Block Copoly Ether Research Articles

A Study of Hydroxyl-Terminated Block Copolyether-Based Binder Curing Kinetics.

In order to determine the curing reaction model and corresponding parameters of hydroxyl-terminated block copolyether (HTPE) and provide a theoretical reference for its practical application, the non-isothermal differential scanning calorimetry (DSC) method was used to analyze the curing processes of three curing systems with HTPE and N-100 (an aliphatic polyisocyanate curing agent), isophorone diisocyanate (IPDI), and a mixture of N-100 and IPDI as curing agents. The results show that the curing activation energy of N-100 and HTPE was about 69.37 kJ/mol, slightly lower than the curing activation energy of IPDI and HTPE (75.60 kJ/mol), and the curing activation energy of the mixed curing agent and HTPE was 69.79 kJ/mol. The curing process of HTPE conformed to the autocatalytic reaction model. The non-catalytic reaction order (n) of N-100 and HTPE was about 1.2, and the autocatalytic order (m) was about 0.3, both lower than those of IPDI and HTPE. The reaction kinetics parameters of the N-100 and IPDI mixed curing agent with HTPE were close to those of N-100 and HTPE. The verification results indicate a high degree of overlap between the experimental data and the calculated data.

Effect of polyol bonding agent on the mechanical properties of hydroxyl‐terminated block copolyether based composite propellant with low aluminum content

AbstractA polyol bonding agent (BA) was utilized to enhance the mechanical properties of propellant with low aluminum content. Through scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS) analysis, it was discovered that BA can physically bond to the surfaces of ammonium perchlorate (AP) and hexogen (RDX). The results of mechanical testing showed that the use of BA can significantly improve the mechanical properties of propellants. Specifically, as the amount of BA increases, the maximum tensile strength (σm) of the propellant also increases, the fracture elongation (εb) initially increases and then decreases, the “dewetting ratio” continuously decreases, and the creep resistance of the propellant also increases. At a BA content of 0.2%, the σm of the propellant reaches 0.6 MPa, the εb exceeds 50%, and the “dewetting ratio” is less than 1.1.

Preparation of ADN-based energetic composite microspheres with excellent anti-moisture absorption and safety

Ammonium dinitramide (ADN) is an ideal solid composite propellant oxidizer. But it also exhibits high hygroscopicity and low safety. Solving these issues will be crucial of ADN in practical applications. In this study, three ADN-based energetic composite microspheres were prepared by suspension assembly process coating ADN with different polymeric materials (glycidyl azide polymer (GAP), fluorine rubber(F2602), and hydroxyl-terminated block copolyether(HTPE)). The experimental results showed that the three prepared samples were spherical particles with regular morphology and uniform particle size. The crystal structure was not changed. The contact angle, moisture absorption and mechanical sensitivity test showed that the ADN-based energetic composite microspheres have low moisture absorption and mechanical sensitivity. In particular, the ADN/F2602 sample, which possesses a lotus-like hydrophobic effect, exhibits a 57.24 % reduction in water absorption compared to the raw ADN, and the contact angle of ADN/F2602 (93.91°) is 4.24 times higher than that of the raw ADN (22.15°). The critical friction susceptibility of ADN/F2602 (168 N) is 2.1 times higher than that of raw ADN (80 N), and the critical impact susceptibility of ADN/F2602 (17 J) is 2.43 times higher than that of raw ADN (7 J). The combustion test showed that the combustion duration of ADN/F2602 increased from 1.353 s to 1.578 s for the raw ADN, and the flame intensity was enhanced. The successful ignition and flame stabilization of ADN/F2602 samples after 24 h storage under a relative humidity of 60 % indicates its good energy release performance in a propellant. Through this study, F2602 as a capping material has good anti-hygroscopic effect, mechanical insensitivity and combustion stability for ADN, which can support the application of ADN as an oxidizer in composite solid propellants.

