Application of the BAMO‐AMMO Alternative Block Energetic Thermoplastic Elastomer in Composite Propellant

A BAMO‐AMMO alternative block (BAAB)‐based thermoplastic composite propellant with 80 % solid content was prepared using BAAB energetic thermoplastic elastomer (ETPE) as the binder, and the formulation was optimized through energy calculation. The densities, heats of explosion, glass‐transition temperatures, and mechanical properties of the samples were determined by surface tension measurements, oxygen bomb calorimetry, differential scanning calorimetry and static tensile tests, respectively. The results showed that this composite propellant can reach a standard theoretical specific impulse of 275.45 s (10 MPa), a density of 1.8102 g cm⁻³, a heat of explosion of 6256 kJ kg⁻¹, a T_g of −50.46 °C, a tensile strength of 1.56 MPa and an elongation at break of 20 %, thus presenting a superior comprehensive property to BAMO‐AMMO random block (BARB)‐based thermoplastic composite propellant.     

Characterization of P(BAMO/AMMO) ETPE Prepared Using Different Diisocyanates

Poly(3,3‐bisazidomethyl oxetane/3‐azidomethyl‐3‐methyl oxetane) energetic thermoplastic elastomers (P(BAMO/AMMO) ETPEs) is one of the most valuable ETPEs in the field of energetic binders. P(BAMO/AMMO) ETPEs were prepared using different diisocyanates (TDI, HMDI, IPDI, and HDI) to investigate the influence of the diisocyanate on the performance of P(BAMO/AMMO) ETPEs. Mechanical properties and heats of formation were investigated. FT‐IR spectroscopy results showed that TDI‐based ETPE has the highest degree of hydrogen bonding with a value of 69.00 %. Mechanical test results showed that the TDI‐based ETPE has better mechanical property with maximum stress at 5.24 MPa and breaking elongation at 390 %. The order for degree of hydrogen bonding and mechanical property of different diisocyanate‐based ETPEs was TDI>HMDI>IPDI>HDI. The heats of formation were calculated by the group additivity method and by the heat of combustion method. The values of heats of formation for TDI‐based ETPE were 3.44 kJ g⁻¹ and 3.75 kJ g⁻¹ according to the two methods. Additionally, TDI‐based ETPE has a lager heat of formation than the other ETPEs.     

Sequence Structure,Morphology and Viscosity Behavior of 3,3‐bis(azidomethyl) Oxetane‐tetrahydrofuran Random Copolyether

In order to reveal the relationship between 3,3‐bis(azidomethyl) oxetane‐tetrahydrofuran copolyether (P(BAMO‐THF)) microstructure and its macro properties, the segment sequence structure of a kind of P(BAMO‐THF) was characterized using quantitative ¹³C‐NMR analysis. It was found that the P(BAMO‐THF) is composed of equimolar comonomers whose randomness factor (R) is 1.09, belonging to a quasi‐ideal random copolymer. Combining DSC and polarizing optical microscopy, it was verified that the thermal‐effect between 28 °C and 41 °C attributes to the melting of the P(BAMO‐THF)spherulites. Using WAXRD, it was suggested that the aggregation of BAMO micro‐blocks among P(BAMO‐THF) polymeric chains causes the formation of spherulites. The viscosity measurement clearly demonstrated that, below 30 °C or above 40 °C, the P(BAMO‐THF) viscosities change slowly as a function of temperature. Conversely, between 30 °C and 40 °C, its viscosities sharply decline with the increase in temperature because of the changes in its morphology.     

Synthesis and Characterization of 3,3′‐Bisazidomethyl Oxetane‐3‐Azidomethyl‐3′‐Methyl Oxetane Alternative Block Energetic Thermoplastic Elastomer

3,3′‐Bisazidomethyl oxetane‐3‐azidomethyl‐3′‐methyl oxetane (BAMO‐AMMO) tri‐block copolymer was successfully synthesized by azidation of a polymeric substrate containing bromo leaving groups, and an alternative block energetic thermoplastic elastomer (ETPE) was prepared by chain extension reaction. The tri‐block copolymer was characterized by Fourier transform infrared (FTIR), ¹H NMR, and ¹³C NMR spectroscopy, X‐ray diffraction (XRD), and thermogravimetric analysis (TGA). It was found that the composition of the copolymer is nearly 1 : 1; crystallinity of the copolymer (71.81 %) is less than that of PBAMO (78.30 %). This is due to a partly mixture between soft and hard segments. Kinetic result shows that a crosslinking network is formed after the decomposition of azide group. Tensile strength of alternative block ETPE is 150 % of traditionally synthesized BAMO‐AMMO ETPE.     

