Wholly Aromatic Polyester Composition Toughness Heat Resistance
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Solution Overview
Problem
Wholly aromatic polyesters with high melting points are difficult to process using conventional devices due to their high heat resistance, which compromises mechanical properties, and existing copolymers lack sufficient toughness, leading to cracking in molded articles.
Innovation Solution
A wholly aromatic polyester composition comprising specific constitutional units (4-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, 1,4-phenylenedicarboxylic acid, and 4,4'-dihydroxybiphenyl) within defined mole percentages, which exhibits optical anisotropy and maintains heat resistance while improving toughness, allowing for processing without specialized equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the melting point is lowered by copolymerizing various components, then processability with general-purpose devices is improved, but heat resistance represented by mechanical property cannot be maintained at high temperature
Solution Approach 1:
The patent changes the chemical composition parameters by introducing specific constitutional units (I) through (V) with defined molar ratios. Unit (I) with rigid aromatic structures maintains high heat resistance, while units (II)-(V) adjust the melting point to 250-350°C, enabling processability with general-purpose devices while preserving thermal stability up to 200°C
Solution Approach 2:
The patent creates a composite polyester structure combining multiple constitutional units with different functions. The rigid aromatic units (I) provide heat resistance, while the combination with units (II)-(V) lowers the melting point. This composite approach achieves both processability and heat resistance simultaneously
2Temperature
If copolymer polyester is used to achieve lower melting point, then processing temperature is reduced, but toughness is low causing cracks in molded articles
Solution Approach 1:
The patent applies local quality by distributing specific constitutional units throughout the polymer chain. Unit (I) is present at 20-80 mol% to provide local rigid segments for toughness, while units (II)-(V) are distributed to ensure low processing temperature. This local arrangement of different units prevents crack propagation while maintaining processability
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 composition achieves good fluidity and heat resistance, enabling successful injection molding, extrusion molding, and compression molding without specific equipment, producing articles with enhanced toughness and no cracking, suitable for various applications including connectors and thermal fixing rolls.
Implementation Method 1
a wholly aromatic polyester which exhibits optical anisotropy when it is molten
Data Source
Figure 1(a)~1(b)
AI summary
The present invention provides a wholly aromatic polyester being excellent in heat resistance and toughness and being capable of being produced in an ordinary polymerization device. The present invention provides a wholly aromatic polyester which exhibits optical anisotropy when it is molten, containing the constitutional unit (I) derived from 4-hydroxybenzoic acid, the constitutional unit (II) derived from 6-hydroxy-2-naphthoic acid, the constitutional unit (III) derived from 1,4-phenylenedicarboxylic acid, the constitutional unit (IV) derived from 1,3-phenylenedicarboxylic acid and the constitutional unit (V) derived from 4,4'-dihydroxybiphenyl, containing, relative to the total of all constitutional units, the constitutional unit (I) in an amount of 35 to 75 mol%, the constitutional unit (II) in an amount of 2 to 8 mol%, the constitutional unit (III) in an amount of 4.5 to 30.5 mol%, the constitutional unit (IV) in an amount of 2 to 8 mol%, the constitutional unit (V) in an amount of 12.5 to 32.5 mol%, the total of constitutional units (II) and (IV) being in an amount of 4 to 10 mol%.