Hydroxy-terminated polybutadiene polymers

In this way one mole of water reacts with two moles of isocyanate. For a urethane prepolymer with an equivalent weight of about 300, it only takes 9 grams of water to effectively consume the prepolymer. This can lead not only to degraded physical properties, but it also forms gas bubbles in the proplnt which lead to voids and higher than predicted burning rates. This sensitivity to water content also exists with hydroxy-terminated polybutadiene polymers cured with... 

Predominantly di-end-functional polymers may be prepared by conducting polymerizations with high concentrations of a functional initiator. Some of the first commercial products of this class, carboxy and hydroxy-terminated polybutadienes, were produced by this route.194... 

For example, using hydroxy-terminated polybutadiene as the binder, RDX as the expl, toluenediisocyanate as a co-polymer, sym-di-(2-naphthyl)-p-phenylenediamine as an antioxidant, and poly butene as the plasticizer in a wt % ratio of 12.1/42.7/5/0.2/40, a castable expl is produced. 

Another class of hydrocarbon binders used in propints are the carboxy-terminated polybutadiene polymers which are cross-linked with either tris[l-(2-methyl)aziridinyl] phosphine oxide (MAPO) or combinations with phenyl bis [l -(2-methyl)aziridinyl] phosphine oxide (Phenyl MAPO). Phenyl MAPO is a difunctional counterpart of MAPO which makes possible chain extension of polymers with two carboxylic acid groups. A typical propint formulation with ballistic properties is in Table 11 (Ref 83) Another class of composites includes those using hydroxy-terminated polybutadienes cross-linked with toluene diisocyanate as binders. The following simplified equations illustrate typical reactions involved in binder formation... 

The first SANS experiments on end-linked elastomers with a well-defined functionality were carried out by Hinkley et al, (22). Hydroxy-terminated polybutadiene was crosslinked by a trifunctional isocyanate, and the resultant polymer was uniaxially stretched. 

Hydroxy-terminated polybutadiene (HTPB) is considered to be the best binder for obtaining high combustion performance, superior elongation properties at low temperatures, and superior mechanical strength properties at high temperatures. This combination of properties is difficult to achieve in double-base propellants. HTPB is characterized by terminal -OH groups on a butadiene polymer. The other type of butadiene polymer used is carboxy-terminated polybutadiene (CTPB), which is cured with an imine or an epoxy resin. It should be noted that CTPB is somewhat sensitive to humidity, which has an adverse effect on its ageing charac-... 

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. 

Millett, J.C.F. Bourne, N.K. Akhaven, J. The response of hydroxy-terminated polybutadiene to one-dimensional shock loading. J. Appl. Polym. Phys. 2004, 95, Mil. 

Supercritical fractionation was investigated for the special-purpose polymers of both the diol and triol of a glycidyl azide polymer and a hydroxy-terminated polybutadiene. Hydroxy polybutadiene is used on a large scale as an ingredient in plastic bonded explosive (PBX) propellant formulations the hydroxy functionality of the polybutadiene reacts with an isocyanate functionality of another prepolymer to form a urethane. In the polysiloxanes section we referred to functionally terminated polymers as macromonomers in the terminology of the urethane industry, however, isocyanate-terminated polyester polymers are normally referred to as prepolymers in their reaction to form the urethane, even though the prepolymers are typically between 1,000 and 10,000 molecular weight. 

Saraf, V., Glasser, W. G., Wilkes, G. L., and McGrath, G. E. Engineering plastics from lignin IV. Structure property relationships of PEG-containing polyurethane networks, Journal Applied of Polymer Science, 30, 2207 (1985). Sarkar, S. and Adhikari, B. Thermal stability of lignin-hydroxy-terminated polybutadiene-co-polyurethanes. Polymer Degradation and Stability, 73, 169-175 (2001). 

Waterborne polyurethane resins are produced from maleinised monoglyceride (MMG) of sunflower oil, hydroxy-terminated polybutadiene, toluene diisocyanate and ethylene diamine. The carboxylic acid groups of MMG are neutralised by triethyl amine, making the resin water dispersible. The monoalkylated castor oil (MCO) or dehydrated castor oil (DCO) is treated with a polyether glycol at 120°C, followed by the addition of IPDI and DBTDL. To obtain a series of aqueous polyurethanes, butane diol and dimethylol propionic acids (DMPA) are added and the mixture heated to 70°C for two hours to produce a NCO-terminated pre-polymer which forms salt with triethylamine, giving a water-soluble polymer. The reaction mixture is dispersed in water and a chain extender, ethylene diamine, is added. Two aqueous polyurethanes, MCPU and DCPU, are finally obtained from MCO and DCO, respectively. 

Inc. aniline ("Baker Analyzed" Reagent) from J.T. Baker Chemical Co. 3-aminopropyltriethoxysilane from Petrarch Systems Inc. TDI (80/20 mixture of 2,4 and 2,6 isomers of toluene diisocyanates) from BASF Wyandotte Corporation Isonol-100 (N,N-bis-(2-hydroxypropyl)aniline) from Upjohn Polymer Chemicals and hydroxy-terminated polybutadiene resin (R-45HT) from ARCO Chemical Co. ARCO lists the properties given in Table 1 for the latter resin. 

Hydroxy-terminated polybutadienes (HTPBD) (11) yield urethane polymers with improved hydrolytic stability and lower moisture vapor... 

The temperature dependence of the relaxation activation energy of hydroxy-terminated polybutadiene-methyl methacrylate AB cross-linked polymer in the glass transition region is shown in Figure 4.8. The parameters C, = 8.77 °C, C2 = 85.07 °C and = 340 K were measured by means of the dynamic mechanical spectra 381 K was chosen as the reference temperature Tq. 

Various workers have discussed aspects other than those mentioned above in studies of the viscoelastic properties of polymers. These include PVOH [62], hydroxy-terminated polybutadiene [63], styrene-butadiene and neoprene-type blends [64], and polyamidoimides [65]. Other aspects of viscoelasticity that have been studied include relaxation phenomena in PP [66] and methylmethacrylate-N-methyl glutarimide copolymers [67], shear flow of high-density polyethylene [68], Tg of PMMA and its copolymers with N-substituted maleimide [69] and ethylene-vinyl acetate copolymers [70], and creep behaviour of poly(p-phenylene terephthalate) [71] and PE [72]. 

Thermo-oxidative breakdown of the cross-linked polymer derived from toluene-2,4-di-isocyanate, methylene bis(4-amino-3-chloroph0iyl), and a hydroxy-terminated polybutadiene occurred, however, by a radical mechanism... 

The chemiluminescence imaging equipment developed by Charles Evans Associates is described and an example is given of the ageing-induced image obtained from a sample of hydroxy-terminated polybutadiene cured with isophorone diisocyanate (a material used as a binder in solid fuel rocket motors). It is demonstrated that the sites of material failures and possibly the sites of incipient failures can be located and studied using chemiluminescence imaging. 1 ref. (ACS, Div of Polymer Chemistry, Atlanta, Georgia, April 1991)... 

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