Superabsorbent Polymer Slip-Strain Control for Swelling Permeability
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Solution Overview
Problem
Existing super absorbent polymers face challenges in achieving a balanced improvement in absorption rate, permeability, and centrifuge retention capacity due to issues with cross-linking density, leading to problems like shape maintenance, fine powder generation, and degradation of physical properties.
Innovation Solution
A polyacrylic acid-based super absorbent polymer with a slip strain of 12.5% or less at 30% swelling and an absolute rate of change in slip strain of 0.04 or less between 30% and 70% swelling is developed, optimizing permeability and absorption rate by controlling inter-particle slip.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If cross-linking polymerization is performed by including a foaming agent in a monomer composition to form a porous structure, then surface area and permeability are improved, but overall physical properties are degraded and shape maintenance capability is reduced
Solution Approach 1:
The patent removes the foaming agent from the polymerization system entirely, replacing it with a different approach using a porogen substance that achieves porous structure formation without the harmful side effects. This extraction of the problematic component resolves the contradiction by eliminating the cause of physical property degradation while maintaining the beneficial porous structure.
Solution Approach 2:
The patent introduces a porogen substance as an intermediary agent that enables porous structure formation without directly becoming part of the polymer matrix. The porogen temporarily occupies space during polymerization, creating pores when removed, thus mediating between the need for surface area and the need to maintain physical properties.
2Area of stationary object
If cross-linking density is increased to improve permeability, then permeability is improved, but centrifuge retention capacity is degraded
Solution Approach 1:
The patent optimizes the cross-linking density parameter to a specific range (0.01-5 parts by weight of cross-linking agent per 100 parts by weight of monomer) that simultaneously achieves adequate permeability and maintains centrifuge retention capacity. This parameter optimization resolves the contradiction by finding the optimal balance point rather than maximizing one parameter at the expense of the other.
3Quantity of substance
If a super absorbent polymer is included at a relatively high ratio in a product to increase absorption capacity, then absorption performance is improved, but fine powder generation increases
Solution Approach 1:
The patent creates a composite structure where polymer particles with controlled cross-linking density and porous morphology are combined in a way that reduces fine powder generation. The specific particle morphology and surface properties achieved through the improved polymerization method reduce particle fragmentation, thus resolving the contradiction between high absorption capacity and low fine powder generation.
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 optimized polymer maintains excellent permeability and absorption rate throughout the swelling process, with improved centrifuge retention capacity and reduced fine powder generation, ensuring balanced physical properties.
Implementation Method 1
the entire polymer absorbs water well
Implementation Method 2
A super absorbent polymer (SAP) is a synthetic polymer material which has the ability to absorb moisture 500 times to 1,000 times its own weight
Implementation Method 3
forming a porous structure in base resin powder to increase the surface area of a super absorbent polymer
Data Source
AI summary
A polyacrylic acid (salt)-based super absorbent polymer has a slip strain (%) of 12.5% or less after the polyacrylic acid (salt)-based super absorbent polymer is subjected to 30% swelling. The slip strain means a value at a time when a storage modulus rapidly decreases with an increase in strain when a change in the storage modulus is observed by increasing the slip strain of each sample from 0.01% to 100% using a rheometer under a frequency of 1 Hz and a temperature of 25° C. The superabsorbent polymer has an absolute value of a rate of change in slip strain at 30% and 70% swelling derived by Equation 1 of 0.04 or less, wherein Equation 1 is Rate of change in slip strain at 30% and 70% swelling=[{(slip strain at 70% swelling)−(slip strain at 30% swelling)}/40].