Co-extruded Polymeric Foam with Peelable Skin Layer
Solution Overview
Problem
Processing polymeric materials with low melt strength into high-quality foams is challenging due to difficulties in maintaining a fine cell structure and surface appearance, as the foam cells tend to grow and distort, compromising the foam's properties.
Innovation Solution
A method involving co-extrusion of a polymeric foam layer with skin layers, using a polyether-block-amide material and a blowing agent, where the foam layer is separated from the skin layer, allowing for the formation of high-quality foams with small cell sizes and high water vapor transmission without crosslinking, which is particularly effective for materials like PEBAX®, PVDF, PLA, and PHA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional foaming methods are used on low melt strength polymeric materials, then the processing is simple, but the foam cells grow and distort resulting in poor cell structure and surface appearance
Solution Approach 1:
The extrusion process is segmented into multiple streams: a first stream containing the polymeric material and blowing agent, and a second stream containing additional polymeric material. These streams are combined to form an extrudate with distinct foam layer and skin layer, allowing independent control of foaming characteristics and structural integrity
Solution Approach 2:
The invention uses composite material structure by combining different polymeric materials in a multi-stream extrusion process. The first stream provides foaming properties while the second stream contributes to structural support, creating a composite extrudate that balances cell structure quality with processing ease
2Strength
If crosslinking is used to improve foam properties, then the mechanical strength increases, but the processing complexity and cost increase
Solution Approach 1:
The invention changes the processing parameters by using a multi-stream extrusion process with controlled material composition and blowing agent distribution. This allows achieving high mechanical properties through physical foam structure control rather than chemical crosslinking, thereby avoiding the complexity of crosslinking equipment and processes
3Loss of substance
If foam density is decreased to save material, then the raw material usage decreases, but the cell structure becomes coarser and surface appearance deteriorates
Solution Approach 1:
The invention applies local quality by creating different regions within the extrudate with distinct properties. The skin layer provides a high-quality surface appearance while the foam layer provides material savings. This spatial differentiation of material properties allows simultaneous achievement of surface quality and material efficiency
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 enables the production of foams with small cell sizes, high mechanical properties, and attractive surface qualities, providing material savings while avoiding the costs and complications of crosslinking, suitable for various applications including films and sheets.
Implementation Method 1
The first stream comprises a polymeric material and a blowing agent
Implementation Method 2
extruding the first stream and at least a second stream to form an extrudate that includes a polymeric foam layer
Data Source
AI summary
Methods of forming polymeric foams are provided. The methods may involve co-extruding a foam layer along with one or more skin layers. In some embodiments, the skin layer(s) may be removed (e.g., in a peeling operation); while, in other embodiments, the skin layer(s) may form part of the final article. The methods are particularly well suited for producing polymeric foams from polymeric materials that are considered to be difficult to foam by those of skill in the art.