Syringe Connection Material Differentiation for Crack Prevention
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Solution Overview
Problem
Syringes made from materials like cycloolefin-copolymer (COC) or cycloolefin-polymer (COP) are prone to cracking due to mechanical stresses from connectors, leading to potential damage or leakage, especially when using connectors made from different materials.
Innovation Solution
The syringe body is made from a hard material like COC or COP, while the connection, particularly the thread, is made from a softer material with a lower E-module and higher impact strength, such as thermoplastic elastomer (TPE) or polypropylene (PP), to absorb stresses and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the syringe body is made from hard material like COC or COP, then the syringe body provides good chemical resistance and pharmaceutical storage properties, but the connection region is prone to cracking under mechanical stress from connectors
Solution Approach 1:
The patent applies local quality by making the connection region (Luer cone and thread) from a different material than the syringe body. Specifically, the connection is made from a material with higher impact strength and elongation at break (e.g., polypropylene, polyethylene, or thermoplastic elastomer) while the syringe body remains in COC or COP. This local material differentiation allows the connection region to absorb mechanical stresses without cracking, while the syringe body maintains its chemical resistance and pharmaceutical storage properties.
2Ease of manufacture
If the connection is made from the same material as the syringe body, then manufacturing is simplified, but mechanical stresses from connectors cause cracks and compromise syringe functionality
Solution Approach 1:
The patent employs composite materials by combining two different materials in a single syringe structure. The syringe body is made from COC or COP while the connection region is made from a complementary material with superior impact strength and elongation properties. This composite approach allows each region to be optimized for its specific function: the body for chemical resistance and the connection for mechanical stress absorption, thereby maintaining both manufacturing feasibility and functional reliability.
3Strength
If a softer material is used in the connection region, then mechanical stresses are absorbed and cracking is prevented, but the E-module is lower requiring careful material selection
Solution Approach 1:
The patent applies parameter changes by selecting materials with specific mechanical properties for the connection region. The connection material is chosen to have a lower E-module (younger modulus) and higher impact strength compared to the syringe body material. Suitable materials include polypropylene (E-module approximately 1.5-2.0 GPa), polyethylene (E-module approximately 0.8-1.5 GPa), or thermoplastic elastomers, which provide the necessary stress absorption while maintaining adequate structural integrity for connector attachment.
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
This design effectively absorbs mechanical stresses and load peaks during connector attachment, preventing cracks and ensuring the syringe's functionality and integrity, while also allowing for the storage of pharmaceuticals over extended periods without significant volume loss.
Implementation Method 1
the connection, in particular the thread consists at least in sections of a second material which is a softer material than the first material... the second material can for example be a thermoplastic elastomer (TPE), an elastomer... characterized in that it has a higher impact strength and/or a lower E-module
Data Source
AI summary
A syringe includes a syringe body, a syringe cone having a distal opening, and a connection arranged in the region of the syringe cone, wherein the syringe body includes a first material and the connection includes a second material, and wherein the first material is different from the second material and the second material is a softer material than the first material.