THE JOURNAL OF i
PHYSICAL CHEMISTRY (RegiRtered in U . S. Patent Office)
VOLUME 59
(Copyright, 1955, by the American Chemical Society)
NUMBER 8
AUGUST 24, 1955
DETONATION PROPERTIES AND REACTION IiIL\iETICS OF !2,4-DINITROTOLUENE1 BY MELVINA.
COOK A N D W I L L I A M
8. P a R T R I D G E
Explosives Research Group, University of Utah, Salt Lake City, Utuh Received August B, 1964
The experiinental detonation velocity-diameter and wave shape-diameter curves for 2,4-dini trotoluene of particle size -65 100 mesh and density 0.95 g./cc. are presented. The velocity-diameter curves are interpreted by means of the nozzle and curved front theories, which predict (best fit) reaction zone lengths of 2.9 em. (total react,ion time about 7 psec.) and 1.5 em. (total reaction time about 4 psec.), res ectively. Within the accuracy of the measurements the detonation wave fronts seemed t o be spherical throughout, a n l the observed steady state radius of curvature/diameter R,/d increased uniformly from 0.57 near the critical diameter to 1.65 (still increasing) a t the maximum diameter studied (25 cm.). The critical diameter d, was between 3.8 and 5 em.
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DNT has long been known to be explosive; in fact, 4500 pounds of DNT exploded accidentally in 1943.2 However, no data are recorded in available literature on the detonation properties or reaction kinetics of DNT, owing perhaps to the lack of interest in DNT as a practical explosive by itself. DNT is, however, used extensively in numerous commercial and some military explosives including various liquid explosives (e.g. , the commercial nitroglycerine-DNT mixture EL 389) and solid .explosives (e.g., “Nitramon,” dynamites, and many others). For studies of the kinetics of chemical reactions in detonation, DNT offers several interesting advantages. Owing to its relatively low detonation temperature, one would expect DNT to react relatively slowly in detonation reactions. As a pure explosive compound DNT offers, moreover, a well defined and readily tractable reaction rate problem. By selecting a single isomer (2,4-DNT in this case) one can obtain D N T in solid forn, in wiform particle size. D N T is, of course, similar chemically to T N T which has been studied extensively and for which reaction rate studies have also been carried out. Whereas one requires specially prepared T N T of large particle sizes t o obtain suitable velocity diameter data for theoretical study, even the (1) This study was supported by Office of Naval Research (Contract Number N7-onr-45107, Project Number 357 239). (2) C. S. Robinson, “Explosives, Their Anatomy and Destructiveness,” McGraw-Hill Book Co., New York, N. Y., 1944. (3) M . A. Cook. G. S. Horsley, W. S. Partridge, and W. 0. Urscnbach (submitted for publication).
regular fine-grained DNT is suitable for this purpose. Indeed -65 100 mesh (2,4)-DNT exhibits a diameter effect on velocity over a much broader range even than -4 6 mesh TNT. This article presents measured velocity-diameter and wave shape (R,/d)-diameter curves for solid 2,4-DNT1 together with the theoretical “best fit” velocity-diameter curves of the nozzle, and curved front5 theories. Ideal detonation properties of DNT computed for densities of 1.04 and 1.59 g./cc. (log F valuese of 3.0 and 6.0) by methods reported previously6~’ are also presented (Table I),
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Experimental The D N T used in this investigation was technical grade 2,4-DNT obtained from the du Pont Company. This product was carefully screened, and the portion through 65 on 100 mesh standard Tyler mesh screens was used in this study. Containers were manila paper tubes of about 1 mm. wall thickness. One end of each tube observed in wave shape studies was cut on a lathe exactly perpendicular to the longitudinal axis. A glass plate was placed over this end of the tube to improve photographic definition of the emerging detonation wave. Pin inserts were placed in the tubes at accurately measured positions for velocity measurement in all except the smallest diameter tubes. I n small diameters windows were cut and lined with scotch tape along the side of the charge for velocity measurements by a streak camera. The charges were all vibrator-packed to obtain (4) H . JAnes, Proc. Roy. SOC.(London), 8189, 415 (1947). ( 5 ) H. Eyring, R. E. Powell, G. H. Duffey and R. B. Parlin, Chem. Reus., 45, 70 (1949); R. B. Parlin end D . ’CV. Robinson, Technical Report No. VII, ERG, Utah University, October 3, 1952. (6) M. A. Cook, G . S. Horsley, A. S. Filler and R. T . Keyes, THIS 88, 1114 (1954). JOURNAL, (7) M:A. Cook, J . Chem. Phys., 15, 518 (1047).
