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1.
Phenyl acetylene terminated poly(carborane‐silanec) (PACS) was synthesized by the couple reaction of methyldichlorosilane with 1,7‐dilithio‐m‐carborane and lithium phenylacetylide. The structure was characterized using FTIR, 1H‐NMR, 13C‐NMR, 29Si‐NMR, and gel permeation chromatography. PACS exhibits solubility in common organic solvents. Thermal and oxidative properties were evaluated by thermogravimetric analysis (TGA). Thermoset exhibits extremely thermal and oxidative property and TGA curves show that the temperature of 5% weight loss (Td5) is 762°C and char yield at 800°C is 94.2% in nitrogen. In air, surprisingly, both Td5 and char yield at 800°C show slight increase, which is greater than 800°C and 95.6%, respectively. After pyrolysis, the char has no additional weight loss up to 800°C in air. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2498–2503, 2007  相似文献   

2.
A series of silylene–acetylene preceramic polymers 3a–e were synthesized by polycondensation reaction of dilithioacetylene with dichlorosilane (H2SiCl2) or/and methyldichlorosilane (MeSiHCl2). Their structures were confirmed by infrared spectra (IR), and 1H and 29Si NMR spectroscopies. Differential scanning calorimetry (DSC) diagrams show exotherms centered at 200 to 233°C temperature range, attributed to crosslinking reaction of the acetylene and Si? H groups. After thermal treatment, the obtained thermosets 4a–e possess excellent thermal stability. Thermogravimetric analysis (TGA) under nitrogen show the Td5s (temperature of 5% weight loss) for all the thermosets are above 600°C, and the overall char yields are between 95.62% and 89.67% at 900°C. After pyrolysis at 1200°C, the obtained ceramic residues 5a–e exhibit good thermo‐oxidative stability with final weight retention between 98.76% and 91.66% at 900°C under air. In particular, perhydroploy(silylene)ethynylene 3a , which has the highest Si/C ratio in silylene–acetylene polymers, has the highest char yield, and the derived ceramic material 5a displays the best thermo‐oxidative stability. Based on Scanning electron microscopy and its associated energy‐dispersive X‐ray microanalysis (SEM EDX) and 13C magic angle spinning nuclear magnetic resonance (MAS NMR) analysis, ceramic 5a contains the highest SiC content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

3.
Methyl‐tri(phenylethynyl)silane (MTPES) was successfully synthesized by the reaction of lithium phenylacetylide with methyltrichlorosilane. The structure was characterized by HRMS, FTIR, 1H‐NMR, 13C‐NMR, 29Si‐NMR, and elementary analysis. Thermal cure process was monitored by DSC, DMA, and FTIR. MTPES was heated to free flowing liquid around 130°C and thermally polymerized at 327–377°C to form thermoset. Thermal and oxidative properties were evaluated by TGA analysis. Thermoset exhibits extremely high heat‐resistance and TGA curve in nitrogen shows the temperature of 5% weight loss (Td5) of 695°C and total weight loss at 800°C of 7.1%. TGA shows a high Td5 of 565°C even in air, although the total weight loss at 800°C was 56.1% of the initial weight, much higher than that in nitrogen. The high heat resistance of MTPES was ascribed to crosslinking reaction concerning ethynyl groups. Aging studies performed at elevated temperatures in air on a thermoset showed that MTPES is oxidatively stable to 300°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2488–2492, 2006  相似文献   

