Crosslinked Nanofibrillar Cellulose for Flexible Membranes
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Solution Overview
Problem
Nanofibrillar cellulose products, such as membranes and coatings, are brittle and lack elasticity, making them unsuitable for medical and scientific applications that require flexibility and biocompatibility, and existing methods for crosslinking with multivalent cations face challenges like uncontrollable fibril aggregation.
Innovation Solution
A method involving anionically modified nanofibrillar cellulose being contacted with multivalent cations to form crosslinked nanofibrillar cellulose products, which are then processed to enhance mechanical strength, flexibility, and biocompatibility, using techniques like diffusion-aided bridging or time-triggered bridging to control crosslinking without aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If nanofibrillar cellulose is used to form membranes or coatings, then the product can be produced with high purity and biodegradability, but the membranes become brittle and lack elasticity
Solution Approach 1:
The patent applies parameter changes by introducing multivalent cations (Ca2+, Mg2+, Zn2+, Al3+) to crosslink the anionic nanofibrillar cellulose chains. This chemical modification changes the physical parameters of the material, transforming it from a brittle state to a flexible, elastic state while maintaining biodegradability. The crosslinking density and type of cation can be adjusted to optimize both mechanical properties and biological compatibility.
Solution Approach 2:
The patent creates a composite material system combining nanofibrillar cellulose with multivalent cations. This composite approach allows the natural cellulose framework to maintain its biodegradability while the crosslinked network provides mechanical flexibility and elasticity. The composite structure enables simultaneous achievement of biological compatibility and mechanical adaptability.
2Strength
If multivalent cations are mixed with anionic nanofibrillar cellulose, then crosslinking can occur to improve mechanical properties, but uncontrollable fibril aggregation and flock formation occur
Solution Approach 1:
The patent applies preliminary action by pre-modifying the nanofibrillar cellulose with anionic groups (such as carboxyl groups) before introducing the multivalent cations. This preparation step ensures that the cellulose is ready for controlled crosslinking. The anionic groups are introduced in a controlled manner during fibrillation or purification steps, creating a stable foundation that prevents uncontrolled aggregation when cations are added.
Solution Approach 2:
The patent uses multivalent cations as intermediaries that mediate the crosslinking process between anionic nanofibrillar cellulose chains. The cations act as bridges that selectively connect fibrils in a controlled manner, preventing direct aggregation. By controlling the addition rate, concentration, and environmental conditions (pH, temperature), the intermediary cations enable uniform crosslinking without fostering flock formation.
3Ease of manufacture
If nanofibrillar cellulose is dried to form self-supporting structures, then membranes can be produced, but shrinkage occurs during drying
Solution Approach 1:
The patent applies preliminary action by introducing multivalent cations into the nanofibrillar cellulose structure before drying. This crosslinking step creates a stable network that maintains dimensional integrity during the drying process. The cations are introduced in a controlled manner during the wet state, and their crosslinking action prevents shrinkage that would otherwise occur during water removal.
Solution Approach 2:
The patent uses parameter changes by modifying the chemical composition through cation crosslinking before dimensional stabilization. This chemical modification changes the physical parameters of the material, creating a crosslinked network that resists shrinkage during drying. The crosslinking density and cation type can be optimized to achieve minimal shrinkage while maintaining self-supporting structure formation.
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 crosslinked nanofibrillar cellulose products exhibit improved mechanical strength, elasticity, and biocompatibility, suitable for medical and scientific applications, including wound healing and cell culture, with enhanced absorption capacity and remouldability, and can be used as flexible coatings or membranes.
Implementation Method 1
The multivalent cations can be used to crosslink the nanofibrillar cellulose and therefore harden the gels
Implementation Method 2
This limits their shrinkage during drying, such as lateral or longitudinal shrinkage of layers, coatings, sheets or membranes
Implementation Method 3
contacting the anionically modified nanofibrillar cellulose with the multivalent cations
Data Source
AI summary
The present application provides a method for preparing nanofibrillar cellulose product, the method comprising providing nanofibrillar cellulose, providing multivalent cations, contacting the nanofibrillar cellulose with the multivalent cations, and allowing reacting for a period of time to obtain cross-linked nanofibrillar cellulose product. The present application also provides a nanofibrillar cellulose product comprising nanofibrillar cellulose and multivalent cations, wherein the nanofibrillar cellulose is crosslinked by the multivalent cations.