Mechanical and Swelling Properties of Copolyurethanes based on Hydroxy-Terminated Polybutadiene and its hydrogenated analog

Copolyurethane networks based on Hydroxy-Terminated Polybutadiene (HTPB) and Hydrogenated HTPB (HHTPB) have been synthesized using toluene diisocyanate as curing agent. Addition of HHTPB results in enhancement of properties, such as tensile strength and modulus, at nearly the same elongation values. It is possible to generate urethane networks with similar modulus and tensile strength with widely varying elongation values and vice versa by jointly altering the comonomer ratio, and the r (NCO/OH equivalent ratio) value. Dynamic mechanical studies have been made to determine the storage and loss moduli, and their variations with temperature. Solid propellant formulations processed with the copolyurethanes have been characterized for their mechanical strengths and burn rates.     

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.     

Polymers from renewable sources. IV. Polyurethane elastomers based on myrcene polyols

Two hydroxy-functionalized liquid rubbers, one a commercially available polybutadiene (PB) and the other a specially synthesized polymyrcene (PM), have been converted into homopoly-urethane elastomers by reaction with 4,4′-diphenylmethane diisocyanate (MDI). Additionally, PB and PM, each in admixture with various amounts of 1,4-butane diol, were reacted with MDI to yield two series of segmented copolyurethanes having different hard-block contents (0–30% w/w). The physical properties of these elastomers have been compared by stress-strain, thermal, and dynamic mechanical analyses, and by swelling experiments. The two series of segmented copolyurethanes have similar morphologies being almost completely phase-separated and variations in physical properties have been empirically related to hard block contents. The PM-based elastomers exhibited higher T_g values, ultimate elongations, and larger swelling ratios, but were softer and possessed lower tensile strengths in comparison with elastomers based on PB. These differences have been related to sol-fraction contents, the nature and distribution of molecular species present in the parent liquid rubbers and hence to polyol functionalities (f _n). Analysis of the stress-strain data from the homopolyurethanes using the Mooney-Rivlin expression enabled the relationship between f _n and elastomer structure to be quantified in terms of the molar mass (M _c) of the polyurethane network chains forming the soft blocks.     

Synthesis and properties of PSF/PTMEG copolyurethanes

A series of polysulfide (PSF)/polyoxytetramethylene glycol (PTMEG) copolyurethanes have been synthesized, which were based on isophorone diisocyanate‐terminated liquid PSF, 2,4‐toluene diisocyanate‐terminated PTMEG, and 2,5‐diamino‐3,6‐dimethylmercaptotoluene (Ethacure‐300). Fourier transform infrared spectroscopy spectra have established the formation of PSF polyurea and PSF/PTMEG copolyurethanes. The properties were investigated by DMA, stress–strain, and hardness analysis. Those results showed that the miscibility of the copolyurethane increases with the increase of PSF polyurea content. With the increase in PTMEG polyurethane content, the tensile strength and elongation increase, whereas the Shore A hardness decreases. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Mechanical Characteristics and Thermal Decomposition Behavior of Polytetrahydrofuran Binder using Glycerol Propoxylate (Mn=260) as Crosslinking Agent

Polytetrahydrofuran (PTHF) is an effective binder ingredient for improving propellant performance, even though it is not an energetic material. PTHF becomes sufficiently rubbery for use as a binder when a triol material such as glycerin is added as a crosslinking modifier. The cured PTHF/glycerin binder had unsatisfactory mechanical characteristics for use as a propellant binder, so a more appropriate crosslinking modifier than glycerin needs to be found. In this study, glycerol propoxylate (GPO), with a molecular weight of 260, was used as a crosslinking modifier, and the curing behavior, tensile properties, and thermal decomposition behaviors of the PTHF binder using GPO were investigated. The PTHF/GPO blend did not solidify when the PTHF/GPO mole ratio (ξ) was greater than a certain value. The PTHF (M_n=650)/GPO blend with ξ≤5 and the PTHF (M_n=1400)/GPO blend with ξ≤3 were used as propellant binders. From the curing behaviors and tensile properties, it was found that the PTHF/GPO binders ensured optimal mixing of the propellant ingredients and casting of the uncured propellant into the rocket motor case, and the tensile properties of the binders changed more drastically with the variation in ξ than did those of the PTHF/glycerin binders. The thermal decomposition behaviors of the PTHF/GPO binders were hardly dependent on ξ and were almost identical to those of the PTHF/glycerin binders.     