4.
In this study, polymer hybrid composites were synthesized by sol‐gel process. 3‐Amino‐propyltrimethoxysilane [APTMS)/γ‐Glycidoxypropyl trimethoxy‐silane (GPTMS); (4, 4′‐Methylene‐dianiline (DDM)] and 1,4‐Bis(trimethoxysilylethyl) benzene (BTB) were added to DGEBA type epoxy resin for anticipated to exhibit excellent thermal stability. Boron trifluoride monoethylamine (BF3MEA) was used as catalyst. The structure of nanocomposites was characterized by attenuated total reflectance (ATR) and solid‐state 29Si NMR which suggest EP‐APTMS‐BTB/EP‐GPTMS‐BTB possesses T3; T1–T0, and T1 structures when the BTB content was lower than 10 wt % and higher 20 wt %, respectively. BF3MEA was proved to be an effective catalyst for the sol‐gel reaction of APTMS, but it could not promote for GPTMS. From TEM microphotographs, EP‐APTMS‐BTB (10 wt %) possesses a dense inorganic structure (particle size around 5–15 nm) compare with the loose inorganic structure of EP‐GPTM‐/BTB (10 wt %). DSC, TGA were use to analyze the thermal properties of the nanocomposites and DMA was used to analyze the dynamic mechanical properties of hybrid composites. The Tgs of all nanocomposites decreased with the increasing BTB content. A system with BTB content lower than 10 wt % showed good dynamic mechanical property and thermal stability (Td5 increased from 336°C to 371°C, char yield increased from 27.4 to 30.2%). The structure of inorganic network affects the Td5 and dynamic mechanical properties of composite. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40984.  相似文献   

5.
A novel bisphthalonitrile containing benzoxazine units (BZ‐BPH) was synthesized via a solventless method from 4,4′‐dihydroxybiphenyl, paraformaldehyde, and 4‐aminophenoxylphthalonitrile. The chemical structure of BZ‐BPH was confirmed by 1H‐NMR and 13C‐NMR analyses. The curing behavior was investigated with DSC, FTIR, TGA, and rheology techniques. The monomer manifested a two‐stage thermal polymerization pattern. The first stage was attributed to the ring‐opening polymerization of benzoxazine moiety, and the second to the polymerization of phthalonitriles. Study about the effect of the catalysts including 4,4′‐diaminodiphenylsulfone and FeCl3 on the polymerization of BZ‐BPH was performed, and the result indicated that the addition of these agents could increase the curing rate and lower the curing temperature. Additionally, the cured product showed excellent thermal and thermo‐oxidative stability, the high char yield was 76.0% by weight at 800°C in nitrogen atmosphere and 81.2% by weight at 600°C in air, and temperature at 5% weight loss (T5%) in nitrogen and air was 477.9°C and 481.7°C, respectively. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

6.
The synthesis and characterization of a novel heat‐resistant boron‐silicon hybrid polymer containing acetylene (PBSA) and its conversion to a highly crosslinked thermoset were discussed. The polymer was synthesized from phenylboron dichloride using Grignard reagent method. The structure of PBSA was characterized by using Fourier transform infrared spectra, 1H‐NMR, 13C‐NMR, and gel permeation chromatography. PBSA was thermosetting, highly heat‐resistant, high‐viscous, orange liquid at room temperature and good solubility in common organic solvents. Differential scanning calorimetry and thermogravimetric analysis analyses showed that the PBSA had excellent thermal and oxidative stability and the temperature of 5% weight loss (Td5) were 650 and 638°C under nitrogen and air, respectively, and the residue at 1000°C were 93.3 and 91.3%, respectively, which indicated that the incorporation of boron and silicon into polymeric backbone was found to improve thermal and oxidative properties. X‐ray diffraction and scanning electron microscope were also used to analyze the formation of pyrolytic products. The results showed that the pyrolysis of PBSA resin was made up of β‐SiC and graphite. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

7.
A novel (main‐chain)‐(side‐chain) vinyl polyperoxide, poly(dipentene peroxide) (PDP), an alternating copolymer of dipentene (DP) and oxygen, has been synthesized by thermal oxidative polymerization of DP. The PDP was characterized by 1H NMR, 13C NMR, FTIR, DSC, TGA, and EI‐MS studies. The overall activation energies of the degradation from Kissinger's method were 28 and 33 kcal/mol, respectively, for the endocyclic and acyclic peroxide units. The side‐chain peroxy groups were found to be thermally more stable than the main chain. Above 45°C the rate of polymerization increases sharply at a particular instant showing an “autoacceleration” with the formation of knee point. The kinetics of autoacceleration has been studied at various temperatures (45–70°C) and pressures (50–250 psi). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1549–1555, 2001  相似文献   

