Thermal characteristics of desensitizing waxes for explosive compositions

Thermodimko Atio. 18 W77) 125-145 0 Elscvier Scientific PuMishing Company. Amserdam

THERMAL CHARACTERlSDCS EXPLOSlVE COMPOSlTlONS

- Printed in Belgium

OF DESENSlTlZlNG

WAXES

FOR

JOEL HARRIS Rcaiittny Arsmaf. Darer, NJ.

(U.S.A.)

Waxes are added to explosive compositions to provide an explosive binder and lubricant for press-loaded explosives and to desensitize both press-Ioaded and cast-loaded explosives. The most significant thetmaI criterion of a good desensitizer is its ability to absorb large quantities of heat at above environmental temperatures- The enthalpy of each wax investigated for explosive incorporation was determined fmm room temperature to liquetkation by means of a Pet-kin-EImer DSC-2. Correlation of enthalpy and desensitization was accomplished by reIating the rest&s of a veIocity projectile impact test on expIosives containing the invcstigated waxes. Melt and solid&cation temperatures are aIso determined from DSC thermograms The temperature at which a wax ceases to absorb Iarge amounts of heat is the temperature at which Iiquefication takes place_ The temperature at which large quantities of heat are released during a cooling cycle is the solidification temperature-Use of wax having too Iow a Iiquefkation temperature results in excess exudation from a Ioaded high explosive charge; too high a Iiquefkation temperature inhbits incorporation of the wax into the molten explosive INIRODUCI-ION

Waxes have been used in cast 60140 RDX/TNT (Composition B) since 1940_The primary putpose for the wax is the desensitization of the RDX part of the explosive. Most waxes used in Composition B are derived from petrokum sources The waxes are mixtures of a variety of hydmcarbon matedaIs_ They are classified broadly into two categories, paraffim and micmcrystaIIine waxes ahhough Iatge quantities of each may be found in each other Paraffm waxes are straight chain-saturated hydmcarbon with few branched chains. In the pure form they range from CtrH38 melting point 28°C to C32l& melting point 71 “C. Their density is approximateIy 0.7g ml-‘. On solidifying paraffins crystalhz as relatively Iarge plates or needles_ Microcrystahine waxes are longchain hydmcarbons in which the branches

I26 cod

of a variety of other hydmcarbons such as olefms, pa&ins, and aromatics_They are chamcterizd by higher molecular weights and higher viscositythan parat% waxes. They crystal&e in miaocrystahine structure. The mechanism as to how waxes desensitize is a subject of much controversy- It is apparent that there are several additive mechanisms of desensitization some of which are3: 1. The absorption of heat to prevent hot spot propagation 2 The wax provides a less intimate contxt of the particlesof explosives with one another. 3. Burning wax releaseshydrogen atoms which functionas a slowing barrier. The object of this investigationwas to determineheat content and melt and solidificationtemperaturesof commerciaLwaxesby differentialscanning calorimetry 0. Those commercial waxes which were tested either met or approached the requirementsof NIL-W-20553 @f_ 2) BIending of waxes was also attemptedEXPERIMENTAL PROCEDURE

