Semi-Continuous Polyurethane Explosive Casting Process
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Solution Overview
Problem
The existing processes for producing composite explosive charges with a polyurethane solid matrix face challenges such as short pot life, long polymerization times, and economic inefficiencies, particularly when manufacturing large quantities of small objects like shells, due to the batch process, and the two-component process has difficulties with homogenization and safety concerns.
Innovation Solution
A semi-continuous process involving the continuous mixing of two components, A and B, with A containing the polyol prepolymer and powdery filler and B containing the polyisocyanate monomer, where the mass ratio of A to B is between 95.05/4.95 and 99.55/0.45, and incorporating a small quantity of polyisocyanate monomer in A to reduce viscosity, allowing for easier mixing and storage while maintaining the desired mechanical and detonation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a batch process is used to mix all constituents in a mixer, then large objects such as underwater mines, torpedoes and bombs can be manufactured, but it is very penalizing and expensive for manufacturing large quantities of small objects like shells
Solution Approach 1:
The explosive composition is divided into two separate paste components (Component A with polyol prepolymer and Component B with isocyanate monomer) that are mixed continuously in a 1:1 mass ratio. This segmentation allows each component to be prepared independently and continuously, enabling high-speed manufacturing of small objects while maintaining the ability to produce large objects.
Solution Approach 2:
The patent implements a continuous mixing process where Component A and Component B are continuously combined in equal proportions to form the explosive paste. This continuous action eliminates the batch process interruptions and enables sustained high-speed production of small munitions, while the process can be scaled for large objects.
2Duration of action of moving object
If the pot life is extended by reducing the rate of crosslinking catalyst, then the paste can be stored longer, but the polymerization time increases and the temperature must be limited
Solution Approach 1:
The crosslinking catalyst function is segmented: Component A contains the polyol prepolymer without catalyst, while Component B contains the isocyanate monomer. The crosslinking reaction is initiated only when the two components are mixed in equal proportions, providing both extended pot life for storage and controlled polymerization time upon mixing.
Solution Approach 2:
The two components are prepared in advance and stored separately with stable pot lives. The crosslinking reaction is preliminarily controlled by the mixing ratio, ensuring that polymerization begins only when components are combined in the correct 1:1 proportion, thus managing both storage duration and reaction time.
3Duration of action of moving object
If two pasty components are mixed continuously to overcome pot life limitations, then components can be stored for several weeks, but it is very difficult to obtain a homogeneous product
Solution Approach 1:
The patent ensures homogeneity by designing Component A and Component B with approximately the same viscosity and loading rate, and by mixing them in equal mass proportions (1:1 ratio). This careful matching of physical properties and stoichiometric mixing guarantees homogeneous mixing while allowing continuous processing and long-term storage of individual components.
4Reliability
If both components are made pyrotechnically active for storage stability, then they can be stored separately, but they must be produced and stored in secure facilities
Solution Approach 1:
The patent converts the potential harm of storing two pyrotechnically active components into a benefit by designing the system so that Component A (polyol prepolymer) and Component B (isocyanate monomer) are individually stable and non-pyrotechnic when stored separately. The pyrotechnic properties are only activated when both components are mixed in equal proportions, thus maintaining storage stability while enabling explosive functionality.
5Duration of action of moving object
If the isocyanate component is prepared as a prepolymer in an intermediate step, then storage is possible, but the solid polyurethane matrix structure differs from the classic batch process
Solution Approach 1:
The patent changes the parameter of isocyanate from monomer form (classic batch process) to a controlled continuous mix with polyol prepolymer, where Component B contains isocyanate monomer that reacts with Component A's polyol prepolymer. This parameter change enables storage of stable components while producing the correct polyurethane matrix structure through controlled continuous mixing and subsequent crosslinking.
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
This process eliminates the drawbacks of previous methods by allowing for increased casting flow rates with reduced pressure, easier homogenization, and storage of components, resulting in a product with identical properties to the classic batch process, reducing requalification needs and operational costs.
Implementation Method 1
The powdery filler is mixed in a mixer with a liquid polymerizable resin, for example a hydroxyl-terminated prepolymer. We obtain a paste that can be poured into a mold and then polymerized by cooking.
Implementation Method 2
By choosing and adjusting resin crosslinking agents, catalysts and other additives, molded parts of varying characteristics can be obtained.
Implementation Method 3
The paste must be used within a fairly short period of time (pot life). The extension of the pot life by reducing the rate of crosslinking catalyst has the counterpart of an increased polymerization time, the temperature being limited, among other things, by the pyrotechnic nature of certain constituents.
Data Source
AI summary
Semi continuous process of forming a composite explosive charge having a charged solid polyurethane matrix comprises: forming a pastry explosive composition (containing a polyol prepolymer, a polyisocyanate monomer, a plasticizer and a pulverulent solid charge having at least one nitro-organic explosive) by continously mixing a liquid component A having the monomer and a pastry component B1 having the prepolymer and the filler in which the plasticizer is distributed between the components; and introducing and thermal crosslinking the composition in to a mould. Semi continuous process of forming a composite explosive charge having a charged solid polyurethane matrix comprises obtaining a pastry explosive composition (containing a polyol prepolymer, a polyisocyanate monomer, a plasticizer and a pulverulent solid charge having at least one nitro-organic explosive) by continously mixing a liquid component A having the monomer at 90-99 wt.% and a pastry component B1 having the prepolymer and the filler together at 1-10 wt.% in which the plasticizer is distributed between the components; introducing the composition in to a mould; and thermal crosslinking the composition in the mould, where the A:B1 weight ratio is 95.05:4.95-99.55:0.45.