Carboxyl-terminated polybutadien

Some ordn uses have been found for carboxyl terminated polybutadiene viz, as rocket motor liners for proplnt mixts contg HTPB (Ref 17) and as part of a terpolymer binder for propints (Ref 16)... 

A Comparison of a Carboxyl-Terminated Polybutadiene-Based Propellant (CTPB) Using N-Butylferrocene as Burning Rate Catalyst With a CTPB—Based Propellant Using Biradical Burning Rate Catalyst... 

This paper discusses the three butadiene prepolymers which have been used most extensively in solid rocket propellants—i.e., the copolymer of butadiene and acrylic acid (PBAA), the terpolymer of butadiene, acrylic acid, and acrylonitrile (PBAN), and the carboxyl-terminated polybutadiene (CTPB). Since the chemistry of all of these carboxyl-containing prepolymers is essentially the same, the discussion of butadiene propellants in this paper is concerned mainly with those based on CTPB. 

Curing Agents for Carboxyl-Terminated Polybutadiene Prepolymers. The types of curing agents used to prepare binders for CTPB propellants are the same as those for PBAN or PBAA. The bifunctionality of CTPB, however, requires that part of the curing agents be polyfunctional to provide for the formation of the tridimensional network. Almost without exception, the polyfunctional aziridines and epoxides used with CTPB undergo side reactions in the presence of ammonium perchlorate, which affects the binder network formation. Kinetic studies conducted with model compounds have established the nature and extent of the cure interference by these side reactions. The types and properties of some of the crosslinkers and chain extenders used to prepare solid propellants are summarized in Table IV. 

Effects of Curing Agent Type. Epoxide-Cured Propellant. Carboxyl-terminated polybutadiene is a linear, difunctional molecule that requires the use of a polyfunctional crosslinker to achieve a gel. The crosslinkers used in most epoxide-cured propellants are summarized in Table IV and consist of Epon X-801, ERLA-0510, or Epotuf. DER-332, a high-purity diepoxide that exhibits a minimum of side reactions in the presence of the ammonium perchlorate oxidizer, can be used to provide chain extension for further modification of the mechanical properties. A typical study to adjust and optimize the crosslinker level and compensate for side reactions and achieve the best balance of uniaxial tensile properties for a CTPB propellant is shown in Table V. These results are characteristic of epoxide-cured propellants at this solids level and show the effects of curing agent type and plasticizer level on the mechanical properties of propellants. 

Figure 8. Molecular weight distribution of carboxyl-terminated polybutadienes...

Figure 19. Comparison of molecular weight distributions of carboxyl-terminated polybutadienes by the solvent precipitation-intrinsic viscosity technique...

Propellants based on carboxyl-terminated polybutadiene characteristically exhibit the highest values of specific impulse which have been achieved for ammonium perchlorate-based composites. These propellants also exhibit satisfactory mechanical behavior over a wide range of temperatures and can be adjusted to meet the burning rate requirements of most applications. 

Propellants based on carboxyl-terminated polybutadienes have been used successfully in many solid rocket motors. These propellants provide... 

Carboxyl-terminated polybutadiene (General Tire Rubber Co.)... 

Further expts were conducted on candidate proplnts for space environments. Horton (Ref 112) subjected a urethane-based propint, a polybutadiene-acrylic acid-acrylonitrile based propint, and a carboxyl-terminated polybutadiene based proplnt to 1.5 x 107 R, as well as to high and low temp and pressure. The data indicated that the urethane proplnt withstood the tests best. Scott et al (Ref 126) conducted tests on two polycarbutene solid proplnts which were irradiated to 107 R and subjected to high vacuum exposure as a function of temp without much change... 

The carboxyl terminated polybutadiene (C-3000) is about equally effective to CTBN in heat distortion temperature and impact but considerably less effective in strength. From the haze data (the percent haze of ERL-4221 modified with 10 phr of CTBN and C-3000 were 17 and 85% respectively) it is quite clear that this elastomer (C-3000) is highly incompatible with the epoxy-hardener system in the cured state. A 2000 molecular weight polybutadiene elastomer, containing no carboxyl groups, was completely incompatible with the epoxy system and segregated in the cured state. 

Figure 11.10 Examples of dissipation spectra (1 Hz frequency), (a) amine-epoxy network containing a carboxyl-terminated polybutadiene. The rubber a peak (arrow) is superimposed on the p peak of epoxy, (b) unsaturated polyester containing polyvinylacetate. The a peak (arrow) is at the onset of the p—a dissipation band.

Furthermore, flexibilized compositions have been described. As flexibilizers, carboxyl terminated polybutadiene [89] or simply poly butadiene [79] were mentioned. 

Another multicomponent heat resistant (Tg = 220 °C) system consists of epoxide resin, carboxyl terminated polybutadiene, glycidyl methacrylate, BPA/DC, diamines and bismaleimides. It contains catalysts and initiators, e.g. Zn octoate, triethylene-diamine and benzoyl peroxide [89]. 

Carbonit - Wetter-Carbonit (german permissible explosive) 370 carboxyl-terminated polybutadiene 62 329... 

Crawford bomb 66 cresylite = mixture of trinitrocresol and picric acid (french) crimping 66 critical diameter 66 CR-propellants = RDX containing rifle powders (USA) cross section ratio -> propellant area ratio 269 crusher 149 362 C.TD. = coefficient of detonation transmission (coefficient de self exitation) (french) 87 CTPB = carboxyl-terminated polybutadiene (USA) 61 329 cumulative priming 66 c.u.p. = coefficient d utilisation pratique (french) 198 cuprene 52 cupric salicylate 163 curing 67... 

Zhang, Y., et al. (2004), Hollow spheres from shell cross-linked, noncovalently connected micelles of carboxyl-terminated polybutadiene and poly(vinyl alcohol) in water, Macromolecules, 37,1537-1543. 

Problem 4.4 A sample (3.0 g) of carboxyl terminated polybutadiene (CTPB) required titration with 20 mL 0.1 N KOH to reach a phenolphthalein end point. Calculate M of the polymer. 

Reaction with acid then yields carboxyl-terminated polybutadiene (CTPB). Hydroxyl end groups are provided by termination with ethylene oxide ... 

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