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1.
Triazole crosslinked polymers were prepared by reacting glycidyl azide polymer (GAP) with the propargyl ‐ terminated poly(tetramethylene oxide) (PTMP) at different molar ratios of azide versus alkyne. Based on the optimum mechanical properties of the GAP/PTMP ‐ 2.5, a series of GAP/PTMP nanocomposites reinforced by either multi ‐ walled carbon nanotubes (MWCNTs) or carboxy ‐ functionalized multiwalled carbon nanotubes (MWCNTs ‐ COOH) were prepared with different mass ratios. The glass transition temperatures (Tg, PTMP) assigned to PTMP of the GAP/PTMP composites almost kept at a constant range when the molar ratio of azide versus alkyne was from 1.0 to 2.5. When the loading MWCNTs was 1.0 wt %, the tensile strength and elongation at break achieved a maximum of 1.77 MPa and 36.3%, respectively. The nanocomposites with nearly similar Tg, PTMP indicated no phase separation in the crosslinked polymers. The results revealed that the improved properties of GAP ‐ based materials could be achieved by changing the molar ratio of azide versus alkyne and the nanofillers content. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45359.  相似文献   

2.
Bis‐propargylhydroquinone (BPHQ) is an alkyne functionalized isocyanate‐free curing agent for hydroxyl terminated azido polymers. Conventionally, glycidyl azide polymer (GAP) is cured by isocyanate based curatives, which are toxic and hygroscopic in nature. The reaction between hydroxyl end group of GAP and isocyanate is highly sensitive to moisture causing voids in the propellant, leading to poor mechanical properties. Herein, an alternate approach was adapted to exploit 1,3‐dipolar cycloaddition reaction between azido group of GAP and the triple bond (–C≡CH) of BPHQ without catalyst at 50 °C forming triazole crosslinked polymer. The curing behavior of GAP‐BPHQ system was studied by rheological method and based on the results the gel time was determined. In addition, the reaction between GAP and BPHQ was carried out with various GAP/BPHQ ratios (0.9 to 2.5) and effects on mechanical properties of resulting triazole polymers were investigated. Post curing hardness of GAP‐BPHQ binder system was tested by surface Shore‐A hardness measurement. The compatibility of BPHQ with energetic oxidizers such as ammonium dinitramide (ADN) and hydrazinium nitroformate (HNF) were also studied by differential scanning calorimetery (DSC) technique and showed good compatibility. The activation energy (E a) of cured GAP‐BPHQ binder was evaluated by DSC using Ozawa and Kissinger methods and are found to be 33.55 and 33.16 kcal mol–1, respectively. The advantage of this curing system between GAP and BPHQ is unaffected by moisture as compared to isocyanate based urethane systems and also no need to control humidity during the processing of propellant. The experimental results reveal that triazole crosslinked polymer system could be a better choice to develop novel energetic binder systems for explosives as well as propellants composition with improved performance and eco‐friendly nature.  相似文献   

3.
Reactive energetic plasticizers (REPs) for use in glycidyl azido polymer (GAP) based polyurethane (PU) energetic binders were investigated. These REPs consisted of an activated terminal alkyne group that was expected to give rise to Huisgen azide‐alkyne 1,3‐dipolar cycloaddition within the specific pot life for a PU formulation to prevent the migration of plasticizers, and with a gem‐dinitro group as an energy resource. A quantitative miscibility investigation between the plasticizers and uncured GAP showed that REPs exhibited better miscibility than conventional energetic plasticizers. The plasticization effect of the REPs on the GAP prepolymer with respect to the reduction of the viscosity illustrated REPs can effectively reduce the viscosity of the GAP prepolymer from 6,015 cP to 150–240 cP at the processing temperature when 50 wt‐% of REP was added. A comparison of the click reactivity and activation energies (Ea) of REPs and GAP prepolymer elucidated that the reactivity of azide‐alkyne cycloaddition depended on the dipolarophilicity of REPs which could be controlled by adjusting the length of methylene spacer between electron‐withdrawing groups (EWG) and neighboring alkynes in REPs. Thermogravimetric analysis manifested REP/GAP‐based PU binders maintained the thermal stability of the control GAP‐based PU binder. The mechanical properties and impact insensitivity of the GAP‐based PU binders were also improved by the incorporation of REPs.  相似文献   