8.
A novel silicon‐containing resin (ESA resin) was successfully synthesized by the condensation reaction of lithium arylacetylide with chlorosilane in high yields. The resin was characterized by the techniques of FTIR, 1H‐NMR, 29Si‐NMR, and gel permeation chromatography. Thermal cure process was monitored by DSC and FTIR methods. This resin could melt at around 100°C and thermally cured at 200–250°C with low exothermal enthalpy. Owing to the high aryl groups containing and the complete crosslinking of ethynyl groups, the cured ESA resin exhibited excellent thermal stability and high char yield. The decomposition temperature $T_{d_5}$ of the cured resin was at 510°C, and the residue yield at 900°C was 82.9% in N2. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

9.
The bisphenols containing methylene spacer were prepared by treating eugenol/2‐allyl phenol with 2,6‐dimethyl phenol/guiacol/o‐cresol in the presence of AlCl3. All the bisphenols were converted to their respective cyanate esters by treating with CNBr. The structural confirmation was done by FTIR, 1H NMR, 13C NMR spectral methods, and elemental analysis. Thermal characterization was done by DSC and TGA. DSC transition shows that the Tg is in the range of 208–239°C. The Tg is highest for the cyanate ester Cy(b) with symmetric structure. The Tg of the cured network depends on the length and symmetry of the monomer, Tg being higher for shorter and the para‐substituted monomers. The T10 values are in the range of 364–381°C. The char yield is in the range of 47–53%. From the char yield, the limiting oxygen index (LOI) value was determined, which is used to confirm the flame retardancy of the cyanate ester resins. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  相似文献   

10.
New aromatic diamine containing preformed amide, ether, and methylene; bis-[(4′-aminobenzyl)-4-benzamide] ether (BABE), was synthesized and characterized by FT-IR, NMR, and mass spectrometry. Aromatic–aliphatic polyamides were prepared from BABE with aliphatic/aromatic diacids via Yamazaki’s polymerization. The polyamides were characterized by FT-IR, 1H NMR, inherent viscosity [ηinh], solubility tests, differential scanning calorimetry [DSC], thermogravimetric analysis [TGA], and X-ray diffraction [XRD]. Polyamides had inherent viscosities 0.35–0.84 dL/g, soluble in aprotic polar solvents like N-methyl-2-pyrrolidone, N, N-dimethyl acetamide and dimethyl sulphoxide containing LiCl due to an amorphous to partially crystalline morphology; as XRD patterns indicated. DSC analysis of polyamides showed glass transition temperatures 166–268 °C. Polyamides showed high thermal stability as they did not degrade below 300 °C, had 10% weight loss temperature higher than 375 °C, and the char yields at 900 °C were 22–55%; indicating potential applications as engineering materials.  相似文献   

11.
《Fuel》1987,66(5):697-701
Effects of carbonization conditions on char reactivity in steam gasification were evaluated by a gravimetric method, using 12 coals varying widely in rank, type and source. The carbonization variables examined were
  • 1.(1) heating rate (5–420K min−1) in steam atmosphere;
  • 2.(2) gaseous atmosphere (N2,H2,H2O andCO2);
  • 3.(3) incomplete devolatilization in N2 (final temperature 200–800 °C);
  • 4.(4) quenching of incompletely devolatilized char; and
  • 5.(5) complete carbonization (900–1400 °C).
The char reactivity to steam depended on the kind of coal but was almost independent of the carbonization conditions of heating rate, gaseous atmosphere and quenching at temperatures below ≈ 1000 °C. Carbonization above 1100 °C reduced the char reactivity, for example by a factor of 7 to 10 at 1300 °C compared with 900–1000 °C, depending on the parent coal. The char deactivation brought about by increasing carbonization temperature could be correlated with a decrease in the micropore volume of the char, unless graphitization was significant.  相似文献   

