2. Secondary Explosives
• Secondary explosives (also known as high
explosives) differ from primary explosives in
that they cannot be detonated readily by heat
or shock and are generally more powerful than
primary explosives.
• Secondary explosives are less sensitive than
primary explosives and can only be initiated to
detonation by the shock produced by the
explosion of a primary explosive.
3. Secondary explosives
• Some secondary explosives are so stable
they can be set on fire without detonating.
• The more stable explosives which detonate
at very high velocities exert a much greater
force during their detonation than the
explosive materials used to initiate them.
• Values of their detonation velocities are in
the range of 5500-9000 m 𝑠−1
5. PETN
• PETN also known as pentaerythritol tetra
nitrate
• Its chemical formula is
6. PETN
• It is insoluble in water, sparingly soluble in
alcohol, ether and benzene, and soluble in
acetone and methyl acetate.
• It shows no trace of decomposition when
stored for a long time at 100°C.
• It is relatively insensitive to friction but is
very sensitive to initiation by a primary
explosive.
7. Properties of PETN
Characteristics Explosive material
Colour Color less crystalline solid
Molecular weight 316.1
Melting temperature/℃ 141.3
Thermal ignition temperature 202
Crystal density at 20 ℃/g cm -
3
1.76
Energy of formation/kJ kg-1 -1509
Enthalpy of formation/kJ kg -1 -1683
8. Properties of PETN
• PETN is a powerful secondary explosive and
has a great shattering effect.
• It is used in commercial blasting caps,
detonation cords and boosters.
• PETN is not used in its pure form because it is
too sensitive to friction and impact.
• It is therefore usually mixed with plasticized
nitro cellulose, or with synthetic rubbers to
form polymer bonded explosives (PBXs).
10. RDX
• RDX also known as Hexogen, Cyclonite
and cyclotrimethylenetrinitramine
• RDX was first prepared in 1899 by Henning
for medicinal use and used as an explosive
in 1920 by Herz. The properties and
preparation of RDX were fully developed
during World War 11.
11. RDX
• It attained military importance during World War I1
since it is more chemically and thermally stable than
PETN and has a lower sensitiveness.
• Pure RDX is very sensitive to initiation by impact
and friction and is desensitized by coating the
crystals with wax, oils or grease.
• It can also be compounded with mineral jelly and
similar materials to give plastic explosives.
• Have greater explosive power than TNT and Picric
acid
12. Properties of RDX
Characteristics Explosive material
Colour White crystalline solid
Molecular weight 222.1
Melting temperature/℃ 202-204
Thermal ignition temperature 260
Crystal density at 20 ℃/g cm
-3
1.82
Energy of formation/kJ kg-1 +417
Enthalpy of formation/kJ kg -
1
+318
13. HMX
• HMX also known as Octogen and
cyclotetramethylenetetranitramine
• HMX is a white, crystalline substance which
appears in four different crystalline forms
differing from one another in their density and
sensitiveness to impact.
• The 𝛽-form, which is least sensitive to impact,
is employed in secondary explosives.
14. Properties of HMX
Characteristics Explosive material
Colour White crystalline solid
Molecular weight 296.2
Melting temperature/℃ 275
Thermal ignition temperature 335
Crystal density at 20 ℃/g cm -3
𝛼 − 𝑓𝑜𝑟𝑚
𝛽 − 𝑓𝑜𝑟𝑚
𝛾 − 𝑓𝑜𝑟𝑚
𝛿 − 𝑓𝑜𝑟𝑚
1.87
1.96
1.82
1.78
Energy of formation/kJ kg-1 +353.8
Enthalpy of formation/kJ kg -1 +252.8