A Perkin-Elmer DSC-2 of temperaturerange -40 to 725“C was calibrated for temperatureand heat of fusion with indium, melting point 156.6O”C,heat of fusion 6-79Calg-‘_ The temperaturewas further calrSxatedwith water of 0 “C, napthalene of 80.5“C, and lead of 327_47”C-The heat of fusion was checked against stearicacid at 69.4”C and lead at 327-47“c_ The calibrationwas accomplished at a heating rate of 10°C min” in an argon atmosphere of flow-rate 20 ml min-‘_ Heat content, liquefication and solid&&ion temperaturesof the waxes listed in Table 1 were obtained with samples of wax of M mg at a range sensitivity(Y axis) of 5 mealset -*- The heat of fusion was calculatedby obtaining the area under the curve of each endotherm and comparing its value in square inches with the value obtained for the star&d ‘mdium.. DSC analysis was conducted from -20°C to 100°C at 10°C mini- By initiatingthe analysis below room temperature,a zero energy line can be established before the wax begins to absorb large amounts of energy. In order to control the crystallization process of the wax, *-he melted wax is cooied at 10“C min-*_ The sample is then reheated after a ten-minute delay. A reheat of the recrystaUzedwax at lO”Crnin- createsa more uniform test condition than do sampIes which were only heated, The resuhs obtained from the recrystallized wax DSC curve show only minor variation from the original heat DSC curve, L.iqu&cation or melt temperaturesin Table 1 were determined from DSC curves by obtaining the temperatureat the be&ming of the curve‘s straight line returnfromanendothermlcpeaktothebaselineofrhecurveduringaheating cycle.The DSC melt temperaturesrepresentpomts where Largeamounts of heat ceasetobe~~sincemeltinghastakenpiace.Inmanyeases,especiallywith slow heating rates of 2 112°C min-I, the DSC melt temperaturesare in close agreement with those determined by visual observation (Table 1) -

127 TABLE

I

-

WAX

Heating or cooling

ANALYSE ra& 10°C mixrl unkss notated; llow-rate, 20 ml mid

Wi?fjgrf Wax

Temp.

hd

Artvz (in..3

of argon. S&ii/Kozion

Lique/icorion

remp- PCI

tpmp. PC..

Heal comen1 caL R-*

(I) :-: 7-3

sunoco8810

cool

77-30 23-93

750 786

27-91

730

77 78

75

r&cat

7.80

77

75

7-06 7-m 7.14

63. 80 61. 80

7-10

62 80

730 6.94 739

61. 83 59. 82

734

60. 82

852 8.30 8.45

? 89

850

89

549

88

451)

(2) 8.3 8.3 83

Purolite Es670

heat46-m ax31 80-7 reheat 28+1

average (3) 7-7 7.7 7-7

hldmmic 17Oc

31-78 cool 79-13 reheat 15-86

average (4) 82

PcsroliteES672

heat 32-98 aKbl 92-I I ElYzat 2eI8

avaage

78 78

360

75. 54 75, 54

40-4

90 !xI

44-O

(5) 8-O

CasLcKwaxm COO1

:;

zz;

WKaI rehcat46-98 47-90

==as

(6)

76 74 76

Standardwaxof Ecnoxdk I23

zz coo1

am

0 85

Itaamic3oal lchat

a-

2e91 19-3 19-90

5-a

65

5.40 5.45

87 86

5.45

87

73 7.7 7.9

70 69

7.80

69

65 6.5 6-7

81

6.60

81

-

65

290

65 65

435

76 80 33a

Temprange t-0

(8)

7.6 7.6 7.6

Indnmk x

z

31-m 76-17 reheat 17-87

a==s

8-O -81) 81)

(11) 8.0 8-0 8-O

L-we-

solidi-

fin_?J

Jcariori remp_ Pi3

jication temp. Kl

65 6.4 68

yhstem M&n cool dIeat

Pctrolite UltraRex

heat r&eat

31-78 66-17 28-76

31-97 96-21 27-98

17-77 62-13 2X-75

avcragr

Hwt concern Cal. 8-l

76 74 7277

650

cd x&eat


A&

36.0

738 7-l 1 7.05

68

730

68

9.85 9-7s 1om

‘93

9.90

91

620 6.00 5.85

69

6-00

64

&I

7-47 7.60

62,84

76

7-70

61,84

7&l

61, 84

76

7-40 6.90 720

63.68 60.85

77. 55

730

62.85

77, 55

62 68 62

34-O

95 89 95

520

60 65 32-O

(I21 iis 83

25% lmc/X-75 hxJmmk %

aJo1 77-8 27-82 rehcatM88

=eragc (13) 7-I ::

75% hIdtale 17oc1x-25 %

hear reheat

30-89 27-90 79-13

a=ws (14) 76 76 7.6 7.6 avcragt

5zlmoco985

heat Icheat recod

.46-95 81-30 B-92 81-49

-730 7.76 6.93 734 750.

