Polyglycidyl nitrate (PGN)‐based energetic thermoplastic polyurethane elastomers with bonding functions

PGN‐based ETPUEs were synthesized using mixture of chain extenders including 1, 4‐butanediol and Diethyl Bis(hydroxymethyl)malonate (DBM). Through the special chain extenders DBM, the –COOR was introduced into the energetic thermoplastic polyurethane elastomers (ETPUEs) and further enhances the adhesion between ETPUE and nitramine solid ingredients in propellants. From the analysis, with the percentage of DBM increasing, the work of adhesion (W_a) between nitramine solid ingredients and ETPUEs increased and the maximum stress (σ_m) of ETPUEs decreased on the other hand. In order to test the bonding functions of different ETPUEs, the RDX/ETPUE propellants were prepared and the stress–strain curves of all propellants were tested. The results showed that the ETPUE‐75 with 75% DBM can prevent the dewetting and improve the mechanical properties of propellants. The ETPUE prepared with chain extender including 1, 4‐butanediol and DBM were valuable for application in propellants. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42026.     

Structure–property relationship of sodium deoxycholate based poly(ester ether)urethane ionomers for biomedical applications

New sodium deoxycholate based poly(ester ether)urethane ionomers were prepared for the development of biomedical materials. A structure–property relationship in the tested biomaterials was established by cross‐examination of the dynamic mechanical and dielectric properties, attenuated total reflection–Fourier transform infrared investigation, thermogravimetric analysis, and surface morphology characterization. A stronger ionic interaction and solvation capacity of the ions and a higher ionic conductivity were manifested in the case of poly(ethylene oxide)‐rich segments than for poly(propylene oxide)‐rich segments in these polyurethane ionomers. The molecular and ionic interactions of the bile‐salt moiety with different polyether cosoft segments influenced chain packing and conformation, supramolecular organization, and the resulting surface morphological microstructures of the polyurethane biomembranes. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42921.     

Thermal decomposition kinetics of rigid polyurethane foam and ignition risk by a hot particle

Rigid polyurethane foam, one kind of building insulation material used in China, is prone to being ignited by hot particles from fireworks or welding processes and has been the fuel for some catastrophic fire accidents. Thermal decomposition has long been recognized to play an important role in the ignition and fire‐spreading processes of materials, and thus, it is important to understand the behavior and kinetics of material decomposition. In this study, the characteristics of the thermal decomposition of polyurethane foam were investigated in an air atmosphere with nonisothermal thermogravimetry and differential scanning calorimetry (DSC). Model‐free (isoconversional) methods and model‐fitting methods were used to study the decomposition kinetics. The results reveal that the decomposition process of polyurethane foam in air presented three main stages: the loss of low‐stability organic compounds (bond fission of the weakest link in the chain), oxidative degradation of organic components, and oxidative degradation of residue material. A scheme containing three consecutive reactions was proposed to describe the decomposition process, and good agreement was found between the experimental and simulated curves. The heat during decomposition was calculated from DSC measurement. On the basis of the kinetics and heat of decomposition, the critical conditions for a hot particle to ignite polyurethane foam was evaluated, and this was helpful for the understanding the ignition risk of polyurethane foam. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39359.     

Thermal degradation of poly(dimethylsilylene) and poly(tetramethyldisilylene‐co‐styrene)

Thermal degradation of poly(dimethylsilylene) homopolymer (PDMS) and poly(tetramethyldisilylene‐co‐styrene) copolymer (PTMDSS) was investigated by pyrolysis‐gas chromatography and thermogravimetry (TG). PDMS decomposes by depolymerization, producing linear and cyclic oligomeric products, whereas PTMDSS decomposes by random degradation along the chain resulting in each monomeric product and various other combination products. The homopolymer was found to be much less stable than the copolymer. The decomposition mechanisms leading to the formation of various products are shown. The kinetic parameters of thermal degradation were evaluated by different integral methods using TG data. The activation energies of decomposition (E) for the homopolymer and the copolymer are found to be 122 and 181 kJ/mol, respectively, and the corresponding values of order of reaction are 1 and 1.5. The observed difference in the thermal stability and the values of the kinetic parameters for decomposition of these polymers are explained in relation with the mechanism of decomposition. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Thermal decomposition behavior of carbon‐nanotube‐reinforced poly(ethylene 2,6‐naphthalate) nanocomposites