Synthesis and properties of unsaturated block copolyether ketones

Block-copolyether ketones containing >C=CCl2 groups, characterized by high thermal and mechanical properties, with quantitative yield and high values of reduced viscosity, were obtained based on various oligomers with condensation degrees of n = 1-20 using the method of acceptor-catalytic polycondensation. The structure of the resulting polyesters was confirmed. The kinetics of polyester structuring at the site of the double bond depending on temperature and dwelling time was studied.

Coordinative Double Hydrophilic All-Polyether Micelles for pH-Responsive Delivery of Cisplatin.

Despite its widespread use in the treatment of numerous cancers, the use of cisplatin still raises concerns about its high toxicity and limited selectivity. Consequently, the necessity arises for the development of an effective drug delivery system. Here, we present an effective approach that introduces a double hydrophilic block copolyether for the controlled delivery of cisplatin. Specifically, poly(ethylene glycol)-block-poly(glycidoxy acetic acid) (mPEG-b-PGA) was synthesized via anionic ring-opening polymerization using the oxazoline-based epoxide monomer 4,4-dimethyl-2-oxazoline glycidyl ether, followed by subsequent acidic deprotection. The coordinative metal-ligand interaction between cisplatin and the carboxylate group within the PGA block facilitated the formation of micelles from the double hydrophilic mPEG-b-PGA copolyether. Cisplatin-loaded polymeric micelles had a high loading capacity, controlled pH-responsive release kinetics, and high cell viability. Furthermore, in vitro biological assays revealed cellular apoptosis induced by the cisplatin-loaded micelles. This study thus successfully demonstrates the potential use of double hydrophilic block copolyethers as a versatile platform for biomedical applications.

Interaction Mechanism of Composite Propellant Components under Heating Conditions.

To examine the interactions between two binder systems-hydroxyl-terminated polybutadiene (HTPB) and hydroxyl-terminated block copolyether prepolymer (HTPE)-as well as between these binders and ammonium perchlorate (AP) at various temperatures for their susceptibility to varying degrees of thermal damage treatment, the thermal characteristics and combustion interactions of the HTPB and HTPE binder systems, HTPB/AP and HTPE/AP mixtures, and HTPB/AP/Al and HTPE/AP/Al propellants were studied. The results showed that the first and second weight loss decomposition peak temperatures of the HTPB binder were, respectively, 85.34 and 55.74 °C higher than the HTPE binder. The HTPE binder decomposed more easily than the HTPB binder. The microstructure showed that the HTPB binder became brittle and cracked when heated, while the HTPE binder liquefied when heated. The combustion characteristic index, S, and the difference between calculated and experimental mass damage, ΔW, indicated that the components interacted. The original S index of the HTPB/AP mixture was 3.34 × 10-8; S first decreased and then increased to 4.24 × 10-8 with the sampling temperature. Its combustion was initially mild, then intensified. The original S index of the HTPE/AP mixture was 3.78 × 10-8; S increased and then decreased to 2.78 × 10-8 with the increasing sampling temperature. Its combustion was initially rapid, then slowed. Under high-temperature conditions, the HTPB/AP/Al propellants combusted more intensely than the HTPE/AP/Al propellants, and its components interacted more strongly. A heated HTPE/AP mixture acted as a barrier, reducing the responsiveness of solid propellants.

Influence of pre-ignition technology on combustion and explosion characteristics of composite propellants

