View
243
Download
7
Category
Preview:
Citation preview
Binding Interaction Between Dantocol and RDX
Chris Williams
Supervised by Dr Stephen ClarkeCo-Supervised Dr Simon Mathew
& Dr Ian Lochert (DSTO)
Introduction
• Components of polymer bonded explosives (PBX)
• Function of bonding agents
• Analysis of interaction between Dantocol and RDX
– Scanning electron microscope– Raman spectroscopy– Diffuse reflectance infrared spectroscopy– Attenuated total reflectance infrared spectroscopy– Nuclear magnetic resonance
• Conclusion
• Future work
Polymer Bonded Explosives
• Nitramine explosive material suspended in a polymer matrix
• Desire for increased safety in handling explosives
• Possess favourable mechanical properties
• Various constituents added to improve properties
– Decrease likelihood of detonation due to external stimuli– Maintain a precise shape under severe stress– High explosive energy
• Commonly used in military application
PBXN-109
• Investigating components of PBXN-109
• Forerunner in PBX formulation developed in 1980’s
• Provide maximum explosive force and minimal sensitivity
Metal fuel
Cure catalyst
Plasticiser
Antioxidant
Bonding agent
Binder
Curing agent
Energetic Filler
Function
20.0
0.02
7.34
0.10
0.26
7.34
0.95
64.0
Nominal Weight %
Aluminium
Triphenylbismuth
Dioctyl adiapate
2,2’-methylenebis(6-tert-butyl)-4-methylphenol
N,N’-di(2-hydroxyethyl) dimethylhydantoin (Dantocol)
Hydroxyl-terminated polybutadiene
Isophorone diisocyanate
RDX
PBXN-109 Components
Bonding Agents
• Bonding agents utilised to overcome problem of dewetting
• Improve bonding through filler reinforcement
• Upon inclusion to a PBX formulation:
– Adsorbs onto RDX crystals– Enables effective crosslinking reaction with binder
• Prevents formation of voids improved mechanical properties
• Dantocol example of a commercial bonding agent
N N
CH3
H3C
O
O
OHHO
N,N’-di(2-hydroxyethyl) dimethylhydantoin
Dewetting
• Nitramine-polymer composites suffer dewetting
• Caused by due to weak adhesion between nitramine crystals and binders
– surface of nitramine crystal
– Isocyanate side reaction with moisture:
• Bonds fail under stress, allowing binder to break free or “dewet”
nitramine
– Puts neighbouring particles under stress
– Void propagates until reaching the filler-binder interface
R N C O H2O R NH2 CO2
R N C O R NH2 R NH CO NH R
• Filler-binder adhesion decreases overtime
– causing mechanical properties to deteriorate
– Increasing sensitivity of the PBX to that of a pure nitramine.
• Voids act as initiation sites for detonation
• Propellant Systems
– Causes an uneven burn Motor failure
Problems Associated
Experimental Aim
• Analyse interaction between RDX and Dantocol
– Coating RDX crystals– Reporting spectral shifts observed upon coating of Dantocol
• Determine functional groups responsible for spectral shifts
• Investigate the strength of the interaction
• Enabling synthesis of improved bonding agents
Coating Technique
• Heat RDX at 60oC under vacuum to remove impurities
• Determine suitable solvent systems to dissolve Dantocol
• Weigh out samples of RDX and Dantocol
– 50%, 10%, 8%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5% (w/w)
• Tumble in centrifuge tube for 3hours
• Centrifuge at 3500rpm for 45mins
• Place sample under high vacuum
• Investigate the coating of bonding agent on RDX crystals
• XL30 Philips-XL30 FEGSEM w EDAX EDS
• Smooth crystalline surface
Scanning Electron Microscope
10% Dantocol Coating
• High level of RDX coverage
• Good adhesion to the surface
4% Dantocol Coating
• Less coverage observed
• Dantocol forms thick, malleable coating