Polymer nanocomposites based on poly (ethylene 2,6‐naphthalate) (PEN) and carbon nanotubes (CNTs) were prepared by direct melt blending with a twin‐screw extruder. Dynamic thermogravimetric analysis was conducted on the PEN/CNT nanocomposites to clarify the effect of CNTs on the thermal decomposition behavior of the polymer nanocomposites. The thermal decomposition kinetics of the PEN/CNT nanocomposites was strongly dependent on the CNT content, the heating rate, and the gas atmosphere. On the basis of the thermal decomposition kinetic analysis, the variation of the activation energy for thermal decomposition revealed that a very small quantity of CNTs substantially improved the thermal stability and thermal decomposition of the PEN/CNT nanocomposites. Morphological observations demonstrated the formation of interconnected or network‐like structures of CNTs in the PEN matrix. The unique character of the CNTs introduced into the PEN matrix, such as the physical barrier effect of CNTs during thermal decomposition and the formation of interconnected or network‐like structures of CNTs, resulted in the enhancement of the thermal stability of the PEN/CNT nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Siloxane‐based segmented poly(urethane‐urea) elastomer: Synthesis and characterization

A series of segmented poly(urethane‐urea) block copolymers were synthesized with varying proportions of polydimethylsiloxane diols in combination with polytetramethylene ether glycol (PTMG) using 4,4'‐methylenediphenyl diisocyanate followed by chain extension with a (50:50 mol %) mixture of 4,4'‐methylene‐bis(3‐chloro‐2,6‐diethylaniline) (M‐CDEA) and 1,4‐butanediol (BD). The molecular structures of polydimethylsiloxane urethane‐ureas were characterized by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. Distribution of siloxane domain and its influence on surface roughness were investigated by scanning electron microscopy (SEM) and atomic forced microscopy (AFM), respectively. The mechanical and thermal properties of the elastomers were studied by thermogravimetric analysis, dynamical mechanical thermal analysis, and tensile measurement. The results showed that by incorporation of polydimethylsiloxane diol and M‐CDEA chain extender in polyurethane formulation, some improvements in thermal stability, fire resistance and surface hydrophilicity were achieved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1743–1751, 2013     

Synthesis and characterization of polyurethane/poly(vinylidene chloride) interpenetrating polymer networks

A series of polyurethane (PU)/poly(vinylidene chloride) (PVDC) interpenetrating polymer networks (IPNs) were synthesized through variations in the amounts of the prepolyurethane and vinylidene chloride monomer via sequential polymerization (80/20, 60/40, 50/50, 40/60, 30/70, and 20/80 PU/PVDC). The physicomechanical and optical properties of the IPNs were investigated. Thermogravimetric analysis (TGA) studies of the IPNs were performed to establish their thermal stability. TGA thermograms showed that the thermal degradation of the IPNs proceeded in three steps. Microcrystalline parameters, such as the crystal size and lattice disorder, of the PU/PVDC IPNs were estimated with wide‐angle X‐ray scattering. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1375–1381, 2007     

The investigation of thermal decomposition pathway and products of poly(vinyl alcohol) by TG‐FTIR

A generalized form of a semiquantitative method has been developed based on the multilinear least‐squares regression technique applied on the entire FTIR absorbance spectrum of a gaseous mixture to determine components concentration. Thermal degradation of poly(vinyl alcohol) samples with high, PVA(98), and low degree of hydrolysis, PVA(80), has been investigated by TG‐FTIR simultaneous analysis performed in an inert atmosphere. Analysis of gaseous products was carried out using a routine developed in Matlab and this routine returns the product concentration with a reasonable RMS error. The correlation coefficients of the original mixture spectrum with the mixed output were obtained at some specific peak temperatures using irAnalysis software. The first process is the loss of physically adsorbed water which followed by two main processes of thermal degradation. In spite of the similarity of evolved gaseous products, two samples showed some differences in components concentrations identified in the volatile mixture. Acetaldehyde has been identified as the main volatile product in the first thermal degradation step of PVA(98) and PVA(80). The second major degradation product of PVA(80) is acetic acid due to presence of more residual acetate group while 2‐butenal have been identified for PVA(98). Water was mainly produced in the first stage of thermal degradation of PVA(98) while it was identified in the first and second stages for PVA(80). This might be attributed to existence of a competition between water and residual acetate group for elimination that postpones the complete elimination of OH group to the second degradation stage. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42117.     

