Hydrogel Composition Viscosity and Yield Stress via Composite Materials
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Solution Overview
Problem
Current polymeric compositions lack high yield point and yield stress properties, and are inadequate as thickeners, emulsifiers, suspending aids, and pharmaceutical controlled release excipients, with a need for improved rheological characteristics and sensory attributes.
Innovation Solution
A hydrogel composition is developed, combining cross-linked poly(acrylic) acid with a thermoplastic polyurethane, utilizing specific cross-linking agents and polyols, which exhibits high viscosity and pleasant sensory characteristics, suitable for use in personal care, healthcare, and pharmaceutical applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If cross-linked poly(acrylic) acid is used as a thickener, then viscosity increases, but yield stress and mechanical properties deteriorate
Solution Approach 1:
The patent combines cross-linked poly(acrylic) acid with thermoplastic polyurethane to create a composite hydrogel system. This composite material integrates the thickening capability of poly(acrylic) acid with the mechanical strength and yield stress properties of thermoplastic polyurethane, resolving the contradiction between viscosity and yield stress by synergistic interaction between the two polymer components
2Strength
If thermoplastic polyurethane is used alone, then mechanical properties improve, but viscosity and thickening capability deteriorate
Solution Approach 1:
The patent creates a composite system where thermoplastic polyurethane provides mechanical strength and structural integrity, while cross-linked poly(acrylic) acid contributes to viscosity and thickening. The combination allows the formulation to achieve both mechanical properties and thickening capability that neither component could provide alone
3Strength
If cross-linking ratio is increased, then gel strength improves, but solubility and swelling capability deteriorate
Solution Approach 1:
The patent optimizes the cross-linking ratio parameter to achieve the desired balance between gel strength and solubility. By controlling the degree of cross-linking, the system maintains sufficient strength while preserving the ability to swell and dissolve, resolving the contradiction through precise parameter optimization
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 hydrogel composition demonstrates strong viscosity at low shear rates and pleasant sensory characteristics, enhancing the efficacy of chemically and physiologically active ingredients, and providing improved mechanical properties and delivery mechanisms.
Implementation Method 1
Hydrogels are polymers that swell in water. The term, 'swelling' refers to the uptake of a liquid by a gel with an increase in volume.
Implementation Method 2
The viscosity behavior of crosslinked polyelectrolyte microgels has been understood in terms of a model based on close packed spheres. At low concentrations, no yield stress and little viscosity is observed because the swollen microgels are not tightly packed. Above some minimum packing concentration the particles are viewed as being closely packed deformable particles and the viscosity builds tremendously.
Implementation Method 3
The solution viscosity behavior of thermoplastic polyurethane is that of a linear polymer in a random configuration. The viscosity is dependent on both the molecular weight of the polymer and the solvency of the dissolution media.
Implementation Method 4
Yield behavior and viscosity only begins when the concentration is such that the particles become closely packed. At low concentrations, no yield stress (where yield stress is defined as the applied stress which must be exceeded to make a structural fluid flow) and little viscosity is observed because the swollen microgels are not tightly packed.
Data Source
Figure 1~2
AI summary
A hydrogel composition from a cross-linked polymer derived from one or more olefinically unsaturated polymerizable carboxylic monomers and a thermoplastic polyurethane composition is disclosed. The hydrogel exhibits high yield stress at low shear. The hydrogel composition provides useful materials for personal care, health care, medical and pharmaceutical applications, among others.