• DRIFT-IR to examine interactions via bond shifts
• Advantageous for analysing solid samples
• Coated RDX samples mixed with KBr
• Ground and analysed in sample tray
Infrared Spectroscopy
DRIFT-IR Spectrum
1537
.70
1570
.45
1590
.15
0.00 0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
0.15
0.16
0.17
0.18
0.19
KM 1500 1520 1540 1560 1580 1600 1620 1640 1660
Wavenumbers (cm-1)
NO2 Asymmetrical stretching vibration
784, 7541039, 1019 , 946, 924
1351, 1312, 1268, 1234, 12191459, 14341593, 1573, 1532Peaks (cm-1)
(NO2)Ring StretchingVs (NO2) + V (N-N)CH2Vas (NO2)Vibrational Bands
-0.00
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0.10
0.11
0.12
0.13
0.14
KM
1000 1500 2000 2500 3000 Wavenumbers (cm-1)
RDX
• Samples pre-ground with KBr
• Excess grinding removed coating
Sample Grinding
RDX 1st Grinding
0.0
0.1
0.2
KM
RDX 2nd Grinding
0.0
0.2
KM
RDX 3rd Grinding
0.0
0.2
0.4
KM
RDX 4th Grinding
0.0
0.1
KM
RDX 5th Grinding
0
1
KM
1000 1500 2000 2500 3000
Wavenumbers (cm-1)
Peak Shifts
0.000.050.100.150.200.25
0.300.350.400.450.50
60011001600210026003100
Wavenumber (cm-1)
Kub
elka
-Mun
k
RDX + 10% Dantocol
1513.05 cm-1
RDX1537.70 cm-1
5.360.430.171.771.871.236.080.98∆V
911.76945.541018.541036.401221.251235.631258.901319.75RDX + 10% Dantacol
917.12945.111018.711038.171219.381234.401264.981318.77RDX
Ring StretchingVs NO2 + V (N-N)Sample
cm-1
0.033.101.520.781.1424.652.220.93∆V
753.42788.041360.071432.741460.121513.051568.231589.22RDX + 10% Dantacol
753.45784.941361.591433.521458.981537.701570.451590.15RDX
RingCH3Vas (NO2)Sample
Peak Shifts
--50% Dantocol
24.651513.0510% Dantocol
24.471513.238.0% Dantocol
20.871516.836.0% Dantocol
19.791517.915.0% Dantocol
18.331519.374.0% Dantocol
15.191522.513.0% Dantocol
11.31526.402.0% Dantocol
14.261523.441.0% Dantocol
8.361529.340.5% Dantocol
∆Vas (cm-1)Vas NO2 (cm-1)RDX & Dantocol
0.10
0.12
0.14
0.16
0.18
0.20
0.22
0.24
149615161536155615761596
Wavef unct ion (cm-1)
RDX + 10% Dantocol
• Attenuated total reflection infrared spectroscopy
• Several advantages over DRIFT-IR
– Overcomes problem of grinding
– Less preparation
– Fewer scans required (256scans – 64scans)
– Reproducible spectra
ATR-IR
ATR-IR Spectra
• Sharp Peaks with low noise interference
• RDX peaks consistent with DRIFT-IR
45
50
55
60
65
70
75
80
85
90
95
100
%T
1000 1500 2000 2500 3000 3500 4000 Wavenumbers (cm-1)
RDX
1537.70 cm-1
RDX and Dantocol IR
20
40
60
80
%T
20
40
60
80
%T
20
40
60
80
%T
1000 1500 2000 2500 3000 3500 Wavenumbers (cm-1)
RDX
1537.70 cm-1
Dantocol
RDX + 50% Dantocol
1518.162 cm-1
Raman Spectroscopy
• Raman used to compare vibration spectra specifically nitro group
• Small spectral shifts observed
• Behaviour consistent with literature
• Nitro shifts coincide with FTIR data
RDX
Raman Peak Shifts
5.38.2409.6
2.00.9456.8Ring Deformation
14.314.0599.6
0.20.2664.0V NO2
0.11.8844.5
0.60.4879.6
1.61.4940.0
1.72.31028.3Ring Stretch
0.50.61213.4
0.50.61270.6
0.80.41306.8
3.85.31383.5Vs NO2
1.60.31428.0CH Deformation
0.20.21592.1Vas NO2
RDX + 3% Dantocol∆V(cm-1)
RDX + 4% Dantocol∆V(cm-1)
RDXV(cm-1)Vibration Band
NMR Complexation
N
N NNO2
NO2
O2N
• Investigate peak shifts upon increasing equivalency Dantocol
• Mole ratio RDX : Dantocol
– 1 : 0, 1 : 0.5, 1 : 2, 1 : 3
• 1H NMR, 300MHz, CD3C
RDX
CH2
6.16ppm
NMR TitrationRDX : Dantocol RDX : Dantocol
1 : 0.5 1 : 1
6.17ppm 6.17ppm3.112ppm 3.127ppm2.843ppm 2.999ppm
RDX : Dantocol RDX : Dantocol1 : 2 1 : 3
6.19ppm 6.19ppm3.135ppm 3.190ppm2.999ppm 3.061ppm
NMR Complexation
6.166.166.17
6.176.186.186.19
6.196.20
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50Dantocol Equivanents
