Aliphatic Polyester Piezoelectric Material Moisture Resistance
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Solution Overview
Problem
Current polymeric piezoelectric materials, such as those based on polylactic acid, suffer from insufficient transparency and reliability due to hydrolysis in moist environments, which affects their performance as piezoelectric elements.
Innovation Solution
A polymeric piezoelectric material comprising an aliphatic polyester with a specific molecular weight range and a stabilizing agent having functional groups like carbodiimide, epoxy, or isocyanate, which enhances piezoelectric constant and moist heat resistance, is developed. The material is produced through a process involving pre-crystallization and uniaxial stretching, followed by annealing, to achieve high reliability and transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a poling treatment is applied to PVDF or P(VDF-TrFE) to generate piezoelectricity, then piezoelectric constant is improved, but reliability deteriorates due to relaxation of dipole orientation over time
Solution Approach 1:
The patent changes the fundamental mechanism from induced polarization to inherent piezoelectricity through molecular orientation during crystallization. By controlling crystallization conditions and molecular structure parameters, the material achieves stable piezoelectricity without poling treatment, eliminating the relaxation problem while maintaining high piezoelectric constant.
Solution Approach 2:
The patent creates a composite structure at the molecular level by incorporating chiral molecules with specific helical structures into the polymer matrix. This composite approach combines the flexibility of polymers with the stable piezoelectric properties of chiral crystalline structures, achieving both high piezoelectric constant and long-term stability.
2Measurement precision
If PVDF is used to achieve high piezoelectricity, then piezoelectric constant is improved, but dielectric constant becomes relatively high which reduces the piezoelectric g constant
Solution Approach 1:
The patent changes the material composition and molecular structure parameters to achieve a different balance between piezoelectric and dielectric properties. By using chiral polymers with specific helical structures and controlling crystallization, the material achieves high piezoelectric constant with lower dielectric constant, thereby improving the piezoelectric g constant (open circuit voltage per unit stress).
3Illumination intensity
If polylactic acid is used for piezoelectricity, then transparency is improved, but reliability deteriorates due to hydrolysis in moist environments
Solution Approach 1:
The patent introduces hydrophobic groups as intermediary structures within the polymer chain. These hydrophobic segments act as barriers to water penetration, protecting the ester bonds from hydrolysis while maintaining the overall transparency and piezoelectric properties of the polylactic acid-based material.
Solution Approach 2:
The patent creates a composite structure by incorporating hydrophobic modifications into the polylactic acid matrix. This composite approach combines the transparency and piezoelectricity of polylactic acid with the moisture resistance of hydrophobic groups, achieving both high transparency and improved moist heat resistance.
4Measurement precision
If stretching operation is applied to orient polymer chains, then piezoelectricity is generated, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary molecular orientation during the crystallization process itself, rather than requiring a separate stretching step after manufacturing. By controlling crystallization conditions to favor oriented crystal formation, the material achieves piezoelectricity directly from the crystallization process, simplifying the manufacturing workflow.
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 resulting polymeric piezoelectric material exhibits improved piezoelectric constant, transparency, and moist heat resistance, ensuring high reliability and stability over time, making it suitable for various applications.
Implementation Method 1
a stabilizing agent (B) with a weight-average molecular weight of from 200 to 60,000 having at least one kind of functional group selected from the group consisting of a carbodiimide group, an epoxy group and an isocyanate group
Implementation Method 2
A film material formed from PVDF or P(VDF-TrFE) is imparted with piezoelectricity by orientating polymer chains by a stretching operation in the stretching direction
Implementation Method 3
building up opposite electric charges on the back and front sides of the film by means of corona discharge, etc. to generate an electric field perpendicular to the film surface
Implementation Method 4
PVDF and P(VDF-TrFE), which are ferroelectric polymers, have superior piezoelectricity among polymers and a piezoelectric constant d31 of 20 pC/N or higher
Data Source
AI summary
A polymeric piezoelectric material is provided that includes an aliphatic polyester (A) with a weight-average molecular weight of from 50,000 to 1,000,000 and having optical activity, and a stabilizing agent (B) with a weight-average molecular weight of from 200 to 60,000 having at least one kind of functional group selected from the group consisting of a carbodiimide group, an epoxy group and an isocyanate group, wherein the crystallinity of the material obtained by a DSC method is from 20% to 80%, a content of the stabilizing agent (B) is from 0.01 part by mass to 10 parts by mass with respect to 100 parts by mass of the aliphatic polyester (A), and internal haze with respect to visible light is 50% or less, as well as a process for producing the same.