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MELVINA. COOKAND WILLIAMS. PARTRIDGE
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EXPERIMENTAL NOZZLE THEORY CURVED FRONT THEORY
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IO DIAMETER -cm.
Fig. 1.-Experimental
and theoretical (curved front and nozzle) velocity-diameter curves for 2,4-DNT.
iiniform density, and the open end was sealed with masking tape. The average density of each charge was measured by total volume and weight determinations. All charges except those a t 25 em. were made a t a length/diameter ( L / d ) ratio of six, and those a t 25 cm. had an L/d of 4.5.
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TABLE I DETONATION PROPERTIES OF DNT log F 3.00 6.00 (H2) moles/kg. 0.54 0.00 ( N2) moles/kg. 4.51 5.07 5.36 0.23 (CO) moles/kg. ( COz) moles/kg. 4.87 6.85 ( H ) moles/kg. 0.00 0.00 (CHd) molesjkg. 2.24 0.11 2.54 6.95 (CHBOH) 1.00 0.13 (HCN) moles/kg. (H20)moles/kg. 4.42 1.20 (NHa) moles/kg. 0.97 0.73 (C) moles/kg. 22.4 24.2 ?L moles/kg. 26.5 21.3 956 1020 Q (kcal./kg.) C, (kcal./kg./”K.) 0.404 0.428 1.04 1.59 Pl (g./cc.) T x (OK.) 3.00 3.17 4.21 D X 10-3 (m./sec.) 5.47 p~ X 10-4 (atm.) 4.49 10.9
For wave sha e measurements, the rotating mirror camera was used tfwoughout. Owing to the low luminosity associated with the detonation wave of D N T , a thin, approximately 1 mm. thick, layer of tetryl was placed between the glass plate and the D N T across the field of view of the camera slit. This procedure was used also in velocity measurements made by the “streak” camera method and gave very satisfactory photographic traces. Wave shapes were photographed placing the charge so that the image of the camera slit coincided with a diameter of the charge. The trace of the emerging detonation wave was converted to actual wave shape by use of the experimental velocity, the appropriate magnification factor determined by photographing a “static image” on the film, and the speed of the camera.
Results and Interpretations The critical diameter of 2,4-DNT (-65 100 mesh) was found to be between 3.8 and 5.04 cm., consistent failures resulting a t 3.8 cm. and consistent detonations a t 5.04 cm. Figure 1 shows the experimental and theoretical detonation velocity-di ameter plots for this explosive. The theoretical D*( pl) (ideal velocity us. density) relation computed by means of the a(u) equation of state and the empirical a(v) curve6J is given by the equation D* 4125 + 227O(pj - 1.0) While it is uncertain from the experimental results that the experimental D-d curve of Fig. 1 should level off at the velocity predicted from this equation, The charges were all fired with cast 50/50 Pentolite boost- the use of this equation in theoretical calculations ers. Velocity was measured in all except the smallest appears t o give as satisfactory agreement as possidiameter charges by an accurate “pin-oscillograph’’ de- ble for each of the theories. At d = 25 cm. the signed and constructed in this Laboratory. For diameters near the critic,al diameter d,, velocity measurements were measured velocity, in fact, was only 100 m./sec. made by means of a rotating mirror “streak” camera hav- lower than D* computed from this equation. An ing a maximum film speed of 5 mm./Nsec. Velocities were experimental evaluation of D* would have required corrected to an average density p1 of 0.95 g./cc. by use of a prohibitive amount of explosive due to the large the theoretical velocity-density slope A D / A p l = 2270 m./ get. However, only a small density correction was required diameters required to obtain ideal detonation, namely, about 35-40 cm. in any case.
