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1.
Left and right single‐handed helical polysilane (L‐HPS and D‐HPS) and racemic helical polysilane (R‐HPS) were synthesized by the Wurtz‐type coupling reaction. The chiral dichloro(methoxycarbonyl ethyl propyl ether)methylsilane monomers applied in copolymerization were derived from methyl d /l ‐lactate. The obtained polymers were characterized by 1H and 13C nuclear magnetic resonance, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy, circular dichroism spectroscopy, gel permeation chromatography and X‐ray diffraction. Infrared emissivity (IRE) values were also investigated. Compared to R‐HPS, L‐HPS, and D‐HPS, a pair of mirror image, showed higher crystallinity, better thermal stability, and lower IRE (8–14 mm) at the values of 0.592 and 0.576, respectively. The higher regular secondary structure of HPSs was attributed to the formation of intermolecular hydrogen bonds. To further study the configurations of L‐HPS, D‐HPS, and R‐HPS, rotational isomeric state scheme with molecular dynamics simulation have been utilized. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46335.  相似文献   

2.
Serine‐based monosubstituted acetylene monomers were synthesized and polymerized with rhodium zwitterion catalyst in THF to afford optically active polyacetylene derivatives (LPA and DPA) and corresponding racemic polyacetylenes (RPA) with moderate molecular weights in good yields. All of the substituted polyacetylenes (SPA) were characterized by FT‐IR, NMR, GPC, UV‐Vis spectroscopy, circular dichroism (CD) spectroscopy, and TGA. LPA and DPA were soluble in common organic solvents and possessed single‐handed helical conformation according to their intense Cotton effect and large specific rotations, while RPA presented random coiled polymer chain. The characterization results showed that helical structure of these SPAs was stabilized by intra‐ and intermolecular hydrogen bonding between the substituents which played a significant role in creating and maintaining the helix. Further, the infrared emissivity properties of them at wavelength of 8 to 14 μm were investigated at room temperature. Consequently, the LPA and DPA exhibited lower infrared emissivity values than RPA, which came down to 0.632 and 0.616. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41210.  相似文献   

3.
Helical polyurethane-imide with optical activity based on R-1,1′-binaphthyl-2′,2-diol (R-BINOL) and racemic polyurethane-imide (racemic-PUI) based on racemic 1,1′-binaphthyl-2′,2-diol (racemic-BINOL) were synthesized by hydrogen transfer addition polymerization procedure and characterized by 1H NMR spectra, Fourier Transform Infrared Spectroscopy (FT-IR), thermal Fourier transform infrared spectroscopy (thermal FT-IR), X-ray diffraction (XRD), circular dichroism (CD) spectroscopy and thermogravimetric analysis (TGA). R-PUI exhibits the single-handed helical conformation and optical activity via CD spectra analysis. The optical rotation of R-PUI is +55.0°, which is larger than that of R-BINOL. The thermal stability of R-PUI is higher than that of racemic-PUI by TG analysis. According to the FT-IR and thermal FT-IR analysis, R-PUI with single-handed conformation possesses prominently interchain hydrogen bonds interactions, which plays an important role in thermal stability and optical activity.  相似文献   

4.
Novel optically active polyurethanes (BPUs) based on chiral 1,1′‐binaphthol were synthesized via direct hydrogen transfer addition polymerization. The polymers were analyzed by FTIR, 1H NMR, DSC‐TGA, CD spectra.The results showed that the specific rotation [α]25D were ?78.0° and +54.6° for the S‐BPU and R‐BPU respectively, and these polymers showed better thermal stability. The circular dichroism spectra of the chiral polymers were almost identical except that they gave opposite signals at each wavelength, and the infrared emissivity values of the S‐BPU and R‐BPU were 0.618 and 0.682, they displayed low infrared emissivity. Meantime the polymers implanted with PEG group exhibit better solubility, however thermal stability reduced to some extent. Some properties of the new optically active polyurethanes were reported. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   

