Viscoelastic behavior of hydroxyl terminated polybutadiene containing glycerin

Hydroxyl terminated polybutadiene (HTPB) is widely used as a propellant binder. A plasticizer is usually added to improve the processing properties, the mechanical properties, and the burning characteristics of the propellant. Glycerin was found to be an effective additive to improve these properties. The glycerin/HTPB blend was hard enough to act as a binder for the composite propellant when the glycerin/HTPB mole ratio was less than 10. Only a small quantity of glycerin was incorporated into the network structure of the cured HTPB. Most of the added glycerin physically entered the voids in the network of the cured HTPB. Addition of a small quantity of glycerin (mole ratio less than 0.1) significantly altered the network density and the viscoelastic properties of the blends. The properties were only slightly dependent on the amount of the added glycerin in the mole ratio range of 0.1–10. The dangling ends were formed in the HTPB network by the addition of glycerin and the network structure was loosened, thereby enhancing the mobility of the chain segment. The viscoelastic properties of the blends followed the time‐temperature superposition principle, and the properties were estimated accurately by the Williams‐Landel‐Ferry approach. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Single Step Synthesis of Nitro‐Functionalized Hydroxyl‐Terminated Polybutadiene

The paper reports the energization of Hydroxyl‐Terminated Polybutadiene (HTPB) by functionalizing explosophore  NO₂ over the HTPB backbone, resulting in the formation of conjugated nitro‐alkene derivative of HTPB. A convenient, inexpensive and efficient “one pot” procedure of synthesizing Nitro‐Functionalized Hydroxyl‐Terminated Polybutadiene (Nitro‐HTPB) is reported. The reaction was carried out with sodium nitrite and iodine. To retain the unique physico‐chemical properties of HTPB, functionalization by  NO₂ group was restricted to 10 to 15 % of double bonds. The Nitro‐HTPB was characterized by FTIR, ¹H NMR, VPO, DSC, TGA etc. The polymer has shown good thermal stability for practical applications. The kinetic parameters for the decomposition of Nitro‐HTPB at 150–300 °C were obtained from non‐isothermal DSC data.     

Studies on Advanced RDX/TATB Based Low Vulnerable Sheet Explosives with HTPB Binder

Hydroxyl‐terminated polybutadiene (HTPB) based sheet explosives incorporating insensitive 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) as a part replacement of cyclotrimethylene trinitramine (RDX) have been prepared during this work. The effect of incorporation of TATB on physical, thermal, and sensitivity behavior as well as initiation by small and high caliber shaped charges has been determined. Composition containing 85% dioctyl phthalate (DOP) coated RDX and 15% HTPB binder was taken as control. The incorporation of 10–20% TATB at the cost of RDX led to a remarkable increase in density (1.43→1.49 g cm⁻³) and tensile strength (10→15 kg cm⁻²) compared to the control composition RDX/HTPB(85/15). RDX/TATB/HTPB based compositions were found less vulnerable to shock stimuli. Shock sensitivity was found to be of the order of 20.0–29.2 GPa as against 18.0 GPa for control composition whereas their energetics in terms of velocity of detonation (VOD) were altered marginally. Differential scanning calorimeter (DSC) and thermogravimetry (TG) studies brought out that compositions undergo major decomposition in the temperature region of 170–240 °C.     

Synthesis,characterization and thermal dissociation of 2‐butoxyethanol‐blocked diisocyanates and their use in the synthesis of isocyanate‐terminated prepolymers

A series of blocked diisocyanates has been synthesized from toluene diisocyante (TDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), 4,4′‐diphenylmethane diisocyanate (MDI) and 2‐butoxyethanol. The synthesis of blocked diisocyanate adducts was confirmed by Fourier transform infrared, ¹H NMR, electron impact mass spectrometry and nitrogen analysis. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and carbon dioxide evolution were used to determine the minimum de‐blocking temperatures. De‐blocking temperatures determined by these three techniques were found to be in the order DSC > TGA > CO₂ evolution. The effect of different metal catalysts on thermal de‐blocking reaction of the blocked diisocyanates was studied, using the carbon dioxide evolution method. It was found that iron(III) oxide has the maximum catalytic activity on de‐blocking. The solubility of the blocked diisocyanate adducts was determined in different solvents. The study revealed that at 30 °C blocked IPDI and HDI adducts show better solubility than adducts based on TDI and MDI. Isocyanate‐terminated prepolymers of blocked diisocyanates and hydroxyl‐terminated polybutadiene (HTPB) were prepared. The storage stability and gelation times of the prepolymers were studied. Results showed that all the diisocyanate‐HTPB compositions are stable at 50 °C for more than three months. However, aliphatic diisocyanate‐HTPB compositions require greater gelation time than aromatic diisocyanate‐HTPB compositions at their respective de‐blocking temperatures. Copyright © 2007 Society of Chemical Industry     