39-O

435

85 79 83 .. 84

,80 80

h.0

-

129 T

TABLE

1 kcwnrinrrpd)

THERIWW WAX ANALYSIS Heating or cooling rate, IOTmin

-1unkssnotated;fIow-rarc,20mlmin-10fargon.

wpighr wax

Temp-

Area

fmg,

Mngp

h2)

er,

L&ejicacion temp_ PC)

solidiJiuaiion

Heat

temp- PCI

Cal_g-I

confenf

‘(Is,

8.2 S-2 8.2

sO%Indramic 17oc X-SO%

32-91 cd 78-15 rrheac 24-89

average (16) 72 71 72

IndlamicX-IS% indramkl7Oc 85%

7-9

64.84 77.53 61.84

7-00 heat 31-94 cool 80-14 reheat 28-91

=s (17)

7-m 6.70 6.93

7-m 650 650

36.0 63.86 80.55 59,86.

6-70

sunoco 1290

7.9 7.9

21-93 76-24 reheat 2743

70 74 67.73

7x0

=v+ragc (18) 7.9

8.10 720 7-80

395

heat

27-82 72-15 reheat 24-80

=veragc

74.

8.00 7.83 784

77

7-90

77

8-70 S-80 8.60

84 84

8.70

84

820 f::

83

42-O

76 70 70

420

(19)

73

Bare!co x715

z

Batch110

39-90 coo! 7e36 reheat 30-87

aw (201 72 7.2 7.2

BalFcox715 Bat& 110

33-89 cool 86-m tieat 32-88

averagt 33-86 80-27 Ideat 12-86

78 78

505

79 83

8.40

83

9.5 92 93

82

93

82

79

50.0

77

81 77

a_0

-lYl-lERSSAL WAX

Iic’ting

or soling

w-1

wi7x

ANALYSIS

Ia&

1o”cnlin

-‘IInbs

Iloam; T-p.

(mlei

fklw-Iar&2omlmin-‘Ma’go’l. Area

Lkple-

SO/i&-

fitL2)

/-

fioriim

rempi PC)

wmp- PC)

rftwc ionrent

Cal_8-l

cm 85. 85 8-5

Baltzox715 74.MO983

32-85 cml. 78-15 reheat 27-83

average

10.42 IO-86 IO-43

82 81

105

82

103 10-O IO-4 10.1 10.4

69.81

103

69. 81

II.0 10.1 10.5 IO-1 105

Nodata

77 77

(23) S-7

Knoxvilk

2-5

I3amcox-715

123

22-89

cd 77-16 Rheat 21-89 maml 78-14 reheal 18-89

average

74 74 71 74

n_o

WI

2.5 6.2

KnoxviNe123 BaleaTz x715

heat s-86 cool 78-15 reheal 70-90 IUYXJI II-78 reheat 17-89

avenge (24) 7-4

105 Barecox715 l%stcaricacid

32-87 cd 81-14 t&eat 28-85 malo 79-10 fetkal15-84

avGa8t

(26) 73

BaIuo x715 w/5% biphalyl

2f°Cmir1 avw

22-37 78-5 rcllcas 17-84 rdEaI 26-85 78-12

54-O

93 4-o

77

E

81

95

79

93

79

920

80

77 773

8.87

77

53.0

77

8.85 8.69 850

77-82 79-82

sss

79.02

78 82

51-O

131 TABLE

I &onrSnwd)

THEEUMALWAXANALiiSIS Heatingor ading wcighr

rate. lO”Cmin-*

unkss

wmr

notated; tlow-raCe. 20 ml mid

Temp_

b&

Area

Liqfe-

Solidi-

HeOr

tine2J

/kation temp. CCJ

Jiirion Kemp- PC)

comem

Fze

m 7-7

slandardwaxof Kmxvilk 123 reinFat rutno1 LehcaL

Zt ‘C mid 2f’C mid a-

(29) 7-6

18-86 71-60 7-92 78-11 12-86 79-30 22-91

for IO’C mid BZiRXOX404

beats-88 81-19 fehcal28-86 Rcod 81-23 &teat 2IeJ5

2f "Cmin-'