Thermal characteristics of energetic polymers based on tetrahydrofuran and oxetane derivatives

Thermal characteristics and decomposition behaviors of energetic polymers based on oxetane derivatives, 3,3'-bis(azidomethyl)oxetane (BAMO), 3-azidomethyl-3'-methyloxetane (AMMO), 3-nitratomethyl-3'-methyloxetane (NMMO), and 3,3'-bis(ethoxymethyl)oxetane (BEMO), were studied by means of differential scanning calorimeter (DSC) and thermogravimetric analyzer (TGA). These polymers were found to exhibit low glass transition and large decomposition onthalpies which were brought about by the attached azide (? N₃) and nitrato (? ONO₂) groups. The decomposition enthalpies depended on the types and contents of the energetic substituents. The NMMO-based polymers exhibited relatively higher decomposition enthalpies and less thermal stability than the others. Furthermore, the thermal stability of the polymers was further improved by partial curing treatment. These results reveal that these polymers are potentially useful for application in energetic propellant binders. © 1995 John Wiley & Sons, Inc.     

Characterization of poly(3,3-bisethoxymethyl oxetane) and poly(3,3-bisazidomethyl oxetane) and their block copolymers

The homopolymers, poly(3,3-bisethoxymethyl oxetane) (polyBEMO), poly(3,3-bisazidomethyl oxetane) (polyBAMO), and triblock copolymers based on these homopolymers and a statistical copolymer center block composed of BAMO and 3-azidomethyl-3-methyl oxetane AMMO were synthesized and characterized by differential scanning calorimetry, modulus-temperature, optical microscopy, membrane osmometry, and solution and melt viscosity. The values of K and a for the Mark-Houwink equation were found to be 7.29 × 10^?3 mL/g and 0.80, respectively, for polyBEMO at 25°C using number-average molecular weights. Glass transition temperatures were in the range ?25 to ?40°C and melting temperatures were between 65 and 90°C for all polymers. The melting temperature was found to increase as expected with molecular weight. Melt viscosities of triblock copolymers with polyBAMO end blocks were at least an order of magnitude lower than those with polyBEMO end blocks and clear optically, suggesting that the polyBAMO-based triblock copolymers formed one phase in the melt, while the polyBEMO-based triblock materials (milk white) phase separated. The addition of filler raised the melt viscosity to a level between that predicted by the Guth-Smallwood and the Mooney equations.     

Preliminary Characterization of Propellants Based on p(GA/BAMO) and pAMMO Binders

In previous papers, the synthesis and characterization of OH‐terminated glycidyl azide‐r‐(3,3‐bis(azidomethyl)oxetane) copolymers (GA/BAMO) and poly‐3‐azidomethyl‐3‐methyl oxetane (pAMMO) by azidation of their respective polymeric substrates were described. The main objective was the preparation of amorphous azido‐polymers, as substitutes of hydroxy‐terminated polybutadiene (HTPB) in new formulations of energetic propellants. Here, the subsequent characterization of both the binders is presented. First of all, several isocyanates were checked in order to optimize the curing reaction, and then two small‐scale formulations of a propellant, based on aluminium and ammonium perchlorate, were prepared and characterized. Finally, the mechanical properties and burning rate were compared to those of a similar propellant based on HTPB as binder.     