On the Correlation between Miscibility and Solubility Properties of Energetic Plasticizers/Polymer Blends: Modeling and Simulation Studies

In this paper, systems for which miscibility (hydroxyl‐terminated polybutadiene–dioctyl adipate or HTPB–DOA) or immiscibility (HTPB–diethylene glycol dinitrate or HTPB–DEGDN) have been firmly established were used to test the usefulness of an atomistic molecular mechanics model. Two specific aspects were discussed: miscibility assessment of a plasticizer/polymer blend, and predictions of the enthalpy of vaporization. Simulations were carried out using Amorphous Cell and Discover packages of the Material Studio software using Compass force field for all calculations. A good agreement has been found for miscibility observations of blends, and for solubility parameter, density, and derived enthalpy of vaporization for pure substances. Therefore, the approach proposed in this work is a useful tool to provide insights on miscibility and properties of a given polymer/plasticizer blend. In addition, it is a promising technique to help in screening among several plastic bonded explosive (PBX) formulations prior to real experimental tests.     

Radiative Ignition of Fine‐Ammonium Perchlorate Composite Propellants

Radiative ignition of quasi‐homogeneous mixtures of ammonium perchlorate (AP) and hydroxyterminated polybutadiene (HTPB) binder has been investigated experimentally. Solid propellants consisting of fine AP (2 μm) and HTPB binder (~ 76/24% by mass) were ignited by CO₂ laser radiation. The lower boundary of a go/no‐go ignition map (minimum ignition time vs. heat flux) was obtained. Opacity was varied by adding carbon black up to 1% by mass. Ignition times ranged from 0.78 s to 0.076 s for incident fluxes ranging from 60 W/cm² to 400 W/cm². It was found that AP and HTPB are sufficiently strongly absorbing of 10.6 μm CO₂ laser radiation (absorption coefficient ≈250 cm⁻¹) so that the addition of carbon black in amounts typical of catalysts or opacitymodifying agents (up to 1%) would have only a small influence on radiative ignition times at 10.6 μm. A simple theoretical analysis indicated that the ignition time‐flux data are consistent with in‐depth absorption effects. Furthermore, this analysis showed that the assumption of surface absorption is not appropriate, even for this relatively opaque system. For broadband visible/near‐infrared radiation, such as from burning metal/oxide particle systems, the effects of in‐depth absorption would probably be even stronger.     

Modeling and measurement of glass transition temperatures of energetic and inert systems

In this article, measurements of glass transition temperature (T_g) changes of two energetic material blend systems were carried out using the differential scanning calorimetry (DSC) technique. On one hand, experimental T_g values were compared to those predicted by the additivity model, Fox and Pochan equations, and, on other hand, to atomistic molecular dynamics simulation results performed in this work. The two blend systems studied were both composed of a polymer, either the inert hydroxyl‐terminated polybutadiene (HTPB) or the energetic polyglycidylazide (GAP), and smaller molecules, which acted as plasticizers, dioctyl adipate (DOA), or glycidylazide oligomers (Gp1). Modeling results show deviations from experimental data, which varied from 5 to 20 K over an absolute scale for pure components and blends. A good fit was found when predicting the effect of adding smaller molecules to HTPB. Simulations were particularly useful for the blend in which the glass transition temperature of one component, DOA, was not experimentally measurable, due to the high crystallinity of the small DOA molecule. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers.     

