Coextruded Polyolefin Foam With TPU Cap Layer
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Solution Overview
Problem
The existing methods for bonding polyolefin foam to urethane-based adhesives and polyurethane foams require surface modification treatments like corona, plasma, or chemicals, which are costly and can be temporary, making them unsuitable for long-term storage and use.
Innovation Solution
Coextruding a polyolefin foam composition with a thermoplastic polyurethane (TPU) cap layer, which eliminates the need for surface treatment due to structural similarities, allowing for direct bonding with urethane-based adhesives and polyurethane foams without degradation over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface modification treatment (corona, plasma, or chemical) is applied to polyolefin foam, then adhesion to urethane-based adhesives and polyurethane foams is improved, but processing complexity and cost increase
Solution Approach 1:
The patent combines the polyolefin foam layer with a TPU cap layer into a single coextruded multilayer structure. The TPU cap layer inherently provides adhesion to urethane-based adhesives and polyurethane foams without requiring separate surface modification treatments, thus merging the foam functionality with the adhesion functionality into one integrated component.
Solution Approach 2:
The patent extracts the surface modification step from the overall process by incorporating the adhesive-functional TPU cap layer directly into the foam structure during coextrusion. This eliminates the need for separate corona, plasma, or chemical treatment steps that would otherwise be required to achieve adhesion.
2Strength
If corona treatment is applied to polyolefin foam surface, then adhesion is improved, but the treatment is temporary and adhesion deteriorates after extended storage
Solution Approach 1:
The TPU cap layer is incorporated into the foam structure during the manufacturing process itself, providing permanent adhesion capability from the outset. This preliminary incorporation of the adhesive-functional layer ensures that the adhesion property is built-in and stable throughout the product's service life, unlike temporary corona treatments.
Solution Approach 2:
The patent changes the material parameter of the cap layer from conventional polyolefin to TPU (thermoplastic polyurethane), which has inherent adhesive properties to urethane-based adhesives and polyurethane foams. This material parameter change creates a permanent chemical affinity that does not degrade over time, resolving the temporary nature issue of corona treatments.
3Strength
If surface modification treatment is applied to polyolefin foam, then adhesion is achieved, but additional processing steps and costs are incurred
Solution Approach 1:
The patent merges the foam core and adhesive cap layer into a single coextruded multilayer structure manufactured in one continuous process. This integration eliminates multiple separate processing steps (foam manufacturing followed by surface treatment), simplifying the overall manufacturing process while maintaining strong adhesion.
Solution Approach 2:
The TPU cap layer serves multiple functions simultaneously: it provides the foam's structural base, ensures adhesion to urethane-based adhesives and polyurethane foams, and eliminates the need for separate surface modification treatments. This multi-functionality reduces both processing steps and costs.
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 approach enables reliable and cost-effective bonding without the need for surface modification, ensuring consistent adhesion even after extended storage periods.
Implementation Method 1
irradiating the coextruded layers with ionizing radiation
Implementation Method 2
a first layer including polypropylene, polyethylene, or a combination thereof and a chemical foaming agent
Data Source
AI summary
The present disclosure is directed to a physically crosslinked, closed cell continuous multilayer foam structure comprising at least one foam polypropylene/polyethylene layer with a TPU cap layer. The multilayer foam structure can be obtained by coextruding a multilayer structure comprising at least one foam composition layer with at least one cap composition layer, irradiating the coextruded structure with ionizing radiation, and continuously foaming the irradiated structure.