Fire-Resistant Cable Insulating Layer Using Geopolymer Composite

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Solution Overview

Problem

Existing fire-resistant insulating layers in electrical and data transmission cables lack satisfactory fire resistance and mechanical properties, and previous solutions are costly and not compatible with preserving mechanical and dielectric properties.

Innovation Solution

A composite material-based fire-resistant insulating layer comprising a cementitious material (5-95% by mass) and a non-woven fibrous material with a flexible structure, along with a geopolymer cement that hardens through internal polycondensation, is used as an internal layer in cables and accessories, providing enhanced fire resistance and mechanical properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional polymer-based insulating layers with fire-retardant fillers are used, then fire resistance is improved, but mechanical properties and flexibility deteriorate

Engineering Contradiction:
Improvefire resistanceVSAvoidmechanical properties
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The patent uses a composite material comprising a polymer matrix (such as polyorganosiloxane) combined with inorganic fillers (such as mica particles, glass fibers, and other fire-retardant additives) to create an insulating layer that simultaneously achieves both fire resistance and mechanical strength. The composite structure allows the polymer to provide flexibility and adhesion while the inorganic fillers provide fire resistance and structural reinforcement.

Inventive Principle:
Principle #40Composite materials

2Reliability

If multiple superimposed insulating strips with mica and glass fibers are used, then fire resistance is improved, but production cost and preparation time increase

Engineering Contradiction:
Improvefire resistanceVSAvoidpreparation time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent combines multiple fire-resistant components (mica particles, glass fibers, and other inorganic fillers) into a single integrated insulating layer formulation applied in one coating process. This eliminates the need for multiple separate application steps required by prior art methods using superimposed strips, thereby reducing preparation time and simplifying production while maintaining fire resistance.

Inventive Principle:
Principle #5Merging (Combining)

3Reliability

If refractory tape with porous base fabric and finely divided alumina or zirconia is used, then fire resistance is improved, but flexibility and ease of handling deteriorate

Engineering Contradiction:
Improvefire resistanceVSAvoidflexibility
Core Design Contradiction:
ReliabilityVSEase of operation

Solution Approach 1:

The patent employs a flexible polymer matrix (such as polyorganosiloxane or other elastomeric polymers) as the base material for the insulating layer, which inherently provides flexibility and ease of handling. Fire resistance is then achieved by incorporating fire-retardant fillers into this flexible matrix, creating a coating that can conform to cable surfaces and withstand handling during installation while maintaining fire-resistant properties.

Inventive Principle:
Principle #30Flexible shells and thin films

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 achieves good fire resistance up to 1000°C for 120 minutes while maintaining mechanical integrity, meeting various fire resistance standards and allowing for easy handling and manipulation of cables without compromising cohesion or resistance.

Implementation Method 1

Geopolymers are essentially inorganic chemical compounds or mixtures of compounds consisting of silico-oxide (-Si-O-Si-O-), silico-aluminate (-Si-O-Al-O-), ferro-silico-aluminate (-Fe-O-Si-O-AI-O-), or alumino-phosphate (-AI-O-P-O-), created by a process of geopolymerization (i.e. polycondensation).

Methodology Applied
Scientific EffectPolycondensation:

Implementation Method 2

Hardening occurs by simple hydration of calcium aluminates and calcium silicates and the binding cement paste retains its strength and stability after hardening.

Methodology Applied
Scientific EffectHydration: Hydrolysis

Data Source

PatentEP3230231B1Cable or cable accessory with a fire-resistant layer
Publication Date: 2023.07.12 NEXANS SA

AI summary

The invention relates to a device comprising a cable and/or a cable accessory, said cable and/or cable accessory containing at least one insulating and fire-resistant layer, as well as to a method for manufacturing a cable and/or accessory of said type.