Multi-layer Thermoformed Foam Articles Density Control
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Solution Overview
Problem
Thermoforming processes often result in finished articles with higher density and reduced thickness compared to precursor foamed sheets, leading to a loss of mechanical stiffness, and it is challenging to produce foamed thermoformed articles with lower density than the precursor sheet.
Innovation Solution
A multi-layer thermoformed polymeric foam article is created using a precursor sheet with layers of polymer foam and solid polymer, where the foam layer density is reduced between 5% and 50% compared to solid polymer, and the thermoformed article maintains a density equal to or less than the precursor sheet, utilizing techniques like co-extrusion and controlled cell distribution to prevent cell collapse.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional thermoforming is applied to foamed sheets, then the sheet can be formed into desired shapes, but the finished article has higher density and reduced thickness leading to loss of mechanical stiffness
Solution Approach 1:
The sheet is divided into multiple layers with different foam densities - a first layer with higher foam density and a second layer with lower foam density. This segmentation allows each layer to contribute differently to the final product properties, maintaining shape while preserving mechanical stiffness through the higher density layer.
Solution Approach 2:
Different regions of the multi-layer sheet have different foam densities tailored to specific functional requirements. The first layer provides structural support and stiffness, while the second layer provides weight reduction and insulation, creating local quality variations that optimize overall performance.
2Shape
If conventional thermoforming is applied to foamed sheets, then the sheet can be formed into desired shapes, but the finished article has reduced thickness
Solution Approach 1:
The sheet is divided into multiple layers with different foam densities - a first layer with higher foam density and a second layer with lower foam density. This segmentation allows each layer to contribute differently to the final product properties, maintaining shape while preserving mechanical stiffness through the higher density layer.
Solution Approach 2:
The invention uses composite materials consisting of multiple polymer foam layers with different densities combined with solid polymer layers. This composite structure allows the final article to achieve the desired shape while maintaining adequate thickness through the combined contribution of all layers.
3Device complexity
If single-layer foamed sheets are used, then the structure is simple, but it is difficult to produce thermoformed articles with lower density than the precursor sheet
Solution Approach 1:
The sheet is divided into multiple layers with different foam densities - a first layer with higher foam density and a second layer with lower foam density. This segmentation allows each layer to contribute differently to the final product properties, maintaining shape while preserving mechanical stiffness through the higher density layer.
Solution Approach 2:
The invention changes the density parameter by incorporating layers with different foam densities. The first layer has higher density (5-50% reduction from solid polymer) while the second layer has lower density, allowing the overall article density to be controlled and potentially reduced below the precursor sheet density.
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
This method allows for the production of thermoformed articles with lower density and potentially thicker sections than the precursor sheet, maintaining or improving mechanical stiffness, and can be applied to various polymer types, including polyolefin and polystyrene, suitable for different applications such as food service trays and deep draw articles.
Implementation Method 1
the thermoformed article has a density equal to or less than a density of the multi-layer precursor sheet... one of the layers of the thermoformed article is a polymer foam layer having a density reduction between 5% and 50% as compared to the solid polymer
Implementation Method 2
thermoforming is a thermoplastic manufacturing process where a plastic sheet is heated to a softening point or forming temperature
Implementation Method 3
through the application of pressure force the sheet into a mold of the specified shape
Implementation Method 4
When in the mold, it is cooled so as to hold its final shape
Data Source
AI summary
Thermoformed polymeric foam articles and methods of forming the same are described. In some embodiments, thermoformed articles are produced from multi-layer foamed sheet where the formed article has a density equal to or less than the precursor multi-layer sheet. One of the layers of the thermoformed article may be a polymer foam layer having a density reduction between 5% and 50% as compared to the solid polymer. Such polymer foam layers can be referred to as “medium density” or “high density” foams. Advantageously, the methods described herein are practical for commercial use and, for example, can be used to produce a variety of thermoformed articles suitable for use in many different applications.