The slow cook-off test is widely used for analyzing the safety of propellants under accidental thermal stimulation. To examine the influence of the pre-ignition technology of a composite propellant on thermal safety and combustion characteristics, a quantitative evaluation experiment of slow cook-off reaction intensity of a typical composite propellant charge was designed and executed, considering hydroxyl-terminated polybutadiene (HTPB) and hydroxyl‑terminated block copolyether (HTPE) propellants containing ammonium perchlorate (AP) and aluminum (Al). The experimental method for quantitative evaluation of the slow cook-off reaction intensity is highly essential to investigate the safety of ammunition. The influence of pre-ignition on reaction intensity was analyzed at different temperatures, the combustion behavior of the heated propellant was studied using a closed bomb experiment, and the influence of pre-ignition on combustion evolution was analyzed. Finally, the process was characterized by theoretical modeling. The results show that the slider speed was 169.3 m/s when the HTPB/AP/Al propellant was ignited at 234 °C. The slider speed was reduced to 43.4 m/s and 61.8 m/s by pre-ignition at 120 °C and 214 °C, respectively. When the spontaneous ignition temperature of HTPE/AP/Al propellant was 212 °C, the slider speed was 110.5 m/s. Pre-ignition at 120 °C and 192 °C reduced the slider speed to 39.4 m/s and 43.7 m/s, respectively. Pre-ignition can effectively reduce the reaction intensity. Under the same conditions, the reaction strength of HTPE/AP/Al propellant is marginally lower than that of HTPB/AP/Al propellant. In the slow heating process before ignition, with the increase in ignition temperature, when HTPB/AP/Al propellant was pre-ignition at 120 °C and 214 °C, the pressurization time was 9.8 ms and 6.4 ms, respectively, while before ignition, the pressurization time decreased to 5.5 ms. At 120 °C and 192 °C, the pressurization time of HTPE/AP/Al propellant was 50.9 ms and 36.6 ms, respectively, while before ignition, the pressurization time decreased to 26.9 ms. The reduction in ignition temperature decreased the pressure growth rate of propellant during combustion and reduced the pressurization time. A calculation model of the propellant combustion process was established to characterize the growth process of the combustion pressure at different ignition temperatures. This model can effectively predict the combustion evolution of composite propellants after the slow cook-off ignition and aid in ensuring propellant safety.

Mechanism of AP effect on slow cook-off response of HTPE propellant

Due to safety requirements, insensitive behaviour under slow cook-off conditions is the desirable behaviour for HTPE (Hydroxyl-terminated block copolyether) propellant. In this paper, in order to study the effect of AP (ammonium perchlorate) on slow cook-off response of HTPE propellants, the slow cook-off behaviour of AP and the effect of HTPE binder on AP were investigated firstly. The results showed that, the weightlessness rate of AP was only 2.2% in closed system till heated to 250°C, but the figure was 35.91 % in opened system. Then the slow cook-off behaviour of two groups of HTPE propellants with different AP content and diameter respectively were tested. The results indicated that, as the AP content increased from 52% to 67%, or the diameter of AP decrease from 400 μm to 5 μm, the violence of slow cook-off response all increased. The possible mechanism was proposed. It expressed that, thermal damage of propellant produced during the slow cook-off test, the combustion sensitivity to pressure of damaged propellant increased as the AP content rise and the AP diameter decrease, leading a more violent response to slow cook-off.

Effect of Block Structure of Copolyether Binder on Slow Cook‐Off Response of Composite Propellant

AbstractAs the typical insensitive propellants, hydroxyl‐terminal block copolyether (HTPE) and hydroxyl‐terminal block copolyether (PET) propellant all belong to copolyether propellants. The two binders of propellants have different arrangements of copolyether structure. But, the effect of copolyether structure arrangement on the slow cook‐off behavior of propellants and its possible mechanism has been unknown. So, in this paper, the slow cook‐off behaviors of HTPE and PET propellants were tested. The result showed PET propellant responded more violently than HTPE propellant. Then, the changes of mass loss, explosion heat, and combustion performance of propellants during the cook‐off test were studied. Combined with the slow cook‐off behavior of AP and binders, the mechanism of block structure effect on slow cook‐off response of propellant was proposed. It expressed that, the binders of HTPE and PET propellant all degraded into liquid products due to the copolyether structure; but the block structure has a significant effect on the chain scission process of copolyether binder, which makes slight degradation and the mild response to slow cook‐off for HTPE propellant. While the binder of PET propellant with the random structure degraded seriously, making more mass loss, bigger explosion heat, and worse combustion performance, the PET propellant responds violently to slow cook‐off.