4.
Instead of the traditional isocyanate curing system as the binder of solid propellant, a triazole curing system has been developed by the reaction of azide group and alkynyl group due to a predominant advantage of avoiding to the interference of humidity. In this work, the propargyl‐terminated polybutadiene (PTPB) was blended with glycidyl azide polymers (GAPs) to produce new composites under the catalysis of cuprous chloride at ambient temperature. The triazole‐crosslinked network structure was regulated by changing the molar ratio of azide group in GAP versus alkynyl group in PTPB, and hence various crosslinked densities together with the composition changes of GAP versus PTPB cooperatively determined the mechanical properties of the resultant composites. Furthermore, the formed triazole‐crosslinked network derived from the azide group in GAP and alkynyl group in PTPB resulted in the slight increase of glass transition temperatures and a‐transition temperatures, and improved the miscibility between GAP and PTPB. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40007.  相似文献   

5.
Glycidyl azide polymer (GAP) was cured through “click chemistry” by reaction of the azide group with bispropargyl succinate (BPS) through a 1,3‐dipolar cycloaddition reaction to form 1,2,3‐triazole network. The properties of GAP‐based triazole networks are compared with the urethane cured GAP‐systems. The glass transition temperature (Tg), tensile strength, and modulus of the system increased with crosslink density, controlled by the azide to propargyl ratio. The triazole incorporation has a higher Tg in comparison to the GAP‐urethane system (Tg−20 °C) and the networks exhibit biphasic transitions at 61 and 88 °C. The triazole curing was studied using Differential Scanning Calorimetry (DSC) and the related kinetic parameters were helpful for predicting the cure profile at a given temperature. Density functional theory (DFT)‐based theoretical calculations implied marginal preference for 1,5‐addition over 1,4‐addition for the cycloaddition between azide and propargyl group. Thermogravimetic analysis (TG) showed better thermal stability for the GAP‐triazole and the mechanism of decomposition was elucidated using pyrolysis GC‐MS studies. The higher heat of exothermic decomposition of triazole adduct (418 kJ ⋅ mol−1) against that of azide (317 kJ ⋅ mol−1) and better mechanical properties of the GAP‐triazole renders it a better propellant binder than the GAP‐urethane system.  相似文献   

6.
Though glycidyl azide polymer (GAP) is a well‐known and promising energetic polymer, propellants based on it suffer from poor mechanical and low‐temperature properties. To overcome these problems, plasticized GAP‐based copolymeric binders were prepared and investigated through the incorporation of flexible‐structural polyethylene glycol (PEG) and polycaprolactone (PCL) into a binder recipe under a Desmodur N‐100 polyisocyanate (N‐100)/isophorone diisocyanate (IPDI) (2 : 1, wt. ratio) mixed curative system. The nitrate esters (NEs) or GAP oligomer were used as energetic plasticizers at various ratios to the polymers. The GAP/PCL binders held the plasticizers much more than the GAP/PEG binders did. The glass transition temperatures (Tg) of segmented copolymeric binders were more dependent on the plasticizer level than the PEG or PCL content. The increase in the plasticizer content decreased the mechanical strength and modulus of binders, while the change of strain was modest. Finally, the NE plasticized GAP‐based solid propellants showed enhanced mechanical and thermal properties by the incorporation of PEG or PCL. The properties of GAP/PCL propellants were superior to those of GAP/PEG propellants.  相似文献   

7.
Traditional composite rocket propellants are cured by treatment of hydroxyl‐terminated prepolymers with polyfunctional aliphatic isocyanates. For development of smokeless composite propellants containing nitramines and/or ammonium dinitramide (ADN), energetic binder systems using glycidyl azide polymer (GAP) are of particular interest. Polyfunctional alkynes are potential isocyanate‐free curing agents for GAP through thermal azide‐alkyne cycloaddition and subsequent formation of triazole crosslinkages. Propargyl succinate or closely related aliphatic derivatives have previously been reported for such isocyanate‐free curing of GAP. Herein, we present the synthesis and use of a new aromatic alkyne curing agent, the crystalline solid bisphenol A bis(propargyl ether) (BABE), as isocyanate‐free curing agent in smokeless propellants based on GAP, using either octogen (HMX) and/or prilled ADN as energetic filler materials. Thermal and mechanical properties, impact and friction sensitivity and ballistic characteristics were evaluated for these alkyne cured propellants. Improved mechanical properties could be obtained by combining isocyanate and alkyne curing agents (dual curing), a combination that imparted better mechanical properties in the cured propellants than either curing system did individually. The addition of a neutral polymeric bonding agent (NPBA) for improvement of binder‐filler interactions was also investigated using tensile testing and dynamic mechanical analysis (DMA). It was verified that the presence of isocyanates is essential for the NPBA to improve the mechanical properties of the propellants, further strengthening the attractiveness of dual cure systems.  相似文献   

