Crystallised Polymer Container Closures for Long-Term Openability
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Solution Overview
Problem
Commercially available containers with different material compositions for the container and closure, such as PET and PE/PO, face challenges in recycling and gas retention, leading to issues like increased friction and difficulty in opening after prolonged storage due to polymer chain diffusion.
Innovation Solution
Both the container and closure are made of a crystallisable polymer material, with at least one of the contacting surfaces being crystallised to prevent polymer chain diffusion and maintain openability over extended periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the container and closure are made of different materials (PET and PE/PO), then the manufacturing flexibility and cost are improved, but the recycling efficiency deteriorates due to the need for material separation
Solution Approach 1:
The invention applies homogeneity by making both the container and closure from the same PET material, eliminating the need for material separation during recycling. This single-material approach maintains manufacturing flexibility while dramatically improving recycling efficiency, as the entire assembly can be processed together without complex sorting requirements.
2Ease of manufacture
If the container and closure are made of different materials (PET and PE/PO), then the manufacturing cost is reduced, but the gas retention properties deteriorate
Solution Approach 1:
The invention uses the same PET material for both container and closure, leveraging PET's superior gas barrier properties throughout the entire assembly. This eliminates the weak link effect where the closure material (PE/PO) would limit the overall gas retention, ensuring consistent high-performance gas barrier characteristics while maintaining cost-effectiveness through material standardization.
3Reliability
If both the container and closure are made of the same crystallisable polymer material (PET), then the recycling efficiency and gas retention are improved, but the friction between contacting surfaces increases after prolonged storage due to polymer chain diffusion
Solution Approach 1:
The invention applies local quality by treating only the contacting surfaces (neck portion and closure inner surface) with a crystallisation process, while the rest of the container and closure remain in their original amorphous or semi-crystalline state. This localized crystallisation creates a low-friction interface that prevents polymer chain diffusion and sticking, ensuring easy openability while maintaining the benefits of same-material construction for recycling and gas retention.
4Reliability
If both the container and closure are made of the same crystallisable polymer material (PET), then the gas retention properties are improved, but the friction between contacting surfaces increases after prolonged storage due to polymer chain diffusion
Solution Approach 1:
The invention uses local quality by selectively crystallising only the contacting surfaces of the container neck and closure, creating a specific low-friction interface zone. This localized treatment maintains the gas retention benefits of PET throughout the entire assembly while preventing excessive friction and sticking at the closure interface, ensuring easy openability even after prolonged storage.
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
Ensures the container assembly can be opened after long storage periods without increased friction, improving recycling efficiency and gas retention properties.
Implementation Method 1
the crystallisable polymer material of the inner cap surface of the closure cap and/or of the outer neck surface of the neck portion is crystallised, to allow the container assembly to be opened after being closed for an elongated period of time
Data Source
AI summary
Container assembly comprising a container and a closure, wherein the container is made of a crystallisable polymer material and comprises a neck portion with an outer cap surface and defines an outlet opening, the neck portion being configured for receiving the closure, wherein the closure includes a closure cap made of a crystallisable polymer material and has an inner cap surface, the closure cap being matched to the neck portion of the container to cover the outlet opening in a closed state, wherein the inner cap surface of the closure cap contacts the outer cap surface of the neck portion when the container assembly is closed, and wherein the material of the inner cap surface of the closure cap and/or of the outer cap surface of the neck portion is crystallised, to allow the container assembly to be opened after being closed for an elongated period of time.