Burning‐rate enhancement of a high‐energy rocket composite solid propellant based on ferrocene‐grafted hydroxyl‐terminated polybutadiene binder

Four different samples of ferrocene‐grafted hydroxyl‐terminated polybutadiene (Fc‐HTPB), containing 0.20, 0.52, 0.90, and 1.50 wt % iron, were synthesized by the Friedel–Crafts alkylation of ferrocene with hydroxyl‐terminated polybutadiene (HTPB) in the presence of AlCl₃ as a (Lewis acid) catalyst. The effects of the reaction conditions on the extent of ferrocene substitution were investigated. The Fc‐HTPBs were characterized by IR, ultraviolet–visible, ¹H‐NMR, and ¹³C‐NMR spectra. The iron content and number of hydroxyl groups were estimated, and the properties, including thermal degradation, viscosity, and propellant burning rates (BRs), were also studied. The thermogravimetric data indicated two major weight loss stages around 395 and 500°C. These two weight losses were due to the depolymerization and decomposition of the cyclized product, respectively, with increasing temperature. The Fc‐HTPB was cured with toluene diisocyanate and isophorone diisocyanate separately with butanediol–trimethylolpropane crosslinker to study their mechanical properties. Better mechanical properties were obtained for the gumstock of Fc‐HTPB polyurethanes with higher NCO/OH ratios. The BRs of the ammonium perchlorate (AP)‐based propellant compositions having these Fc‐HTPBs (without dilution) as a binder were much higher (8.66 mm/s) than those achieved with the HTPB/AP propellant (5.4 mm/s). © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Kinetic Parameters of PBX Based on Cis‐1,3,4,6‐tetranitroocta‐hydroimidazo‐[4,5‐d] imidazole Obtained by Isoconversional Methods using Different Thermal Analysis Techniques

The thermal decomposition kinetics of the interesting polycyclic nitramine cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole (BCHMX) and its polymer bonded explosive (PBX) based on polyurethane matrix, have been investigated using different thermal analysis techniques and methods. The used polyurethane matrix is based on hydroxyl‐terminated polybutadiene (HTPB) cured by hexamethylene diisocyanate (HMDI). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used nonisothermally, whereas the vacuum stability test (VST) was used isothermally. Kinetic parameters were determined by using isoconversional (model‐free) methods. Furthermore, the Advanced Kinetics and Technology Solution (AKTS) software was used to determine the kinetic parameters of the studied samples in order to provide a comparison. It was found that the decomposition temperature of BCHMX/HTPB is lower than that of pure BCHMX. All the applied techniques as well as computational results showed that BCHMX/HTPB has a lower activation energy than pure BCHMX. The different methods used, Kissinger, Ozawa, Flynn, and Wall (OFW) and Kissinger‐Akahira‐Sunose (KAS) methods presented activation energies in the same range of the AKTS software results. Also the results proved that VST technique could be a useful tool to present results suitable for calculation of the kinetic parameters of explosives.     

Rheokinetic modeling of HTPB–TDI and HTPB–DOA–TDI systems

A study of the effect of temperature on a mixture of polymer and curative in the processing of rocket propellants is reported. Experimental viscosity of a hydroxyl‐terminated polybutadiene–toluene diisocyanate (HTPB–TDI) system was measured using a Brookfield viscometer model DV III. Viscosity showed dependence on temperature as well as time. The viscosity data of the HTPB–TDI system showed a linear relationship with temperature, with a change in slope at 45°C. The time dependence model showed a fourth‐order curve fit, which gave better results over the exponential model fit. The activation energy required for flow of the HTPB–TDI system was found to be 15.5 kJ/mol. Experimental viscosity measurements at various temperatures was also carried out on a hydroxyl‐terminated polybutadiene–dioctyl adipate –toluene diisocyanate (HTPB–DOA–TDI) system. The temperature dependence showed a decrease in viscosity with an increase in temperature up to 60 min, beyond which the viscosity increased. Viscosity showed a linear relation with temperature, with a change in the slope at 50°C instead of at 45°C for HTPB–TDI system. Beyond 50°C the data followed a polynomial model similar to that of the HTPB–TDI system, and the results matched well with the experimental data. The activation energy of the HTPB–DOA–TDI system increased with an increase in the binder weight ratio. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1331–1335, 2003     