Thermal and mechanical properties of two kinds of hydroxyl-terminated polyether prepolymers and the corresponding polyurethane elastomers

In order to analyze the differences in performance between two kinds of hydroxyl-terminated polyether (HTPE) binders, the curing reaction kinetics of the prepolymers and polyfunctional isocyanate (N-100) molecules and the thermal properties of the prepolymers and the corresponding polyurethane (PU) elastomers were studied by non-isothermal differential scanning calorimetry. The mechanical properties of PU elastomers were also studied by uniaxial tensile tests. With these data, the binder type could be chosen more appropriately for its application in rocket propellant formulations. The results showed that the reactivity of hydroxyl-terminated block copolyether (TPEG) with an isocyanate group is higher than that of hydroxyl-terminated random copolyether (PET). The chain flexibility of TPEG was less than that of PET, but the stereoregularity and crystallization ability of the former were superior. Compared to the prepolymers, the chain flexibility of the corresponding PU elastomers was reduced, and the crystallization ability became weaker such that their onset of crystallization was delayed. After the prepolymers were reacted with N-100, the thermal properties of PU elastomers remained consistent with their respective prepolymers. In summary, it was concluded that the mechanical properties of TPEG/N-100 PU elastomer films were found to be superior to the PET/N-100 films.

Polymeric nanomaterials as electrolyte and electrodes in supercapacitors

The energy challenge requires a broad range of options for energy harvesting, storage, and conversion. We have produced polymeric coatings by spraying, to be used as electrolyte and electrodes in a flexible electrochemical double layer capacitor. A thermoplastic polyurethane and a low molecular weight block copolyether were employed with LiClO4 to prepare solid polymeric electrolytes. Carbon black (CB) and multi-walled carbon nanotubes (MWNTs) were dispersed in the polymer blend electrolyte to produce nanostructured composite electrodes. The conductivities increased with the addition of block copolyether and carbon nanotubes to the electrolyte and electrode, respectively. Scanning electron microscopy (SEM) and atomic force microscope (AFM) images of the nanocomposite electrodes showed nanoagglomerates of CB connected by carbon nanotubes. The solid supercapacitor prepared with these new materials as electrolyte and electrodes showed superior performance to other similar systems. The resulting safe and flexible multilayer device can meet the requirements of modern devices.

Self-Assembly of an Amphiphilic Siloxane Graft Copolymer in Water

The micelle formation and micelle structure of an amphiphilic poly(dimethylsiloxane)-graft-polyether copolymer in aqueous solution were investigated with a variety of experimental techniques. We measured the CMC by three different methodsDPH solubilization, methyl orange hypsochromic shift, and pyrene fluorescence I1/I3 ratio. The microviscosity was evaluated from DPH anisotropy values that were obtained by fluorescence polarization measurements. The microviscosity in the siloxane copolymer micelles was found lower than that in Pluronic block copolyether micelles. The micelle size and structure were obtained from small-angle neutron scattering (SANS) using the hard sphere model. The micelle hydrodynamic radius and the micelle size distribution were monitored by dynamic light scattering (DLS). The degree of hydration was estimated from a combination of DLS and SANS results. The temperature effect on CMC was found to be small; however, a structural transition of micelles from spheres to ellipsoids was obser...