001 7-4

BarrcoX404 BaLdI

cool

24 “c mid

3046

reheat

81-19 2!5+3

82-24

IO_08

(32) 7.6

Biphcnyl

Bal?xo x715 10% biphcflyl

Rheat cd

8.65 887 832 8.48

67. 70. 77

8.70

70. 77

70. 78

lO_Oo 9.10 9.35 860

88

9-40

86

939

87

86

_ 68.64 69.65 69.64

80

82

1055

81

Krbxvilk Bareco x715

dlcaL

80

9.72

87

81

65-77 50-45

500

69

75-10 2s84

EZ 9.73

54_0 295

SO 78-M

74

76-80

755

26-88 78-10

9-01 S-91

w-89

9-w

2f 'Cmin-' ‘average -

555

89

9_24 9_80

9-75 50% 123 50%

48.0

80

82

a=ms (331 83

69.63

70.75

h&26-84 reheat cool at 2f “C-’

Cal_g-J

70

z

av=s (31) 72

842 fS

8322

heat

110

of argon_

9.00

54.0 76-81 74

754 75.6

132

_‘TI-EXMAL WAX ANALYSIS Ekating or coding rate lO”Cmh -* unkss nacaied; now_iath2Omdl-‘ofargon. We&hr wax

Tmp.

nnrgl

Ama fimJ)

amp-

ET

WI 725

I

40% Knoxville 123 60% -Bare&m x715 2f “c lnin-’

21-m

8-87

80

cool 83-17 Ixaeat 35-89 lExd ax20

8-40 0-45 8.40

79

Barea, x71.5 10% biphenyi 2f “C mirl

rcka1 m

5-9

77

17-86

IO-35

79

AIIIOCOESkX

Ross

754s reheat 47-82 rsmoi 75-36

cod reheat

3S76 62-22 3-fl

aw

(38) 7-O

remp-

9-76

5%Ba3uxsX4w -in BaxEmx715

2f “C mid

z

17-86 77-14 reheat 9-85 78-15 fehat 22-36 79-17

6.77 6-771

alI_

g-1

iS 77 76

50-O

74 79

7-10

74

6-86

79

6.60 6-41 6-43

68 66

650

67

9.72 8.90 982 9_00 9.02

80

74

49.0

62

62

37_0

77 81 77 80

8.70 9.50

cOnwrzr tx-.-.

502

101)

SW-70

ml 75

ccl

783

1055 935

n-9

Hear

77

12-86 75-5

ilvelage

(36)

SMdifiCUCOR

8.60

aif?

liqujkariun

79 80

78

575

133 TABLE

I

komrizuedJ

THERMAL WAX ANAL&‘ Hating or cooling rate. 10”Cmh-I

unkss notated; flow-tate. 20 ml mid Area (in._‘l

wpilehr wnx hd

LiqieJkafion rentp. KJ

of argon. Sdkflfiation lemon

CcJ

Hear cvment Cal- g-1

(401 8-o

Rosswax S-1034

reheat23-98 alol 79-14

heal

2w8

8-70 862 9-10

21 “c mid

(41) 81

Rosswax 56-1204 2f “C mis-’

reheat

76-27 2%73

68

-

66 68 68

8-90

68

9_00 9-00

695

66

471)

65 66

WV

9-00

695

7-76 750 750 7-04

76

66

47-O

(42) 86

IndramkGLL:

2f “C mid

hcat29-94 81-12 reheat z-73 coo1 8322

avtragc (43) 93

IndramicKPL

sreheat27+0 read -18 reheatu-88 nxod 79-24

aw

46 39

Barr00 x715 Ros wax 56114 2f “C mid

alo1 reheat

27-S 7%15 18-a

3750

8-44 832 8-60 8-40

73

8.40

72

IO-4 9-69 102

80

73 72 73 73

77 81

10.0

Balsa x715 wwsaa Batch 6!i2

24

UC

38.0

78

ayefagt (45) 66

82

7-60

2f “C mid

WV

80 82

82-27

8.26

:z

z

::: 800 851

82-34

a00

SO-0

81 81. 85

81, 85

80 82-

&-I8

25 “c mix+

82 81, 85

81

53.5

(2

Baraa,X-AY lwdl658

2f % ruin-‘.

s-108 98-58 49-108 98-56 4Y-IO8 99-58

avtragc


Baren, x717 Ehxsh 655

44-101 40-101

2f oc min-‘8

3s101 93-52

284%

-83-21 _

2f =+cm&‘*.

