Chitosan Flame Retardant via Hypophosphorous Acid Depolymerization
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Solution Overview
Problem
Chitosan's poor solubility and brittleness limit its processing and application as a flame retardant, requiring multiple processing steps and the addition of phosphorus components, which complicates its use in coatings and increases costs.
Innovation Solution
A flame retardant composition comprising chitosan, a modified chitosan, an aqueous acid, and a polyol or crosslinking agent, where hypophosphorous acid is used to dissolve and depolymerize chitosan, reducing processing steps and costs, and enhancing flame retardancy by forming oligochitosan with improved solubility and antimicrobial properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chitosan is used as a flame retardant, then flame resistance is improved, but solubility and processability deteriorate due to poor solubility in most solvents
Solution Approach 1:
The patent changes the chemical parameters of chitosan by controlling the degree of deacetylation and molecular weight through enzymatic hydrolysis. This produces oligochitosan with specific properties that balance flame retardancy with improved solubility and processability in aqueous solutions
Solution Approach 2:
The patent creates composite formulations by combining oligochitosan with other flame retardant components and additives. This composite approach enhances the overall flame resistance while maintaining processability through the synergistic effects of the components
2Reliability
If chitosan is used as a flame retardant, then flame resistance is improved, but brittleness increases limiting application flexibility
Solution Approach 1:
The patent modifies the physical parameters of chitosan by controlling molecular weight reduction through enzymatic hydrolysis. The resulting oligochitosan has lower molecular weight which reduces brittleness and improves flexibility while maintaining flame retardant properties
Solution Approach 2:
The patent formulates composite coatings that combine oligochitosan with flexible polymers or plasticizers. This composite structure maintains the flame resistance of chitosan while the other components provide the necessary flexibility and toughness
3Reliability
If conventional processing methods are used for chitosan, then flame retardancy is achieved, but multiple processing steps and phosphorus component addition are required increasing complexity and cost
Solution Approach 1:
The patent combines multiple functions into a single material by producing oligochitosan that inherently provides flame retardancy, solubility, and processability. This eliminates the need for separate phosphorus component additions and multiple processing steps required by conventional methods
Solution Approach 2:
The patent enables oligochitosan to self-provide flame retardant properties through its inherent chemical structure and decomposition behavior. The material serves its own flame protection function without requiring additional phosphorus-based additives or complex multi-step processing procedures
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 solution results in a more easily processable and effective flame retardant coating with improved flexibility, reduced water solubility, and enhanced flame resistance, allowing for thermoformability and extrudability, while maintaining antimicrobial properties.
Implementation Method 1
Chitosan forms a polyvalent cation in acidic solutions when the amines along the polysaccharide chains are protonated
Implementation Method 2
Chitosan can be dissolved in a variety of aqueous acids
Implementation Method 3
hypophosphorous acid is used to dissolve and depolymerize chitosan
Implementation Method 4
chitosan can be physically crosslinked to form insoluble gels by introducing polyvalent cations
Implementation Method 5
Control of the gelation procedure is difficult, typically resulting in gels that form immediately upon mixing
Implementation Method 6
Chitosan as an intumescing, thermoformable flame retardant
Data Source
AI summary
A flame retardant composition comprising chitosan or a modified chitosan, as well as a method for preparing a flame retardant comprising chitosan or a modified chitosan, is provided. Also provided are methods for making a flame retardant article using the described flame retardant composition. In various embodiments, the flame retardant composition is prepared by dissolution of chitosan or a modified chitosan by an aqueous acid, followed by evaporation of the water. In various embodiments, the flame retardant composition can further include at least one additional component selected from the group consisting of a polyol, flame retardant, nitrogen containing compound, carbonate containing compound, crosslinking agent, and combinations thereof.