12.
The organic–inorganic hybrid boron‐containing phenol–formaldehyde (BPFR) resin/SiO2 nanocomposites was synthesized in‐situ from boric acid, phenol, and tetramethoxysilane. The structure of BPFR modified and the distributions of silicon element were studied by Fourier‐transform infrared spectroscopy, energy dispersive X‐ray spectrometry, and transmission electron microscope, respectively. The glass transition temperature (Tg) was determined by torsional braid analysis. The results show that silicon element distribution is homogeneous, and the size of nanosilica is about 40–60 nm. The thermal stability and kinetics parameters of thermal degradation were determined by thermogravimetry analysis (TGA). TGA results show that the resin modified has higher heat resistance property when the additive quantity of SiO2 was 3 wt%. The temperature of 5% weight loss is 487.7°C, which is 12.4°C higher than that of common BPFR. The residual ratio of 3 wt% SiO2/BPFR was 62.3% at the temperature of 900°C, which is 11.2% higher than that of common BPFR. The mechanics loss peak Tp of 3% SiO2/BPFR is 33°C higher than common BPFR. Fiberglass‐reinforced BPFR modified by 3 wt% SiO2 has better mechanical and dielectric properties than that of common BPFR. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers  相似文献   

13.
The thermal degradation of graphite and glass-reinforced phenolic insulators have been studied at high temperature by using thermogravimetry analysis (TGA) and Differential Scanning Calorimetry (DSC) analysis. TGA was carried out in a stream of pure nitrogen over temperature range ambient to 900°C and DSC analysis to 500°C. A heating rate of 10°C/min was used for the determination of degradation temperature and heating rates of 5, 10, 20, 30, and 50°C/min were used for the estimation of degradation temperature (Tmax) of the insulator at high temperature service and calculation of activation. Activation energy of phenolic resin was calculated as 356 kJ mol−1 using the Ozawa method. Tmax was determined as 661°C for 20% conversion. The specific heat capacity of graphite phenolic was found as 970 J kg−1 K−1 at 100°C. The half-life of the phenolic resin was determined to be approximately 116.2 s at 3500°C. The thermal analysis has been conducted using transient heat conduction and the in-depth temperature distribution was evaluated along the rocket nozzle. The better insulator thickness, including the safety factor for graphite and E-glass-reinforced phenolics, were calculated as 3 and 2 mm, respectively. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:1877–1883, 1998  相似文献   

14.
A novel acetylene‐ and maleimide‐terminated benzoxazine, 3‐(3‐ethynylphenyl)‐3,4‐dihydro‐2H‐6‐(N‐maleimido)‐1,3‐benzoxazine (MBZ‐apa), was successfully synthesized with N‐(4‐hydroxyphenyl)maleimide, paraformaldehyde, and 3‐aminophenylacetylene. The structure of the benzoxazine is confirmed by FTIR and 1H‐NMR spectroscopies. MBZ‐apa is easily dissolved in common organic solvents. Differential scanning calorimetry (DSC) was used to study thermal cross‐linking behavior of MBZ‐apa. The DSC curve shows only a single exothermic peak due to the oxazine ring‐opening polymerization and the polymerization of the acetylene and maleimide groups occurring simultaneously in the same temperature range. Dynamic mechanical analyses (DMA) reveals that the novel polybenzoxazine exhibits high glass‐transition temperature (Tg) (ca. 348°C). The storage modulus arrives at 4.5 GPa in the range of room temperature to 330°C. The polybenzoxazine exhibits good thermal stability as evidenced by thermogravimetric analysis (TGA). Pyrolysis‐gas chromatography/mass spectrometry (Pyrolysis‐GC/MS) was employed to characterize the polybenzoxazine. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

