Polymers, Propellants, and Explosives A Tutorial. By Richard R. Zito Richard R. Zito Research LLC 3255 E. Lincoln St.

Transcription

1 Polymers, Propellants, and Explosives A Tutorial By Richard R. Zito Richard R. Zito Research LLC 355 E. Lincoln St., Tucson AZ 85714

2 PART 1: BASICS

3 Types of Energetic Reactions (WISE Series C Course 3) Detonation: A supersonic decomposition reaction propagates through the energetic material to produce an intense shock in the surrounding medium, air, or water. All energetic material will be consumed in about 1 microsecond. This is the most violent reaction! Partial Detonation: The amount of damage, relative to full detonation, depends on the proportion of material that detonates. Explosion: Ignition and rapid burning of confined energetic material builds up high local pressures leading to violent pressure rupturing of the confining case or structure. Deflagration: Involves a chemical reaction proceeding at subsonic velocity along the surface of and/or through an energetic material producing hot gases at high pressure (propulsion). The energetic material may be consumed in hundreds of milliseconds. Burning: The energetic material ignites and burns non-propulsively. This is the least violent reaction.

4 The Explosive Train (WISE Series C Course 3) Large amounts of energetic material capable of detonation are almost never used in energetic subsystems! Instead A sequence of energetic materials are used in an explosive train, beginning with a small amount of relatively sensitive material (e.g. lead azide) and proceeding through a series of explosives of increasing insensitivity and increasing quantity (e.g. nitrocellulose, TNT, etc.). S&A Booster Main Charge Detonator Lead

5 Why do some compounds explode? An explosion involves the rapid evolution of both gas and energy (WISE Series C Course 3). Consider sodium azide.. Many azides are very explosive! Lead azide, mercury azide, m and barium azide explode on impact and are used in detonation caps. NaN (s) Na(l) + 3N (g) 3 N (azide ion) 3 - N bond energy = 946 kj/mole For binary compounds the N N bond energy is exceeded only by the C O (carbon monoxide) bond energy (1073 kj/mole). Carbon monoxide is another important combustion product as well as CO (O=C=O) with a total bond energy of (695) 1390 kj/mole.

6 Ammonia is a basic raw material used in the manufacture of energetics. Haber Process: N (g) + 3 H (g) NH 3 (g) DH= -46 kj/mole Ammonia will react with both oxygen and water to yield: NH 3 + H O NH + OH NH 3 + O H NO H O Next Slide

7 Many nitrogen compounds are explosive!!!! Chemical Name Formula Combustion Products Comments ammonium nitrate (s) NH 4 NO 3 N O (g) + H O (g) Can detonate by another high explosive (TNT) or traces of acid and chlorine ion as catalysts. Trinitrotoluene (s) (TNT) ( C 7 N 3 O H ) 6 5 3N + 5H O + 7CO + 7C NO or H H 3 N + 5H + 1CO + C O N NO CH 3 nitro group High Explosive

8 Nitrogen Explosives, Propellants, and Oxidizers Continued Chemical Name Formula Combustion Products Comments RDX (Research Department Explosive) C H N O High Explosive O N N N NO N NO Propane- 1,,3 trinitrate nitroglycerine ) C H N O Unstable colorless, oily, liquid. Will be discussed in detail later.

9 Nitrogen Explosives, Propellants and Oxidizers Continued Chemical Name Formula Combustion Products Comments pentaerythrital tetranitrate (PETN) C H N O High Explosive NO 3 NO 3 O 3 N O N 3 cellulose nitrate ( nitrocellulose ) (Will be discussed in detail in the next section.) Variable: C H N O C H N O C H N O High Explosive and Propellant

10 Nitrogen Explosives, Propellants and Oxidizers Continued Chemical Name Formula Combustion Products Comments mercury fulminate O-N C-Hg-C N-O Lead Styphnate (lead,4,6 trinitroresorcinate) O O N NO Pb + H O- Hg (ONC) Pb C H N O Various: N, CO, HgO, CO, Hg, Hg(CN), Hg(OCN), Hg(OCN)CN Will Detonate! Will Detonate! NO