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August, 1955
REACTION RATESOF AMMONIUM NITRATEIN DETONATION
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of 2.5 and 3.2 cm. Those of the curved front theory were computed for ao = 1.25 and 1.75 cm. From the evidence of best fit, the best total reaction time according to the nozzle theory was about 7 psec. whilethatforthecurvedfronttheorywasabout4psec. The curve front theory requires that the radius of curvature in the detonation wave in ideal ex-6 1.0 plosives (D = D*) should always be equal to the a: length of propagation L. However, studies a t this Laboratory show that R/d increases with L only over the first three to four charge diameters after which it attains a steady state or constant value R,. In non-ideal explosives ( D < D*) R/d increases with L over even shorter distances than in ideal explosives and reaches a lower steady state ( R J d ) I I 0 value than in ideal explosives. Figure 2 shows the 0 10 20 R,,,ld curve obtained for 2,4-DNT. showing- a value Diameter, cm. Fig. 2.-Steady state radius of curvature/diameter (Rm/d) of 6.57 a t d = 5 cm. (just above d,) and a maximum value (still increasing with diameter) of 1.6 a t the us. diameter ( d ) curves for 2,4-DNT. 2.0
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d = 12.72 cm. d = 25.2 em. d = 7.54 cm. R,/d = 1.48 cm. R,/d = 1.63 cm. = 1.15 om. Fig. 3.-Typical rotating minor “streak” camera traces of the wave shape of 2,4-DNT (-65 100 mesh.)
R,/d
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The theoretical curves of the nozzle theory shown largest diameter studied, 25 cm. Typical wa\rc in Fig. 1 were computed for reaction zone lengths uo shape traces for DNT are shown in Fig. 3.
IiEACTION RATES OF AMMONIULV NITRATE I N DETONATION’ MELVINA. COOK,EARLE B. MAYFIELD AND WILLIAM S. PARTRIDGE Explosives Research Group, Universil!l of Utah, Salt Lake City,Utah Received August 87, 1864
Detonation velocity and wave shape were measured as a function of charge diameter over wide diameter ranges in the explosives ( I ) cast 70.7/29.3 composition B-arnmoiiiuin nitrate (AN), ( 2 ) cast 50/50 amatol (TNT-AN), (3) a loose-packed mechanical mixture of 50/50 TNT-AN, and ( 4 ) pure AN. The velocity-diameter curves were interpreted by the existing theories (‘kozzle,” “curved front”) of reaction rates in detonation. Comparisons of the computed reaction rates of AN in low and high density 50/50 TNT-AN showed that the specific rate constant was two t o three times as great a t a density pi of 1.53 g./cc. as a t p, = 1.0 g./cc. This seems to show that the detonation temperature is about 300 to 600’ higher a t pi = 1.53 than at p , = 1.0 which bears out the approximate validity of the covolume a ( v )equation of state for this explosive. Wave shape measurements showed consistently spherical wave fronts of steady state radius of curvatui,e/diameter (R,/d) ratios between 0.5 and 3.8 depending on the explosive and its diameter and density. The R,/d ratio in pure AN was near unity in all cases and showed no definite diameter dependence. In loose-packed 50/50 TNT-AN, R m / d was 0.51 a t the critical diameter and 2.1 a t the maximum diameter studied (25 om.). I n 50/50 cast amatol R,/d increased from below unity near the critical diameter to 2.3 (still increasing) a t the maximum diameter studied (20 cm.) and in cast composition B-AN, R,/d increased from below unity a t the critical diameter to a maximum value of 3.8 which maintained for all diameters greater than 3.8 cm.
Introduction In a previous art.icle2the rate of reaction of T N T in detonation was studied by analyzing the velocity (D)vs. diameter (d) curves obtained for pure T N T of various particle sizes. The existing theories on the influence of chemical reaction rate 011 the nature (1) This study was supported by Otlice of Naval Research (Contract
Number N7-onr-45107,Project Number 357 239). (2) M . 4. Cook, G. S. Horsley, \Y. S. Partridge, a n d \V. 0. Ursenbsch, to be published in J . Chem. Phys.
of the D ( d ) relations were used in this analysis, namely, the “1102zle,”3 and the “curved front”4 theories. By fitting all the curves in each case by the use of one empirical constant and the calculated theoretical hydrodynamic velocity D”, the (3) H. Jones, Proc. Rozl. Soc. (London), 189A,415 (1947). (4) (a) H. Eyring, R. E. Powell, G. H . Duffey and R . B . Parlin, Chem. Reus., 45, 1B (1949); (b) R. B. Parlin and D. W. Robinson, Technical Report No. VII, Ootober 3, 1952, Explosives Research Group, University of Utah.
