Hydroxy Terminated Polybutadiene: Chemical Modifications and Applications

Quantum Chemical Modeling of Propellant Degradation

An ab initio quantum chemical approach for the modeling of propellant degradation is presented. Using state-of-the-art bonding analysis techniques and composite methods, a series of potential degradation reactions are devised for a sample hydroxyl-terminated-polybutadiene (HTPB) type solid fuel. By applying thermochemical procedures and isodesmic reactions, accurate thermochemical quantities are obtained using a modified G3 composite method based on the resolution of the identity. The calculated heats of formation for the different structures produced presents an ∼2 kcal/mol average error when compared against experimental values.

Hexogen Coating Kinetics with Polyurethane-Based Hydroxyl-Terminated Polybutadiene (HTPB) Using Infrared Spectroscopy

The kinetics of hexogen coating with polyurethane-based hydroxyl-terminated polybutadiene (HTPB) using infrared spectrometry was investigated. The kinetics model was evaluated through reaction steps: (1) hydroxyl and isocyanate to produce urethane, (2) urethane and isocyanate to produce allophanate, and (3) nitro and isocyanate to produce diazene oxide and carbon dioxide. HTPB, ethyl acetate, TDI (toluene diisocyanate), and hexogen were mixed for 60 min at 40 °C. The sample was withdrawn and analyzed with infrared spectroscopy every ten minutes at reference wavelengths of 2270 (the specific absorption for isocyanate groups) and 1768 cm⁻¹ (the specific absorption for N=N groups). The solvent was vaporized; then, the coated hexogen was cured in the oven for 7 days at 60 °C. The effect of temperature on the coating kinetics was studied by adjusting the reaction temperature at 40, 50, and 60 °C. This procedure was repeated with IPDI (isophorone diisocyanate) as a curing agent. The reaction rate constant, k₃, was calculated from an independent graphic based on increasing diazene oxide concentration every ten minutes. The reaction rate constants, k₁ and k₂, were numerically calculated using the Newton–Raphson and Runge–Kutta methods based on decreasing isocyanate concentrations. The activation energy of those steps was 1178, 1021, and 912 kJ mole⁻¹. The reaction rate of hexogen coating with IPDI was slightly faster than with TDI.

MODIFICATION OF POLYBUTADIENE RUBBER: A REVIEW

Developments in modification of polybutadiene rubber (PBR) using various reagents and catalysts have been reviewed. Hydrogenation and functionalization occurring at the site of unsaturation along chain length are discussed. Hydrogenation involving various metal catalyzed processes is discussed. Suitable conditions that are effective during hydrogenation and functionalization are mentioned in this article. Reactivity ratios associated with microstructures of polybutadiene rubber and possible mechanisms involved are described in the review. The importance of reaction conditions during reactivity and their impact on product properties are highlighted. A specific method that needs to be adopted in order to achieve expected product properties is discussed. Various industrial applications of modified PBR and their commercial products in the global market are discussed.

Compartmentalized polymerization in aqueous and organic media to low-entangled ultra high molecular weight polyethylene

Catalytic polymerization in compartmentalized aqueous or non-aqueous media, respectively, with functional-group tolerant Ni(ii) catalysts yields low-entangled UHMWPE.

Synthesis of telechelic polyolefins

A comprehensive review of all the methodologies developed for the synthesis of telechelic polyolefins is reported.

Understanding and controlling the glass transition of HTPB oligomers

In this paper, we use a combination of experiment and simulation to achieve enhanced levels of synthetic control on the microstructure of the much-used binder material hydroxyl terminated polybutadiene (HTPB).

Evaluation on Curing Properties and Kinetics of Isophthalonitrile Oxide

N,N-dihydroxybenzene-1,3-dicarboximidoyl dichloride was synthesized from benzene-1,3-dicarboxaldehyde and characterized by fourier transform infrared spectroscopy (FT-IR) and nuclear magnetic resonance (1H and 13C NMR). The elastomer was prepared through the 1,3-dipolar cycloaddition of reaction between liquid polybutadiene (LPB) and isophthalonitrile oxide in this work. The tensile strength of different elastomer was enhanced from 0.14 MPa to 0.33 MPa as the elongation at break decreased from 145% to 73%, and the modulus increased from 0.09 kPa to 0.47 kPa. The parameters of kinetic indicated that the curing reaction was fi rst order reaction and the apparent activation energy of each curing system was less than 10.10 kJ/mol when the content of N,N-dihydroxybenzene-1,3- dicarboximidoyl dichloride was increased from 7% to 12%. These results suggested that nitrile oxides achieved curing of polymer binders at room temperature and this work had defi nite guiding signifi cance for the application of nitrile oxides in polymer binders.

Effect of Solvent and Functionality on the Physical Properties of Hydroxyl-Terminated Polybutadiene (HTPB)-Based Polyurethane

The present article reports the investigation on the effects of solvent and position of functionality on various physical properties of polyurethanes (PUs) based on hydroxyl-terminated polybutadiene (HTPB). The PU films (curative)  were prepared by coupling HTPB (P0) with isophorone diisocyanate (IPDI) in various solvent media. The PUs obtained in different solvent media displayed similar thermal profile and glass transition temperature (T _g), but their tensile properties varied significantly. Optimized tensile properties were observed when tetrahydrofuran was used as the solvent media. In the course, the investigation of the functionality effect, tetrazole (M1, M2, and M3) were covalently attached at the terminal carbon of HTPB to obtain three modified HTPBs (P1, P2, and P3), thereby coupling with IPDI to obtain the corresponding tetrazole functional PUs films. Pristine (P0-PU) and functional PU (P1-PU, P2-PU, and P3-PU) films have similar thermal profile and T _g (-76 °C), but they have a notable enhancement in tensile properties; for example, tensile strength and elongation at break of P0-PU were found to be 3.21 MPa and 727%, respectively, whereas these values were 4.84 MPa and 958%, respectively, in the case of P3-PU. It was observed that on increasing the number of methylene group from 1 to 3 between HTPB and tetrazole moiety, the strength of hydrogen bonding increases, which facilitates better packing of urethane network in the PU and hence improves the tensile properties. Also, modification of pristine HTPB with tetrazole derivatives enhanced the calorific values of the resulting PUs.