Aramid Nonwoven Carrier with Refractory Platelet Coating

Solution Overview

Problem

There is a need for a method to provide a thin inorganic refractory layer that can be safely handled and processed into a multi-layer composite for use as a flame barrier component in thermal and acoustic blankets for aircraft structures, while maintaining mechanical strength and flexibility.

Innovation Solution

A multilayered sheet comprising a flame-resistant wet-laid nonwoven paper with an inorganic refractory layer, where the paper contains meta-aramid or para-aramid fibers and a polymeric binder, and the refractory layer consists of inorganic platelets such as clay, vermiculite, or mica, with specific properties like dry areal weight, moisture content, tensile strength, and air permeability, is formed by depositing an aqueous slurry of refractory platelets onto the paper and drying it at controlled temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Temperature

If a thin inorganic refractory layer is provided for flame barrier applications, then thermal insulation performance is improved, but handling safety and processing difficulty worsen

Engineering Contradiction:

Improvethermal insulation performanceVSAvoidhandling safety

Core Design Contradiction:

TemperatureVSEase of operation

Solution Approach 1:

The patent applies this principle by using a flexible nonwoven carrier made of heat-resistant fibers (aramid, polyimide, or vinylidene fluoride) that can support the thin refractory layer. The carrier provides the necessary mechanical strength and flexibility for safe handling, while the thin refractory coating (15-50 gsm) maintains excellent thermal insulation properties. This combination allows the composite structure to be handled safely like a flexible sheet while providing superior flame barrier performance.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent applies this principle by creating a composite material consisting of a nonwoven heat-resistant carrier combined with a thin inorganic refractory layer. The carrier provides mechanical strength, flexibility, and handling safety, while the refractory layer provides thermal insulation and flame barrier properties. This composite structure resolves the contradiction by integrating two materials with complementary properties, allowing both thin refractory coating and safe handling to be achieved simultaneously.

Inventive Principle:

Principle #40Composite materials

2Temperature

If the refractory layer is made thin for flame barrier applications, then thermal insulation is improved, but mechanical strength deteriorates

Engineering Contradiction:

Improvethermal insulationVSAvoidmechanical strength

Core Design Contradiction:

TemperatureVSStrength

Solution Approach 1:

The patent applies this principle by using a flexible nonwoven carrier made of heat-resistant fibers (aramid, polyimide, or vinylidene fluoride) that can support the thin refractory layer. The carrier provides the necessary mechanical strength and flexibility for safe handling, while the thin refractory coating (15-50 gsm) maintains excellent thermal insulation properties. This combination allows the composite structure to be handled safely like a flexible sheet while providing superior flame barrier performance.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent applies this principle by creating a composite material consisting of a nonwoven heat-resistant carrier combined with a thin inorganic refractory layer. The carrier provides mechanical strength, flexibility, and handling safety, while the refractory layer provides thermal insulation and flame barrier properties. This composite structure resolves the contradiction by integrating two materials with complementary properties, allowing both thin refractory coating and safe handling to be achieved simultaneously.

Inventive Principle:

Principle #40Composite materials

3Strength

If a thick refractory layer is used to improve mechanical strength, then handling safety improves, but thermal insulation performance deteriorates

Engineering Contradiction:

Improvemechanical strengthVSAvoidthermal insulation performance

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The patent applies this principle by using a flexible nonwoven carrier made of heat-resistant fibers (aramid, polyimide, or vinylidene fluoride) that can support the thin refractory layer. The carrier provides the necessary mechanical strength and flexibility for safe handling, while the thin refractory coating (15-50 gsm) maintains excellent thermal insulation properties. This combination allows the composite structure to be handled safely like a flexible sheet while providing superior flame barrier performance.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent applies this principle by creating a composite material consisting of a nonwoven heat-resistant carrier combined with a thin inorganic refractory layer. The carrier provides mechanical strength, flexibility, and handling safety, while the refractory layer provides thermal insulation and flame barrier properties. This composite structure resolves the contradiction by integrating two materials with complementary properties, allowing both thin refractory coating and safe handling to be achieved simultaneously.

Inventive Principle:

Principle #40Composite materials

4Strength

If a dense nonwoven carrier is used to improve mechanical strength, then handling safety improves, but flexibility deteriorates

Engineering Contradiction:

Improvemechanical strengthVSAvoidflexibility

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent applies this principle by using a flexible nonwoven carrier made of heat-resistant fibers (aramid, polyimide, or vinylidene fluoride) that can support the thin refractory layer. The carrier provides the necessary mechanical strength and flexibility for safe handling, while the thin refractory coating (15-50 gsm) maintains excellent thermal insulation properties. This combination allows the composite structure to be handled safely like a flexible sheet while providing superior flame barrier performance.

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 resulting multilayered sheet provides a strong, flexible, and lightweight flame barrier with effective thermal insulation and acoustic properties, allowing for easy handling and processing, and maintains structural integrity during thermal exposure.

Implementation Method 1

depositing an aqueous slurry of inorganic refractory platelets onto one surface of a carrier to form a layered sheet

Methodology Applied

Scientific EffectDeposition: Deposition (physical)

Implementation Method 2

drying the layered sheet at a temperature of from 80 to 110 degrees C until the residual moisture content, measured according to ISO 287 (1985), in the refractory layer is no greater than 10 percent by weight

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentEP2838723B1Multilayered sheet

Publication Date: 2020.09.16 EI DU PONT DE NEMOURS & CO

Figure 1

AI summary

This invention pertains to a layered sheet comprising a flame resistant wet-laid nonwoven paper having a first and second surface and an inorganic refractory layer adjacent to at least one surface of the paper wherein the refractory layer has a dry areal weight of from 15 to 50 gsm and the bond strength between the refractory layer and the surface of the paper is from 0.25 lb/in to 0.8 lb/in, wherein the carrier comprises from 40 to 70 weight percent of aramid fibers and from 30 to 60 weight percent of polymeric binder, is hydrophilic, has a smoothness on at least one surface of no greater than 150 Sheffield units, a thickness of from 0.025 to 0.175 mm and a density of from 0.60 to 1.1 g/cc.