A comparison of triazole cross‐linked polymers based on poly‐AMMO and GAP: Mechanical properties and curing kinetics

Triazole cross‐linked polymers based on poly(3‐azidomethyl‐3‐methyl oxetane) (poly‐AMMO) and glycidyl azide polymer (GAP) were prepared using bis‐propargyl‐1,4‐cyclohexyl‐dicarboxylate (BPHA) as curing agent, respectively. Swelling tests demonstrated that cross‐linking densities of the resulted polymers both increased with the increase of BPHA. Triazole cross‐linked polymers based on poly‐AMMO showed superior tensile strength and elongation at break than those of GAP at comparable stoichiometry. The curing kinetics was also investigated by FTIR, and GAP exhibited faster reaction rate when reacted with BPHA than that of poly‐AMMO. In addition, with the increase of cross‐linking density, the glass transition temperature (T_g) of as‐prepared polymers significantly increased, and poly‐AMMO‐based polymers showed stronger T_g‐raising effect than GAP‐based polymers. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43341.     

Structure of Urethane Copolymers of 3,3‐Bis(azidomethyl)oxetane and 3‐Azidomethyl‐3‐methyloxetane

Polyurethane copolymers of 3,3‐bis (azidomethyl) oxetane (BAMO) and 3‐azidomethyl‐3‐methyloxetane (AMMO) with molecular structures of types B(AB)n, A(AB)n, (BB)n and ABn with different ratios of oligomeric units were investigated, where A is the non‐crystallizable “soft” block of oligoAMMO and B is the “hard” block of oligoBAMO and the included urethane diol fragments. The amorphous‐crystalline structures of copolymers BAMO and AMMO were elucidated by wide angle X‐ray diffraction measurements. The influences of the molecular structure and the ratio of oligomeric units on the structural parameters were identified. The degree of crystallinity is in a range from 8 to 22 % and sizes of the crystallites were determined. The defectivenesses of first and second kind in the structure were evaluated, which show high values of the first kind defectiveness (approx. 20 %), which describes the displacement of theoretical lattice sites and the existence of unequal sizes of the lattice sites, and minor values for the second kind defectiveness (approx. 3 %), which describes the lattice site disorder in large distances. Small‐angle X‐ray diffraction measurements were used to investigate the domain structures of copolymers BAMO and AMMO. The distribution and sizes of the crystallites in the structures of the copolymers were calculated.     

Probing the compatibility and interaction of energetic binders based on 3,3‐bis(azidomethyl)oxetane with some explosives: thermal,interfacial and simulation studies

Several polymer binders based on 3,3‐bis(azidomethyl)oxetane (BAMO) were studied to explore the compatibility and interaction of the energetic binders with three common energetic oxidants. The compatibilities were studied by differential scanning calorimetry and ratings were obtained according to evaluated standards. The results showed that all the binders based on BAMO had good compatibility with cyclotrimethylenetrinitramine, cyclotetramethylenetetranitroamine and hexanitrohexazaiso‐wurtzitane. The work of adhesion (W_a) between binders and explosives was tested via measurement of contact angle and the results are in the following order: chain‐extended poly(3,3‐bis(azidomethyl)oxetane) (PBAMO) by isophorone diisocyanate (IPDI‐CE) with diethyl bis(hydroxymethyl) malonate (IPDI‐DBM‐CE) > chain‐extended PBAMO by IPDI‐CE > PBAMO. In addition, similar results were found in the binding energies reported by molecular dynamics, and the average values of E_binding for the IPDI‐DBM‐CE system were larger than E_binding for the other systems due to the formation of hydrogen bonds between –COOEt and –NO₂, which improve the bonding abilities. © 2017 Society of Chemical Industry     

Reliability studies of gelcast fused silica between organic and inorganic binder systems

Fused silica ceramics was prepared by using conventional organic binder, mathacrylamide‐N,N′‐methylenebisacrylamide (MAM‐MBAM) system by gelcasting process. Mechanical properties of green bodies were studied as a function of solid loading varying from 60 to 72 vol%. After evaluating the green body mechanical properties, the samples were densified at different sintering temperature from 1200 to 1450°C with definite intervals of 50°C and subjected to flexural strength analysis. Variation in flexural strength with sintering temperature was observed and correlated with the quantity of devitrification of fused silica during sintering. Quantification of devitrified cristobalite was carried out by using 20 wt% rutile (TiO₂) as an internal standard by X‐ray diffraction. It was found that, as the cristobalite content increased, flexural strength decreased. Reliability studies were carried out for the samples having maximum flexural strength with and without crystalline content. Reliability studies have shown that for this organic binder system the sample sintered at 1300°C is crystalline free and most reliable product. The mechanical properties and reliability of this product processed with organic binder are compared with inorganic binder system. Results indicate that the sample fabricated using inorganic binder system is exhibiting high Weibull modulus and thus better reliability.     

