Double-Network Hydrogel Substrate for Anisotropic Shrinkage
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Solution Overview
Problem
Conventional hydrogels are soft and fragile in a hydrated state, brittle and hard in a dehydrated state, with poor mechanical properties, limited stretchability, and notch-resistance, failing to meet consumer needs for conformance, comfort, and leakage prevention in absorbent products.
Innovation Solution
A double-network polymer system comprising a cross-linked, covalently-bonded polymer and a reversible, partially ionicly-bonded polymer, which is stretched and dehydrated to create a substrate with a moisture level of less than 15% and a latent retractive force, allowing it to shrink in one dimension and expand in another upon rehydration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional hydrogels are used, then they can absorb fluids, but they are soft and fragile in hydrated state and brittle and hard in dehydrated state with poor mechanical properties
Solution Approach 1:
The patent applies composite materials by creating a double-network hydrogel system where two different polymer networks (polyacrylamide and polyacrylic acid with calcium ions) are combined. This composite structure allows the material to simultaneously achieve high fluid absorption capacity and superior mechanical strength, eliminating the fragility problem of conventional single-network hydrogels while maintaining excellent absorbency.
2Length of moving object
If conventional hydrogels are stretched, then they have limited stretchability, but they lack elasticity and notch-resistance
Solution Approach 1:
The double-network composite structure provides both extended stretchability and enhanced reliability. The interconnected polymer networks distribute stress evenly, enabling the material to stretch significantly while maintaining elasticity and resistance to notching, solving the trade-off between stretchability and mechanical reliability.
3Strength
If hydrogels are dehydrated to improve mechanical strength, then they become brittle and hard, but they lose flexibility
Solution Approach 1:
The patent utilizes parameter changes by controlling the moisture content and ionic composition of the hydrogel. By adjusting the concentration of calcium ions and the ratio of polyacrylamide to polyacrylic acid, the material achieves optimal mechanical strength while maintaining flexibility and elasticity, eliminating the need to sacrifice flexibility for strength.
4Shape
If shrinking fibers are used to achieve tight fit, then they can shrink in water, but they are hardly soluble and do not possess elastic properties
Solution Approach 1:
The double-network hydrogel composite provides both shrinkage capability and elastic properties. The reversible ionic cross-linking between calcium ions and polyacrylic acid chains allows the material to shrink when wetted while simultaneously providing excellent elasticity and stretchability, overcoming the limitations of conventional shrinking fibers.
Data Source
AI summary
A substrate includes a double-network polymer system including a cross-linked, covalently-bonded polymer and a reversible, partially ionicly-bonded polymer, wherein the substrate has a moisture level less than or equal to 15 percent of the total weight of the substrate, and wherein the substrate includes a latent retractive force. A method for manufacturing a substrate includes producing a double-network hydrogel including a cross-linked, covalently-bonded polymer and a reversible, ionicly-bonded polymer; elongating by force the double-network hydrogel in at least one direction; dehydrating while still elongated the double-network hydrogel to form a substantially-dehydrated double-network polymer system; and releasing the force to produce the substrate.