On the functionalization and characterization of hydroxyl-terminated polybutadiene with octyl-1-azide and the evaluation of polyurethane elastomers based on such modified HTPB

Hydroxyl-terminated polybutadiene (HTPB) has been modified with azido-containing substances to be applied in propulsion systems. Pristine HTPB has compatibility issues with energetic polar substances and plasticizers, which is a drawback to develop new high-energy propellants. This work presents a path for the functionalization of HTPB, carried out through a controlled bulk reaction of it with octyl-1-azide. Then it was reacted with isophorone diisocyanate with or without dioctyl adipate (DOA). Structural, thermal, rheological, and dynamic-mechanical assessments were accomplished. Infrared revealed the arising of absorption bands associated to the CN stretching. From ¹³C and ¹H nuclear magnetic resonances, it is possible to deduce the presence of amine, aziridine, and imine chemical groups, which may promote compatibilization with other polar and energetic substances. The chemical modification induced an increase of viscosity. With respect to the glass–liquid and glass–rubber transitions, the modification shifted them slightly to higher temperatures, but created stiffer networks, in agreement with the increase of polarity and chain interaction due to the presence of N-containing functionalities. Regarding the solid elastomer binder, the storage shear modulus and molecular mobility were influenced by the type of HTPB and DOA content. In general, the modified HTPB has physical properties like pristine HTPB.     

Modification of epoxy resin by isocyanate‐terminated polybutadiene

Hydroxy‐terminated polybutadiene was functionalized with isocyanate groups and employed in preparation of a block copolymer of polybutadiene and bisphenol A diglycidyl ether (DGEBA)‐based epoxy resin. The block copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy and size‐exclusion chromatography (SEC). Cured blends of epoxy resin and hydroxy‐terminated polybutadiene (HTPB) or a corresponding block copolymer were characterized by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMTA), and scanning electron microscopy (SEM). All modified epoxy resin networks presented improved impact resistance with the addition of the rubber component at a proportion up to 10 wt % when compared to the neat cured resin. The modification with HTPB resulted in milky cured materials with phase‐separated morphology. Epoxy resin blends with the block copolymer resulted in cured transparent and flexible materials with outstanding impact resistance and lower glass transition temperatures. No phase separation was discernible in blends with the block copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 838–849, 2002     

Study of Thermal Reactivity and Kinetics of HMX and Its PBX by Different Methods

Vacuum Stability Test (VST) was used to determine the thermal behavior and kinetic parameters of 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and its mixture with hydroxyl-terminated polybutadiene (HTPB) as a binder coded as HMX/HTPB.Model fitting and isoconversional method were applied to determine the kinetic parameters based on VST results.For comparison,non-isothermal thermogravimetry analysis data (TGA) was also used to calculate the kinetic parameters by using Kissinger,OFW (Ozawa,Flynn,and Wall) and KAS (Kissinger-Akahira-Sunose) methods.Advanced Kinetics and Technology Solution (AKTS) software was also used to determine the decomposition kinetics of the studied samples.Differential Scanning Calorimetry (DSC) was employed to determine the decomposition heat flow properties of the studied samples.Results show that the activation energies obtained using VST results is 360.1kJ/ mol for pure HMX and 186.9kJ /mol for HMX/HTPB.The activation energies obtained by the three different methods using TGA results are in the range of 360-368kJ/mol for pure HMX and 190-206kJ/mol for HMX/HTPB.It is concluded that values of kinetic parameters obtained by VST are close to that obtained by the different techniques using TG/DTG results.The onset decomposition peak of HMX/HTPB is lower than that of HMX where the HTPB binder has negative effect on the thermal stability of HMX.The results of all the applied techniques prove that HMX/HTPB has lower activation energy and heat release than the pure HMX.HTPB polymeric matrix has negative effect on the kinetic parameters of HMX.     

