Explosions 2

Question 1

What are some examples of peaceful uses of explosives?

Answer 1

• Mining/quarrying
• Excavation (for construction)
• Cladding (explosion welding)
• Forensic investigations
• Research

Question 2

What are the traditional reactants in gun powder deflagration?

Answer 2

KNO3, S and C

Question 3

What does changing the relative proportions of the reactants in the deflagration process of gun powder do?

Answer 3

Changes what products are formed

Question 4

What is the deflagration process?

Answer 4

2 KNO3 + S + 3 C –> K2S + N2 + 3 CO2

Question 5

What is the oxidiser and fuel in the deflagation process?

Answer 5

KNO3 is an oxidiser, S and C are fuels
* KNO3 contains oxygen = oxidiser
* Carbon is usually a fuel
* Look at the oxidation state changes to know if Sulphur is a fuel or oxidiser

Question 6

Fact about black powder

Answer 6

• Generally deflagrates incompletely

Question 7

How is ‘gun cotton’ made?

Answer 7

Nitration of cellulose fibres to produce nitrocellulose

Question 8

Gunpowder bombs

Answer 8

Gunpowder bombs
* Very dangerous
* Enclosed black powder (causing it to be pressurised) can detonate easily

Question 9

Picric Acid

Answer 9

• First commonly used high explosive
• Stable(ish)
• Made from phenol (found in coal tar), treated with nitric acid in the presence of another acid

Question 10

Why do you need the presence of another acid when forming an explosive with nitric acid?

Answer 10

To generate an effective electrophile to get the nitro groups to be added effectively

Question 11

TNT

Answer 11

• Less sensitive than picric acid (almost impossible to prematurely detonate)
• Nitration of toluene in the presence of H2SO4

Question 12

Nitration of toluene is much slower than for phenol, why?

Answer 12

Phenol is electron rich
* Lower activiation barrier

Question 13

RDX/HMX

Answer 13

• Research and Development explosive
• Her Majesty’s explosive
• High brisance - shattering power (can pierce armour)

Question 14

Nitroglycerin

Answer 14

• High explosive - non-military use
• Nitration of glycerol
• Very unstable on its own (volatile)
• Adsorb nitroglycerin onto the surface of diatomaceous earch to stabilise it (dynamite)

Question 15

Ammonium nitrate (NH4NO3) as a high explosive

Answer 15

• Combined with fuel oil (C11-20 alkanes) makes ‘ANFO’ - high explosive used in quarrying
• ANFO is a tertiary explosive - even less sensitive than a secondary explosive
• Hard to detonate - needs a blasting cap of more controlled high explosive
• Restrictions on the amount of NH4NO3 that people can buy because it is easy to make into a ‘fertiliser bomb’

Question 16

Plastic explosives

Answer 16

• Designed to be formable
• A mixture of mostly explosive and a bit of plasticiser
• Broader range of applications because it is formable

Question 17

What is a plasticiser?

Answer 17

An additive which makes a substance mouldable

Question 18

Polymer bonded explosives (PBX)

Answer 18

• ~ 95% explosive with a polyer binder
• Explosive is encapsulated in a matrix of polymer
• Can reduce the sensitivity of an explosive because polymers are less sensitive
• Can adapt properties like chain length or branching to optimise the explosive
• Can make a polymer with an explosive functional group

Question 19

What are some applications of polymer bonded explosives?

Answer 19

• Nuclear weapons
• Cruise missiles
• Any high performance application

Question 20

What is an integral sacrificial barrier in PBX’s?

Answer 20

The polymeric binder acts as a cushion and protects (captures) much of the blast overpressure - elastic/plastic response or deformation so all the gas/energy goes in one direction

Question 21

What is a drop tower and how is it used?

Answer 21

Used to test the safety/stability of explosives
* Impactor is dropped onto the explosive, look to see how much force is required for detonation

Question 22

What is the order of initiation?

Answer 22

C-ONO2 > N-NO2 > C-NO2
* C-ONO2 is more likley to detonate than N-NO2