11 Nitrogen Explosives, Propellants, and Oxidizers Continued Chemical Name Formula Combustion Products Comments diazo dinitro phenol (DDNP) O O N N NO C H N O Will Detonate! (less sensitive to friction) Ammonium Chlorate (NH ClO ) 4 3 Ammonium Perchlorate (NH ClO ) 4 4 (Heat) (Heat) NH Cl + 3 O (g) 4 NH Cl + 4 O (g) 4 Oxidizer for solid propellant Oxidizer (more stable than chlorates)

12 Nitrogen Explosives, Propellants, and Oxidizers Continued Chemical Name Formula Combustion Products Comments unsymmetrical dimethyl hydrazine (UDMH) H C 3 H 3C N-N H H C H N 8 Rocket fuel (hypergolic with NO, LOX, or HNO 3 ) PEL = 0.5 PPM hydrazoic Acid (HN ) 3N + H 3 sodium azide (NaN ) Na(l) + 3N (g) 3 nitronium perchlorate NO ClO 4 Definition: Hypergolic fuel spontaneously ignites on contact with its oxidizer, or air. Colorless, dangerously explosive liquid. Reacts violently with organic matter

13 Nitrogen Explosives, Propellants, and Oxidizers Continued Chemical Name Formula Combustion Products Comments dinitrogen pentoxide (N O 5 ) 4NO + O Colorless unstable O O crystals N-O-N O O NO + NO - 3 nitrogen fluorodichloride NFCl Explosive tetraflurohydrazine N F 4 Explosive reaction with hydrogen

14 Nitrogen Explosives, Propellants, and Oxidizers Continued Chemical Name Formula Combustion Products Comments nitrogen trichloride NCl 3 A pale yellow explosive photosensitive oil difluoroamine HNF A colorless explosive liquid chlorine nitrate ClNO 3 Reacts explosively with organic mater fluorine nitrate FNO 3 Intrinsically explosive Nitrogen dioxide + nitric acid NO + HNO 3 Powerful oxidizing agent with aniline This list contains the more common and simpler nitrogen explosive, propellants, and oxidizers, and should not be considered complete!!! NH

15 Non-Nitrogen Energetics Chemical Name Formula Combustion Products Comments Lower aluminum alkyls AlR 3 Al(OH) + 3H +6H O 3 Salts of aluminum hydride H H Al H H =AlH 4 - M + AlH 4-4H + Al(OH) + M + - OH +4H O 3 A reactive liquid that is hypergolic in air, exploding with water. Explosively hydrolyzed by water Salts of gallium hydride + - M GaH 4

16 Non-Nitrogen Explosives Continued Chemical Name Formula Combustion Products Comments boron triiodide I B I I BI 3 3H O 3HI + B(OH) 3 White solid below 43 C. Explosively hydrolyzed. beryllium alkyls R-Be-R H O Be(OH) + H methylpotassium KCH 3 Pyrophoric Hypergolic with air, explosively hydrolyzed. hydrides (NaH, RbH, CsH, BaH) NaH H+ Na + + H (g) The hydrides in general are very reactive with air and water (hypergolic). This is only a partial list for the lighter elements.

17 PART II: POLYMERS

18 What is a polymer? Definition: A polymer is a large molecule (macromolecule) whose structure depends on the monomer(s) (small molecule(s)) used in its preparation. M. Stevens Note: Webster s definition is wrong!!! Let A and B be monomer, then several types of polymers are possible:..-a-a-a-a....-a-b-a-b-a-b-...-a-a-b-a-b-b-a-b-..a-a-a-b-b-b-a-a-a-b-b-b- Homopolymer Alternating Copolymer Random Copolymer Block Copolymers.and there are many other variations on these basic schemes!

19 How are polymers formed? Monomers must have reactive ( sticky ) ends. Let R and R be monomers without their reactive end groups. Let g and g be reactive end groups. Examples of monomer linkages: 1) g-r-g + g -R -g..-r-gg - R -g g-r- + NO WASTE PRODUCTS A B -A-B-A-B- (alternating copolymer) Special Case: g-r-g + g-r-g -R-gg-R-gg-R-gg-. + NO WASTE PRODUCTS A A..-A-A-A-A-A-. (homopolymer)

20 Formation Continued. The production of waste products complicates the simple picture. Let R and R be monomers without their reactive end groups. Let g and g be reactive end groups. Examples of monomer linkages: 1) g-r-g + g -R -g..-r-link- R -Link -R- + WASTE PRODUCTS (LEAVING GROUP) A B -A-B-A-B- (alternating copolymer) Where Link = gg minus waste products Link = g g minus waste products Note that g-r-g R-Link (although R is shared) and g -R -g R -Link (although R is shared)

21 Formation Continued Special Case: g-r-g + g-r-g -R-Link-R-Link-R-Link-. + WASTE PRODUCTS (LEAVING GROUP) A A..-A-A-A-A-A-. (homopolymer) Link = gg minus leaving group Note g-r-g R-Link. However, the sub-molecule R is shared.