8.
The acid curing agent content and foaming temperature could be reduced by improving the resol reactivity. In this study, highly active and solid phenol?resorcinol?formaldehyde copolymer resins (PRFRs) with different resorcinol/phenol (R /P ) molar ratios and formaldehyde/(phenol + resorcinol) [F /(P + R )] molar ratios were synthesized through the copolymerization of resorcinol, formaldehyde, and phenol. Phenol?resorcinol?formaldehyde foams (PRFFs) were prepared with synthetic PRFRs. The results showed that PRFR‐2 exhibited higher reactivity, faster curing speed, and better thermal stability. In addition, the foam produced with the PRFR‐2 had improved mechanical and flame retardation properties and a compressive strength of 0.18 MPa, a flexural strength of 0.25 MPa, and a limited oxygen index (LOI) greater than 37%. The increased reactivity of the PRFRs correlated with the changing mechanical properties of PRFFs because of the effects of resorcinol and the molar ratio of formaldehyde to phenol and resorcinol. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44881.  相似文献   

9.
Depending upon the advantages of high efficiency, insensitivity to humidity and so on, the reaction of azide groups in glycidyl azide polymers (GAP) with alkynyl compounds has been used as a substitute of the urethane curing strategy to develop GAP‐based binder for solid propellant. In this work, an alkynyl compound of dimethyl 2,2‐di(prop‐2‐ynyl)malonate (DDPM) reacted with GAP to produce new crosslinked materials under the catalysis of Cu(I)Cl at ambient temperature, and showed great potential as a binder in composite propellant. As the feeding molar ratio of DDPM vs. GAP increased from 1 : 1 to 5 : 1, the crosslinking densities of as‐prepared materials gradually increased, together with simultaneous enhancement of Young's modulus and tensile strength. The breaking elongation showed the maximum value of ca. 82% when the feeding molar ratio of DDPM vs. GAP was 3 : 1. In addition, with an increase of the crosslinking densities, the glass transition temperatures of as‐prepared materials significantly increased from ?43.9°C to ?5.1°C while the mechanical loss peaks also gradually broadened and shifted up to high temperature, and even presented two peaks at the feeding molar ratio of DDPM vs. GAP higher than 4 : 1. It indicated that the formation of triazole‐based network resulted in structural heterogeneity in the as‐prepared materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40636.  相似文献   

10.
Glycidyl azide polymer (GAP) is an important energetic binder candidate for new minimum signature solid composite rocket propellants, but the mechanical properties of such GAP propellants are often limited. The mechanical characteristics of composite rocket propellants are mainly determined by the nature of the binder system and the binder‐filler interactions. In this work, we report a detailed investigation into curing systems for GAP diol with the objective of attaining the best possible mechanical characteristics as evaluated by uniaxial tensile testing of non‐plasticized polymer specimens. We started out by investigating isocyanate and isocyanate‐free curing systems, the latter by using the crystalline and easily soluble alkyne curing agent bispropargylhydroquinone (BPHQ). In the course of the presented study, we then assessed the feasibility of dual curing systems, either by using BPHQ and isophorone diisocyanate (IPDI) simultaneously (synchronous dual curing), or by applying propargyl alcohol and IPDI consecutively (sequential dual curing). The latter method, which employs propargyl alcohol as a readily available and adjustable hydroxyl‐telechelic branching agent for GAP through thermal triazole formation, gave rise to polymer specimens with mechanical characteristics that compared favorably with the best polymer specimens obtained from GAP diol and mixed isocyanate curatives. The glass transition temperature (Tg) of non‐plasticized samples was heightened when triazole‐based curing agents were included, but when plasticized with nitratoethylnitramine (NENA) plasticizer, Tg values were very similar, irrespective of the curing method.  相似文献   

11.
The combination of radical‐promoted cationic polymerization, atom transfer radical polymerization (ATRP) and click chemistry was employed for the efficient preparation of poly(cyclohexene oxide)‐block‐polystyrene (PCHO‐b‐PSt). Alkyne end‐functionalized poly(cyclohexene oxide) (PCHO‐alkyne) was prepared by radical‐promoted cationic polymerization of cyclohexene oxide monomer in the presence of 1,2‐diphenyl‐2‐(2‐propynyloxy)‐1‐ethanone (B‐alkyne) and an onium salt, namely 1‐ethoxy‐2‐methylpyridinium hexafluorophosphate, as the initiating system. The B‐alkyne compound was synthesized using benzoin photoinitiator and propargyl bromide. Well‐defined bromine‐terminated polystyrene (PSt‐Br) was prepared by ATRP using 2‐oxo‐1,2‐diphenylethyl‐2‐bromopropanoate as initiator. Subsequently, the bromine chain end of PSt‐Br was converted to an azide group to obtain PSt‐N3 by a simple nucleophilic substitution reaction. Then the coupling reaction between the azide end group in PSt‐N3 and PCHO‐alkyne was performed with Cu(I) catalysis in order to obtain the PCHO‐b‐PSt block copolymer. The structures of all polymers were determined. Copyright © 2010 Society of Chemical Industry  相似文献   