5.
The isocyanate‐terminated polyurethane pre‐polymer (PPU) was synthesized via the step‐growth polymerization approach by using polycarbonate diol (PCDL, Mn = 2000) and isophorone disocyanate (IPDI) as monomers, dibutyltin dilaurate (DBTDL) as the catalyst. Subsequently, the hyperbranched polyurethane (HBPU) was synthesized by graft copolymerization using PPU, hyperbranched poly(amide–ester) polyol (HPAE) and 1,4‐butanediol (BDO). The molecular structure of HBPU was characterized by means of FTIR, 1H‐NMR, and 13C‐NMR. It was observed that HBPU was synthesized as anticipated. The thermal and mechanical properties, the microstructure, and morphologies of the filmed HBPU and LPU (linear polyurethane) were tested, respectively. The filmed HBPU, revealed better thermal stability, and higher Tg accompanied with lower viscosity than those of filmed LPU. Additionally, the mechanical experiment showed that the filmed HBPU exhibited enhanced mechanical properties because it contained certain amounts of HPAE. Compared with its linear analog (LPU) specimen, the tensile strength of the filmed HBPU containing 10 wt % HPAE increased by 1.9 times (up to 28.15 MPa), and its elongation at break increased by 1.5 times (up to 543.8%), resulting from the dual effects of the hydrogen bonding and the crosslinking density in the HBPU system. The morphologies of filmed HBPU were characterized by means of WAXD and SEM, which indicated that increasing the content of HPAE lowers the crystallinity of HBPU. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2671–2679, 2013  相似文献   

6.
胡文田  杨荣  许亮  宋艳  李锦春 《化工学报》2015,66(5):1976-1982
以六氯环三磷腈(HCCP)、对羟基苯甲醛及亚磷酸二乙酯等为原料,成功合成了一种反应型磷-氮膨胀阻燃剂六(4-磷酸二乙酯羟甲基苯氧基)环三磷腈(HPHPCP),HPHPCP结构经傅里叶红外光谱(FTIR)、核磁共振(NMR)证实。热失重(TG/DTG)表明HPHPCP具有较高的热稳定性及良好的成炭性,氮气氛下的起始分解温度为162.7℃,800℃时残炭量大于40%(质量分数);利用HPHPCP的羟基结构,应用于硬质聚氨酯泡沫塑料中,可以显著提高聚氨酯硬泡的阻燃性能,添加30%的HPHPCP就可以使聚氨酯氧指数达到27%。  相似文献   

7.
Melamine amino trimethylene phosphate (MATMP) as a novel nitrogen‐phosphorus flame retardant, was synthesized by the reaction of melamine with amino trimethylene phosphonic acid (ATMP) in aqueous solution. The structure of MATMP was characterized by Fourier transform infrared spectroscopy, solid state 31 P nuclear magnetic resonance, and thermogravimetric analysis. Rigid polyurethane (RPU) foams were prepared by one‐shot and free‐rise method, using MATMP as a flame retardant. The flame retardant, mechanical and thermal properties of MATMP in RPU foams were studied. It is found that the RPU foam containing 15 wt % MATMP (sample RPUMA‐15) can pass the UL‐94 V0 test with a limiting oxygen index of 25.5%. The cone calorimeter test results show that the peak heat release rate of RPUMA‐15 is reduced about 34% compared with that of untreated RPU foam. SEM results indicate that the RPU foams with MATMP can form the good and compact char during burning which provides better flame retardancy. The compressive strength of the RPU foams filled with MATMP first increases and then slightly decreases with an increase in the MATMP content comparing with that of untreated RPU foam. Moreover, thermal conductivities of the MATMP filled RPU foams are about 0.03 W/m K. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45234.  相似文献   

8.
Novel optically active and racemic poly(N‐propargylamides) bearing tyrosine pendants (LPT, DPT, and RPT) were synthesized and characterized. The polymers possessed moderate molecular weights and were thoroughly soluble in common organic solvents. The secondary structure of these three polymers in chloroform was studied and the results indicated that LPT and DPT could adopt helical structures with predominantly one‐handed screw sense according to their intense Cotton effect and large specific rotation values, while RPT adopted random coiled polymer chain. The amide groups could form amide‐amide hydrogen bonds to engender the twist of dihedral angle and the strong steric repulsion of phenol groups might have the opposite effect on the helix. The helical structure of the optically active polymers were conclusively constructed and stabilized by the optimization of intra‐ and intermolecular hydrogen bonding and steric repulsion of the side chains. Moreover, the infrared emissivity values of LPT and DPT at 30 °C were 0.682 and 0.671, which were much lower than RPT. LPT and DPT also showed superior heat resistance due to their unique helical conformation. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44824.  相似文献   