103

9.36 9-20 9.35 9.40

IO2

938

102

828 8.07 824

98 97

95 97 102 98 97

85-35 _

58-4

93

97

93

z

averagt

BaIUX.BX902

9.59

831

97

7.90 750’ 9.43 f-04

87

761.

87

87

93

545

82. -. ,.1

84.., 83.

,._~.. ..48z..

TABLE 1 (conri~ued) .mwAL WAX ANALYSIS Heating or cooling late_ IOTmin-*

unks

notated; tkw-fate

Temp_ range cc2

cw 65

Bans0 x901

20-93 82-26 2141 82-25 84~32

2t “C min-”

(52) 38 3-I

79-21 27-86 El-21 22-86 80-W

Bamm X718 B2mm x715

23 ‘C tin+

noc awztagcd

LiqueJication temp- PC)

8-60 7-92 8.12 7-95 8-40

8!5

8.15

86

8060 897 8.69 879 856 8.76

a=w3e

aAma

Area Cin.l,

20mlmixr1

of axgon Solidiftcation temp- PC)

Heat colxtcnt c-al.g-t

- 81 82, 86 ii

79

82

43.0

79.73 79. 77

-

79 79. 76 79

79. 76

485

in UHaI.

Solidificationtemperaturesin Table 1 were obtained during a cooling cycle from the temperatureat the top of a straight line departure from the baseke when heat was released.The release of heat manifests itself by the solidifien of the wax. Temperaturesobtained are in dose agnxment with solidificationtempexatures observed in the test tubes (Table I)- DSC was normally run at IO “C mix?: a slower c&kg rate of 2 112°C min-‘, however, results in solidification temperatues which are more accmate anddcsertothoseobtainedby observation of the therrhal behavior of the wax in an oil bath, The data appearingin Table 2 was obtained by observing the physical state of the waxes in 16mm 0-D. by 1SOmm length test tubes placed in S temperalunxontrolle&siIicone oil bath. While the oil is constantlystirred, the tempfxature is raisfzd1 “C every five minutes for liquekation measureme& and decreased I “C every ten minutes for sokiiiin measurement-Liqt&ikationtemperaniresarereportedasthetemperatureatwhichthe~partofthesoIidwax has liquefii- The solidifiin tempemture’is reported as the temperature at .whicfia~~~tofprecipitateappears-Thechangeofstatetemperature ofthewaxesare~bynteansof~~placed~~htesttubeThegreatest-temm gra++Sw~tilenno~ is 1/2Qc’sinck the oil ++t&y s&e&

136 TABLE2 TEMPERATURES

I.

2 3. 4. 5. k 8, 9. IO_ Ii_ 12 I3_ 14. IS_ I& I?_ 18. E 2122_ 23. 24_ 25 26: 2-l_ 28. 29_ 30_ 3131% 32

OF VISUALLY

OBSERVED PHASE CHANGES

sonoc0 8810 TmntixmNS TNTlHNS wax of Knom 123rlwT 10% Barea, x715 in-m-r 1% SaRw As15 15% B2ram in X715 in TNT 2% riobwax 107 10% Hoiowax 10s in x715 10% smmwax ABIS in x75 wax of Knom 123 x715 BanwJ 10% biphenyl