Homogeneous assay for measuring low-density lipoprotein cholesterol in serum with triblock copolymer and α-cyclodextrin sulfate

We have developed a fully automated method for measuring LDL-cholesterol (LDL-C) in human serum without the need for prior separation, using a nonionic surfactant, polyoxyethylene-polyoxypropylene block copolyether (POE-POP), and a sodium salt of sulfated cyclic maltohexaose, alpha-cyclodextrin sulfate. Of the surfactants tested, POE-POP with a higher molecular mass of the POP block and a greater hydrophobicity reduced the reactivity of cholesterol in lipoprotein fractions; the reactivity in descending order was LDL >> VLDL > chylomicron approximately HDL. Gel filtration chromatographic studies revealed that POE-POP removed lipids selectively from the LDL fraction and allowed them to participate in the cholesterol esterase-cholesterol oxidase coupling reaction system. By contrast, alpha-cyclodextrin sulfate reduced the reactivity of cholesterol, especially in chylomicrons and VLDL. A combination of POE-POP with alpha-cyclodextrin sulfate provided the required selectivity for the determination of LDL-C in serum in the presence of magnesium ions and a small amount of dextran sulfate without precipitating lipoprotein aggregates. There was a good correlation between the results of LDL-C assayed by the proposed method and the beta-quantification reference method involving 161 sera with triglyceride concentrations ranging from 0.3 to 22.6 mmol/L.

ＰＥＯ‐ＰＰＯ‐ＰＥＯ‐ブロックコポリエーテルをベースとする抗血栓性セグメント化ポリウレタンウレアの疲労試験と力学的性質

ＰＥＯ‐ＰＰＯ‐ＰＥＯ‐ブロックコポリエーテルをベースとする抗血栓性セグメント化ポリウレタンウレアの疲労試験と力学的性質

Block copolyurethanes based on polyoxytrimethylene glycols

AbstractTrimethylene oxide was polymerized to polyoxytrimethylene glycol by two synthetic routes. High molecular weight polytrimethylene oxide was synthesized using a coordination catalyst system consisting of triethylaluminum, acetylacetone, and water, then ozonized and reduced with lithium aluminum hydride in anhydrous ether to form hydroxyl end‐capped polyoxytrimethylene glycol. In the second route, the polyoxytrimethylene glycols were synthesized directly by the cationic polymerization of trimethylene oxide with boron trifluoride/ethyl ether as catalyst and 1,4 butanediol as co‐initiator. (AB)n block copolyether–urethane–ureas based on these polyoxytrimethylene glycols were synthesized and characterized by differential scanning calorimetry, and dynamic mechanical and stress–strain measurements.

Gas permeability of various block copolyether—urethanes

The effect of chemical structure and fabrication variables on the gas permeability of several block copolyether—urethane—urea and copolyether—urethane membranes was determined. It was found that the gas permeability of the copolyether—urethane—ureas increased in a linear manner with an increase in the polypropylene glycol segment molecular weight. Copolymers with a polyethylene glycol segment were found to be less permeable than those with propylene glycol segments. This may be due to the ability of polyethylene glycol to crystallize. For both copolymer systems, the type of chain extender used affected gas permeability. Again, these effects may be due to the degree of phase separation and to the nature of chain packing with the different extenders (i.e., the better the packing the lower the permeability). Changes in casting solvent, or the addition of salts such as LiBr or urea, had only minor effects on gas permeability.

Polymer degradation. II. Mechanism of thermal degradation of polyoxypropylene glycol–toluene 2,4‐diisocyanate polymer (POPG–TDI) and a block polyether glycol–TDI polymer

AbstractFurther studies on the thermal degradation of POPG‐TDI polymer have been carried out. It has been shown that at temperatures of ∼200°C., the predominant degradation process involves random scission of the urethane linkages to give substantial amounts of isocyanate and hydroxyl. Kinetic data suggests that the weakest links in POPG‐TDI polymer are spaced at intervals of ∼10,000 in molecular weight and that they may be eliminated by pretreatment of the POPG with ethylene oxide to form a block copolyether which is used to prepare the polyurethane. At temperatures exceeding 250°C. and a greater conversion to volatile fragments (>10%) the kinetics of degradation of POPG‐TDI are similar to results for POPG and indicate scission of the polyether bonds by a combination of intramolecular proton abstraction and free radical unzipping reactions, in agreement with previous studies of POPG of much higher molecular weight.