9.
《Ceramics International》2020,46(2):2010-2015
Al0.97Y0.03PO4 thermal radiation material was prepared by homogeneous precipitation method. The influences of Y-doping on crystallization behavior, infrared vibration absorption, surface chemical elemental composition, chemical environment, grain size and infrared emissivity property were analysed in detail by X-ray diffraction, X-ray photoelectron spectroscopy, Solid state NMR, Scanning electron micrograph and infrared emissivity spectrometer, respectively. It is found that the doping of Y greatly improves the infrared radiation property and reduces the grain size. Compared with non-doped AlPO4, Al0.97Y0.03PO4 thermal radiation material possesses a higher infrared emissivity of 0.931 ± 0.002, which suggests that it will have a promising application in the field of infrared heating and drying.  相似文献   

10.
An infrared emissivity coating material containing γ-Al2O3 was prepared on 2024 aluminium alloy surface by the microarc oxidation (MAO) method. The microstructure of the coatings was analysed by SEM, XRD and EDS techniques. The infrared emissivity properties tested at 500 °C were investigated by an infrared radiometer based on a Fourier transform infrared spectrometer. The results show that the infrared emissivity values of coated Al samples depend on the phase composition and surface roughness of the coatings. Corresponding to increasing coatings thickness, the gradually increasing γ-Al2O3 content and some oxide compounds containing Si and P contribute to the higher infrared emissivity value (about 0.85) in the wavelength range of 8–20 μm. The increasing surface roughness leads to an obvious increase in emissivity from 0.2 to 0.4 at wavelength 3–5 μm.  相似文献   

11.
Optically active polyacetylene@CdTe Quantum Dots (HPA@CdTe and RPA@CdTe) composites have been prepared based on the surface modification of CdTe quantum dots (QDs). The as-prepared HPA@CdTe and RPA@CdTe were characterized by Fourier-transform infrared spectroscopy, UV–Vis absorption spectra, X-ray diffraction, thermogravimetric analysis, transmission electron microscopy and scanning electron microscopy. The infrared emissivity of HPA@CdTe and RPA@CdTe was also investigated. The results indicate that the polyacetylenes were successfully grafted onto the surfaces of the CdTe QDs without destroying the original crystalline structure of the CdTe QDs. Moreover, the infrared emissivity values of the HPA@CdTe and RPA@CdTe composites were reduced to 0.392 and 0.454, which possess much lower infrared emissivity values than those of the pure polymers and nanoparticles. The results are attributed to interfacial interactions between the organic and inorganic components. Furthermore, the helical conformation may also reduce the infrared emissivity due to the more ordered stereo structure and regular secondary structure.  相似文献   

12.
Chiral amino acid-based monosubstituted acetylene monomers [N-tert-butoxy-carbonyl-l-phenylalanine-N′-propargylamide (LP), and N-tert-butoxycarbonyl-l-serine-N′-propargylamide (LS)] were (co)polymerized with rhodium zwitterion catalyst in THF to afford helical polyacetylenes (PAs) with moderate molecular weights (4400–14,800) in good yields. The optically active PA copolymers were soluble in common organic solvents and proven to adopt predominately single-handed helical conformations according to their intense Cotton effect and large specific rotations. Various contents of amino acid units in side chains facilitated controllable helical secondary structure while the helix was primarily stabilized by hydrogen bonding and steric repulsion between the substituents. Intramolecular hydrogen bonds constructed between hydroxyl and amide groups, in particular, played a significant role in adjusting the helicity and orderliness of the helix. The infrared emissivity values of the PAs at wavelength of 8–14 μm were measured and the correlation between helical conformations and their effect on infrared emission were systematically investigated. The results showed that more well-ordered and compact screw-sense could enhance the performance of organic polymers in lowering their infrared emissivity. Among all the as-prepared PAs, poly(LP50-co-LS50) exhibited the lowest infrared emissivity value (ε25 = 0.632) and possessed excellent resistance against heat.  相似文献   

