Multi-Material Cryogenic Closure for Seal Integrity and Puncturability
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Solution Overview
Problem
Current elastomeric closures for cryogenic containers lose their seal integrity and become brittle at temperatures below -50°C to -65°C, allowing contamination and evaporation of cryophilic materials due to glass transition, and existing materials with lower glass transition temperatures are either expensive or have undesirable properties.
Innovation Solution
A multi-material elastomeric closure comprising a cryophilic elastomer with a glass transition temperature below -80°C and a non-cryophilic elastomer with a higher glass transition temperature, physically or chemically bonded together, such as in a laminate form, to maintain seal integrity and permeation resistance at cryogenic temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single elastomeric material is used for closure at cryogenic temperatures, then the closure becomes hard and brittle below glass transition temperature, but using materials with lower glass transition temperature may increase cost or introduce contamination
Solution Approach 1:
The closure is divided into two distinct elastomeric layers: a first elastomeric layer with glass transition temperature above -80°C providing puncturability and permeation resistance, and a second elastomeric layer with glass transition temperature below -80°C providing seal integrity at cryogenic temperatures. This segmentation allows each layer to perform its specific function without compromise.
Solution Approach 2:
The invention uses a composite structure combining two different elastomeric materials with complementary properties. The first elastomer (e.g., butyl rubber) provides chemical stability and puncturability, while the second elastomer (e.g., polybutadiene or silicone) maintains elasticity and sealing at cryogenic temperatures, creating a material system that exhibits properties superior to either component alone.
2Reliability
If elastomeric closure is used at cryogenic temperatures, then seal integrity is compromised below glass transition temperature, but alternative materials may be expensive or have undesirable properties
Solution Approach 1:
The closure structure separates the functional requirements into two layers, allowing the use of conventional, well-established elastomeric materials (butyl rubber, polyisoprene) for the first layer and specialized cryogenic elastomers (polybutadiene, silicone) for the second layer, optimizing both performance and manufacturability.
Solution Approach 2:
Different regions of the closure have different material properties optimized for their specific functions: the first elastomeric layer (outer region) provides puncturability and permeation resistance, while the second elastomeric layer (inner region contacting container) provides cryogenic sealing, allowing each material to be selected for its local performance requirements.
3Ease of operation
If conventional elastomeric closure is used, then puncturability is good, but seal integrity fails at cryogenic temperatures
Solution Approach 1:
The dual-layer elastomeric structure assigns puncturability function to the first elastomeric layer (with higher glass transition temperature) while assigning seal integrity at cryogenic temperatures to the second elastomeric layer (with lower glass transition temperature), allowing both properties to coexist in different parts of the same closure.
Solution Approach 2:
The closure exhibits spatially varying material properties: the outer first elastomer layer maintains puncturability characteristics, while the inner second elastomer layer maintains sealing elasticity at low temperatures, with each layer optimized for its specific operational requirement.
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 multi-material closure provides a complete seal at cryogenic temperatures, preventing contamination and evaporation, while retaining puncturability and permeation resistance, allowing for immediate removal of containers from lyophilization without warming.
Implementation Method 1
a cryophilic elastomer having a glass transition temperature at cryogenic temperatures
Implementation Method 2
high resistance to permeation or migration of the material inside the container to the outside
Data Source
Figure 1~4
AI summary
A multi-material, cryogenic, elastomeric closure is provided for sealing a container for samples of cryophilic biological materials, pharmaceuticals or the like. The closure includes at leas one cryophilic elastomer having a glass transition temperature (Tg) below the cryogenic temperature to which the sample is to be subjected and at least one non-cryophilic elastomer having a Tg above the cryogenic temperature. The cryophilic and non-cryophilic elastomers are present in such a manner as to maintain a complete seal of the container opening at the cryogenic temperature.