Polymers from renewable sources. IV. Polyurethane elastomers based on myrcene polyols

Two hydroxy-functionalized liquid rubbers, one a commercially available polybutadiene (PB) and the other a specially synthesized polymyrcene (PM), have been converted into homopolyurethane elastomers by reaction with 4,&4prime;-diphenylmethane diisocyanate (MDI). Additionally, PB and PM, each in admixture with various amounts of 1,4-butane diol, were reacted with MDI to yield two series of segmented copolyurethanes having different hard-block contents (0–30% w/w). The physical properties of these elastomers have been compared by stress–strain, thermal, and dynamic mechanical analyses, and by swelling experiments. The two series of segmented copolyurethanes have similar morphologies being almost completely phaseseparated and variations in physical properties have been empirically related to hard block contents. The PM-based elastomers exhibited higher T_g values, ultimate elongations, and larger swelling ratios, but were softer and possessed lower tensile strenghts in comparison with elastomers based on PB. These differences have been related to solfraction contents, the nature and distribution of molecular species present in the parent liquid rubbers and hence to polyol functionalities (f?_n). Analysis of the stress–strain data from the homopolyurethanes using the Mooney–Rivlin expression enabled the relationship between f?_n and elastomer structure to be quantified in terms of the molar mass (M?_c) of the polyurethane network chains forming the soft blocks.     

Synthesis and Characterization of Novel Bisphenol-C-formaldehyde-acrylate-toluene Diisocyanate-PEG-400 Copolyurethanes

Bisphenol-C-formaldehyde-acrylate-TDI polyurethane and bisphenol-C-formaldehyde-acrylate-TDI-PEG-400 [0.001 mol (PUA-I), 0.0005 mol (PUA-II), and 0.00025 mol (PUA-III)] copolyurethanes have been synthesized at room temperature. The polyurethane formation is verified by Fourier transform infrared spectroscopy (FTIR). The PUA-I-III are further characterized for their thermo-mechanical and electrical properties and also their chemical resistance against water, 10% each of aqueous NaCl, HCl, HNO₃, H₂SO₄, NaOH, and KOH. Density, tensile strength, and volume resistivity increased, while electric strength decreased with decreasing concentrations of PEG-400. Copolyurethanes possess weight-gain tendency in acidic and alkaline environments and possess excellent hydrolytic stability in harsh acidic, alkaline, and saline environments. In acidic and alkaline environments, the % weight-gain tendency is found to increase with decreasing PEG-400 content. The DSC transitions in conjunction with TG data confirmed multistep decomposition of copolyurethanes. The PEG-400 affected thermal stability to a considerable extent. Copolyurethanes may find applications as good insulators as well as coating materials for harsh environments.     

Effects of NCO/OH ratio and catalyst concentration on structure,thermal stability,and crosslink density of poly(urethane‐isocyanurate)

Poly(urethane‐isocyanurate)s were synthesized by reacting toluene diisocyanate and poly(propylene glycol) with various stochiometric ratios (1–3) in the presence of different concentrations of dibutyltin dilaurate (DBTDL) and ferric acetylacetonate (FeAA). The influence of the NCO/OH ratio and the catalyst type and concentration on the extent of urethane and isocyanurate formation were examined using Fourier transform IR spectroscopy. No trimer formation was observed in the presence of the FeAA catalyst. The percentage of the trimer group and the trimer/urethane content were found to be increased with increasing the stochiometric ratio or DBTDL concentration. The thermal decomposition of the copolyurethanes in an inert atmosphere was studied by means of thermogravimetry (TG). The TG curves showed three decomposition steps with the principal degradation temperature at about 355–385°C. The effects of the NCO/OH ratio, catalyst type and concentration, and heating rate on the thermal stability of the copolyurethanes were determined. The Flynn–Wall, Kissinger, and Ozawa methods were used to calculate the activation energies of thermal decomposition. The swelling behavior of solid copolyurethanes in toluene showed that, as the DBTDL concentration and/or NCO/OH ratio increased, the swelling ratio and average molecular weight between crosslinks were decreased whereas the crosslink density was increased. The sol fraction of solid copolyurethanes was examined and found to be reduced when the percentage of DBTDL or the stochiometric ratio was raised. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 963–972, 2003     

