Crosslinked Styrenic Block Copolymer Chemical Resistance
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Solution Overview
Problem
Styrenic block copolymers used in medical gloves lack chemical resistance to organic solvents, which limits their application in medical fields where exposure to chemicals like methyl methacrylate monomer is common, and the introduction of chemical cross-linking compromises their mechanical properties.
Innovation Solution
A composition of styrenic block copolymers that are both physically and chemically cross-linked, using miscible polymers and cross-linking agents to form covalent bonds while maintaining non-covalent interactions between styrenic end blocks, enhancing chemical resistance without sacrificing mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chemical cross-linking is introduced to improve chemical resistance, then resistance to organic solvents is improved, but mechanical properties are compromised
Solution Approach 1:
The patent creates a composite cross-linking system combining two distinct mechanisms: physical cross-links through styrenic end block associations and chemical cross-links through covalent bonds formed by cross-linking agents. This composite approach allows the material to benefit from both the mechanical property preservation of physical cross-links and the chemical resistance of chemical cross-links, resolving the contradiction between these two requirements
2Strength
If physical cross-linking is used to maintain mechanical properties, then elasticity and flexibility are preserved, but chemical resistance to organic solvents is insufficient
Solution Approach 1:
The patent merges two cross-linking mechanisms that were previously used separately into a unified system. The physical cross-links (styrenic end block associations) provide mechanical properties while chemical cross-links (covalent bonds) provide chemical resistance. The synergistic combination of these two mechanisms resolves the contradiction by allowing each to fulfill its primary function simultaneously
3Reliability
If sulphur vulcanization is applied to achieve cross-linking, then chemical resistance is improved, but reaction conditions require very high temperatures and long times
Solution Approach 1:
The patent changes the cross-linking parameters by using alternative cross-linking agents and mechanisms that operate under milder conditions. Instead of requiring very high temperatures and long reaction times like traditional sulphur vulcanization, the system uses cross-linking agents that can form covalent bonds under more moderate conditions, thereby reducing the time and energy investment required while maintaining chemical resistance
4Productivity
If accelerators are added to speed up vulcanization, then cross-linking speed is improved, but skin sensitization and allergic contact dermatitis are caused
Solution Approach 1:
The patent extracts and eliminates the harmful accelerators from the vulcanization system. By using alternative cross-linking mechanisms and agents that do not require accelerator chemicals, the system achieves cross-linking without the skin sensitization and allergic contact dermatitis problems caused by traditional accelerator molecules, thereby removing the harmful factor while maintaining productivity
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 resulting films exhibit improved chemical resistance and maintain high tensile strength, meeting international standards for medical gloves while being insoluble in organic solvents, thus addressing the limitations of purely physically cross-linked SBCs.
Implementation Method 1
said physical crosslinking comprises non-covalent interaction between styrenic end blocks of the one or more SBCs and the one or more polymers miscible with the styrenic end blocks
Implementation Method 2
said chemical crosslinking comprises covalent bonds between chains of SBC
Data Source
AI summary
Elastomeric styrenic block copolymer (SBC) compositions comprise one or more SBCs and one or more polymers miscible with styrenic end blocks of the one or more SBCs, the block copolymer compositions being both both physically and chemically crosslinked, where the chemical crosslinking comprises covalent bonds between chains of SBC and the physical crosslinking comprises non-covalent interaction between styrenic end blocks of the one or more SBCs and the one or more polymers miscible with the styrenic end blocks. The block copolymer compositions are useful in forming immersion articles such as surgical gloves.