PEI Composite Sheet Porosity for Foaming Solvent Evacuation
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Solution Overview
Problem
The in situ foaming method for thermoplastic materials faces challenges in controlling the evacuation of foaming solvents like acetone, leading to surface defects and poor adhesion between the foam and skins, which affects the mechanical performance of sandwich panels.
Innovation Solution
A composite sheet with controlled porosity, comprising a textile structure impregnated with polyetherimide (PEI), is developed, allowing optimal acetone evacuation and achieving a porosity of 3-8% by weight, which is evenly distributed and regular, ensuring good surface tension and adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the foaming solvent (acetone) is present in significant quantity to enable in situ foaming, then the foaming process can be achieved, but the solvent tends to soften the skins, generate surface defects, and limit adhesion between foam and skins
Solution Approach 1:
The patent applies porous materials by incorporating a porous layer between the foam core and the composite skin. This porous layer acts as a barrier that allows controlled evacuation of the foaming solvent while preventing direct contact between excessive acetone and the skin, thereby avoiding softening and surface defects. The porosity enables gas permeability while maintaining structural integrity and adhesion.
Solution Approach 2:
The porous layer serves as an intermediary element between the foam core and the composite skin. It mediates the interaction by allowing controlled solvent evacuation while preventing harmful direct contact between the acetone and the skin, thus resolving the contradiction between enabling foaming and preventing skin degradation.
2Reliability
If the skin is made from PEI-impregnated glass fabric to achieve adhesion through mechanical interlocking and self-adhesion, then bonding between skin and foam is improved, but control over solvent evacuation becomes difficult
Solution Approach 1:
The porous layer provides controlled porosity that facilitates solvent evacuation while the PEI-impregnated glass fabric maintains adhesion through mechanical interlocking and self-adhesion. The porous structure allows acetone to escape in a controlled manner, preventing pressure buildup and skin softening, while the fabric ensures reliable bonding.
Solution Approach 2:
The invention uses composite materials by combining the PEI-impregnated glass fabric with an additional porous layer. This composite structure integrates the adhesion properties of the fabric with the solvent evacuation control of the porous layer, achieving both reliable bonding and controlled solvent removal.
3Object-affected harmful factors
If the composite sheet has high porosity to acetone to enable solvent evacuation, then surface defects are prevented, but the structural integrity and tension of the skin may be compromised
Solution Approach 1:
The porous layer provides the necessary porosity for acetone evacuation to prevent surface defects, while being positioned as a separate layer rather than compromising the dense structure of the PEI-impregnated glass fabric skin. This allows the skin to maintain its structural integrity and tension while the porous layer handles solvent removal.
Solution Approach 2:
The skin structure is segmented into two functional layers: the PEI-impregnated glass fabric layer that provides structural integrity and adhesion, and the porous layer that provides solvent evacuation pathways. This segmentation allows each layer to optimize its specific function without compromising the other.
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 sheet enables effective gas evacuation during foaming, preventing surface defects and ensuring good tension, thereby enhancing the mechanical performance and adhesion of the sandwich panels.
Implementation Method 1
allowing optimal evacuation of the gases during the foaming process, in particular the acetone
Implementation Method 2
wherein the polyetherimide (PEI) impregnates and consolidates the textile structure
Data Source
AI summary
A composite sheet including at least a textile structure and a polyetherimide (PEI), the latter impregnating and densifying the textile structure, the sheet having a porosity of between approximately 3% and approximately 8% by mass of acetone sorption, and preferably between approximately 4% and approximately 5%, as measured by the acetone uptake method; the manufacturing method including continuous or semi-continuous molding; the sheet being used inter alia as a skin of a foamed structure made from PEI.