13.
In order to improve the efficiency of intumescent flame retardant (IFR), bamboo kraft lignin (BKL) was chemically functionalized by grafting melamine (MEL) and diethyl phosphite (DEP) and used for rigid polyurethane (RPU) foam. The BKL, MEL, and DEP in IFR system were used as char forming agent, gas, and acid source, respectively. The FTIR and XPS results indicated that the nitrogen (N) and phosphorus (P) containing BKL was successfully synthesized. The limiting oxygen index (LOI) value of N-BKL and N/P-BKL RPU foams were higher than BKL RPU foam, suggesting that N-BKL and N/P-BKL improved flame retardancy of the foams. The total heat release (THR), heat release rate (HRR), effective heat of combustion (EHC), and fire growth rate (FIGRA) values of N-BKL and N/P-BKL RPU foams were much lower than that of BKL RPU foam. The flame retardancy index value of N/P-BKL RPU foams was higher comparing to N-BKL RPU foam. These results indicated that the synergistic interaction between N containing compound of MEL and P containing compound of DEP led to the improvement flame retardant properties. Comparing to BKL RPU foam, the N/P-BKL RPU foam increased 74°C of maximum weight loss temperature and decreased 18.1 wt% of mass loss, indicating enhanced thermal stability. The morphology of char after cone calorimeter testing showed the N/P-BKL RPU foam presented more continuous and compact char residues, which could reduce heat and mass transfer, protecting underlying materials from further combustion in a fire, thus resulting in good flame retardancy and thermal stability properties. This work suggests a promising route to enhancing the flame-retardant performance of RPU foam using nontoxic and more environmentally friendly grafted bamboo lignin.  相似文献   

14.
Semi-interpenetrating polymer networks (semi-IPN) of linear polyurethane (LPU) and heterocyclic polymer network (HPN) were characterized by IR spectroscopy, small-angle X-ray scattering, differential calorimetry with diathermal shells (temperature interval 130-500 K), and dynamic mechanical analysis (temperature interval 150-500 K and frequency range 0.3-30 Hz). The main results obtained may be summarized as follows: (1) The affinity of HPN towards the soft LPU microphase is responsible for the absence of large-scale heterogeneity of semi-IPNs on their base (at least, at low HPN/LPU ratios). (2) Phenomenological analysis of small-scale, Arrhenius-like subglass relaxations (γ1 and γ2 in LPU and in HPN, respectively) revealed little interference of HPN with relaxation centers (RCs) of LPU in semi-IPNs, while the local environment of RCs in HPN, on the contrary, strongly depended on semi-IPN composition.  相似文献   

15.
《Ceramics International》2023,49(10):14997-15002
The infrared high emissivity ceramic material plays an important role in thermal protection of hypersonic vehicles. LaCrO3, characterized by excellent thermal stability and high emissivity, can be applied as infrared high emissivity material. LaCrO3 and Mg2+ doped LaCrO3 were prepared via solid state reaction method. XRD analyses showed that LaCr1-xMgxO3 (x = 0, 0.1, 0.2, 0.25, 0.3) were single-phase solid solutions. The doping-effect of Mg2+ on the infrared emissivity was investigated. In the range of 2.5–8 μm, the infrared emissivity of all doped materials had significant improvement, the average emissivity of materials increased from 0.66 to 0.83. In the range above 8 μm, the emissivity of all materials had a similar trend and compared to LaCrO3, the emissivity of Mg2+ doped LaCrO3 had little decrease.  相似文献   

16.
《Ceramics International》2022,48(18):26003-26012
In this study, a high-entropy RMgAl11O19 (HE-RMA, R = La, Pr, Nd, Sm, Gd) and LaMgAl11O19 (LMA) coatings were fabricated by atmospheric plasma spraying. The phase composition, microstructure, thermal stability, infrared emissivity performance and shock resistance were comparatively characterized. The results showed that doping multiple rare-earth cations could be conductive to enhance the infrared emissivity. The as-sprayed HE-RMA coating exhibited the highest infrared emissivity, which reached up to 0.971 at 1000 °C. The reason for the improvement of the infrared emissivity was attributed to introduced impurity energy level resulting from doping cations, which could reduce the forbidden bandwidth and increase probability of electronic transition. Meanwhile, HE-RMA coating exhibited better shock resistance at 1100 °C due to superior fracture toughness (1.84 ± 0.41 MPa·m1/2) during thermal cycling test at 1100 °C. In addition, HE-RMA coating still exhibited high infrared emissivity (0.932 at 1000 °C) at 1100 °C annealing for 100 h with only a slight reduction.  相似文献   

