Carboxy-terminated polybutadiene

CTPB = carboxy-terminated polybutadiene HTPB = hydroxy-terminated polybutadiene PBAN = polybutadiene-acrylic acid-acrylonitrile and PBAA = polybutadiene-acrylic acid. 

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... 

Some typical stress-strain curves for a carboxy-terminated polybutadiene proplnt (CTPB) containing 86% solids are given in Figure 8, and for a PBAA propellant (see Table 13) containing 83% solids in Figure 9 (Ref 52). The authors concluded that the CTPB proplnts studied were highly susceptible to humidity degradation... 

The influence of ambient aging at 70°F and accelerated aging at 160°F on the stress-strain behavior of carboxy-terminated polybutadiene, polybutadiene-acrylic acid, polybutadiene-acrylic acid-acrylonitrile, and hydroxy-terminated polybutadiene composite propints is shown in Figures 10 and 11. The elastomers and curative agents for these formulations are listed below... 

Under increasing strain the propint volume increases from the voids created around the unbonded solid particles. Nonlinearities in Young s modulus and Poisson s ratio then occur. Francis (Ref 50) shows this effect for a carboxy-terminated polybutadiene composite propellant with 14% binder as in Figure 12. He concludes that nonlinearities in low-temperature properties reduce the predicted stress and strain values upon cooling a solid motor, and therefore a structural analysis that neglects these effects will be conservative. However, when the predictions are extended to a pressurized fiberglas motor case, the nonlinearities in properties produce greater strains than those predicted with linear analysis... 

The crude product from the above reaction mixt was fractionated into a distilled product (bp 200°/0.3 Torr) with an average molecular weight of 514 and a residue with an average molecular weight of 940. These were evaluated as catalysts and compared to prior art ferrocenes in a standard carboxy-terminated polybutadiene formula cured with MAPO. The results are shown in Table 31... 

The biradical catalysts described previously for double-base propints (Ref 80) are also effective for hydrocarbon propints. Table 34 shows how p,p,-biphenylene-bis(diphenylmethyl) compares to n butyl ferrocene as a catalyst in a carboxy-terminated polybutadiene. These catalysts are claimed to overcome all of the processing difficulties, chemical stability and volatility disadvantages attributed to catalysts based on ferrocene and carborane derivatives. Another somewhat similar functioning catalyst, the free radical compd, 2,2-diphenylpicrylhydrazyl,... 

Polybutadiene-polydimethylsiloxane segmented copolymers were prepared by the reaction of epoxy-terminated PDMS and carboxy-terminated polybutadienes, in refluxing toluene under catalytic action of potassium hydroxide 243). Molecular weights of the copolymers obtained were usually in the low range. No other characterization data were available. 

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-... 

Boron is one of the essential materials for obtaining high specific impulse of a ducted rocket However, the combustion efficiency of boron-containing gas-generating pyrolants is low due to incomplete combustion of the boron particles in the ramburner.[i3-i l Fig. 15.20 shows the combustion temperature ofa boron-containing pyrolant with and without boron combustion as a function of air-to-fuel ratio, 8. A typical boron-containing pyrolant is composed of mass fractions of boron particles b(0-30), ammonium perchlorate ap(0.40), and carboxy-terminated polybutadiene ctpb(0-30). If the boron particles burn completely in the ramburner, the maximum combustion temperature reaches 2310 K at 8 = 6.5 and v = Mach 2 p =... 

Poly butadienes. Hydroxyl-terminated polybutadienes are comparatively late comers and are still in the development stage. They combine the high specific impulse of the well-proved carboxy-terminated polybutadienes with the clean, stoichiometric urethane reaction yielding propellants with unsurpassed mechanical properties. 

Compatibility. Owing to the high reactivity of the isocyanate group, polyurethane propellants require a more sophisticated processing technique than the rather foolproof, carboxy-terminated polybutadiene aziri-dine and/or epoxy-cured propellant systems. Processing is even more complicated if bonding agents (see below) are present, which are used to bolster mechanical properties in practically any modern propellant. 

A specific requirement of solid propellant binder polymers is the small tolerance allowed in the reproducibility of the product properties. As a result, some polymers that cannot be specified easily must be adjusted lot by lot in accordance with qualification tests. This is illustrated graphically by the data of Figure 1, where different lots of a carboxy-terminated polybutadiene procured to the same specification are compared with the different equivalents of the BITA (butylene imine adduct of trimesic... 

Inert binders Polybutadiene and cellulose derivatives are used as binders for LOVA formulations [24]. The commonly used polybutadiene-based binders are hydroxy-terminated polybutadiene (HTPB) and carboxy-terminated polybutadiene (CTPB)/poly(butadiene-acrylonitrile) (PBAN) while the most commonly used cellulose derivatives are ethyl cellulose (EC), cellulose acetate (CA), cellulose acetate butyrate (CAB) and cellulose... 

Ammonium perchlorate Carboxy-terminated polybutadiene Aluminium Other additives 2600 3500... 

HMX was first evaluated with hydrocarbon binders (Butarez, a carboxy-terminated polybutadiene, and Butyl rubber) because of their high thermal stability, in addition to the expected advantages of high impetus levels and low flame temps. In the Butarez binder, an 85% HMX level produced an impetus of 370000 ft-lbs/lb and a flame temp of 2540°K. At 84% HMX, the system was under-oxidized, at 86% the flame temp exceeded 2600°K. Because of a less favorable heat of formation, higher HMX loadings were required for the Butyl rubber system, ie, about 87% HMX and 13% Butyl rubber vs 85% HMX and 15% Butarez for an impetus of 370000 ft-lbs/lb. In the hydrocarbon formulations, the Butarez polymer appeared more attractive thermodynamically... 

Butarez = carboxy terminated polybutadiene (german) butanetriol trinitrate 48 BWC = board wood cellulose (UK)... 

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