15.
Imidazole, 2‐methylimidazole and benzimidazole‐blocked aromatic and aliphatic diisocyanates have been prepared and polymerized with pyromellitic dianhydride in the presence of a basic catalyst. The polymers are characterized with FTIR, 1H NMR and 13C NMR spectroscopy and GPC, DSC and TGA. The structure–property relationship of blocked diisocyanates are discussed in terms of molecular weight of the polyimides obtained. Considering the blocking agent, GPC results show that the benzimidazole blocked adduct yields higher molecular weight polymer than the 2‐methylimidazole‐blocked adduct which, in turn, yields higher molecular weight polymer than the imidazole‐blocked adduct. Considering the structure of the isocyanate, the molecular weight of polymer increases from isophorone diisocyanate to hexamethylene diisocyanate and to toluene diisocyanate (TDI). DSC traces of the polymers derived from TDI show glass transitions (Tg) in the temperature range 152–180 °C and the values increase from the polymer based on imidazole‐blocked TDI to 2‐methylimidazole‐blocked TDI and to benzimidazole‐blocked TDI. © 2000 Society of Chemical Industry  相似文献   

16.
A new hybrid polymer electrolyte system based on chemical‐covalent polyether and siloxane phases is designed and prepared via the sol–gel approach and epoxide crosslinking. FT‐IR, 13C solid‐state NMR, and thermal analysis (differential scanning calorimetry (DSC) and TGA) are used to characterize the structure of these hybrids. These hybrid films are immersed into the liquid electrolyte (1M LiClO4/propylene carbonate) to form plasticized polymer electrolytes. The effects of hybrid composition, liquid electrolyte content, and temperature on the ionic conductivity of hybrid electrolytes are investigated and discussed. DSC traces demonstrate the presence of two second‐order transitions for all the samples and show a significant change in the thermal events with the amount of absorbed LiClO4/PC content. TGA results indicate these hybrid networks with excellent thermal stability. The EDS‐0.5 sample with a 75 wt % liquid electrolyte exhibits the ionic conductivity of 5.3 × 10?3 S cm?1 at 95°C and 1.4 × 10?3 S cm?1 at 15°C, in which the film shows homogenous and good mechanical strength as well as good chemical stability. In the plot of ionic conductivity and composition for these hybrids containing 45 wt % liquid electrolyte, the conductivity shows a maximum value corresponding to the sample with the weight ratio of GPTMS/PEGDE of 0.1. These obtained results are correlated and used to interpret the ion conduction behavior within the hybrid networks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1000–1007, 2006  相似文献   

17.
Several boron-containing organosilicon polymers were synthesized from a sodium-coupling reaction of silicon and boron halides with and without alkyl halide in hydrocarbon solvents. The B–Si preceramic polymers were characterized using techniques such as IR, UV, and NMR spectrometry, gel permeation chromatography, elemental analysis, molecular weight measurement, and thermal analyses (TGA, DSC, DTA, and TMA). The chemical structures of the preceramic polymers were postulated based on the analytical results. Black ceramic materials were obtained from the precursor polymers upon thermal degradation at temperatures above 1000°C in an inert atmosphere. The precursor polymers had a ceramic yield of up to 70%. Thermogravimetric analysis of the ceramic material in air at a flow rate of 100 mL/min showed it was stable up to 1000°C with little weight gain or loss. Several methods were used to characterize the ceramic materials: XRD, solid NMR, high-temperature DTA, elemental analysis, and acid digestion. The analyses indicated that the ceramic materials comprised a mixture of silicon carbide (SiC), silicon borides (SiB4, SiB6), and amorphous Si–B–C ceramics, with small amounts of silica and free silicon.  相似文献   

