Thermally Expandable Adhesive Sheet with Permeable Layers
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Solution Overview
Problem
Existing adhesive sheets face challenges in adhering complex structures and filling narrow gaps between adherends, as they are either too tacky or difficult to position accurately.
Innovation Solution
A thermally expandable adhesive sheet with two adhesive layers on either side of a substrate and adhesive permeable layers on the surface of the adhesive layers, allowing the adhesive to expand and permeate through the permeable layers to reach the outer surface for bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive is applied to the surface of the substrate, then the adhesive sheet can bond adherends, but the adhesive sheet becomes tacky and difficult to position accurately
Solution Approach 1:
The adhesive is prepared in advance in a solid or semi-solid state within the adhesive layer, allowing the sheet to be positioned accurately without tackiness. Upon heating, the adhesive transforms and becomes tacky, providing bonding strength only when needed after proper positioning.
Solution Approach 2:
The adhesive's physical state is changed from solid/semi-solid at room temperature to tacky/melted state upon heating. This parameter change allows the adhesive to be non-tacky during positioning and becomes bonding-active only after the adhesive sheet is correctly positioned and heated.
2Length of stationary object
If the adhesive sheet thickness is reduced to fit narrow gaps, then the sheet can be disposed in narrow gaps, but the adhesive cannot effectively fill the gap
Solution Approach 1:
The adhesive layer is designed to expand thermally when heated, increasing its volume significantly. This allows a thin adhesive sheet to be inserted into narrow gaps, and upon heating, the adhesive expands to fill the entire gap volume, ensuring complete coverage and bonding.
Solution Approach 2:
The adhesive layer transitions from a static thin state at room temperature to a dynamic expanding state upon heating. This dynamic behavior allows the adhesive to adapt its volume to match the gap size, ensuring effective gap filling regardless of the initial thin configuration.
3Ease of operation
If the adhesive sheet is made tack-free at room temperature, then the sheet is easy to position, but the adhesive does not emerge to the surface for bonding
Solution Approach 1:
The adhesive undergoes a phase transition from solid/semi-solid to liquid/tacky state upon heating. At room temperature, the adhesive remains in a non-tacky state for easy positioning. When heated, the phase transition causes the adhesive to become tacky and emerge through the permeable layer to the surface, enabling bonding.
Solution Approach 2:
The permeable layer acts as an intermediary that prevents adhesive emergence at room temperature while allowing it upon heating. This intermediary layer maintains the adhesive in a contained state during positioning and facilitates its emergence to the surface when thermal energy is applied.
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 adhesive sheet remains tack-free until heated, allowing for easy positioning and preventing unintended adhesion, while the thermal expansion fills gaps between adherends, enhancing workability and ensuring strong bonding.
Implementation Method 1
heating the adhesive sheet initiates thermal expansion of the adhesive constituting the adhesive layers of the adhesive sheet. When the adhesive thermally expands, the adhesive then permeates through the adhesive permeable layer
Data Source
AI summary
[Problem] To provide a thermally expandable adhesive sheet which is tack-free in the state prior to use and exhibits high workability using a different means than that of related art. [Solution] The present invention provides a thermally expandable adhesive sheet (1) including: a substrate (3); two thermally expandable adhesive layers (5) each provided on either side of the substrate; and two adhesive permeable layers (7) each provided on a surface of the two adhesive layers, the adhesive permeable layers being permeable to the adhesive at the time of the thermal expansion of the adhesive. By heating the adhesive sheet, it is possible to expand the adhesive sheet while simultaneously allowing the adhesive to emerge on the outermost surface of the adhesive sheet.