Synthesis and characterization of poly(pyridylurea) and poly(pyridylthiourea), potentially semiconducting polymers

Poly(pyridylureas) and poly(pyridylthioureas) were synthesized by reacting 2,6‐diaminopyridine with phosgene and thiophosgene, respectively, using THF and pyridine as solvent. The synthesized polymers were characterized by IR‐spectroscopy, elemental analysis, and X‐ray photoelectron spectroscopy. Thermal stability of the polymers was determined by thermal degradation between 35°C and 700°C. The 50% weight loss of polypyridylureas was above 400°C while for the polypyridylthioureas it was above 450°C. Undoped poly(pyridylureas) and poly(pyridylthioureas) behave as semiconductors, σ = 10^?9 (Ω cm)^?1. After doping with I₂ and SbF₅, the electrical conductivity increases several orders of magnitude, σ = 10^?7(Ω cm)^?1. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Effects of reaction and cure temperatures on morphology and properties of poly(ester‐urethane)

Poly(ester‐urethane) was synthesized from poly(ethylene glycol adipate) (PEG) and 2,4‐toluene diisocyanate (TDI) to study the effects of reaction temperature and cure temperature on the crystallization behavior, morphology, and mechanical properties of the semicrystalline polyurethane (PU). PEG as soft segment was first reacted with TDI as hard segment at 90, 100, and 110°C, respectively, to obtain three kinds of PU prepolymers, coded as PEPU‐90, PEPU‐100, and PEPU‐110. Then the PU prepolymers were crosslinked by 1,1,1‐tris (hydroxylmethyl) propane (TMP) and were cured at 18, 25, 40, 60, and 80°C. Their structure and properties were characterized by attenuated total reflection Fourier transform infrared, wide‐angle X‐ray diffraction, scanning electron microscopy, dynamic mechanical analysis, and tensile testing. With an increase of the reaction temperature from 90 to 100°C, the crystallinity degree of soft segment decreased, but interaction between soft and hard segments enhanced, leading to the increase of the glass transition temperature (T_g) of soft domain and tensile strength. When the cure temperature was above 60°C, miscibility between soft and hard segments of the PEPU films was improved, resulting in relatively low crystallinity and elongation at break, but high soft segment T_g and tensile strength. On the whole, all of the PEPU‐90, PEPU‐100, and PEPU‐110 films cured above 60°C possessed higher tensile strength and elongation at break than that of the films cured at other temperatures. The results revealed that the reaction temperature and cure temperature play an important role in the improvement of the crosslinking structure and mechanical properties of the semicrystalline PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 708–714, 2006     

Gel‐spinning of partially saponificated poly(vinyl alcohol)

DMSO/water (80/20 volume ratio) solutions of commercial poly(vinyl alcohol)s (a‐PVA₉₉, a‐PVA₈₈) with degrees of saponification of 99.3 and 88 mol % were gel‐spun into methanol (−20 and −70°C). The dry filaments obtained were drawn at 200°C (a‐PVA₉₉) and 150–180°C (a‐PVA₈₈). The maximum draw ratio and Young's modulus were 26 and 34 GPa for a‐PVA₉₉ and 21 and 24 GPa for a‐PVA₈₈ (drawing temperature: 160°C). So, at first, the dry filaments obtained for a‐PVA₈₈ were drawn at 150–180°C until 10 times their original length. Moreover, the predrawn a‐PVA₈₈ filaments were perfectly saponificated under fixing at the both ends and then the filaments were redrawn at 200°C. The maximum draw ratio and Young's modulus for the filaments (a‐PVA_88→99) predrawn at 150°C were 28 and 39 GPa, respectively. The a‐PVA_88→99 filaments had two melting peaks (228 and 236°C). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2872–2876, 2000     

