Fluorine Elastomer Blend Segmentation for Low Hardness and Processability
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Solution Overview
Problem
Existing fluorine-containing elastomer blends for sealing materials face challenges in achieving low hardness and low modulus while maintaining excellent roll processability and physical properties.
Innovation Solution
A blend of high-molecular-weight, medium-molecular-weight, and low-molecular-weight fluorine-containing elastomers, with specific molecular weight ranges and ratios, is used, along with controlled polymerization and chain transfer agents to achieve the desired properties, and vulcanization with polyol-based or organic peroxide-based crosslinking agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a fluorine-containing elastomer with high molecular weight is used to improve physical properties, then strength and durability are improved, but roll processability deteriorates
Solution Approach 1:
The elastomer is segmented into multiple molecular weight populations (three peaks in GPC curve) where each population contributes differently: high molecular weight for physical properties, medium for processability, and low for extrudability. This segmentation resolves the contradiction by distributing functions across different molecular weight segments rather than relying on a single molecular weight polymer.
Solution Approach 2:
The invention changes the molecular weight distribution parameters from a single-peak or broad distribution to a specific multi-peak distribution with controlled Mw/Mn ratios and peak positions. By precisely controlling the molecular weight parameters (Mn, Mw, peak positions), the invention achieves both high physical properties and good processability simultaneously.
2Ease of manufacture
If a fluorine-containing elastomer with low molecular weight is used to improve roll processability, then roll processability is improved, but physical properties deteriorate
Solution Approach 1:
The elastomer is segmented into multiple molecular weight populations where low molecular weight components improve processability while high molecular weight components maintain physical properties. The medium molecular weight population acts as a bridge to balance both requirements, resolving the contradiction through functional distribution across segments.
Solution Approach 2:
The invention creates a composite molecular weight distribution system where different molecular weight populations work together synergistically. The combination of low, medium, and high molecular weight elastomers forms a composite structure at the molecular level, where each component contributes its strengths to the overall performance.
3Strength
If a fluorine-containing elastomer with high molecular weight is used to achieve low hardness, then low hardness and low modulus are achieved, but extrudability deteriorates
Solution Approach 1:
The elastomer is segmented into three molecular weight populations where low molecular weight components specifically address extrudability, medium components balance the properties, and high components maintain low hardness and low modulus. This segmentation allows the low molecular weight fraction to improve extrudability without sacrificing the softness provided by the high molecular weight fraction.
Solution Approach 2:
The invention changes the molecular weight distribution parameters to include a significant low molecular weight population (Mn ≤ 13,000) while maintaining high molecular weight components. This parameter change in the distribution shape enables simultaneous achievement of low hardness and good extrudability.
4Ease of manufacture
If a multi-peak type molecular weight distribution is used to improve extrudability, then extrudability is improved, but manufacturing complexity increases
Solution Approach 1:
The manufacturing process is segmented into two independent polymerization steps, each producing elastomers with specific molecular weight characteristics. This segmentation of the manufacturing process into discrete, controllable steps makes the complex multi-peak distribution achievable through standard industrial processes rather than requiring complex single-step synthesis.
Solution Approach 2:
The invention performs preliminary polymerization actions to create elastomers with predetermined molecular weight distributions before blending. By pre-controlling the molecular weight characteristics in separate polymerization steps and then blending, the complex multi-peak distribution is achieved through preliminary preparation rather than complex real-time control.
Data Source
AI summary
Provided is a fluorine-containing elastomer blend comprising 5 to 60 wt.% of a high-molecular-weight, fluorine-containing elastomer having a number average molecular weight of 3,000,000 or more, 20 to 80 wt.% of a medium-molecular-weight, fluorine-containing elastomer having a number average molecular weight of 100,000 to 1,000,000, and 10 to 50 wt.% of a low-molecular-weight, fluorine-containing elastomer having a number average molecular weight of 7,000 to 13,000; the number average molecular weight Mn of each tluorine-containing elastomer being measured by liquid chromatography using tetrahydrofuran as a developing solvent at a polymer concentration of 0.5 wt.% at a measurement temperature of 35°C. The fluorine-containing elastomer blend can achieve low hardness and low modulus while improving roll processability.