PTC-Effect Composite Material for Heater Stability

Solution Overview

Problem

Existing polymer-based electrically conductive composite materials exhibit limited electrical conductivity and stability due to factors like filler migration and low thermal conductivity, making them unsuitable for high-density current applications and repeated heating cycles.

Innovation Solution

A co-continuous composite material is developed using high-density polyethylene (HDPE) and polyoxymethylene (POM) with carbon black as the conductive filler, where HDPE is pre-filled with carbon black to confine it within one phase, reducing migration and enhancing stability, and POM improves thermal conductivity and structural strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high concentrations of conductive filler (e.g., carbon black >20 wt%) are used in single-polymer composites to improve electrical conductivity, then conductivity increases, but cost increases, viscosity increases, and mouldability deteriorates

Engineering Contradiction:

Improveelectrical conductivityVSAvoidmouldability

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The invention uses a two-polymer matrix system (polyolefin and polyamide) instead of a single polymer, creating a composite material structure that enables better filler distribution and interaction. This composite approach allows achieving good electrical conductivity at lower filler concentrations (10-20 wt%) while maintaining processability, resolving the contradiction between conductivity and mouldability

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention creates distinct regions within the composite material where conductive filler concentrates at the interface between polyolefin and polyamide phases. This local concentration strategy enables effective conductivity enhancement without requiring uniformly high filler concentrations throughout the entire material, thus preserving mouldability while improving electrical properties

Inventive Principle:

Principle #3Local quality

2Reliability

If co-continuous composites with immiscible polymers are used to achieve different filler distributions, then conductivity can be improved, but filler migration occurs between phases reducing stability over time

Engineering Contradiction:

Improveelectrical conductivityVSAvoidfiller stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The invention introduces a compatibilizer (grafted polyolefin-polyamide) as an intermediary substance between the polyolefin and polyamide phases. This compatibilizer stabilizes the interface between the two immiscible polymers, preventing conductive filler migration while maintaining the co-continuous structure and its electrical conductivity benefits

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a two-polymer matrix system (polyolefin and polyamide) instead of a single polymer, creating a composite material structure that enables better filler distribution and interaction. This composite approach allows achieving good electrical conductivity at lower filler concentrations (10-20 wt%) while maintaining processability, resolving the contradiction between conductivity and mouldability

Inventive Principle:

Principle #40Composite materials

3Ease of manufacture

If single-polymer matrices are used to simplify material composition, then manufacturing is easier, but thermal conductivity is low and PTC effect is reduced

Engineering Contradiction:

Improvematerial simplicityVSAvoidthermal conductivity

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The invention uses a two-polymer matrix system (polyolefin and polyamide) instead of a single polymer, creating a composite material structure that enables better filler distribution and interaction. This composite approach allows achieving good electrical conductivity at lower filler concentrations (10-20 wt%) while maintaining processability, resolving the contradiction between conductivity and mouldability

Inventive Principle:

Principle #40Composite materials

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 composite material achieves improved electrical conductivity, thermal conductivity, and stability over time, with a positive-temperature-coefficient effect that limits self-heating to a safe temperature, ensuring reliable performance in electrical heater devices, especially in vehicle components.

Implementation Method 1

conductive polymeric materials, obtained by mixing electrically conductive particles—typically carbon black—within an insulating matrix

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a small expansion of the matrix due to the increase in temperature leads to a considerable variation of electrical resistance

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 3

PTC-effect composite material... in particular distinguished by a positive-temperature-coefficient (PTC) electrical resistance... used for heating aeriform substances

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS11495375B2PTC-effect composite material, corresponding production method, and heater device including such material

Publication Date: 2022.11.08 ELTEK SPA

AI summary

A co-continuous mouldable polymeric composite with PTC effect has a matrix that comprises at least two immiscible polymers (HDPE, POM), and an electrically conductive filler (CB) in the matrix. At least one of said immiscible polymers is high-density polyethylene (HDPE), and at least one other of said immiscible polymers is polyoxymethylene (POM).