74-72!s

82 82

69-7

80-85

79

m-85 79-82 71-105 70-76 78

795

x715 Barea, 5% bipknyl

79

X715 Banxo 2% bijebalyi x715BaxEo 1% bipheny1 x715 Bamo 6O/Knoxville40% 50% Bamm/50% Knoxvik 80% BaJuornK lcnow BaKm x715 85% x715/15% Kxloxv& 90% Baiuo X715/10% ?cnoxvii 95% BaJum X715/5% KmxviIk 98% BaIeal X71512% lcnoxde 50% Baluo X715I~ hTM Barcco x715/stearicacid 1% B2mxl x715 Barea, X715/Knoxvik 5OEiO Kmxvikn0% Mdcoil Rosnwax 561114 l7ur ia1 HNS ROSSWZX 56111410-4487 g Barea x715 0_4%0 g R.oswax 561204O-7 g Bamaa x715 O-7 g Rosswax 56-1034O-6 g Bacw X715 0.6g Rosswax s-1034 Rosswx 56-I## Trrf-086s X715 O-16g

795 80 79s 79s 81.0 811) Notes Nousl Notest Noust & -80 78-82 73-81 79 83 Notes

2%

Barar, x404 ixl!x?IZ

z

773 79-785 79.5-785 80-79 77s75 77-76 79 79 78 79 80 2 81 80’ 77-75 80 78-71 78-77 78

82 Mushtill Mushtiil79 81

: 82 -,

RDx+TN-r

n

78

81

X715+blycfhyknc AC 400 Stmoco 88lO+RDX+TNr smoal 8810 pbmyl .jn X7ls+TM+RDx

775-7s 79

82

E-zz&~m 8 33_ ROSSovaX20% FIawo x715 80% z 36. 37, 38_ 39.

No tsl

_

76

TABLE 2 konrinuea3 OF VISUALLY OBSERVED PHASE CHANGES

TEMPERA-

Healing

cc,

Coo&g PC. soIid#kation

fiquejkzlion 40. 41.

86% TM biphenyl20 16% X715 HNS 0.1 TNT+HN!s

72 77s 73

78

74

Polyethyknc 400+x715 Bamm EiiphcnylX715 RDXnNTmNs 44_ 95% Barea, X715 5% steak acid 90% Barem 10% ultrafkr 90% Bafeco 10% sunoa, 1290 z: 4t 43.

No cm 78-81

90-32 78-74 70-70 80

E8:

80

No

test

trade name is listed with the wax in Table 1. Bareco waxes were obtained from the Petrolite Corporation. turer

or the

The resuhs of thermal analysis by means of a Perk&Elmer DSC-2 are shown in Table l_ Thermal anaiysis was conducted at a heating rate of 10“C min-’ and, for more accuracy,at 2 l/2 “C min-‘. The DSC was calibrated

10 i% t

2

I

n

I

27

I

37

F~1_731~gSu~ow8810~& luofd speed, 2ommmic’.

I

I

I

47 57 67 Temperature OC

I

77

I

87

I

97

Eialzhgiatc.l~~min-‘;fbsr-~mmlmica-~of~ :.

I38 ,

._

:

.-

TABLE3 PROJFCTILE IMPACT TEST f~=fcdpcrsCMd;mftT=tanprarwe~hcnan~irIiquid;sdidT=~solidifrationtcmpaafumofawax;cal =cdoriexg = grams

for-both temperatureand energy equivaknce~ using pure in&m (m-p_ 156.60“C; heat _-_ -._ of .._ ~~I$OIJ6.8Ocalg;‘) and pure lead (m.p. 327.47“c, heat of f&ion 5SOcal g-l)_ The temperaturewas also chaked with naphthalene(m-p. 8OS”c). was always within fO.Z”C. T~peratureacrwacy Confinning temperatureanaIy+ was conducted on some of the m&e promisingwaxesandwaxmixturesinath ermostSically~ntroUed, siliine oil bath which was constantlystirred. These resuIt.s,obtained mostly at a heating rate of 1 “C per fwe minutes and a cooling rate of 1 “C per ten minutes, are reported in Table 2 The waxes were put in test tubes, capped and placed in the oil bathSolid&&on of blends of waxes stretchesover ran& of temperature.Beginning and final temperaturesof solidificationof wax bier& are reported in Table 2.

