Poly-GLYN

Composite propellants consist of an oxidizer (AP/AN/ADN), a metallic fuel such as Al, Mg etc and a binder, usually a polymer which also serves as a fuel. Vacuum stability tests (VSTs) suggest that composite propellants are intrinsically more stable than SB, DB and propellants. However, use of more exotic ingredients such as oxidizers (ADN and hydrazinium nitroformate, HNF), binders [poly([NiMMO)] and poly([GlyN)] are likely to introduce severe compatibility-related problems [30, 31]. Some recent research in this direction indicates that stability of such propellants is largely determined by the chemical and mechanical properties of propellants. However, early evidence of deterioration generally comes from a change in their mechanical properties rather than from chemical investigations [32]. 

W.B.H., Marshall, E.J., and Paul, N.C. (1995) Stability of cured poly(GlyN) and end modified poly(GlyN). Proc. Inti. Symp. on Energetic Materials Technology, American Defense Preparedness Association, Phoenix, Arizona, USA, Sept. 24-27, 1995, p. 288. 

There are a number of inert binders such as polyester, epoxy, polysulfide, polyurethane which have been reported as binders for composite propellants and plastic bonded explosives (PBXs). At present, hydroxy-terminated polybutadiene (HTPB) is regarded as the state-of-the-art workhorse binder for such applications. However, the recent trend is to use energetic binders such as poly [3,3-bis(azidomethyl oxetane)] [poly(BAMO)], poly (3-azidomethyl-3-methyl oxetane) [poly(AMMO)], PNP, GAP diol and triol, nitrated HTPB(NHTPB), poly(NiMMO), poly(GlyN) and nitrated cyclodextrin polymers poly(CDN) for PBXs and composite propellants in order to get better performance. 

The chemistry and properties together with applications of other energetic binders such as GAP, NHTPB, poly (NiMMO), poly (GlyN) and poly (CDN) will be described in Chapter 4 on propellants because of their extensive use in that segment of explosive industry. 

Structure (4.20) Poly(glycidyl nitrate) [Poly(GlyN)]... 

Uncured poly(GlyN) prepolymer exhibits good chemical stability and has a satisfactory shelf-life. However, the ageing characteristics of isocyanates cured PU rubbers are unsatisfactory contrary to (NiMMO) rubbers which have good ageing characteristics. Long term ageing trials have shown that the cured... 

A family of high performance and clean space motor/gas generators and large launch vehicle solid propellants based on poly(GlyN) binder, ammonium nitrate oxidizer and small amounts of aluminum and/or boron with optimized performance at low solids loading (without the presence of plasticizers) and also poly(GlyN) binder, ammonium nitrate oxidizer and aluminum or magnesium fuel have been reported in the literature [141, 142]. These solid propellant formulations produce essentially no HC1 or chloride ions in the exhaust and are considered eco-friendly. 

Similarly, high performance solid propellants consisting of Poly(GlyN) binder, ammonium perchlorate oxidizer and beryllium/beryllium hydride fuel which also do not require the presence of plasticizers and offer optimum performance at low solids loading have been reported for space launch vehicles [143]. 

To summarize, the cost of production of NHTPB is lower than that of poly(NiMMO) or Poly(GlyN). However, NHTPB s performance is poor in comparison to them. On the basis of trials conducted so far, it seems likely that poly(GlyN) will prove to be a world leader in the field of energetic polymers. A summary of the properties of energetic binders for use with both explosives and propellants is given in Table 4.6a,b. 

Current methodologies for the manufacture of energetic materials such as NHTPB, Poly(NiMMO) and Poly(GlyN) etc. use environmentally undesirable solvents such as dichloromethane. However, the adoption of the Montreal Protocol by most of the countries has limited the use of these halogenated hydrocarbons. To address current and futuristic legislations, DERA Scientists have developed various strategies to enable the manufacture of energetic materials in an environmentally friendly manner. Such an approach is to use Uquid or supercritical carbon dioxide as a solvent Carbon dioxide exhibits supercritical fluid behavior at a temperature >31.1 °C and a pressure >73.8 bar. 

Bunyan, P.F., Clements, B.W., Cunliffe, A.V., Torry, S.A., and Bull, H. (1997) Stability studies on end modified poly(GlyN). Proc. American Defense Preparedness Association (ADPA), Ind... 

As discussed under explosives and propellants, a number of energetic binders GAP, NHTPB, poly(NiMMO), poly(GlyN), poly(BAMO), poly(AMMO) and BAMO-AMMO copolymers etc. have been reported in the recent past and are at various stages of development and introduction for bulk production of explosives and propellants for various applications. These polymeric binders are reasonably stable and are of established compatibility with a wide range of ingredients used for explosive and propellant formulations. The data on their explosive properties impact, friction and electric spark sensitivities, indicate that it is safe to handle these materials. However, there appears to be no report in the open literature on... 

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