Hydrophilic PU Foam Loading for Stable Silver Salt Distribution
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Solution Overview
Problem
Existing methods for incorporating antimicrobial additives like silver salts into polyurethane foam wound dressings face limitations due to solubility issues, stability of suspensions, and the risk of precipitating in processing equipment, leading to uneven distribution and reduced additive doses.
Innovation Solution
Introduce the antimicrobial additive, such as silver sulfate, as a slurry phase or solid concentrate directly into the isocyanate phase during polyurethane foam manufacturing, maintaining stability and allowing for high concentrations without increasing viscosity, ensuring homogeneous distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silver salt is dissolved or suspended in the aqueous phase at the time of polyurethane foam manufacture, then the additive can be incorporated into the foam, but the quantity is limited by solubility and suspension stability, and particle size control is poor
Solution Approach 1:
The patent uses a surfactant as an intermediary substance to enable the incorporation of silver salt into the polyurethane foam. The surfactant acts as a mediator between the hydrophilic silver salt and the hydrophobic polyurethane matrix, allowing the silver salt to be incorporated in quantities exceeding its solubility limit in the aqueous phase while maintaining suspension stability throughout the foam manufacturing process
2Quantity of substance
If high concentration of dense additive is added to the aqueous phase, then the desired dose can be achieved, but the additive settles too readily in process equipment, necessitating constant agitation
Solution Approach 1:
The surfactant serves as a stabilizing intermediary that prevents the dense silver salt particles from settling in process equipment. By adsorbing onto the particle surfaces and providing steric or electrostatic repulsion, the surfactant maintains suspension stability even at high additive concentrations, eliminating the need for constant agitation and simplifying the manufacturing process
Solution Approach 2:
The patent changes the physical-chemical parameters of the additive mixture by introducing surfactant, which modifies the interfacial properties and prevents aggregation and settling of silver salt particles. This parameter change allows high concentration loading without the operational complexity of continuous agitation
3Manufacturing precision
If filler or additive is added to the isocyanate phase, then distribution can be improved, but the risk of self-polymerisation increases, potentially seizing up equipment
Solution Approach 1:
The surfactant acts as a protective intermediary when additive is incorporated into the isocyanate phase. It forms a barrier around the additive particles, preventing premature reaction with isocyanate groups that would trigger self-polymerisation. This allows the additive to be evenly distributed throughout the isocyanate phase before foam formation, improving homogeneity without compromising equipment reliability
4Reliability
If silver salt is used as antimicrobial additive in porous foam, then wound exudate can be handled, but solubility limits and density issues affect antimicrobial performance
Solution Approach 1:
The surfactant enables incorporation of silver salt beyond solubility limits by forming stable micellar or emulsion structures in the aqueous phase. This intermediary mechanism allows higher concentrations of antimicrobial silver salt to be incorporated into the foam matrix, enhancing antimicrobial performance while maintaining processing stability
Solution Approach 2:
The patent utilizes the porous structure of the polyurethane foam to accommodate and distribute silver salt particles throughout the three-dimensional matrix. The porosity provides space for additive incorporation and facilitates release of silver ions to the wound surface, overcoming the limitations of solubility and density while maintaining reliable antimicrobial activity
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 method enables stable, high-concentration antimicrobial additive distribution within the foam, providing rapid and sustained release of silver ions, enhancing the antimicrobial performance of wound dressings while simplifying the manufacturing process.
Implementation Method 1
Reactive hydrophilic PU foam chemistry uses an 'aqueous' phase which may include 'surfactant' polyol, which reacts with an organic 'isocyanate' phase of a prepolymer or monomer containing isocyanate groups
Implementation Method 2
Additive, silver sulfate advantageous for PU foam-based wound dressings, is mixed into a part of the isocyanate phase of a reactive PU foam-forming system
Implementation Method 3
a powder charge comprising one or more additives loaded in said structural matrix framework
Data Source
Figure 1~2b
Figure 3a~3b
Figure 4a~7
AI summary
Flexible polyurethane (PU) material which comprises a flexible hydrophilic polyurethane foam porous matrix comprising two matrix faces and therebetween a structural matrix framework defining a network of cells, having a cell network surface and therein a network of pores and a powder charge comprising one or more additives loaded in said structural matrix framework wherein said material is a foamed polymer of a system comprising an isocyanate prepolymer or monomer phase and an aqueous phase, wherein said system comprises one or more slurry phases or solid concentrates of said powder charge, or an insoluble portion thereof, as said isocyanate phase or part thereof and/or as said aqueous phase or part thereof and/or in a carrier liquid phase; and/or comprising a powder charge of silver salt loaded in said structural matrix framework in a population of silver salt particles defined by particle size distribution about a mean particle size of greater than or equal to 1 micron, said material comprising silver salt in population of particles corresponding to silver salt comprised in powder charge pre-loading; methods for manufacture thereof, systems for control thereof, devices containing said material and methods for treatment therewith and uses thereof.