Aliphatic Polyisocyanate Crosslinking for Pyrotechnic Propellants
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The use of aromatic diisocyanates in composite pyrotechnic products is carcinogenic, mutagenic, and toxic, necessitating a substitute that maintains mechanical and thermal protection properties while avoiding CMR substances.
Innovation Solution
A process using aliphatic polyisocyanates as crosslinking agents, predominantly in oligomeric forms, to create a composite pyrotechnic product with a bridging ratio of 0.9 to 1.5, ensuring mechanical strength and thermal protection without CMR substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aromatic diisocyanates are used as crosslinking agents, then mechanical properties and thermal protection are improved, but carcinogenicity, mutagenicity and reproductive toxicity occur
Solution Approach 1:
The patent changes the chemical composition parameter of the crosslinking agent from aromatic diisocyanate to aliphatic polyisocyanate, specifically using oligomeric forms with controlled functionality (2.3-3.7) and molecular weight (500-5000 g/mol). This parameter change eliminates the harmful aromatic structures while maintaining the crosslinking functionality needed for mechanical strength and thermal protection properties
Solution Approach 2:
The patent employs oligomeric aliphatic polyisocyanates that can be fully consumed in the crosslinking reaction, leaving no residual monomeric harmful substances. The oligomeric nature ensures complete reaction with hydroxyl groups, eliminating long-lived harmful residues while providing the necessary crosslinking density for product performance
2Object-affected harmful factors
If aliphatic polyisocyanates in oligomeric forms are used as crosslinking agents, then CMR substances are eliminated, but maintaining mechanical strength and thermal protection properties becomes challenging
Solution Approach 1:
The patent optimizes multiple parameters of the aliphatic polyisocyanate oligomers: functionality (2.3-3.7), molecular weight (500-5000 g/mol), and bridging ratio (0.9-1.5). These parameter adjustments ensure sufficient crosslinking density to achieve mechanical strength and thermal protection properties comparable to aromatic diisocyanate systems while maintaining safety
Solution Approach 2:
The patent creates a composite crosslinking system combining aliphatic polyisocyanate oligomers with the energetic binder matrix. The oligomeric structure provides multiple reaction sites that form a complex three-dimensional network within the binder, achieving the desired mechanical and thermal properties through this composite material architecture
3Reliability
If oligomeric aliphatic polyisocyanates with functionality 2.3-3.7 are used, then reactivity and stability are improved, but process optimization becomes more complex
Solution Approach 1:
The patent establishes specific parameter ranges for the oligomeric aliphatic polyisocyanates: functionality (2.3-3.7), molecular weight (500-5000 g/mol), and bridging ratio (0.9-1.5). These defined parameters create a controlled reaction system with improved reactivity and stability, though they require systematic optimization during process development
Solution Approach 2:
The patent implements monitoring and control of the bridging ratio (NCO/OH ratio) during the crosslinking process. By measuring and adjusting this key parameter, the process achieves optimal reactivity and stability while producing consistent product quality, transforming the complexity into a controllable feedback-driven process
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 achieves comparable mechanical and peeling properties to products using aromatic diisocyanates, with improved reactivity and stability, and is scalable for industrial use.
Implementation Method 1
crosslinked via its telechelic hydroxyl functions with at least one polyisocyanate type crosslinking agent
Implementation Method 2
a glycidyl polyazide with hydroxyl terminal functions, the number average molecular weight of which is between 700 and 3000 g/mol
Implementation Method 3
the heat treatment of said homogeneous paste cast in said at least one structure
Implementation Method 4
the thermal protection (PT)/binder/product assemblies also present interesting peeling properties
Data Source
AI summary
The present invention relates to the field of solid propulsion. More specifically, it relates to a process for preparing composite pyrotechnic products (composite solid propellants) comprising the use of a specific crosslinking system consisting of aliphatic polyisocyanates: - existing, for more than 99.6% by mass, in the form of oligomers and, for less than 0.4% by mass, in the form of at least one monomer, - having an overall functionality of 2.1 to 3.0, and - used in an amount that ensures a bridging ratio Rp(NCO/OH) of 0.9 to 1.5. The present invention also relates to composite pyrotechnic products (composite solid propellants) that can be obtained by the process of the invention. These composite pyrotechnic products (composite solid propellants) are particularly suitable for the propellant charges of strategic or tactical missiles.