Thermal stability of modified end‐capped poly(lactic acid)

The influence of functional end groups on the thermal stability of poly(lactic acid) (PLA) in nitrogen‐ and oxygen‐enriched atmospheres has been investigated in this article using differential scanning calorimetry, thermogravimetric analysis (TGA), and dynamic mechanical analysis (DMA). Functional end groups of PLA were modified by succinic anhydride and l ‐cysteine by the addition–elimination reaction. PLA was synthesized by azeotropic condensation of l ‐lactic acid in xylene and characterized by nuclear magnetic resonance. The values of the activation energies determined by TGA in nitrogen and oxygen atmospheres revealed that the character of functional end groups has remarkable influence on the thermal stability of PLA. Moreover, DMA confirmed the strong influence of functional end groups of PLA on polymer chains motion. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41105.     

Rheological and thermal properties of glycidyl azide polyol‐based energetic thermoplastic polyurethane elastomers

The purpose of this study was to investigate the effects of polyol on glycidyl azide polyol (GAP)‐based energetic thermoplastic polyurethane elastomers (ETPEs). Briefly, a series of GAP/polyol‐based ETPEs (GAP/polyol ETPEs) with different copolyol ratios and hard segment contents were synthesized using GAP‐diol with common polyol and 4,4‐methylenebis(phenylisocyanate)‐extended 1,5‐pentanediol as soft and hard segments, respectively, by solution polymerization in dimethylformamide. The three types of polyols used were poly(tetramethylene ether) glycol (PTMG), polycarbonate‐diol (PCL‐diol) and polycaprolactone‐diol (PCD‐diol). The synthesized GAP/polyol ETPEs were identified and characterized using Fourier transform infrared and ¹H NMR spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and rheometric mechanical spectrometry. For GAP/PCL ETPEs with lower hard segment content, DSC results showed that the GAP segment failed to interact with either the PCL segment or PCL melting. In addition, the results of DMA showed that the presence of PCL segments in ETPEs improved the storage modulus below the melting temperature of the PCL block. Further, the crystalline PCL segments were attributed to reinforcing the ETPEs in a manner similar to that of the hard domain. As the hard segment content increased in the GAP/polyol ETPEs, both GAP/PTMG ETPEs and GAP/PCL ETPEs exhibited microphase separation transitions, while rheological experiments demonstrated a sudden decrease in complex viscosity in neighboring microphase separation transitions. © 2012 Society of Chemical Industry     

Thermal decomposition of poly(oxytetramethylene) glycol

Studies of thermal decomposition on poly(oxytetramethylene) glycol have been conducted by pyrolysis gas chromatography–mass spectrometry, infrared spectroscopy, and thermogravimetric anaylysis (TGA). The major volatile decomposition products are suggested to be a series of molecules made up by the repetition of oxytetramethylene with formyl and/or methyl ends. Absorption peaks, associated with formyl appear in infrared spectrum of a sample preheated at 523°K lower than the onset temperature obtained from the TGA curve. The isothermal TGA curves fit well to the Shimha rate equation for the random decomposition of polymers. The proper activation energies obtained from the thermally controlled and the isothermal TGA data are approximately 60–70 kJ mol⁻¹ and lower than those for other polymers in ordinary thermal decomposition. These data suggest that the major reaction in the thermal decomposition of poly(oxytetramethylene) glycol is an ether cleavage. Two pathways, a radical scission accompanied by β‐hydrogen transfer and a nonradical reaction through a four‐membered ring transition state, are proposed and discussed for the ether cleavage. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1538–1544, 2000     

Thermal stability and molecular interaction of polyurethane nanocomposites prepared by in situ polymerization with functionalized multiwalled carbon nanotubes

