Recyclable Thermoformable Sheet for Complex Packaging Shapes
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Solution Overview
Problem
Conventional thermoformable sheets used for packaging are non-recyclable, making it difficult to recycle thermoformed packages and posing environmental sustainability challenges due to their complicated curved forms and sharp-edged shapes.
Innovation Solution
A recyclable thermoformable sheet composed of an exterior film with 50-100% polyolefin-based polymers, a printed pigment layer, an adhesive layer, and an inner layer with 60-100% polypropylene polymer, which allows for thermoforming into complex shapes while ensuring recyclability through the use of a recyclable adhesive and ultraviolet barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional thermoformable sheets (thick polystyrene film or polyester film) are used to achieve complicated curved forms and sharp-edged shapes, then the thermoformability is sufficient, but the sheets are non-recyclable and pose environmental sustainability challenges
Solution Approach 1:
The invention uses a composite structure consisting of an inner layer (60-100% polypropylene, 100-350 microns thick) and an exterior film (50-100% polyolefin-based polymers, 6-50 microns thick). This composite material combines the thermoformability needed for complex shapes with recyclability, as both layers are made from recyclable polyolefin materials. The inner layer provides structural integrity while the exterior film enables coloring and printing, and both can be recycled together.
2Manufacturing precision
If the inner layer thickness is increased to impart desired thermoformability and UV barrier properties, then the thermoformability improves, but the sheet becomes thicker and more material is used
Solution Approach 1:
The invention applies different thicknesses and material compositions to different functional layers: the inner layer is thicker (100-350 microns) to provide structural support, thermoformability, and UV barrier properties, while the exterior film is thinner (6-50 microns) to enable coloring and printing functions. This local differentiation of quality optimizes material usage by giving each layer the specific properties it needs without unnecessarily thickening the entire sheet.
3Reliability
If a recyclable adhesive (plastomer adhesive) is used instead of conventional EVA adhesive, then the recyclability of the sheet improves, but the adhesion strength may be compromised
Solution Approach 1:
The invention changes the chemical composition parameter of the adhesive from conventional EVA (ethylene-vinyl acetate) to a recyclable plastomer adhesive that is compatible with polyolefin materials. This parameter change enables the entire laminate to be recyclable as a single stream, eliminating contamination issues. The plastomer adhesive maintains sufficient adhesion strength through its compatibility with the polyolefin-based exterior film and inner layer, allowing the layers to remain bonded during normal use while enabling recycling at end-of-life.
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 thermoformable sheet can be thermoformed into complex shapes without defects, such as cracks or color inhomogeneity, and is recyclable, promoting environmental sustainability by avoiding contamination in recycling streams.
Implementation Method 1
The inner layer may further impart ultraviolet barrier properties to the thermoformable sheet
Data Source
AI summary
A thermoformable sheet includes an exterior film, a printed pigment layer, an adhesive layer, an inner layer, and an interior sealing layer. The exterior film includes between 50% and 100% polyolefin-based polymers, by weight. The inner layer includes between 60% and 100% of polypropylene polymer, by weight. The inner layer further includes a thickness between 100 microns and 350 microns. The printed pigment layer and the adhesive layer are located between the exterior film and the inner layer.