HTPB/增塑剂表面自由能研究

为了研究不同黏结体系的表面自由能随温度的变化规律,利用表面能测试仪器测试了HTPB黏结体系的表面自由能,分析了HTPB与增塑剂体积比、增塑剂种类、温度对体系表面自由能的影响。结果表明,HTPB在所给温度范围内表面自由能基本无变化;己二酸二异氰酸酯(DOA)的表面自由能随温度升高呈现线性降低;在HTPB/DOA不同的体积浓度的混合溶液中,当HTPB/DOA体积比为1∶1时,在工艺温度60~65℃范围内,表面自由能最低;在DOA、癸二酸二辛脂(DOS)、邻苯二甲酸二辛脂(DOP)三种增塑剂分别与HTPB体积比1∶1混合时,在工艺温度60~65℃范围内,HTPB/DOA的黏结体系具有更低的表面自由能,DOA增塑效果最好;不同黏结剂体系的表面自由能对温度的灵敏度具有较大差异,其中HTPB/DOA黏结体系的表面自由能对温度更灵敏。     

Terminal functionalized hydroxyl‐terminated polybutadiene: An energetic binder for propellant

We report the functionalization of hydroxyl terminated polybutadiene (HTPB) backbone by covalently attaching 1‐chloro‐2, 4‐dinitrobenzene (DNCB) at the terminal carbon atoms of the HTPB. The modification of the HTPB by the DNCB does not alter the unique physico–chemical properties and the microstructure of the parent HTPB. IR, ¹H‐NMR, ¹³C‐NMR, size exclusion chromatography (SEC) and absorption spectroscopy studies prove that the DNCB molecules are covalently attached to the terminal carbon atoms of the HTPB. The π electron delocalization owing to long polymer chain, strong electron withdrawing effect of the DNCB molecule are the major driving forces for the covalent attachment of the DNCB at the terminal carbon atom of the HTPB. We are the first to observe the existence of intermolecular hydrogen bonding between the terminal hydroxyl groups of the HTPB. IR study shows that the attached DNCB molecules at the terminal carbon atoms of the HTPB breaks the intermolecular hydrogen bonding between the HTPB chains and forms a hydrogen bonding between the NO₂ groups of the DNCB and the OH groups of the HTPB. Absorption spectral study of the modified HTPB indicates the better delocalization of π electron of butadiene due to the strong electron withdrawing effect of the DNCB molecules. Theoretical calculation also supports the existence of hydrogen bonding between the OH and NO₂ groups. Theoretical calculation shows that the detonation performance of both the DNCB and the HTPB‐DNCB are promising. HTPB‐DNCB is the new generation energetic binder which has potential to replace the use of HTPB as binder for propellant.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

HTPB‐based polyurethaneurea membranes for recovery of aroma compounds from aqueous solution by pervaporation

Hydroxyterminated polybutadiene (HTPB)‐based polyurethaneurea (PU), HTPB‐PU, was synthesized by two‐step polymerization and was firstly used as membrane materials to recover aroma, ethyl acetate (EA), from aqueous solution by pervaporation (PV). The effects of the number–average molecular weight (M_n) of HTPB, EA in feed, operating temperature, and membrane thickness on the PV performance of HTPB‐PU membranes were investigated. The membranes demonstrated high EA permselectivity as well as high EA flux. The DSC result showed two transition temperatures in the HTPB‐PU membrane and contact angle measurements revealed the difference of hydrophobicity of the membrane at both sides, which were induced by glass plate and air, respectively, due to movement of the soft hydrophobic polybutadiene (PB) segments in HTPB‐PU chains. Furthermore, the PV performance of the HTPB‐PU membrane with the hydrophobic surface facing the feed was much better than that with the hydrophilic surface. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 552–559, 2007     

Understanding the Compatibility of the Energetic Binder PolyNIMMO with Energetic Plasticizers: Experimental and DFT Studies

