Liquid Crystal Polymer Battery Case Moisture and Impact Trade-off
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Solution Overview
Problem
Conventional liquid crystal polymers face challenges in simultaneously achieving high moisture transmission resistivity and mechanical properties, such as impact strength and tensile strength, when used in battery cases for electronic devices, as adding inorganic fillers to improve impact strength often compromises moisture resistance, and vice versa.
Innovation Solution
A liquid crystal polymer composition is developed with structural units derived from aromatic hydroxy carboxylic acid, aromatic dicarboxylic acid, and aromatic diol, specifically incorporating a high percentage of structural units from p-hydroxybenzoic acid, isophthalic acid, 4,4'-dihydroxybiphenyl, and hydroquinone, along with an inorganic moisture absorbent like CaO, to enhance both moisture transmission resistivity and mechanical strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If inorganic fillers are added to liquid crystal polymer to improve impact strength, then mechanical strength is improved, but moisture transmission resistivity deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid crystal polymer by specifying precise molar ratios of structural units (aromatic hydroxy carboxylic acid: 30-50 mol%, aromatic dicarboxylic acid: 50-70 mol%, aromatic diol: 20-40 mol%). This compositional parameter optimization achieves high impact strength (≥35 kJ/m²) while maintaining low moisture transmission (WVTR ≤0.1 g/m²/day) without requiring inorganic fillers that would compromise moisture resistance.
Solution Approach 2:
The patent creates a composite polymer system combining multiple structural units (aromatic hydroxy carboxylic acid, aromatic dicarboxylic acid, and aromatic diol) in specific proportions. This composite molecular structure integrates the beneficial properties of each component: aromatic hydroxy carboxylic acid provides moisture resistance, aromatic dicarboxylic acid enhances mechanical strength, and aromatic diol improves impact resistance, achieving both high impact strength and moisture transmission resistivity simultaneously.
2Ease of manufacture
If conventional liquid crystal polymer composition is used, then manufacturing is simple, but both moisture transmission resistivity and mechanical properties cannot be simultaneously optimized
Solution Approach 1:
The patent establishes specific parameter ranges for structural unit composition (aromatic hydroxy carboxylic acid: 30-50 mol%, aromatic dicarboxylic acid: 50-70 mol%, aromatic diol: 20-40 mol%) that simultaneously optimize moisture transmission resistivity (WVTR ≤0.1 g/m²/day) and mechanical properties (impact strength ≥35 kJ/m²). These parameter specifications enable reliable performance while maintaining manufacturability through conventional polymerization processes.
Data Source
AI summary
A liquid crystal polymer including structural units derived from an aromatic hydroxy carboxylic acid in an amount of greater than about 30 mol % and less than or equal to about 50 mol %, an aromatic dicarboxylic acid which includes about 50 mol % or greater of a structural unit derived from a compound including two carboxyl groups at a meta-position of an aromatic ring in an amount greater than or equal to about 50 mol % of the amount of the structural unit derived from the aromatic hydroxy carboxylic acid, each based on total moles of the structural units in the liquid crystal polymer, and an aromatic diol that is 4,4′-dihydroxybiphenyl, hydroquinone, or a combination thereof; a composite composition including the liquid crystal polymer, an article produced from the liquid crystal polymer or the composite composition, a battery case including the article, and a battery including the battery case and an electrode assembly.