Polyether‐amide segmented copolymers based on ethylene terephthalamide units of uniform length

Segmented copolymers were synthesized using the crystallizable bisesterdiamide segment (N,N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) T2T‐dimethyl (a one‐and‐a‐half repeating unit of nylon 2,T) and poly(tetramethyleneoxide) segments. Poly(tetramethyleneoxide) (PTMO) is amorphous and has a low T_g. The segment length was varied from 650 to 2800 g/mol by extending PTMO₆₅₀ using dimethyl isophthalate. The polymers were synthesized in the melt, and test samples were prepared by injection molding. The melting behavior, as well as the torsion modulus spectrum as a function of temperature, were studied using DSC and DMA, respectively. The T2T‐PTMO polymers were found to have sharp glass (T_g) and flow transitions (T_fl), and the modulus at the rubbery plateau appeared to be virtually temperature independent. The T_g value was found to be independent of the diamide concentration, thus indicating that the T2T segments were fully crystallized. The T_fl was found to decrease with increasing soft segment length; this was ascribed to a “solvent” effect of the amorphous phase of the crystalline T2T units. The difference between the melting and crystallization temperatures was found to be low, thus suggesting that on cooling, there is a high rate of crystallization. When ethanediol was added as a T2T segment extender, amide‐ester‐amide segments were introduced. These amide‐ester‐amide segments form a separate lamellar phase with a much higher melting temperature (>300°C). It was found that the crystallization rate of the T2T units was enhanced by the presence of the amide‐ester‐amide segments, indicating that upon cooling, the crystallized amide‐ester‐amide segments form the nucleation sites for the nonextended T2T segments. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1173–1180, 2001     

3,3‐Bis(azidomethyl)oxetane (BAMO) Synthesis via Pentaerythritol Tosyl Derivates

3,3‐Bis(azidomethyl)oxetane (BAMO) is the most widely known azido oxetane in terms of the number of its polymers and copolymers applied as energetic binders e.g. in rocket propellants and plastic formulations of explosive materials. However, this compound continues to be a rather expensive monomer today. The aim of this study was to find a suitable synthetic route to produce this monomer in a large scale and to optimize it. The chosen route of synthesis was based on the application of tosyl pentaerythritol derivatives as the starting material. The BAMO synthesis by this method involves three stages, namely: pentaerythritol tosylation, tritosylpentaerythritol cyclization to 3,3‐bis(tosylmethyl)oxetane (BTMO), and substitution of the BTMO tosyl groups with azido groups. In this work all the stages of the synthesis were optimized. BAMO was obtained in an overall yield of 61 %. The structure of the obtained compounds was verified by two techniques, namely: ¹HNMR and FT‐IR.     

Mechanical Properties of Plateau Burn Azide Composite Propellants

The effects of cure ratio, crosslinking density, ammonium perchlorate (AP) particle size, and other additives on the mechanical properties of azide polymer composite propellants were characterized. The equivalence ratio of 1.0 and IPDI/TPA=7/3 were effective on low temperature mechanical properties. Relatively high amount of plasticizer was required in BAMO/NMMO binder and preferred the equivalence ratio of 1.0 to retain itself in the three-dimensional binder matrix. Excellent elasticity was obtained at a temperature range between −20°C and 2°C and normal strain rate dependency was obtained at from 54°C to −20°C. Glass transition occurred at −30°C to −35°C in Sample 17. The increase in contact area between AP particle and binder and in bonding strength played an important role on the prevention of the propagation of crack around a boundary and, therefore, ϵ_m was increased with decrease of particle size. Almost exactly the same σ_m, however, was observed in whole temperature range with increment of 5% to 10% in ϵ_m.     

