Thermoplastic Sandwich Panel Adhesion via Glass Transition Control

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Solution Overview

Problem

Existing sandwich panels for aircraft cabin interiors face issues with porosity, health concerns due to phenolic resins, and recyclability, as well as complexity and time required for surface preparation and production.

Innovation Solution

A thermoplastic sandwich panel is developed using a thermoplastic foam core and face sheets with a glass transition temperature difference, adhered using heat and pressure without polycondensation reactions, eliminating porosity and allowing for easier production and recycling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If phenolic resin is used to adhere face sheets to core layer, then adhesion between layers is achieved, but porosity formation occurs and surface quality deteriorates

Engineering Contradiction:

Improveadhesion strengthVSAvoidsurface quality

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The patent changes the chemical parameters of the adhesive system from phenolic resin (thermoset) to polyurethane adhesive (thermoplastic). This parameter change eliminates the polycondensation reaction that produces water vapor, thereby preventing porosity formation and improving surface quality while maintaining adhesion strength.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the curing phenolic resin system with a thermoplastic polyurethane adhesive that does not require chemical curing. This substitution eliminates the harmful byproducts of polycondensation and avoids porosity, achieving both good adhesion and smooth surface finish without additional surface preparation.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Strength

If phenolic resin is used in sandwich panel construction, then structural integrity is achieved, but health hazards and recyclability issues arise

Engineering Contradiction:

Improvestructural integrityVSAvoidhealth hazards

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent converts the harmful phenolic resin system into a beneficial thermoplastic polyurethane adhesive system. The new adhesive provides equivalent or superior structural integrity while eliminating health hazards associated with phenolic resin exposure and enabling recyclability of the sandwich panel structure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent changes the material parameter from thermoset phenolic resin to thermoplastic polyurethane adhesive. This fundamental material parameter change eliminates the health hazards of phenolic resin and enables the entire sandwich panel to be recyclable, while maintaining the required structural integrity for aircraft cabin applications.

Inventive Principle:

Principle #35Parameter changes

3Strength

If phenolic resin adhesive is used, then layer adhesion is achieved, but production time increases due to surface preparation requirements

Engineering Contradiction:

Improveadhesion strengthVSAvoidproduction time

Core Design Contradiction:

StrengthVSLoss of time

Solution Approach 1:

The patent replaces the phenolic resin system with thermoplastic polyurethane adhesive that eliminates porosity formation. This substitution removes the need for time-consuming surface preparation steps such as pore filler application and manual sanding, thereby reducing production time while maintaining adhesion strength.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

4Strength

If thermoset resin is used in sandwich panel, then structural properties are achieved, but recyclability is prevented

Engineering Contradiction:

Improvemechanical propertiesVSAvoidrecyclability

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent changes the fundamental material parameter from thermoset resin to thermoplastic polyurethane adhesive. This parameter change enables the sandwich panel to be recyclable while maintaining all required mechanical properties for aircraft cabin applications, as thermoplastic materials can be melted and reprocessed.

Inventive Principle:

Principle #35Parameter changes

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 results in improved mechanical properties, reduced production time, and compliance with safety and cosmetic requirements, including enhanced peel strength and recyclability, while eliminating the need for surface treatment and health hazards from phenolic resins.

Implementation Method 1

Adhering the first and the second face sheets to the core layer by applying heat and pressure to the sandwich structure wherein the heating is done at or above the melting temperature of the thermoplastic adhesive film

Methodology Applied

Scientific EffectMelting: Melting

Implementation Method 2

Preparing or providing a first and a second face sheet made of a thermoplastic based matrix polymer having a glass transition temperature (TBMP Tg) lower than or equal to the core Tg; heating is done at or above the TBMP Tg

Methodology Applied

Scientific EffectGlass transition:

Data Source

PatentUS20250001723A1Sandwich panel of thermoplastic polymers

Publication Date: 2025.01.02 DIAB INT AB

AI summary

A thermoplastic sandwich panel comprising a core layer arranged between a first and a second face sheet. wherein the core layer is a thermoplastic foam made of a polymer having a glass transition temperature (core Tg) wherein the face sheets comprise a thermoplastic based matrix polymer (TBMP) and reinforcing fibres: wherein the thermoplastic based matrix polymer has a glass transition temperature (TBMP Tg) equal to or lower than the core Tg.