Polyurethane (PU) nanocomposites were prepared through conventional and in situ methods with multiwalled carbon nanotubes (MWNTs) functionalized with poly(ϵ-caprolactone). The thermal degradation and stability of PU–MWNT nanocomposites were investigated with nonisothermal thermogravimetry and were explained in terms of the interaction between MWNTs and PU molecules with Fourier transform infrared spectroscopy. The difference in thermal stability between the conventional and in situ nanocomposites was also compared. The thermal degradation of all the nanocomposite samples took place in two stages and followed a first-order reaction. The degradation temperature of the in situ nanocomposites was higher than that of the conventional nanocomposites with the same loading of MWNTs. The activation energy at 10% degradation and the half-life period were also higher in the in situ nanocomposites compared to the conventional nanocomposites. Such higher thermal stability of the in situ nanocomposites was ascribed to covalent bond formation between MWNTs and PU chains, which could result in better dispersion of MWNTs in the PU matrix for the in situ nanocomposites than for the conventional nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermal decomposition kinetics of poly(nButMA‐b‐St) diblock copolymer synthesized by ATRP

The reaction mechanism of decomposition process and the kinetic parameters of the poly(n‐butyl methacrylate‐b‐styrene), poly(nButMA‐b‐St), diblock copolymer synthesized by atom transfer radical polymerization (ATRP) were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA curves showed that the thermal decomposition occurred in one stage. The apparent activation energies of thermal decomposition for copolymer, as determined by the Kissinger's, Flynn–Wall–Ozawa and Tang methods, which does not require knowledge of the reaction mechanism (RM), were 112.52, 116.54, and 113.41 kJ/mol, respectively. The experimental results were compared with master plots, in the range of the Doyle approximation. Analysis of experimental results suggests that in the conversion range studied, 3–18%, the actual RM is an A₂ sigmoidal type. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Strategy for kinetic parameter estimation—Thermal degradation of polyurethane elastomers

The kinetics of the thermal degradation of polyurethane (PU) elastomers based on poly(ether polyol) soft segments and an aromatic type of diisocyanate were investigated by thermogravimetric analysis (TGA) under a nitrogen atmosphere employing four heating rates. The corresponding kinetic parameters of the two degradation stages were estimated by minimizing the output error functional and by the Kissinger method. In evaluating the kinetic parameters of the two‐step PU thermal decomposition, a differential thermogravimetry curve was applied as an objective functional in a regression procedure. Parameter estimation was obtained by minimizing the weighted quadratic output error functional with the modified Nelder–Mead simplex search algorithm. The confidence regions in the preexponential factor‐activation energy space were established for both the first and second stages of degradation. The effect of the molecular weight of the soft segment and the content of the hard segment on the activation energy of the degradation process was constructed by response surface methodology. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 764–772, 2007     

Interchain crosslinkable polymer blends of polyurethane and polyacrylic elastomer (sulfur cure)

Blends of polyurethane and polyacrylic elastomers prepared by three different blending techniques have been studied in different blend ratios. The processability of the polyurethane elastomer was improved as a result of blending with the polyacrylic elastomer. The blending technique has a significant role in determining the physical properties of the blends. Improvement of physical properties was observed in the blends containing the interchain crosslink bonds. IR spectral analysis suggested the formation of interchain crosslink between the two elastomers phases on heat treatment, before the addition of any curatives. Thermal stability of the blends was also improved when preblending and preheating techniques were applied. The extraction of the single phase by solvent was also restricted to a significant extent for the preheated sample probably due to the interchain crosslinking. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 845–853, 2004     

Curing behavior of anionic poly(urethane urea) dispersions crosslinked with partially methylated melamine formaldehyde