发射药中粘结剂对耐热安全性的影响

通过对以ＰＮＰ为主和以ＮＣ为主两种粘结剂配方的发射药进行耐热性试验。结果表明,当含能粘结剂采用耐热聚合物时,可使整个发射药的耐热安全性有明显的提高。     

高能固体推进剂用粘合剂的研究进展

较为系统的从双基推进剂、复合固体推进剂、改性双基推进剂和NEPE推进剂等方面综述了其所用粘合剂的种类及其研究发展概况。介绍了当今新型含能粘合剂的类别和发展状况,并根据目前推进剂的发展要求,指出其粘合剂的发展趋势是含能化的热塑性弹性体。     

Synthesis and characterization of novel hydroxyl-terminated N?N–bonded resins

Novel resins containing carbonyl or thiocarbonyl moiety; N N bonds; ethereal linkage; and terminal hydroxyl groups, that is, bis(bisvanillincarbonohydrazone-4′-oxy)butane 1,4-diyldiether and bis(bisvanillinthiocarbonohydrazone-4′-oxy)butane 1,4-diyldiether, have been synthesized by condensing bisvanillincarbono- and bisvanillinthiocarbono-hydrazone, respectively, with 1,4-dibromobutane. The resins were characterized by elemental and hydroxyl equivalent analyses, infrared and ¹H– and ¹³C–NMR spectra, and other properties relevant to their use as propellant binders, such as calorific value, thermal analysis, viscosity, and burning rate measurements. Both these resins have convenient viscosity, indicating their suitability as binders for processing high solid loading, at slightly above room temperature. The resins could be cured easily with toluene diisocyanate and glycerol. The DTA–TG data show that the cured samples start to decompose exothermically at relatively low temperatures, in the range around 160°C. The resins ignite immediately on coming in contact with pure nitric acid, indicating their hypergolic nature. The burning rates of the ammonium perchlorate–based propellant compositions having these resins as binders are much higher than those processed with a conventional butadiene binder. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3204–3211, 2001     

Condition monitoring of a thermally aged hydroxy‐terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer by nuclear magnetic resonance cross‐polarization recovery times

A hydroxy‐terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) elastomer is commonly used as propellant binder material. The thermal degradation of the binder is believed to be an important parameter governing the performance of the propellant. The aging of these binders can be monitored by mechanical property measurements, such as modulus or tensile elongation. These techniques, however, are not easily adapted to binder agents that are dispersed throughout a propellant. In this paper we investigated solid‐state nuclear magnetic resonance (NMR) relaxation times as a means to predict the mechanical properties of the binder as a function of aging time. Proton (¹H) spin–lattice and spin–spin relaxation times were insensitive to the degree of thermal degradation of the elastomer. Apparently, these relaxation times depend on localized motions that are only weakly correlated with mechanical properties. A strong correlation was found between the ¹³C cross‐polarization (CP) NMR time constant, T_cp, and the tensile elongation at break of the elastomer as a function of aging time. A ramped‐amplitude CP experiment was less sensitive to imperfections in setting critical instrumental parameters for this mobile material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 453–459, 2001     

含1,1–二氨基–2,2–二硝基乙烯推进剂的能量特性参数计算研究

利用国军标方法及CAD系统软件,在标准条件(pc∶p0=70∶1)下,计算了含1,1-二氨基-2,2-二硝基乙烯(FOX-7)的各类推进剂的能量特性参数,分析了氧化剂(AP、RDX、CL-20)及黏合剂(HTPB、PET、GAP、PBAMO)等成分对FOX-7推进剂能量特性的影响。结果表明,将AP加入HTPB/FOX-7推进剂配方中取代FOX-7可有效改善氧条件,有利于推进剂能量的提高。在黏合剂含量较低(质量分数<8%)的推进剂体系中,使用惰性黏合剂有利于提高推进剂的能量;而在黏合剂含量较高(质量分数>10%)的推进剂体系中,使用含能黏合剂提高推进剂能量的幅度优于惰性黏合剂,且GAP优于PBAMO。用FOX-7取代NEPE推进剂中的AP,推进剂最大理论比冲可达2 567 N.s/kg。由GAP/FOX-7/RDX组成的无烟推进剂,在很宽的范围内都可以达到2 400 N.s/kg以上的理论比冲值。     

