Non-crosslinked Polymeric Gum Binder for Propellant Powders
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Solution Overview
Problem
The development of composite pyrotechnic products for tube weapons faces challenges with vulnerability due to nitrocellulose-based binders, which can ignite from physical impacts, and the use of thermoplastic or thermosetting binders presents difficulties in mechanical working and industrial-scale manufacturing, especially with high energetic fillers like RDX, requiring complex and costly solvent-based processes.
Innovation Solution
The use of a non-crosslinked polymeric gum binder, such as polyurethane-polyester or polyurethane-polyether gums, with a high molecular weight and specific Mooney viscosity, allows for high energetic charge loading without the need for solvents or crosslinking agents, enabling easier processing and reduced vulnerability, and can include energetic plasticizers for enhanced performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If nitrocellulose-based binders are used in composite pyrotechnic products, then the binder provides good binding properties and processability, but the vulnerability of the powder increases due to ignition from physical impacts
Solution Approach 1:
The patent changes the chemical composition parameters of the binder by using polyurethane-polyester or polyurethane-polyether gums instead of nitrocellulose. This substitution maintains binding properties and processability while fundamentally altering the chemical reactivity to reduce vulnerability to impact ignition.
2Object-affected harmful factors
If inert thermoplastic binders are used to reduce vulnerability, then the powder vulnerability decreases significantly, but the charge rate must be increased to close to 80% of total mass to deliver necessary energy
Solution Approach 1:
The patent optimizes the binder composition parameters by selecting specific polyurethane-polyester or polyurethane-polyether gums with appropriate molecular weights and Mooney viscosities. This allows achieving the necessary binding strength with reduced binder quantities (10-22% by mass), thereby enabling higher charge rates without compromising mechanical integrity.
3Object-affected harmful factors
If inert thermosetting binders are used to reduce vulnerability and improve mechanical strength, then the powder vulnerability decreases and mechanical strength improves, but the manufacturing process becomes complex and difficult to implement on an industrial scale
Solution Approach 1:
The patent extracts and eliminates the crosslinking step from the manufacturing process by using non-crosslinked polymeric gum binders. This removes the complexity associated with crosslinking agents, curing conditions, and process control, while still achieving reduced vulnerability and adequate mechanical strength through the inherent properties of the polymeric gums.
Solution Approach 2:
The patent employs simple, readily available polymeric gum binders that do not require complex crosslinking chemistry. These binders provide sufficient performance for industrial-scale manufacturing without the need for sophisticated process control, making the manufacturing process simpler and more economically viable.
4Ease of operation
If thermoplastic binders are used to allow mechanical working at temperature, then the product can be shaped, but the mechanical properties become too sensitive to thermal variations
Solution Approach 1:
The patent uses polyurethane-polyester or polyurethane-polyether gums that combine the processability advantages of thermoplastic materials with improved thermal stability. These polymeric gums provide a balanced structure that allows mechanical working while maintaining more stable mechanical properties across temperature variations compared to conventional thermoplastic binders.
Data Source
AI summary
The present invention relates to composite pyrotechnical products, in particular to propellant powders for barrelled weapons, in which the composition, expressed in weight percentages, includes: 78 % to 90 %, advantageously 80 % to 86 %, of organic energy loads; and 10 % to 22 % of a polymer gum, selected among the polyurethane-polyester gums, the polyurethane-polyether gums and the mixtures thereof, in which the average molecular weight by number is higher than 20,000 g/mol and in which the Mooney viscosity is from 20 to 70 ML (5 + 4) at 100 °C. The invention also relates to the method for obtaining said products. Said products are particularly useful given the properties thereof and how easily they can be obtained.