12.
合成了三种含酯基和三种含醚键的炔单体,通过核磁共振氢谱(1H NMR)、红外光谱(FT-IR)、质谱(MS)、液相色谱(LC)对其结构进行了表征。用这六种炔单体与叠氮单体反应制备了一系列新型聚三唑酯树脂(PTAE)和聚三唑醚树脂(PTAO)。利用差示扫描量热分析(DSC)、FT-IR、动态力学热分析(DMA)、力学试验机和热失重分析(TGA)表征了树脂的固化行为、固化树脂的力学性能、耐热性和热稳定性。结果表明PTAE和PTAO树脂易溶于有机溶剂,可低温(60℃)固化,固化树脂的弯曲强度超过了100 MPa,可达158 MPa,玻璃化转变温度(T g)超过180℃,高者达251℃,热分解温度可达360℃。  相似文献   

13.
Composites of poly(D ,L ‐lactide) (PDLLA) with hydroxylapatite (HA) and PDLLA with tertiary calcium phosphate (TCP) were prepared by in situ modification with methylenediphenyl diisocyanate (MDI) and molded by piston extrusion at temperature between Tg and Tm of PDLLA. Mechanical properties of the composites increased obviously when compared with the unmodified bioactive ceramic particles/PDLLA composites. The effect of MDI contents on mechanical properties of the composites was studied. At the optimum conditions of 1.0/1.0molar ratios of ? NCO groups in MDI to ? OH groups in PDLLA, bending strength 68.4 MPa and bending modulus 2281.5 MPa, were achieved in composite HA/PDLLA/MDI with 15 wt % HA. Both increased by nearly 30% when compared with that of solution cast HA/PDLLA composites. Interfacial adhesion and compatibility between PDLLA and bioactive ceramic particles (HA and TCP) were investigated. Scanning electron microscopy (SEM) indicated that the interface between HA particles and PDLLA was blurred and HA particles were closely surrounded by PDLLA matrix in HA/PDLLA/MDI composites. Oriented fibrils along with longitudinal direction of extrusion die were also observed on the surfaces of HA/PDLLA/MDI composite. It is confirmed that MDI has improved interfacial adhesion and compatibility between HA particles and PDLLA phase. Fibril structures formed in the extrusion, and it contributed a great deal in enhancing the mechanical properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4085–4091, 2006  相似文献   

14.
GAP‐modified nitrocellulose powders were prepared by an internal solution method and applied in cross‐linked modified double base (XLDB) propellants. It was found that GAP‐modified nitrocellulose powders exhibit high round, no bonding between the particles and excellent fluidity. When the amount of GAP increased from 10.0 % to 30.0 %, the median diameter (d50) of powders decreased from 134.53 μm to 94.54 μm. The thermal decomposition process of GAP appeared also in the GAP‐modified nitrocellulose powders, but the thermal decomposition peak temperatures of  N3 and the GAP main chain were found to be lower for the 10.0 % and 20.0 % GAP‐modified samples than the corresponding peak temperatures for pure GAP, respectively. The plasticizing properties of GAP‐modified nitrocellulose powders are better than that of pure nitrocellulose powders, and the drop weight impact sensitivity of the modified powders is reduced as the mass ratio of GAP increases. It was experimentally shown that GAP‐modified nitrocellulose powders can improve the mechanical characteristics of the propellant with a maximum tensile strength (σm) between 0.36 MPa<σm< 1.10 MPa and an elongation at maximum tensile strength (εm) between 28.8 %<εm<51.8 % at temperatures of −40, +20 and +50 °C.  相似文献   

15.
The morphologies of energetic block copolymers based on glycidyl azide polymer (GAP) were investigated by dissipative particle dynamics simulation. The results show that the morphologies could be used to qualitatively explain the variation in the mechanical properties of poly(azidomethyl ethylene oxide‐b‐butadiene) diblock copolymers (DBCs) and that bicontinuous (B) phases could effectively improve the mechanical properties. Among our designed DBCs, only GAP–acrylic acid, GAP–acrylonitrile, and GAP–vinyl amide could form B phases at very narrow regions of GAP contents. The triblock copolymers with their linear topologies could maintain the B phases in the broader region of GAP contents. We hope these results can provide help in the design and synthesis of new energetic block copolymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

