Over-current Protection Device Using PVDF-PTFE Composite
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Solution Overview
Problem
Conventional over-current protection devices face challenges with high processing temperatures, generation of corrosive gases, and limited stability in harsh environments, particularly under drastic temperature and climate changes, which affect their performance and manufacturing costs.
Innovation Solution
A conductive composite comprising a first crystalline fluorinated polymer with a low melting temperature and a second crystalline fluorinated polymer with a higher melting temperature, along with conductive and non-conductive fillers, is used to create an over-current protection device that can be processed at lower temperatures, reducing environmental hazards and enhancing stability and resistance recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high crystalline melting temperature polymers (FEP, PFA, PTFE) are used in conductive composite, then the device can withstand high temperature, but the processing temperature becomes excessively high (270-340°C), causing pyrolysis and corrosive gas generation
Solution Approach 1:
The patent uses a composite material system combining PVDF polymer matrix with PTFE particulates (1-50 micrometers). The PVDF provides the base polymer structure while the dispersed PTFE particulates contribute to high-temperature resistance. This composite approach allows the device to withstand high temperatures without requiring the entire material to be processed at excessively high temperatures, as the PTFE particulates can be incorporated into the PVDF matrix at lower processing temperatures
Solution Approach 2:
The patent applies local quality by dispersing PTFE particulates (with melting point 320-390°C) throughout the PVDF polymer matrix. The PTFE particulates are distributed in specific concentrations (1-50 micrometers in size) to provide localized high-temperature resistance where needed, while the bulk PVDF matrix can be processed at lower temperatures. This localized incorporation of high-temperature resistant material achieves the desired thermal performance without subjecting the entire manufacturing process to excessively high temperatures
2Reliability
If processing temperature is increased to manufacture conductive composite with high melting point polymers, then the device achieves high temperature stability, but corrosive gases are generated and environmental hazards increase
Solution Approach 1:
The patent changes the processing temperature parameter from the conventional 270-340°C (required for FEP, PFA, PTFE) to a lower range suitable for PVDF processing. By selecting PVDF as the base polymer, the processing temperature can be reduced while still achieving high-temperature stability through the addition of PTFE particulates. This parameter change eliminates or reduces pyrolysis and corrosive gas generation that occurs at excessively high processing temperatures
3Ease of manufacture
If polyolefin polymers are used in conductive composite, then the manufacturing process is simpler, but the device behaves abnormally when temperature changes drastically due to low crystalline melting temperature (less than 130°C)
Solution Approach 1:
The patent employs a composite material system where PVDF (a fluorinated polymer with higher melting point than polyolefins) serves as the base polymer matrix, and PTFE particulates are dispersed throughout. This composite structure combines the ease of processing associated with crystalline polymers while achieving a significantly higher operating temperature range. The PVDF-PTFE composite maintains structural integrity and electrical performance under drastic temperature changes that would cause polyolefin-based devices to fail
Solution Approach 2:
The patent changes the polymer selection from polyolefins (melting point <130°C) to PVDF (a fluorinated polymer with higher thermal stability). This parameter change in material selection, combined with the addition of PTFE particulates, raises the effective service temperature range of the conductive composite while maintaining reasonable processability. The PVDF polymer provides a balance between processing ease and high-temperature performance that polyolefins cannot achieve
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 solution enables the production of over-current protection devices with improved resistance recovery, superior humidity and temperature resistance, and reduced manufacturing costs, while minimizing the generation of corrosive gases, thus addressing the limitations of existing technologies.
Implementation Method 1
The first crystalline fluorinated polymer has a first crystalline melting temperature of between 150 and 190 degrees Celsius
Implementation Method 2
The second crystalline fluorinated polymer are disposed in the conductive composite, having a second crystalline melting temperature of between 320 and 390 degrees Celsius
Implementation Method 3
The conductive filler and the non-conductive filler are dispersed in the conductive composite
Data Source
AI summary
An over-current protection device includes a conductive composite having a first crystalline fluorinated polymer, a plurality of particulates, a conductive filler, and a non-conductive filler, wherein the plurality of particulates include a second crystalline fluorinated polymer. The first crystalline fluorinated polymer has a crystalline melting temperature of between 150 and 190 degrees Celsius. The plurality of particulates including the second crystalline fluorinated polymer are disposed in the conductive composite, having a crystalline melting temperature of between 320 and 390 degrees Celsius and having a particulate diameter of from 1 to 50 micrometers. The conductive filler and the non-conductive filler are dispersed in the conductive composite.