US3457329A - Inert simulant composition for a plastic bonded explosive - Google Patents

Description

United States Patent 3,457,329 INERT SIMULANT COMPOSITION FOR A PLASTIC BONDED EXPLOSIVE Wallace E. Silver and Jack Sherman, China Lake, Calif.,

assignors to the United States of Amercia as represented by the Secretary of the Navy N0 Drawing. Filed Feb. 21, 1968, Ser. No. 707,924 Int. Cl. C08f 29/20 U.S. Cl. 260-857 2 Claims ABSTRACT OF THE DISCLOSURE An inert simulant formulation for a high explosive composition which has the density, thermal conductivity, and thermal coeflicient of expansion of the duplicated explosive and also possesses equivalent physical strength, rigidity under stress, and machinability. This formulation provides inexpensive and safe testing of mock missiles and rocket warheads and other components utilizing high explosives.

Background of the invention The present invention is for an inert simulant composition for a high explosive.

In the field of explosives inert simulants or duplications thereof having the necessary characteristics for their practical use in mock warheads and similar missile components using high explosives are not known. A few compositions duplicating only one or two properties of the explosive were found but proved unsuccessful because density was the property most frequently simulated. A typical explosive simulant consisting of castor wax, ferrous oxide, calcium sulfate and wood rosin simulated only the pressed density and had the great drawbacks of melting at 187 F. Any elfective valuation of arerodynamic heating effects on -a mock missile war head containing this composition was precluded.

Summary of the invention This invention is for an inert simulant composition for plastic bonded explosives which comprises a mxture of polytetrafluoroethylene (sold under the trade name Tef- Ion"), a linear polyamide (sold under the trade name Zyte1) and entaerythritol. It duplicates the linear coefficient of thermal expansion and thermal conductivity of a plastic bonded explosive in addition to density and is also of comparable strength, easily bonded to other surfaces and readily machinable. Accordingly, this invention solved the longstanding need for an inert simultant composition possessed of suflicient of the characteristics of high explosives for use in effectively evaluating mock missile warheads and other devices which contain or use high explosives. This invention also provides an economical, practical and safe simulant for development and testing situations involving high explosive.

Description of the invention (1) Density, 1.700i0.010 gms./cc. (2) Linear Coeflicient of Thermal Expansion in the temperature range of 70 C. to 0 C., 5105x10 in./in.- C. (3) Thermal F.-ft.

Conductivity, 0.210.05 B.t.u.-ft./11r.-

"ice

The composition by weight percent which most closely simulated the plastic-bonded explosive is as follows:

Ingredients: Percent by weight Powdered polytetrafluoroethylene 69.8 Powered linear polyamide 3.5 Pentaerythritol 26.7

The polytetrafluoroethylene used in this application is sold under the trademark Teflon and is described in United States Patent No. 2,230,654. It has a density of 2.1--2.2 gms./cc., linear coefficient of thermal expansion (-70 C. to 0 C.) 7.2 10- in./in.- C., and thermal stability of 0.14 B.t.u.-ft./hr.- F.-ft. The linear polyamide sold under the trademark Zytel is a nylon resin of the general type described in United States Patents 2,071,250, 2,071,254 and 2,130,948. The linear polyamide used herein has a density of 1.1 gms./cc., a linear coefficient of thermal expansion (70 C. to 0 C.) 12.3 X 10 in./in.- C., and thermal conductivity of 0.16 B.t.u.- ft./hr.- F.-ft.

To make a fifty pound batch of the inert simulant, 1.75 lbs of Zytel 63 granular (soluble grade), and 54 lbs. of methanol were placed in a forty gallon slurry kettle. Water at 125 F. was turned on in the kettle jacket and the mixture stirred moderately (100 r.p.m.) until all the Zytel 63 was dissolved (60-120 minutes). Care should be taken not to exceed 115 F. fluid temperature inside the kettle. When the Zytel is completely dissolved, the stirring rate should be increased to 200 r.p.m. and first, 34.9 lbs. of powdered Teflon, then 13.35 lbs. of pentaerythritol should be gradually added by hand. Stirring should be continued at 200 r.p.m. for another 15 minutes to completely disperse both the Teflon and the entaerythritol. When the complete dispersion in the lacquer has taken place, increase the stirring rate to 400 r.p.m. At this point, the mixture is water quenched, and the Zytel is released from solution with the methanol coating the pentaerythritol, while the methanol is drawn 01f in solution with the quench water. A large quench of to 100 lbs. of F.- F. water is added to initiate break-up of the mix into small particles. Stirring is continued at approximately 400 r.p.m. while adding the 80 F.85 F. water as a constant rate until the kettle volume is filled. At this point, the proper particle size is achieved. The jacket is then drained of warm water, and 75 F.80 F. cold water is added through the jacket to cool the mix. Stirring is stopped, the cold water is turned off, and the particles are allowed to settle. The supernatant liquid is then decanted off, and the remaining water-simulant mixture is manually withdrawn'from the kettle. The mixture is filtered for several hours to remove additional liquid, and then oven dried overnight at F. in flat trays. The dried material should possess the following particle size distribution: 10% will remain in a 5 mesh screen and less than 5% will pass through a 40 mesh screen.

The compositon contained about 69.8% by weight Teflon, 3.5% by weight Zytel and 26.7% by weight pentaerythritol. A tabulation of the physical properties for the plastic bonded explosive and its inert simulant determined by using duplicate samples are listed below:

This composition is pressable and is presently being successfully used for mock warhead configurations in several missile programs and to simulate the explosive charge of various bombs which are used in conjunction with other well developed rocket programs.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. An inert simulant formation for high explosive compositions comprising an admixture of about 70 percent by weight polytetrafluoroethylene, about 27 percent by weight pentaerythritol and about 4i0.5 percent by weight linear polyamide to simulate a density from 130010.110 gms./cc., thermal conductivity from 02:0.05 B.t.u.-ft./ hr.- F.-ft. and thermal coeificient of expansion in the temperature range of --70 C. to C., 5i0.5 10- in./in.-C. of said explosive composition.

2. An inert simulant formulation for a plastic-bonded explosive consisting of the following:

References Cited UNITED STATES PATENTS 3,018,203 1/1962 Guth 14945 X 3,108.917 10/1963 McIrvine 149105 X 3,375,122 3/1968 Roth 106204 BENJAMIN R. PADGETT, Primary Examiner S. J. LECHERT, Assistant Examiner US. Cl. X.R.