Carboxyl-terminated polybutadiene, reaction

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. 

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

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... 

As these anions are not reactive enough to continue propagation, the chains are effectively terminated. By adding a proton donor subsequently to the polymerization system, the peroxy and carboxyl anions are converted to OH and COOH groups. A notable example of the application of the latter reaction is the preparation of carboxyl ion terminated polybutadiene by anionic polymerization of butadiene with bifunctional initiators, followed by termination with CO2 ... 

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. 

The role of R3AI is reduced to the alkylation of lanthanoids. Some support for this supposition is provided by the formation of carboxylates when the reaction mixture after butadiene polymerization on the NdCl3(THF)2 t3Al system is treated with carbon dioxide [9]. The protolysis of the product gives polybutadiene with COOH terminal groups. Quantum-chemical studies to model the active centres of butadiene polymerization on the Nd-Al catalytic system are also in agreement with this supposition on the mechanism of polymerization. 

Writing the polymerisation reactions for the formation of Polyesters from (o-hydroxy acids and formation of carboxy terminated polybutadiene (CTPB) from butadiene in presence of an azo initiator, predict the number of carboxyl groups per molecular chain in each case. 

These hydrocarboxylation reactions have been conducted v ith terminal alkenes containing a series of functional groups. As summarized in Equation 17.40, these reactions occur in the presence of keto, cyano, formyl, acetoxy, carboxylic acid, and amide functionality. In addition, these reactions have been conducted with polybutadienes containing pendant vinyl groups to form polymers possessing pendant carboxylic acid functionality (Equation 17.41). 

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