Electrically conductive PTC ink with double switching temperatures and applications thereof in flexible double-switching heaters
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Solution Overview
Problem
Existing polymeric PTC heaters suffer from low resistance magnification at switch temperature, transition temperature region issues, resistance hysteresis, and a strong Negative Temperature Coefficient (NTC) effect that can lead to safety risks and operational inefficiencies.
Innovation Solution
A PTC ink composition with double switch temperatures is developed, using two polymers with different melting or softening points to provide distinct PTC effects at different temperature ranges, eliminating the NTC effect and achieving high resistance magnification factors up to 250, thereby ensuring safe and reliable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single polymer PTC heater is used, then it provides heating function, but it exhibits strong NTC effect causing safety risks and operational inefficiencies
Solution Approach 1:
The heater is segmented into multiple independent PTC heating elements, each with its own positive temperature coefficient characteristics. This segmentation eliminates the harmful NTC effect that plagues single-polymer heaters, as each segment independently provides safe self-regulating heating without the dangerous negative temperature coefficient region.
Solution Approach 2:
The invention uses composite material structure with multiple polymers having different melting or softening points. Each polymer contributes PTC characteristics at different temperature ranges, creating a composite heating element that maintains reliable operation across a broader temperature spectrum while eliminating the NTC effect through material composition rather than simple segmentation.
2Power
If PTC heater operates at switch temperature, then heating is provided, but resistance magnification is low causing excessive power dissipation
Solution Approach 1:
The invention changes the physical parameters of the heating elements by selecting polymers with specific melting or softening points tailored to the application requirements. By adjusting these parameters, the resistance magnification at switch temperature is optimized to achieve the desired balance between heating power and energy efficiency, reducing excessive power dissipation while maintaining effective heating.
3Temperature
If PTC heater uses broad temperature range polymer, then wide temperature coverage is achieved, but temperature stability deteriorates due to transition region
Solution Approach 1:
The heating system is divided into multiple PTC elements, each optimized for a specific temperature range based on the polymer's melting or softening point. This segmentation allows each element to provide stable heating within its optimal range, avoiding the temperature stability issues that arise when a single polymer attempts to cover a broad temperature spectrum.
Solution Approach 2:
Different regions of the heating system use polymers with locally optimized properties for their specific temperature requirements. Each PTC element has tailored characteristics suited to its operational temperature zone, achieving both wide overall temperature coverage and local temperature stability without the compromises required by a single broad-range polymer.
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 provides a PTC ink with enhanced safety and reliability by eliminating the NTC effect, allowing for minimal power dissipation at switch temperature and maintaining temperature stability across a wide range, reducing the risk of overheating and material degradation.
Implementation Method 1
a first resin that provides a first PTC effect at a first temperature range
Implementation Method 2
a second resin that provides a second PTC effect at a second temperature range
Implementation Method 3
eliminating the NTC effect and achieving high resistance magnification factors up to 250
Data Source
AI summary
An article comprising a double-switching heater that comprises a double-switching PTC ink deposited on a flexible substrate to form one or more resistors. The double-switching PTC ink comprises a first resin and a second resin; the first resin provides a first PTC effect within a first temperature range (T1, T2); the second resin provides a second PTC effect within a second temperature range (T3, T4), where T3≥T2; the first resin has an NTC effect above the first temperature range; the second PTC effect is greater than the first PTC effect; and the second PTC effect overlaps with, and is greater than, the NTC effect of the first resin. The substrate can be either thermal polyurethane, nylon or a polyester blend.