Foamed Plastic Cup Wall Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing disposable containers, such as plastic-lined paper cups, are difficult to recycle due to the separation of materials and often leak when tilted, while conventional injection-molded cups with foaming agents achieve only a 30% density reduction and require a thick wall for thermal insulation.
Innovation Solution
A method involving a mould with alternating cavity-forming surfaces to create a sandwich structure of inner and outer skins with expanded cellular foam, allowing for a 200% density reduction and eliminating seams, enabling easier recycling and improved thermal insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional injection moulding with blowing agent is used to create foamed structure for thermal insulation, then thermal insulation is improved, but density reduction is limited to maximum 30 wt% and wall thickness must be increased
Solution Approach 1:
The cup wall is segmented into multiple layers with alternating foamed and non-foamed regions. The cavity-forming surface includes alternating first and second regions that create corresponding alternating first and second thicknesses in the injected plastic composition, with the first thickness being greater than the second thickness. This segmentation allows selective foaming in thicker regions while maintaining structural integrity in thinner regions.
Solution Approach 2:
Different regions of the cup wall are given different properties: the first regions with greater thickness are designed to foam and provide thermal insulation, while the second regions with lesser thickness maintain higher density for structural strength. This local differentiation of material properties optimizes both insulation and structural requirements without uniform wall thickening.
2Ease of operation
If paper cup with plastic lining is used, then disposable use is enabled, but recycling becomes difficult due to difficulty in separating materials
Solution Approach 1:
The cup is manufactured as a homogeneous single-material structure using only thermoplastic polymer material throughout, eliminating the need for plastic linings on paper cups. This homogeneity enables easy recycling while maintaining disposable functionality, as the entire cup can be processed through standard thermoplastic recycling streams without material separation.
3Ease of operation
If paper cup with seam is used, then disposable container is formed, but liquid leakage occurs when cup is tilted due to seam at join area
Solution Approach 1:
The cup is formed as an integral seamless structure where the plastic composition is injected directly into the mould cavity and solidifies in place. The alternating thickness regions are created within a single continuous piece of material without requiring separate joining operations, eliminating seams and potential leakage paths while maintaining the disposable container function.
4Temperature
If thick wall is used in conventional injection moulding, then thermal insulation is achieved, but material usage increases
Solution Approach 1:
The wall thickness is segmented into alternating first and second thicknesses around the circumference of the cup. The first thickness regions provide thermal insulation through foaming, while the second thickness regions use less material. This segmentation reduces overall material usage while maintaining adequate thermal insulation through the strategically placed thicker foamed regions.
Solution Approach 2:
The thicker first regions are designed to form a foamed structure with cellular pores that provide thermal insulation. This porous structure achieves insulation with less material than solid walls would require, as the air pockets within the foam cells reduce thermal conductivity while maintaining structural adequacy.
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 method results in a recyclable container with reduced material usage, no seams for leakage prevention, and enhanced thermal insulation, while maintaining the required stiffness and appearance.
Implementation Method 1
a blowing agent is added to the thermoplastic polymer to create a foamed structure to further improve the thermal insulation, and to reduce the density of the foamed wall
Implementation Method 2
allowing the plastic composition between the first and second solid skins, and the molten plastic composition at the alternating first and second thicknesses of the plastic composition, to expand by foaming
Implementation Method 3
the first cavity-forming surface is such that a distance between the first cavity-forming surface and the second cavity-forming surface alternates between a first distance and a second distance around at least a portion of the circumference of the region
Implementation Method 4
allowing the plastic composition to form, in the said at least one region, a first solid skin adjacent to and in contact with the first cavity-forming surface and having a first circumferential length, and a second solid skin adjacent to and in contact with the second cavity-forming surface
Data Source
AI summary
Methods of forming an article from a molten plastic composition comprising a polymer and a blowing agent. The methods include injecting the molten plastic composition into a mould, allowing the plastic composition to form a first solid skin adjacent to an in contact with a first cavity-forming surface of the mould and a second solid skin adjacent to and in contact with a second cavity-forming surface of the mould, and then opening the mould before the molten plastic composition between the first and second solid skins in at least one portion of the circumference of a region of the mould cavity defining an annular cross-section of the cavity has solidified.