
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Solution Overview
Problem
High molecular weight vinylidene fluoride (VDF) polymers produced through emulsion polymerization often contain gels and insoluble fractions due to long chain branches and defects, which hinder their use in electrochemical cell components and membrane manufacturing, as they exhibit non-negligible gel content and peculiar rheological behavior.
Innovation Solution
An aqueous dispersion of VDF polymer with iodine-containing chain ends and a weight-averaged molecular weight of at least 500 kDalton, processed via emulsion polymerization with an inorganic initiator and an iodine-containing chain transfer agent, maintaining a specific melt viscosity to weight-averaged molecular weight ratio, resulting in a quasi-linear structure and reduced gel content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If emulsion polymerization is used to produce high molecular weight VDF polymers, then the polymerization temperature can be reduced and pressure lowered, but the polymers contain gels and insoluble fractions due to long chain branches and defects
Solution Approach 1:
The patent changes the chemical parameter by introducing iodine-containing chain transfer agents to control the polymerization process. This chemical modification allows achieving high molecular weight while suppressing long chain branch formation and gel content, thus resolving the contradiction between low temperature polymerization and polymer purity
Solution Approach 2:
The iodine-containing chain transfer agent acts as an intermediary substance that mediates the polymerization process. It controls chain growth and termination, preventing excessive branching and gel formation while maintaining high molecular weight, thereby enabling pure polymer production at reduced temperatures
2Quantity of substance
If higher molecular weight is targeted in emulsion polymerization, then the polymer properties improve for electrochemical applications, but the number of inversions and branches increases
Solution Approach 1:
The patent modifies the chemical parameters by using iodine-containing chain transfer agents with specific structures and ratios. This enables achieving high molecular weight (Mw ≥ 500 kDalton) while maintaining structural regularity with minimal inversions and branches, as the chain transfer agent controls the polymerization kinetics to favor linear chain growth
3Ease of manufacture
If emulsion polymerized VDF polymers are used, then economic and environmental advantages are gained, but the polymers exhibit peculiar rheological behavior and non-negligible gel content
Solution Approach 1:
The patent changes the chemical composition parameters by incorporating iodine-containing chain transfer agents and controlling their ratio with the initiator. This produces polymers with Mw ≥ 500 kDalton and specific melt viscosity characteristics that provide good rheological behavior and processing properties while maintaining the economic and environmental benefits of emulsion polymerization
4Reliability
If VDF polymers with high molecular weight are produced, then durability and chemical inertia are improved, but solubility and processing become difficult due to gels and insoluble fractions
Solution Approach 1:
The patent modifies the polymer structure parameters by using iodine-containing chain transfer agents to control chain growth. This produces high molecular weight polymers (Mw ≥ 500 kDalton) with minimal gel content and improved solubility, enabling both durability and ease of processing in electrochemical applications
Solution Approach 2:
The patent converts the potential harm of high molecular weight (which usually causes poor solubility) into a benefit by using chain transfer agents to create controlled architectures. The result is high molecular weight polymers that remain soluble and processable, turning the usual disadvantage into an advantage
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 VDF polymers with improved solubility and moderate liquid viscosity, suitable for electrochemical cell components and membrane manufacturing, while minimizing gel content and long chain branches, enhancing processing efficiency and performance.
Implementation Method 1
emulsion polymerization of VDF in an aqueous medium in the presence of an inorganic initiator
Implementation Method 2
emulsion polymerization of VDF in an aqueous medium in the presence of an inorganic initiator and an iodine-containing chain transfer agent
Data Source
AI summary
The present invention pertains to an aqueous dispersion of a vinylidene fluoride polymer having a high molecular weight and possessing a substantially linear structure, leading to reduced amount of gels/insoluble fractions, to a method for its preparation and to its use for the manufacture of electrochemical cell components, such as electrodes and/or composite separators or for the manufacture of membranes.