PTC Material Composition Reducing NTC Effect Without Cross-Linking
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Solution Overview
Problem
Most positive temperature coefficient (PTC) materials exhibit undesirable negative temperature coefficient (NTC) effects immediately after displaying PTC characteristics, leading to unwanted current flow and increased production costs due to the need for cross-linking to reduce NTC effects.
Innovation Solution
A PTC material composition comprising a thermoplastic polymer, conductive fillers, and a polymeric additive with a melting or softening temperature greater than the thermoplastic polymer, which reduces the NTC effect without the need for cross-linking, allowing for tailored operation at various temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If cross-linking is used to reduce NTC effects, then NTC effect is reduced, but production cost increases and manufacturing complexity increases
Solution Approach 1:
The invention changes the chemical composition parameters of the polymer system by introducing a third polymer component with specific characteristics (high melting point, crystalline structure) to modify the PTC behavior and reduce NTC effect without requiring cross-linking reactions
Solution Approach 2:
The invention creates a composite polymer system combining three different polymer components with complementary properties: a polyolefin base polymer, a polyamide or polyester secondary polymer, and a high-melting-point crystalline polymer, where each component contributes specific functional characteristics to achieve reduced NTC effect
2Object-generated harmful factors
If cross-linking is used to reduce NTC effects, then NTC effect is reduced, but device complexity increases
Solution Approach 1:
The invention changes the processing parameters from requiring cross-linking reactions (chemical modification) to using a multi-component polymer blend (physical mixing), thereby reducing manufacturing complexity while achieving the same functional outcome of NTC reduction
3Reliability
If standard PTC composition is used, then PTC characteristics are achieved, but NTC effect occurs after switching temperature
Solution Approach 1:
The invention applies preliminary anti-action by incorporating a third polymer component specifically designed to counteract the NTC effect that would naturally occur after the PTC switching temperature, thereby preventing the harmful NTC behavior before it can manifest
Solution Approach 2:
The invention uses a composite polymer system where the third high-melting-point crystalline polymer component interacts with the conductive filler network to maintain structural integrity at elevated temperatures, preventing the filler re-organization that causes NTC effect
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 a reduced NTC effect, maintaining high resistivity and preventing re-organization of conductive fillers, thereby enhancing the PTC material's performance and reducing production costs.
Implementation Method 1
the polymer additive has a melting or softening temperature greater than the melting temperature of the thermoplastic polymer
Implementation Method 2
The mechanism for the PTC anomaly in semi-crystalline polymers is attributed to the relatively large change in specific volume of the polymer at the onset of melting
Implementation Method 3
Polymeric PTC composites are based on semi-crystalline polymers and conducting fillers whose concentration is just above the percolation threshold
Implementation Method 4
the mobility of the conductive fillers increase, resulting in a reconnection of the conductive fillers opposing the initial contact loss and PTC effect
Data Source
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AI summary
Positive temperature coefficient (PTC) compositions having a reduced negative temperature coefficient effect (NTC) are provided that are achieved without crosslinking the thermoplastic base material. The PTC compositions include a thermoplastic base resin, an electrically conductive filler and particles of a polymeric additive dispersed in the PTC composition.