22 Waste Products Waste products (called leaving groups) are typically very small stable molecules like water (e.g. during polyester or cellulose formation) or carbon dioxide (e.g. during homopolymerization of isocyanate). The thermodynamic stability of these small molecules drives the equilibrium of polymer formation reactions to the right (completion).

23 An Example of Polymer Formation (Cellulose a natural polymer) H O b(1,4) Glycoside Linkage (b pyranose Form)

24 Properties of Polymers

25 The Testing of Polymers

26 PART III: SIMPLE (1 COMPONENT) EXPLOSIVES AND MONERGOLS

27 What is nitrocellulose (cellulose nitrate)? (nitric acid) + - H O H NO 3 - Cell-OH + HNO 3 Cell-NO 3 + H O Cellulose + nitric acid nitrocellulose + water

28 How much nitrogen (nitrate) is enough? ~ OH - groups replaced per ring (4 per unit) (10% N by wt.) Rocket Fuel All natural OH - groups replaced (~13.5% N by wt.) Harmless (lacquers, textile fibers, plastics) Gun Cotton Note: First man-made plastic (Parkesine) 186. Eventually became celluloid M13 rocket for the Katyusha launcher (Musée de l Armée) Note: Cellulose nitrate will burn in space.

29 What other alcohols can be made to explode? (Sugar, cellulose, and glycerin are all on the alcohol (OH -) family) C C C OH OH OH + HNO 3 OH H O C C C NO 3 NO 3 NO 3 Glycerol ( glycerin ) (1,,3 propanetriol) Glycerin nitrate ( nitroglycerin ) (1,,3-Propane trinitrate) Dynamite is nitroglycerin stabilized by absorption onto diatomaceous earth.- invented by Alfred Nobel in 1866

30 How much cellulose is enough? Oatmeal 3.3% cellulose (by wt.) Wood 30-40% cellulose Cotton 90% cellulose Exploding cookies?!?! Magicians flash paper Munitions

31 PART IV: COMPOSITE ENERGETICS

32 Solid Propellants and Rocket Motors OXIDIZER CASING GRAIN BINDER (polyurethane) FUEL NOZZLE

33 Solid Propellants and Rocket Motors- Cont. Casing Grain Thrust Neutral Profile (Binder-casing interface) O + H O O + H O SOLID FUEL ROCKET MOTOR Regressive Profile Progressive Profile Time

34 What is Polyurethane?

35 Binder Formation Problems 1) Volumes of diisocyanate and dihydroxy compounds must be equal to within ±1%. ) Excess dihydroxy compounds result in suspension of liquid droplets. 3) Excess diisocyanate additional crosslinking change in binder properties less elastic binder.

36 Binder Formation Problems - Continued 4) Reaction of diisocyanate with water vapor forms polyuria and CO gas. Water Vapor DISCARD!!!

37 Binder Formation Problems - Continued 5) Contamination of dihydroxy compounds with water vapor can result in gas bubbles when mixed with the diisocyanate. Some of these bubbles will remain in the solidified in the binder. 100 m Gas Bubble

38 Polyurethane will react with oxygen in air! (Crosslinking Reactions Hardening, Embrittlement) A) B)

39 Polyurethane will react with water vapor in air! (Scission Reaction Softening, Weakening)

40 The net effect of aging after 8,151 days (.3 years)

41 What is Viton? Hexafluoropropylene vinylidene fluoride 1) Viton is a common binder for explosives. ) HF acid is a byproduct of viton combustion. 3) Any combustion residue must be handled using protective equipment.

42 Summary 1) Types of energetic reactions. ) The explosive train. 3) Why do some molecules explode? 4) The structure of explosive molecules. 5) What are polymers, how are they formed, and what are their properties? 6) What are composite energetics? 7) How do rocket motors work? 8) What are polyurethane binders? 9) What kind of chemical reactions can polyurethane binders undergo? 10) What is a Viton binder and how is it formed?