A rigid‐body pendulum rheometer was used to observe the isothermal cure behavior of an anionic poly(urethane urea) dispersion crosslinked with different amounts of partially methylated melamine formaldehyde (PMMF). In this experiment, the anionic poly(urethane urea) dispersion had a large number of >N? H crosslinking or branching sites in urethane and urea groups per molecule, which allowed a large amount of PMMF to couple with the elastic polyurethane (PU) backbone. The test results showed that the cure response of the PU dispersion crosslinked with PMMF was a function of the concentration of PMMF and indicated that 30 phr PMMF could be the optimum amount of the crosslinking agent and that 120°C was the optimum temperature for the curing process. In addition, PMMF self‐condensation could take place during the curing process. The self‐condensation of PMMF also was monitored by a thermogravimetric method. Moreover, the dynamic mechanical properties of PMMF‐crosslinked PU films were affected by the concentration of PMMF. From the curing behavior and dynamic mechanical analysis test results, it was reasonable to assume that highly PMMF branched PUs with partial crosslinking structures could be formed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Thermal degradation kinetics of poly(N‐adamantyl‐exo‐nadimide) synthesized by addition polymerization

The thermal decomposition behavior and degradation kinetics of poly(N‐adamantyl‐exo‐nadimide) were investigated with thermogravimetric analysis under dynamic conditions at five different heating rates: 10, 15, 20, 25, and 30°C/min. The derivative thermogravimetry curves of poly(N‐adamantyl‐exo‐nadimide) showed that its thermal degradation process had one weight‐loss step. The apparent activation energy of poly(N‐adamantyl‐exo‐nadimide) was estimated to be about 214.4 kJ/mol with the Ozawa–Flynn–Wall method. The most likely decomposition process was an F1 deceleration type in terms of the Coats–Redfern and Phadnis–Deshpande results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3003–3009, 2007     

Structures and properties of polycarbonate modified polyether‐polyurethanes prepared by transurethane polycondensation

Thermoplastic polycarbonate modified polyether‐polyurethane (PEPU) elastomers were prepared by transurethane polycondensation method using poly(oxytetramethylene) glycol of M_n = 2000 and dimethyl‐hexane‐1,6‐dicarbamate as the main raw materials, 1,4‐butanediol as a chain extender and polycarbonate diol (PCDL) as an additive in the presence of dibutyltin oxide as a catalyst. The effect of the PCDL on the PEPUs' structure, intrinsic viscosity, molecular weight, mechanical, optical, and thermal properties, and water resistance were studied. The polycarbonate modified PEPUs showed better mechanical and thermal properties, but lower molecular weight and optical properties than the PEPUs. The PEPUs modified by PCDL1000 exhibited better performance, including mechanical, optical, and thermal properties, than those by PCDL2000. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42804.     

Kinetic analysis of thermal degradation in poly(ethylene–vinyl alcohol) copolymers

Thermal analysis of EVOH copolymers with different ethylene content, were performed by TGA/DTGA under dynamic conditions. Apparent kinetic parameters were determined using different classical kinetic approaches. The apparent activation energy values obtained confirm that thermal stability of EVOH increases with ethylene content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3157–3163, 2003     

Preparation and characterization of poly(ether ester) thermoplastic elastomers containing the 2,6‐naphthalenedicarboxyl group

Poly(ether ester) elastomers (PEEs) were synthesized in which dimethyl terephthalate (DMT) was the primary diester compound in the hard segment (H/S) and dimethyl 2,6‐naphthalene dicarboxylate (NDC), which has a more rigid aromatic chemical structure than DMT, was the secondary diester in the H/S. The block PEEs with poly(tetramethylene terephthalate) (PTMT) and/or poly(tetramethylene 2,6‐naphthalate) (PTMN) as the H/S and poly(tetramethylene ether glycol terephthalate) (PTMEGT) as the soft segment (S/S) were synthesized through transesterification and polycondensation of DMT, NDC, 1,4‐butanediol (BD), and poly(tetramethylene ether) glycol (PTMEG) of molecular weight 1000. The melting temperature and heat of fusion of the PEEs decreased with increasing NDC content up to an NDC content of 44.4% in the H/S, but increased on further increase of the NDC content. In addition, the higher the fraction of NDC in the H/S, the higher the glass transition temperature of the copolymer. X‐ray diffraction analysis revealed that the crystallinity of the sample decreases as the NDC content in the H/S is increased relative to that of DMT. Increasing the PTMN content in the H/S reduced the effect of UV photodegradation on the elongation at break. The results show that the introduction of the NDC component into the H/S as a secondary diester compound improves the UV resistance of the resulting PEE. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3473–3480, 2003