I

0.6 meal / set

I 77

I 67

I I I I 57 47 37 -27, Temperature “C

Y-

+-

Range 5 miliicalories/second

Y-

f-

I

Range 5 millicalories/second

140 Fw l-10 are thermal heating curves of the waxes appearingin Table 1. Results from a projectileimpact test ftim some pubkhed and unpublished res~~Itsare listed in Table 3 (ref_ 3)_

Sunoco Wax 8810 was one of the desensitizerwaxes used in many explosive compositionsfor over 15 years. A discontinuanceof its production resulted w s in research to find a substitute wax. The thermal ce of the ideal replacementwould be similar in changes of state temperaturesand have a simiku orgreaterbeatcuntentCTaMe2,No_ l;Fe 1 and2). One syntheticwax, Bar2co Wax X715, comes closest to possessing all the _ a desirable thermal charactenstlff and develops a greater heat content than does Sunoco 8810,Cable 1, No_ 1%?.2;Fw_ 8 and 9). Solidificationtemperature,however, is slightly higher- Some wax solidificationoazurred before the moStenexplosive solidified_Most additives to the Bareu~ Wax failed to lower the change of state temperatureand while hiphenyladditive lowered the change of state temperaturesof the wax, it aIs0 Iowered the change of state temperatureof TNT_ _ Since the Sunoco 8810 is a biend of Sunoco 985 @&bIe 1, No. 14; Fis_ 6) and Sunoco 1290(Table 1, No. 17; Fig. 7) blending of other waxes was attempted-

1

27

I

37

I

I

47

57

I

67 Temperature

I

77 “C

I

87

I

97

14x One seemingly successful mix results from a blend of Bareco X715 and Standard an acceptable heat of fusion but a change Wax of Knoxville 123, which possess of state temperature which is unacceptab!e (Table 1, No. 28). BIends of 44MO% Knoxville Wax 123 and 5060% Rareco X715 provide satisfactory thermal characteristics (Table l)_ Another wax which possesses the desired properties is Amoco Rskar SW-70 (Table 1, No_ 36) This wax, descrii in ref_ 1, is not avail able, however, in Iarge amounts_ Rosswax 561114, an mkerite wax, was promising in that it has a large heat of fusion, but it was found to possess a high percentage of low-melting components which could lead to exudation (Table 1, No_ 40) and did not mix with Barexo X715. Sunoco 1290 wax appeared to have a melting point at 70°C when initially heated which would be too low to prevent exudation in storage. After the wax was cooled at 10°C min-’ and reheated, it showed a melting point at 73 “C which would be acceptable. It solidified at 74 “C which is desirable and compares favorably with the Amoco SW-70 used by the Navy_ The curve for 1290 wax shows a preliminary melting at 67°C but it has been found, particularly with Indramic

37

47

77 57 67 Temperature “C

F~6-76mssuoaa,985htaring~Heatiogratc,1O”cmin-’;~-rate~mimin-’of~; tuonkr sped 2OOmin-*-

c

143 Wax 170°C that the higher melting component in this case 73 “C (Fig- 7) can encapsulate the already soft or liquid component. The encapsulation by the higher melting componentwould tend to precludeexudation of wax at 70 “C storage condition from an explosive composition. Waxes 45-52 (Table 1) are synthetics_Waxes X715, X717, X718, X719 are straigbt&ain parattii waxes syn&sized by the Petrol&e Corporation No_ 52 representsan attempt to mix X715, which may solidify at a temperatureslightly too high, and X718 (TabIe 1, No. 46) which is decidedly too low in temperature of solidification-The results of mixing mable 1, No_ 52) seem encouraging from the point of view of wax compatibilityand temperatureof solidification. To zwzrtain whether DSC reported changes of state temperatures are acauate, sampks of wax were weighed and placed in test tubes in a temperaturecontrolled,stirred oil bath. PiIot plant conditions were &Mated in the oil bath, and changes of state visuaIly observed. Data obtained from these experiments appearsin Table Z The oil bath was subsequentlyutilizedto observe the behavior of RDX, TNT, and wax during cycling Visual observation of the solidificationof wax and explosive in test tubes indicates that separationof wax and explosive oazurs on solidification.If a wax solidified at neariy the same temperahue as the TNT, a mechanical mixture of