The opto-mechanical behaviour of diacetylene-containing segmented block copolymers

Summary The effects of mechanical deformation on the optical properties of segmented copolyurethanes have been studied using resonance Raman spectroscopy. Linear elastomeric and glassy copolyurethanes, each containing diacetylene-urethane (DA-U) hard segment domains dispersed in a continuous polyether-urethane (PE-U) matrix, were prepared in bulk and themally cross-polymerised in the solid state. The crosslinked copolymers produced intense Raman spectra in which the triple bond stretching Raman band at ∼2080 cm^-1 is well defined and shifts to lower frequency under the application of tensile stress. Shifts in Raman spectra have been used to monitor stress concentrations around defects such as holes and notches machined into copolyurethane sheets. The copolyurethanes are readily applied as surface coatings to various subtrates, and their use as optically stress/strain-sensitive materials (optical strain sensors) is demonstrated.     

氟碳黏合剂研究进展

综述了国内外氟碳黏合剂研究进展,对主要品种的氟碳黏合剂的发展历程、性能、应用以及发展趋势作了简要评述。认为端羟基氟碳缩甲醛聚醚和含氟氧杂丁环聚醚是值得关注的高能量密度推进剂用黏合剂品种,其在特殊性能材料等民品领域也有较广阔的应用。     

Migration of Plasticizer between Bonded Propellant Interfaces

Plasticizer migration across bonded propellant interfaces during cure has been shown to have a measurable effect on propellant properties compared to each propellant by itself. This shows that the curing period is significant to the migration phenomenon. The plasticizer migration has been shown to have a direct influence on tensile strength for short aging periods up to the point the plasticizer reaches equilibrium. The tensile data for short aging periods have been shown to follow an empirical equation connecting the physical characteristics of plasticizer migration with increasing propellant tensile strength. The diffusion coefficient has been evaluated on the basis of this relation from a plot of σ versus t^1/2 and was in good agreement with the diffusion coefficient from the plasticizer content data.     

低易损发射药配方用粘结剂与力学性能关系探索研究

采用低温抗冲强度、高温抗压强度及延伸率试验方法,对低易损发射药配方用情性粘结剂与力学性能的关系进行了探素试验研究.经试验研究,发现醋丁纤维素较其它惰性粘结剂对低易损发射药力学性能的贡献优越.同时对不周规格醋丁纤维素特性进行了试验研究,提出CAB-Ger可作为该发射药配方的基础粘结剂,进一步进行性能改善研究.     

颗粒粘结高燃速推进剂燃速设计方法的研究

介绍了颗粒粘结高燃速固体推进剂的工艺特点,利用推进剂燃烧特征化学基团方法预估了几种小药粒和速燃粘结剂的燃速,提出了颗粒粘结高燃速固体推进剂燃速的设计方法.     

固体推进剂用含能黏合剂体系研究进展

黏合剂含能化是近年来推进剂研究的热点之一,对叠氮基黏合剂和硝酸酯增塑聚醚黏合剂体系的制备、燃烧性能和能量性能进行了简要总结,并对今后黏合剂的发展做了展望。     

Synthesis,Characterization and Thermal Properties of Poly(glycidyl azide‐r‐3‐azidotetrahydrofuran) as Azido Binder for Solid Rocket Propellants

Azido polymers have been investigated as energetic binders in the area of solid rocket propellants. However, the low temperature mechanical properties of them are not comparable with the traditional propellant binders. In this work, a new kind of azido binder named poly (glycidyl azide‐r‐3‐azidotetrahydrofuran) (PGAAT) was successfully synthesized. The molecular structures of monomers and copolymers were characterized. The sensitivity and thermal properties of the azido binder were studied. The cationic copolymerization of 3‐methylsulfonyloxytetrahydrofuran with ternary cyclic ethers was confirmed. The PGAAT azido binder exhibited attractive features like low glass transition temperature (T_g, −60 °C) and high energy (1798 J/g). The results indicate that the polymer is a suitable candidate binder for the solid rocket propellants.