Freeze Dryer Shelf Hydrophobic Coating Stopper Adhesion
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Solution Overview
Problem
Freeze dryer shelves experience sticking issues with rubber stoppers during the container closure process, leading to potential container separation and breakage, which causes downtime and material loss due to adhesion and vacuum cavity formation.
Innovation Solution
The surface of the freeze dryer shelves is treated with a hydrophobic or non-wetting coating, such as Teflon, or roughened to inhibit sticking, using techniques like thermal spraying, plasma spraying, laser beam etching, or electron beam etching, to reduce adhesion and prevent vacuum cavity formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shelf surface is smooth and untreated, then the container closure process is simple, but the stoppers stick to the shelf surface causing container separation and breakage
Solution Approach 1:
A coating layer is applied to the shelf surface to act as an intermediary between the stopper and the shelf. This coating prevents direct adhesion between the stopper rubber and the shelf surface, eliminating the sticking problem while maintaining the simplicity of the container closure process.
Solution Approach 2:
The surface properties of the shelf are changed by applying a coating with different adhesion characteristics. The coating has low adhesion to rubber stoppers, preventing the formation of strong bonds during the compression process and eliminating the harmful sticking effect.
2Ease of operation
If pressure is applied to the stopper for a long time or at high pressure, then the stopper is fully inserted into the container, but the stopper sticks to the shelf surface
Solution Approach 1:
The coating on the shelf surface serves as a mediator that allows high pressure to be applied for effective stopper insertion while preventing the stopper from adhering to the shelf. The coating provides a non-sticking interface that decouples the insertion function from the adhesion problem.
3Ease of operation
If the stopper has a raised target ring, then needle insertion is facilitated, but a vacuum cavity forms causing the stopper to stick to the shelf
Solution Approach 1:
The coating acts as an intermediary that prevents vacuum cavity formation between the stopper's target ring and the shelf surface. The coating fills or seals the cavity space, preventing vacuum formation while allowing the target ring structure to remain for needle insertion purposes.
4Ease of operation
If silicone oil is applied to the stopper to aid insertion, then stopper insertion is facilitated, but a quasi-viscous layer forms causing sticking
Solution Approach 1:
The coating on the shelf surface serves as a superior intermediary that prevents the quasi-viscous silicone oil layer from causing adhesion. The coating provides a non-sticking surface that counteracts the adhesive properties of the silicone oil, allowing the oil to continue facilitating stopper insertion without causing sticking.
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 treatment prevents stopper adhesion to the shelf, ensuring smooth container closure and unloading processes, reducing the risk of container breakage and downtime, and allowing compatibility with various stopper designs.
Implementation Method 1
The coating preferably comprises a hydrophobic or non-wetting material to inhibit the sticking of a stopper to the shelf through any quasi-viscous layer formed between the coating and a stopper when the shelf is pressed against the stopper
Implementation Method 2
The surface may be roughened to inhibit the sticking to the shelf of a rubber stopper pressed against that surface during the application of pressure to the stopper to push the stopper into a container
Data Source
Figure 1~2
Figure 3~6
Figure 5
AI summary
A freeze dryer shelf (10) comprises opposed, parallel first and second plates (12, 14) having at least one flow channel (18) located therebetween for conveying a diathermic fluid between the plates. One of the plates has a surface treated to inhibit the sticking to the shelf of a rubber stopper pressed against that surface during the application of pressure to the stopper to push the stopper into a container.