Br Catalyst Research Articles

Synthesis and characterization of poly(vinyl ferrocene) grafted hydroxyl-terminated poly(butadiene): A propellant binder with a built-in burn-rate catalyst

The graft copolymer hydroxyl-terminated polybutadiene-g-polyvinyl ferrocene (HTPB-g-PVF) was synthesized free radically from HTPB and vinyl ferrocene (VF) in benzene, using azobisisobutyronitrile as the radical initiator at 75°. The graft copolymer was analysed for its structural and thermal characteristics. The chemically bound ferrocene in HTPB-g-PVF, catalysis the oxygen up-take and oxidative degradation reactions of HTPB, and the mechanisms of the catalysis are discussed. The most probable grafting sites on HTPB and the mechanism of grafting also are discussed. The extent of the grafting, which was a function of VF concentration, was low. The graft copolymer also was tried as a propellant-binder-cum-burn-rate (BR) catalyst in a composite solid propellant, using toluene diisocyanate and trimethylol propane as curatives with dibutyl tin dilaurate as the curing catalyst, and the BRs of the propellants were evaluated at 3.9 MPa. The BRs increased with the extent of VF grafting but not proportionally. The BRs also were compared with those of reference HTPB propellants containing VF, Fe2O3, copper chromite, and so forth as BR catalysts. Chemically linked ferrocene in the binder augmented the propellant BR, probably because of the presence of catalytically active sites in the binder for its degradation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4090–4099, 1999

Synthesis and characterization of poly(vinyl ferrocene) grafted hydroxyl‐terminated poly(butadiene): A propellant binder with a built‐in burn‐rate catalyst

The graft copolymer hydroxyl-terminated polybutadiene-g-polyvinyl ferrocene (HTPB-g-PVF) was synthesized free radically from HTPB and vinyl ferrocene (VF) in benzene, using azobisisobutyronitrile as the radical initiator at 75°. The graft copolymer was analysed for its structural and thermal characteristics. The chemically bound ferrocene in HTPB-g-PVF, catalysis the oxygen up-take and oxidative degradation reactions of HTPB, and the mechanisms of the catalysis are discussed. The most probable grafting sites on HTPB and the mechanism of grafting also are discussed. The extent of the grafting, which was a function of VF concentration, was low. The graft copolymer also was tried as a propellant-binder-cum-burn-rate (BR) catalyst in a composite solid propellant, using toluene diisocyanate and trimethylol propane as curatives with dibutyl tin dilaurate as the curing catalyst, and the BRs of the propellants were evaluated at 3.9 MPa. The BRs increased with the extent of VF grafting but not proportionally. The BRs also were compared with those of reference HTPB propellants containing VF, Fe2O3, copper chromite, and so forth as BR catalysts. Chemically linked ferrocene in the binder augmented the propellant BR, probably because of the presence of catalytically active sites in the binder for its degradation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4090–4099, 1999

Vinyl polymerization by Ziegler catalysts

Methylmethacrylate and styrene were polymerized with Co(acac)3-AlEt2 Br catalyst system in benzene at 40°C. Rate of polymerization is linear to monomer concentrations. Maximum percent conversion of polymer was obtained when Al/Co⩾2 with styrene and Al/Co⩾3 with methylmethacrylate. With increase in aging time catalytic activity decreases. Activation energy was found to be 60 KJ mol−1. with styrene and 40 KJ mol−1. with methylmethacrylate.

Studies on the Liquid Phase Oxidation of Nitroalkylbenzenes Catalyzed by Transition Metal and Bromide Ions

Abstract The liquid phase autoxidation of nitroalkylbenzenes catalyzed by transition metal and bromide ions in acetic acid was investigated at 55–85 °C. A remarkable synergistic effect was found on the mixtures of metal catalysts composed of cobalt and other transition metals, the maximum reaction rate being observed at the molar ratio of Co : Mn : Br=1 : 0.005–0.01 : 1–2. The rate of oxygen absorption of p- or m-nitroalkylbenzenes wasas affected by the partial pressure of oxygen, showing deviation from the first order dependency on the substrate concentration in contrast to the case of ordinary alkylbenzenes. The results can be explained by the retardation effect due to nitro compounds which might result from the reaction with alkyl radicals and the deactivation of metal catalysts. o-Nitroalkylbenzenes except nitroethylbenzene show a great resistivity against the oxidation. The retardation effect can be ascribed to the inhibiting effect due to inactive free radicals and also to the various reduced products resulting from the intramolecular reaction of nitro groups and active radicals. It was found that the autoxidation of p-nitrotoluene catalyzed by Co–Mn–Br catalyst proceeds very rapidly at temperatures as low as 85 °C, yeilding mostly p-nitrobenzoic acid along with a small amount of p-nitrobenzaldehyde.

Polymerization of styrene with the VOCL3–AlEt2Br catalyst system

AbstractThe rate of polymerization with the VOCl3–AlEt2Br catalyst system at 30°C. in n‐hexane reached a maximum at an Al/V molar ratio of 1.5. At this ratio, the rate of polymerization was first‐order with respect to catalyst and second‐order with respect to monomer concentrations. The apparent activation energy calculated was 6.4 kcal./mole. Diethylzine was found to act as a chain transfer agent. However, the molecular weights of polymers obtained were low. The possibility of bromide‐containing catalyst sites acting in the termination reaction has been investigated. The average valence of vanadium is discussed in relation to molecular weights.