16.
Biodegradable poly(l -lactic acid) (PLLA)/eggshell (ES) powder composites were prepared by melt blending and uniaxial stretching above the glass-transition temperature of PLLA. Scanning electron microscopy analyses revealed that micropores appeared in stretched composites. Porosity was affected by two factors, stretch ratios, and ES contents. Differential scanning calorimetry and wide-angle X-ray diffraction results demonstrated that strain-induced crystallization in α-form could be achieved in PLLA matrix. This superstructure improved multifunctional performance of PLLA composites. The exceptional combination of strength, modulus, and ductility of stretched PLLA90/ES10 composites with a stretch ratio of 6 were demonstrated, exceeding neat PLLA with the increments of 148, 190, and 507% in breaking strength, modulus, and elongation at break (140.8 MPa, 3810 MPa, and 35.2%), respectively. Meanwhile, the enhancement of thermomechanical properties due to high crystallinity and controllable degradation rates resulting from porosity were obtained by adjusting the composites compositions and/or stretch ratios. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48158.  相似文献   

17.
The depolymerization of poly(ethylene terephthalate) (PET), by an alcoholysis reaction is an easy operation and gives prospects for the utilization of wastes. PET waste was first depolymerized by glycolysis reaction at three different molar ratios of diethylene glycol (DEG), in the presence of manganese acetate as a transesterification catalyst. Copolyesters of PET modified with varied mole ratios of p‐hydroxybenzoic acid (PHBA) were reported to exhibit excellent mechanical and chemical properties due to their liquid crystalline behaviour. Here we study the effect of incorporating (PHBA) units into the building structures of different unsaturated polyesters synthesized originally from glycolysed PET waste. Modified unsaturated polyesters were synthesized by depolymerizing PET with DEG, and the obtained oligoesters were reacted with PHBA and maleic anhydride (MA). The molar ratio of the added PHBA was varied to investigate its effect on the mechanical characteristics of these modified unsaturated polyesters. The data obtained reveal that increasing the molar ratio of PHBA within the studied range of concentrations leads to a pronounced improvement in the mechanical characteristics, which is represented mainly by the values of/maximum compression strength (σmax) and Young's modulus (EY). © 2002 Society of Chemical Industry  相似文献   

18.
A simple method based on photochemically induced copper(I)‐catalyzed azide ? alkyne cycloaddition click reaction (CuAAC ) is developed for the preparation of thermoset networks from soybean oils as renewable resources. The incorporation of clickable azide and alkyne functionalities into epoxidized soybean oils is done by simultaneous ring‐opening reactions between the epoxide group of soybean oils and sodium azide and propargyl alcohol, respectively. The obtained azide‐ and alkyne‐functionalized soybean oils are easily transformed crosslinked networks via the photoinduced CuAAC reaction in ambient conditions. The introduction of additional multifunctional monomers in the formulation not only increases the crosslinking density but also improves the mechanical properties of the thermoset material obtained. In a comparison of the two formulations, the sample containing additional multifunctional monomers has a higher glass transition temperature, storage modulus and damping properties. © 2017 Society of Chemical Industry  相似文献   

19.
Two kinds of flexible chain polymer, poly(ethylene oxide‐co‐tetrahydrofuran) (P(EO‐co‐THF)) and polyalkylene oxide (PAO), were chosen to improve the mechanical properties of the network of glycidyl azide polymer (GAP)–based elastomers. The mechanical properties of the GAP binder system at 25 and −40 °C can be improved effectively. The effects of P(EO‐co‐THF) and PAO on the network parameters, hydrogen bonding effect, and crystallization property were studied to determine the enhancement mechanism. Based on the results, it can be concluded that for copolyurethane elastomers prepared with PAO content less than 15 wt % and P(EO‐co‐THF), the mechanical properties were enhanced by the reduction of bulk side groups in GAP, which improved the chemical crosslinking density, hydrogen bonding effect in elastomers, and the motility of the molecular chains, while for elastomers prepared with more than 15 wt % PAO, the crystallization of the PAO segments played a major role in the improvement of mechanical properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43840.  相似文献   

20.
为了改善GAP推进剂的力学性能,研究了在GAP胶片制备中添加端炔基PEG400(C≡PEG400)与端炔基PET4000(C≡PET4000)2种炔类交联剂对GAP胶片交联密度、玻璃化温度、力学性能的影响。结果表明,在添加炔类交联剂之后,胶片的交联密度上升,玻璃化温度存在相应的升高,拉伸强度也有明显提高;而其断裂延伸率在添加C≡PEG400后会有所下降,添加C≡PET4000后上升。  相似文献   

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