18.
The oxetane‐modified polysiloxane (Oxe‐PSiO) was synthesized via the partial hydrolysis/condensation of tetraethyl orthosilicate (TEOS) and then transesterification reaction with 3‐ethyl‐3‐(hydroxymethyl)oxetane (EHO), and characterized by FT‐IR, 1H NMR, 13C NMR, and 29Si NMR spectroscopy. Using the water/TEOS molar ratios of 0.8–1.2, the number‐average molecular weights and polydispersity indices were obtained by GPC to range from 1.013 to 2.716 g mol?1 and around 2.0, respectively. The viscosity of Oxe‐PSiO prepared from the water/TEOS molar ratio of 1.2 sharply increased to 177,545 cps from 438 cps of that from the molar ratio of 0.8. A series of cationic UV‐curable formulations were prepared by blending the Oxe‐PSiO synthesized with the water/TEOS molar ratio of 1.0 into an commercial oxetane‐based resin, 3,3′‐[oxydi(methylene)]bis(3‐ethyloxetane), in different weight ratios. The photopolymerization kinetics studied by photo‐DSC in the presence of triphenylsulphonium hexafluoroantimonate as a cationic photoinitiator showed that both the maximum photopolymerization rate and final oxetane conversion in the cured film decreased with increasing Oxe‐PSiO loading mainly due to the sharp increase in viscosity. The DMTA and DSC results both indicated the improvement in thermal stability, showing 12 and 13.4°C, respectively, higher Tg for the cured film with 50 wt % Oxe‐PSiO loading compared with the pure polymer. Moreover, the temperatures (T10% and T50%) at the weight loss of 10 and 50% and final char yields measured by TGA increased with increasing Oxe‐PSiO content. After adding 50 wt % Oxe‐PSiO, compared with the pure polymer the T10% increased from 349 to 361°C, while the T50% increased from 409 to 424°C, and with a char yield increase of 8.2% at 800°C. In addition, its greatly increased crosslinking density due to the formation of silica network resulted in the enhancement in pencil hardness from B of the pure polymer to 2H grade. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

19.
This study is focused on structural changes induced by increasing treatment temperature of sol‐gel–derived La2O3?Al2O3?Ga2O3?5B2O3 system. The structure of samples heated for 30 min up to 900°C was investigated by X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and magic‐angle spinning nuclear magnetic resonance (MAS‐NMR) analysis of 27Al, 11B, and 71Ga nuclei. The vitreous structure is preserved inclusively after 800°C treatment, and starting with 850°C the only crystalline phase evidenced in XRD patterns is of LaAl2.03B4O10.54 type, of La(Al,Ga)2.03B4O10.54 composition. The FTIR results point out the presence of BO3, AlO4, and AlO6, and starting with 800°C treatment also of BO4 and AlO5 structural units, but more detailed information related to boron, aluminum, and gallium environments is obtained from the analysis of MAS‐NMR data. These data evidenced in both amorphous xerogels and in crystallized samples a high fraction of penta‐coordinated aluminum and gallium.  相似文献   

20.
Heterocyclic molecules are generally used in the proton conducting membranes as dopant or polymer side group due to their high proton transfer ability. Composite proton conducting membranes based on poly(vinylphosphonic acid) (PVPA) and poly(5‐(methacrylamido)tetrazole) (PMTet) were produced. The homopolymers, prepared from their corresponding monomers, were blended at several mol ratios to obtain the polymer electrolyte membranes. All samples were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), differantial scanning calorimetry (DSC), cyclic voltammetry (CV), and impedance analysis. Besides, the morphology of the membranes was studied by X‐ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). FTIR spectra confirmed the formation of hydrogen bonding network between PVPA and PMTet units. TGA showed that the polymer electrolyte membranes were thermally stable up to ~210°C. CV curves demonstrated the oxidative stability of the samples in 3 V region. In anhydrous conditions, the maximum proton conductivity was determined as 0.06 Scm?1 at 150°C for PMTetP(VPA)4. POLYM. ENG. SCI., 55:260–269, 2015. © 2014 Society of Plastics Engineers  相似文献   

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