Novel poly(amide‐hydrazide)s and copoly(amide‐hydrazide)s from bis‐(4‐aminobenzyl) hydrazide and aromatic diacid chlorides: Synthesis and characterization

A new aromatic diamine, viz., bis‐(4‐aminobenzyl) hydrazide (BABH), which contains preformed hydrazide and methylene linkage, was synthesized starting from α‐tolunitrile. The BABH and intermediates involved in its synthesis were characterized by spectroscopic methods. Novel poly(amide‐hydrazide)s were synthesized by low temperature solution polycondensation of BABH with isophthaloyl chloride (IPC) and terephthaloyl chloride (TPC). Furthermore, two series of copoly(amide‐hydrazide)s, based on different mol % of BABH and bis‐(4‐aminophenyl) ether (ODA) with IPC/TPC were also synthesized. Poly(amide‐hydrazide)s and copoly(amide‐hydrazide)s were characterized by inherent viscosity [η_inh], FTIR, solubility, X‐ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The polycondensation proceeded smoothly and afforded the polymers with inherent viscosities in the range of 0.18–0.93 dL/g in (NMP + 4% LiCl) at 30°C ± 0.1°C. These polymers dissolved in DMAc, NMP or DMSO containing LiCl. The solubility of copolymers was considerably improved in line with less crystalline nature due to random placement of constituent monomers during the copolymerization. XRD data indicated that poly(amide‐hydrazide)s from BABH alone and IPC/TPC had higher crystallinity than the corresponding copoly(amide‐hydrazide)s derived from a mixture of BABH and bis‐(4‐aminophenyl) ether (ODA). Polymers showed initial weight loss around 160°C which is attributed to the cyclodehydration leading to the formation of corresponding poly(amide‐oxadiazole)s. Copolyamide‐hydrazides showed T_max between 400 and 540°C which is essentially the decomposition of poly(amide‐oxadiazole)s. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Low Risk Synthesis of Energetic Poly(3‐Azidomethyl‐3‐Methyl Oxetane) from Tosylated Precursors

Azidated oxetanic polymers such as poly(3‐azidomethyl‐3‐methyl oxetane), are under investigation as “energetic” binder to be used as an alternative to polybutadiene in solid rocket propellants. The classic synthetic route for the production of the polymer is through an azidated monomer where the N₃⁻ functionality has been previously introduced by nucleophilic displacement of a suitable, usually a halogen, leaving group. However, this could involve critical steps with manipulation of a highly unstable liquid monomer. Here it is shown that the azidation can be performed as the final step of the preparation by substitution of the tosyl group in a preformed polymer. The procedure assures good yield and purity of the product and satisfactory rate of reaction, being the energetic functionality always kept in a safe form, which shows low shock and friction sensitivity. Poly(3‐azidomethyl‐3‐methyl oxetane) was prepared by azidation of poly(3‐tosyloxymethyl‐3‐methyl oxetane) in dimethylsulfoxide, testing several operating conditions. Moreover, hypothesizing a second order kinetics, the rate constant and the activation energy for the azidation step have been estimated.     

Synthesis and properties of poly(aryl ether ketone ketone)/poly(aryl ether ether ketone ketone) copolymers with pendant cyano groups

2,6‐Diphenoxybenzonitrile (DPOBN) was synthesized by reaction of phenol with 2,6‐difluorobenzonitrile in N‐methyl‐2‐pyrrolidone in the presence of KOH and K₂CO₃. Poly(aryl ether ketone ketone)/poly(aryl ether ether ketone ketone) copolymers with pendant cyano groups were prepared by the Friedel–Crafts electrophilic substitution reaction of terephthaloyl chloride with varying mole proportions of diphenyl ether and DPOBN using 1,2‐dichloroethane as solvent and N‐methyl‐2‐pyrrolidone as Lewis base in the presence of anhydrous AlCl₃. The resulting polymers were characterized by various analytical techniques, such as FT‐IR, differential scanning calorimeter, thermal gravimetric analysis, and wide‐angle X‐ray diffraction. The crystallinity and melting temperature of the polymers were found to decrease with increase in concentration of the DPOBN units in the polymer. Thermogravimetric studies showed that all the polymers were stable up to 514°C in N₂ atmosphere. The glass transition temperature was found to increase with increase in concentration of the DPOBN units in the polymer when the molar ratios of DPOBN to DPE ranged from 10/90 to 30/70. The copolymers containing 30–40 mol % of the DPOBN units exhibit excellent thermostability at (350 ± 10)°C and have good resistance to acidity, alkali, and organic solvents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3601–3606, 2007