Chem
ical
Shi
ft (p
pm)
RDX CH2 Peak Shift
Hydrogen Bonding
• Data indicates hydrogen bonding responsible for bonding
• Between nitro of RDX and hydroxyl functional group of Dantocol
RDX Dantocol
N N
H3C
H3C
O
O
O OHH
N N
N
N
NO
O
O O
N
O
O
Synthesis of Bonding Agents
• Alternate bonding agents derived from Dantocol
• Used to determine if hydrogen bonding is responsible for interaction
• 1st compound substituted hydroxyl group for strong proton donating
carbamate
• 2nd compound functioned to block the hydroxyl groups
Bond Promoting Carbamate
• Dantocol reacted with phenyl isocyanate under reflux conditions
• Product separated by column chromatography
• Characterised by NMR and Mass Spectroscopy
10ml TolueneHeated 24hrs
N,N’-di(2-ethyl phenylcarbamate) dimethylhydantoin
N N
H3C
H3C
O
O
O OC
O
NH
CNH
O
N N
H3C
H3C
O
O
HO OH
N C O2
Product Interaction
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
%T
1000 1500 2000 2500 3000 3500 4000 Wavenumbers (cm-1)
• SEM to determine adequate coating
• DRIFT spectroscopy and ATR consistent with peak change at 1537.7cm-1
RDX + 10% Bonding Agent
• 1529.4cm-1
Tert-butyldimethylsilyl Chloride Protection
• Dantocol reacted with tert-butyldimethylsilyl Chloride
• Product separated by column chromatography
• Characterised by NMR and Mass Spectroscopy
Methlene chloride, ImidazoleHeated 24hrs
N,N’-(tert-butyldimethylsilyl) dimethylhydantoin
Si
CH3
CH3
CH3
CH3
CH2ClN N
H3C
H3C
O
O
HO OH
N N
H3C
H3C
O
O
O OSi
CH3
CH3
CH3
CH3
CH3SiH3C
CH3
CH3
CH3
CH3
Tert-butyldimethylsilyl Chloride Protection
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
KM
1000 1500 2000 2500 3000 3500 4000 Wavenumbers (cm-1)
• SEM to determine adequate coating
• DRIFT spectroscopy and ATR produce similar spectra to uncoated RDX
• Conclusive evidence of hydrogen bonding at the interface
RDX + 10% Bonding Agent
1533.85cm-1
Conclusion
• RDX coated with Dantacol was analysed using ATR, DRIFTs, Raman, NMR
• Peak shifts indicate the nitro group interacts with hydroxyl group to form a
stable complex
• This was confirmed by synthesis of Dantocol derivatives
• Prevention of hydrogen bonding by reaction with hydroxyl group
• Promoted hydrogen bonding by formation of proton donating carbomate
Future Developments
• Further characterisation by analytical methods (NMR,
spectrophotometry, DSC, TGA)
• Informatively design and synthesise second generation bonding agents
• Exploit the understanding the molecular interactions to design highly
sensitive explosive detection devices
1. Hamshere, B.L., Lochert, I.J., Dexter, R.M., Evaluation of PBXN-109 : the explosive fill for the
Penguin Anti-Ship Missile Warhead, W.S. Division, Editor. 2003, Defence Science & Technology
Organisation: Edinburgh. p. 30.
2. J. M. Bellerby, C.K., Explosive-Binder Adhesion and Dewetting in nitramine-filled energetic
materials. Propellants, Explosives, Pyrotechnics, 1989. 14(2): p. 82-85.
3. Bailey, A., et al., The identification of bonding agents for TATB HTPB polymer bonded explosives.
Philosophical Transactions of the Royal Society of London Series a-Mathematical Physical and
Engineering Sciences, 1992. 339(1654): p. 321-333.
4. C. Sue Kim, H.Y.P.N.N.A.G., Developement of neutral polymeric bonding agents for propellants with
polar composites filled with organic nitramine crystals. Propellants, Explosives, Pyrotechnics, 1992.
17(1): p. 38-42.
5. Guy Perrault, R.L., Jean-Francois Drolet, High-energy explosive or propellant composition. 1981, Her
Majesty the Queen in right of Canada, as represented by the Minister of National Defence: United
States. p. 9.
Reference
Recommended