KR100702573B1 - Polymeric bonding agent for composite solid propellant - Google Patents

Abstract

The present invention relates to a polymeric binder for a mixed solid propellant, wherein the terpolymer of acrylonitrile or methacrylonitrile, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, acrylic acid or methacrylic acid It provides a polymer binder consisting of. This binder has a carboxylic acid functional group capable of hydrogen bonding with a nitramine oxidant, which is effective in enhancing the mechanical properties of the mixed solid propellant by increasing the mutual bonding force between the filler and the binder having a very weak bonding force.

Propellant, polymeric binder, nitramine, hydrogen bond

Description

Polymer binder for mixed solid propellers {POLYMERIC BONDING AGENT FOR COMPOSITE SOLID PROPELLANT}

1 is a schematic diagram showing a chemical structure in which a nitramine oxidant and a carboxylic acid functional group form hydrogen bonds.

Figure 2 is a graph showing the results of measuring the mechanical properties of the solid propellant using the binder of the present invention.

The present invention relates to a polymer binder for a mixed solid propellant, and more particularly, to a polymer binder for improving the mechanical properties of a propellant by improving the binding force between the oxidant and the binder of the solid propellant.

The hybrid solid propellant is composed of 70 to 90% of solid oxidant particles, 10 to 30% of binder, plasticizer, and combustion additive. Since the mechanical properties of the solid propellant are greatly influenced by the bonding force between the oxidizing agent and the binder, the binder used for the purpose of enhancing the bonding force between the interface of the two components is a very important factor in the development of the mixed solid propellant. .

Many binders are used to improve the mechanical properties of hydroxy terminated polybutadiene (HTPB) propellants, which use ammonium perchlorate as a main oxidation agent, but cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine}, and HNIW {hexanitrohexaazaisowurtzitane} Little is known about binders that enhance the mechanical properties of propellants using nitramine oxidants such as oxidants.

Until now, methods for improving the mechanical properties of mixed solid propellants using nitramine oxidants have been proposed to coat oxidants and to use neutral polymeric bonding agents (NPBA).

The coating method of nitramine oxidant itself is similar to the polarity before the propellant mixing, so it is treated with nitrocellulose which has good affinity with oxidant. As the adsorbed nitrocellulose chemically bonds through binder and urethane reaction, mechanical properties are enhanced. . The adsorbed nitrocellulose, however, is dissolved and removed by the binder component in large amounts during the propellant mixing process, leaving only part of the coating, and the binding with the nitramine oxidant only depends on the van der Waals forces acting on each other. Its bonding strength is very weak.

The method of using a neutral polymeric binder was patented by CHung S. Kim in 1990 (US Patent 4,915,755), and has a functional group having a high affinity with a nitramine oxidant and at the same time combined with a binder such as polyethylene glycol (PEG). It is to use a polymer compound having a number average molecular weight (Mn) of 5,000 to 100,000 having a hydroxyl group. This neutral polymeric binder is characterized by no pre-coating in the example using nitrocellulose mentioned above, can be mixed during the propellant manufacturing process, and has a solubility parameter similar to that of the nitramine oxidant and binder components. It has a glass transition temperature (Tg) that is similar to the temperature of the propellant manufacturing process and can be easily adsorbed onto the surface of the nitramine oxidant through temperature changes. In addition, since it has a large number of hydroxyl groups in the molecule, it is adsorbed on the surface of the oxidant to form a hard shell to form a strong bond with the binder component and also serves as a crosslinking agent.

This neutral polymer type binder has a solubility factor that allows it to be adsorbed to the nitramine oxidant and has a polar nitrile functional group, which makes it easier to adsorb to the nitramine oxidant than the nitrocellulose. to be. However, it is impossible to form a hard crust on all surfaces of the nitramine oxidant, which is 0.05 to 3.0 wt% of the binder component, which accounts for more than 70 wt% of the total composition of the propellant. It acts as a disadvantage to disturb the even distribution.

In addition, although the neutral polymeric binder has a very good adsorption force on the surface of the oxidizer, the binding force formed between the oxidant and the binder is dependent on van der Waals' forces, and thus a greater binding force than the use of nitrocellulose cannot be expected. . Since it has only a large number of hydroxyl groups, it is believed that the role of increasing the strength of the propellant is increased by increasing the crosslinking density of the binder, which acts as a crosslinking agent and maintains the shape between the nitramine oxidizer.

It is an object of the present invention to develop a binder for the purpose of enhancing the mechanical properties of a mixed solid propellant composed of various nitramine oxidants and binders.

In order to achieve the above object, the present invention provides a nitramine oxidizer such as cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine}, HNIW {hexanitrohexaazaisowurtzitane}, inorganic oxidizers such as ammonium perchlorate and ammonium nitrate, and metal fuel such as aluminum and zirconium. It provides a polymeric binder that effectively enhances the mechanical properties of the mixed solid propellant using the filler, the binder is 0.3 ~ 15.0wt% acrylic acid or methacrylic acid, 10.0 ~ 30.0wt% 2-hydroxyacrylate or 2-hydroxymethacrylate, 55.0-8.7 wt% acrylonitrile or methacrylonitrile. The binder has a number average molecular weight in the range of 3,000 to 100,000.

The polymeric binder of the present invention consists of a terpolymer of acrylonitrile or methacrylonitrile, 2-hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, acrylic acid or methacrylic acid, and has a very high binding force. It is very effective in enhancing the mechanical properties of the mixed solid propellant by acting to increase the mutual bonding force between the weak filler and the binder.