The development of energetic binders with suitable energetic plasticizers is required to enhance the mechanical properties and to reduce the glass transition temperature of propellant and explosive formulations. The compatibility of the energetic binder poly(3‐nitratomethyl‐3‐methyloxetane) (polyNIMMO) with five different energetic plasticizers viz. bis(2,2‐dinitro propyl)acetal (BDNPA), dinitro‐diaza‐alkanes (DNDA‐57), 1,2,4‐butanetriol trinitrate (BTTN), N‐N‐butyl‐N ‘(2‐nitroxy‐ethyl) nitramine (BuNENA) and diethyleneglycoldinitrate (DEGDN) was studied by differential scanning calorimetry (DSC), rheology, and DFT methods. The results obtained for the pure binder were compared with the results obtained for the binder/plasticizer blend in regard of the decomposition temperature and the format of the peak indicated the compatibility of polyNIMMO with the plasticizers. The glass transition temperatures of the blends were determined by low temperature DSC and showed desirable lowering of glass transition temperature with single peak. The rheological evaluation revealed that the viscosity of the binder is considerably lowered by means of flow behavior upon addition of 20 % (w/w) plasticizer. The addition of BuNENA and DEGDN has maximum effect on the lowering of viscosity of polyNIMMO. The predicted relative trend of interaction energies between plasticizer and binder is well correlated with the corresponding trend of viscosity of binder/plasticizer blends. These experimental studies verified by theoretical methods are valuable to design practical blends of new plasticizers and binders.     

Development of Composite Solid Propellant Based on Nitro Functionalized Hydroxyl‐Terminated Polybutadiene

This paper presents an overview of a modified composite propellant formulation to meet future requirements. The composite propellant mixtures were prepared using nitro functionalized Hydroxyl‐Terminated Polybutadiene (Nitro‐HTPB) as a novel energetic binder and addition of energetic plasticizer. The new propellant formulation was characterized and tested. It was found that the Nitro‐HTPB propellant with and without energetic plasticizer exhibited high solid loading, high density, and reasonable mechanical properties over a wide range of temperatures. It was shown that the burning rate of Nitro‐HTPB propellant is up to 40% faster than that of the HTPB propellant. These results are encouraging and suggest that it should be possible to improve the ballistic performance of popular HTPB propellants through use of the studied Nitro‐HTPB binder.     

Application of Amorphous Boron Granulated With Hydroxyl‐ Terminated Polybutadiene in Fuel‐Rich Solid Propellant

Amorphous boron powder granulated with HTPB, whose particle diameter could be controlled, was prepared by mechanical mill method. It was found that amorphous boron powder could be granulated with HTPB binder to form B‐HTPB particles, whose median particle diameter (d₅₀) and specific surface area are in the range of 125.0–431.0 µm and 0.02–0.1 m² g⁻¹, respectively. The B‐HTPB particles could be dispersed in the HTPB binder with relatively low viscosity compared with direct addition of amorphous boron powder to the HTPB binder. The experimental results showed that the content of boron particles in a fuel‐rich propellant could be increased by addition of B‐HTPB particles and the combustion characteristics of the fuel‐rich solid propellant could be improved.     

Mathematical modeling of rheological properties of hydroxyl‐terminated polybutadiene binder and dioctyl adipate plasticizer

Solid composite propellants contain 80–90% of a crystalline oxidizer like ammonium perchlorate and powdery metallic fuel like aluminum with 10 to 15% organic binders like HTPB or CTPB, to bind the solids together and maintain the shape under severe stress and strain environment. Also, the propellant must not crack or become brittle at subzero temperatures. Formulating and processing of the highly filled composite propellants are difficult tasks and need a thorough understanding of rheology, even apart from a knowledge of propellant chemistry, particulate technology, manufacturing methods, and safe handling of explosives and hazardous materials. The flow behavior or rheology of the propellant slurry determines the ingredients and some of the abnormalities of the motor during firing. The propellant viscosity and mechanical properties are determined by the binder system, and the unloading viscosity of the propellant slurry is dependent on the initial viscosity of the binder system, solid loading, particle size, and its distribution, shape, temperature, and pressure. In the present report an attempt is made to study the dependency of viscosity of the HTPB binder system on temperature, plasticizer level (composition), and torque (angular velocity of spindle). The viscosity measurements were made using a Brookfield viscometer model DV III at different plasticizer levels (10–50%), temperatures (30–65°C), and torques (50–100%). The data indicate that the viscosity of HTPB, DOA, and their mixture decreases with increasing temperature and is constant with torque. The Arrhenius equation gives the energy for viscous flow to be ?35 kcal/mol for HTPB. The variation of viscosity with temperature of HTPB/DOA and their mixture follows a mathematical model expressed as where T is the temperature and a₁, a₂, a₃, a₄, and a₅ are the constants. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1002–1007, 2002