CE

I

37

I

47

I

I

I

57 67 77 Temperature

I

87 “C

Fs lo_ 7-4 mg Amoco-GkaR SW-70 htwing cum. 2omimirr’ of algon;n%xxdcr SPed. 2ommmirr’-

I

97 Hearing

me

IO-Cmin-*;

flow-rate,

the ma.rity of the wax and explosive can be produced with stirring. With considerationfor both the eutecticformed by RDX and TNT and the super cooling observed in the test tube experiments (TabIe 2, No. 32, 34, 36, 38), a wax soIidi%ation tempexatureof 72-78 “C would be recommendedto produce the mechanical mixtureSince waxes meIt over a range of temperaturerather than at one partkular -point, the meiting point is a nebulous requirement.Some waxes reputed to melt at 80 “c were found to have large amounts of their components melting at 60 “C (TabIe 1, No. 2 and 3)_ These Iow-meiting components would likely exude when a composition is exposed to the 71 “C environmental test other waxes reputed to have melting points of 80 “C were found to have componentswhich remained so&i until 86 to 87°C. projectile impact test consists of 1/2x l/2 inch cykirical projecties propellea by incrementsof 4 or more grams of propellant fired from a 0.50 c&ii gun’_ The data are reported as the velocity of the projectifewhich caused no igniknsintfzrlsu ccessiveshots into 2 x 1 inch cylindersof explosive compositiqn (No Go) ma& 3), and the next higher level of velocity of the projectilewhich brought about an ignition of the explosive compositi&L T@e criteriaof ignition wasavkualindicationofsmoke.orfrre_ _.’ -

145 The Go velocity shows some correllation with enthalpy of the waxes CTabIe 3). The wax with the kugest enthalpy also desensitized the expIosive to the extent that the greatest projectile velocity was required for Ignition. The temperature at which an increase in enthalpy also desensitized the explosive to the extent that the greatprojectile velocity was requ’ked for ignition_ The temper-

ature at which an increase in enthalpy occurs also afkcts the desensitization. Indramic 17Ck is a low temperature heat absorber and seems to desensitize better than would be indicated by its enthalpy value. A possible inwmpati ility is indicatti by the decreased velocity which ignited the Composition $ with the

PetroIite ES 670 wax_ Actual bomb tests have indicated that 1” wax changes the ignition characteristics of bombs6. In conclusion the DSC provides a means of determining the tnthalpy, Iiquefication and solidification temperatures and a means to screen waxes. It is recommended that a wax used as a desensitizer in a composition wntaining TNT has a solidification temperature of 72 to 78°C and an knthalpy value of at least 4Ocal g-’ from 25°C to the melt temperature. REFERENCE R C_ ESowas.J. G_ Remans and W_ A. Z&man. Ind- Eng_ Chem. Prod_ Res Dew_. 12 (1973) 2. _Milirar)-Spcrc~carion. Wax Lkern&ing MU.- W-20553B. 18 Mar. I%2 D. FLSaga. Cor~pairion B Wax Srud~. Picztinny Arsenal, Doves. NJ_. presa~led at Annual Meeting of Lading Se&m_ American ll?Mense W ksocialion. Apr. 74. AD918877. Perk.&Umer. Inuru&n .Manual DSC-2 D~erenhl Scanning CaIorimewr. Norwak. Corm. MM. L Weia and E. L Litch fdd. Projecritelmpacr lniriationof CJndemed ExpkMzs. Bureau of Mines Repon 6986. July 1%7_ I_ U&in. Properties oJRL)X compOriiion B WirhoufLk_wnsi~~~ngWm. Picatirsy Arsenal. Doer. NJ.. PATR 1435. July 1944