In the present invention, in order to have a greater binding force with the oxidant than the binder known so far, the focus of the nitro group of the nitramine oxidant acts as an electron pair donor (hydrogen bond donor), as shown in Figure 1 To develop a polymeric binder having a carboxylic acid functional group capable of hydrogen bonding with a nitramine oxidant.

In general, hydrogen bonds are bonds formed between atoms that have a non-electron pair that can be acted as an electron pair donor by being bonded to atoms with high electronegativity between molecules or in a molecule. Hydrogen bonds are formed. Therefore, using this principle, carboxylic acid having a very positive hydrogen atom was introduced into the polymeric binder to strongly hydrogen bond with the oxygen atom of the nitro functional group acting as an electron pair donor.

The polymer-type binder is composed of acrylic acid or methacrylic acid capable of hydrogen bonding, acrylonitrile or methacrylonitrile, which binds to the nitramine oxidizing agent to increase the polarity of the binder, and 2-hydroxy capable of bonding with a binder. It consists of hydroxyethyl acrylate or 2-hydroxyethyl methacrylate, and synthesized by solution polymerization method by mixing three monomers as shown in the structural formula below. At this time, the number average molecular weight (Mn) of the synthesized binder was 3,000 to 100,000, and showed various glass transition temperature (Tg) and solubility characteristics according to the type and content of the monomer used, but the difference was not large.

Example 1

The polymeric binder of the present invention was synthesized in the following manner.

In a 500 ml 3-neck round-bottom flask, place a thermometer, cooler and add 150 ml of acetonitrile and a magnetic stirrer. A scale addition funnel containing a reaction mixture solution of 2.3 ml acrylic acid, 66.0 ml acrylonitrile, 20.7 ml 2-hydroxyethyl acrylate, and 2.5 ml normal butanethiol was installed. About 30 ml of the reaction mixture solution was added to the reaction vessel, and the temperature was raised to 50 ° C. in an oil bath with gentle stirring. When the temperature reached 50 ° C., 2.0 g of AIBN (2,2′-azobisisobutyronitrile) was added as an initiator and stirred. After about 10 minutes, while the remaining reaction mixture solution was slowly added, the temperature of the reaction mixture was maintained at 70 ℃. After the addition of the reaction mixture solution, the reaction mixture was further reacted at 70 ° C. for 6 hours, the oil bath was removed, and the reaction mixture was cooled to room temperature. The reaction mixture was mixed with 250 ml of acetone, precipitated in 700 ml of diethyl ether, and the solvent was removed and dried to obtain 51.1 g of a polymeric binder. At this time, the number average molecular weight was 43,000 and Tg was 56 ° C.

Example 2

In order to determine the effect of the binder by applying the polymeric binder of the present invention to the propellant and measuring the mechanical properties, the preparation and mechanical properties of the propellant were measured by the following method. The composition of the propellant is as follows.

1) Prepolymer: 10.0wt% [PCP0260 / PCP0310 = 4/1]

 * Polycaprolacton (PCP)

2) Plasticizer: 16.0wt% [BTTN / TMETN = 3/1]

 * BTTN (Butanettriol trinitrate), TMETN (Trimethylol ethane trinitrate)

3) Curing agent: 1.2wt% isophorone diisocyanate (IPDI)

4) Binder: 0.4wt% Polymeric Binder (PBA) of the present invention

5) Oxidizer: 51.0wt% [AP (ammonium perchlorate) / HNIW = 3/2]

6) Metal Fuel: 20.0wt% Al

7) Additive: 0.4wt% stabilizer / hardening catalyst

After mixing the raw materials of the composition for 3 hours with a propellant mixer, the prepared propellant mixture was vacuum cast in a mold and cured for 7 days at 50 ℃ oven. The hardened propellant was cut into a dumbbell-type Joint Army Navy NASA Air Force (JANNAF) uniaxial specimen, and the mechanical properties of the propellant were measured by the stress-strain and elastic modulus test method (KS M6518).

The results of applying the polymeric binder of the present invention to the propellant are shown in FIG. 2. The mechanical properties of the propellant, such as tensile strength (Sm) and elongation (εm), were significantly improved compared to when no binder was used or a neutral polymer binder was used.

In particular, when the neutral polymer type binder was used as in the case where no binder was used, the 'knee phenomenon', in which the binding between the oxidant and the binder was broken first and only the binder was increased, respectively. When the polymeric binder containing 1.0% and 3.0% was used, it could be seen that the 'knee phenomenon' did not appear at all.

From these results, it can be seen that the polymeric binder of the present invention greatly enhances the binding force between the oxidizing agent and the binder through strong hydrogen bonding with the nitramine oxidizing agent.

According to the present invention, the polymeric binder can greatly enhance the mechanical properties of the mixed solid propellant by greatly increasing the bonding force between the oxidant and the binder through a strong hydrogen bond with the nitramine oxidant.

Claims (4)

A binder used in a mixed solid propellant containing a nitramine oxidant, the binder comprising a polymer having a carboxylic acid functional group capable of hydrogen bonding with the nitramine oxidant. Polymeric binders. The method of claim 1, wherein the binder is 0.3-15.0 wt% acrylic or methacrylic acid, 10.0-30.0 wt% 2-hydroxyacrylate or 2-hydroxy methacrylate, 55.0-89.9 wt% acrylonitrile A polymeric binder which is a terpolymer of aryl or methacrylonitrile. The polymeric binder of claim 2, wherein the binder has a number average molecular weight of 3,000 to 100,000. delete

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