17.
AlPO4 based coatings were prepared on Ti‐6Al‐2Zr‐1Mo‐1V titanium alloy using aluminum phosphate as a binder and Al2O3/Cr2O3 based mixing particles as the fillers. The microstructure, phase and chemical composition of the coatings were analyzed by SEM, XRD and EDS techniques. The high temperature infrared emissivity values of coated and uncoated titanium samples were tested. The results show that the coating had a higher infrared emissivity value (>0.8) than titanium substrate (0.15–0.3) in the wide wavelength range of 5–20 mm, which is attributed to the uniform dispersion of high emissivity Al2O3 and Cr2O3 particles in the AlPO4 binder matrix. The coated titanium samples exhibited excellent oxidation resistance performance with significantly decreased oxidation rates at 600 and 800°C. The mass gain of the coated sample kept at a low and stable constant of 0.15 mg/cm2, significantly lower than that of titanium substrate (0.54 mg/cm2) when oxidized at 600°C up to 100 h.  相似文献   

18.
In order to introduce multifunctional properties into flexible cotton fabric, graphene and waterborne anionic aliphatic polyurethane composites were prepared and then deposited on the surface of the fabric substrate through facile pad-dry-cure process. The fabrics thus obtained were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, and their functional properties such as far-infrared emission, electrical conductivity, and ultraviolet (UV) blocking were studied. The coating process enhanced the far-infrared emissivity up to 0.911 in the wavelength range of 4–18 μm. In addition, the ultraviolet protection factor (UPF) of the fabric with 0.8-wt% graphene could reach 500, up to 60-fold higher than that of pristine cotton fabric (UPF 8.19), and its electrical resistivity was decreased from 1.15 × 107 to 2.94 × 10−1 Ω m, which is almost 8 orders of magnitude. The fabrics have also been found to be stable even after 10 cycles of laundering.  相似文献   

19.
《Ceramics International》2020,46(13):20695-20706
In this study, three different vitreous ceramic coatings have been designed to improve radiation heat transfer and thereby increase the thermal efficiency of fired heaters or furnaces working at high temperatures. The vitreous ceramic coatings were produced through Electrophoretic Deposition technique (EPD) of ceramic suspensions. These ceramic formulations were designed based on components which increase emissivity, such as SiO2 and a Black dye (based on chromium, copper and iron oxides), added in 25 wt%. These coatings showed emissivity values around 0.89 at room temperature and around 0.82 at 550 °C in the middle infrared (MIR) spectral range, with slight differences between them. The SiO2 and Black dye additions provide an important protective effect on the coatings’ thermal stability as it was proved by the absorbance level at long times, higher than 85% in the near infrared (NIR) spectral range. These results were also supported by microstructural characterisation, substrate-coatings adhesion strength and thermal stability tests.  相似文献   

20.
《Ceramics International》2019,45(10):13004-13010
In this study, the REO-HfO2 (REO = Tb4O7, Gd2O3 and Sm2O3) coatings and pure HfO2 coatings were prepared by atmospheric plasma spraying. The chemical compositions, morphologies, infrared radiation performance and thermal resistances of the coatings were systematically investigated. The experimental results showed that the Tb4O7-HfO2, Gd2O3-HfO2, Sm2O3-HfO2 and pure HfO2 coatings had infrared emissivity values of 0.863, 0.852, 0.854 and 0.621, respectively, at room temperature. Based on the phase analysis, the higher infrared emissivity of the REO-HfO2 coatings could be attributed to the fact that the newly formed RE2Hf2O7 (RE = Tb, Gd and Sm) phase, which had a defective fluorite-type structure, and the RE3+ ions enhanced the lattice absorption and electron absorption. Additionally, the Tb4O7-HfO2 coating exhibited a relatively higher infrared emissivity than those of the Gd2O3-HfO2 and Sm2O3-HfO2 coating over the wavelength range of 1–15 μm, which was due to the relatively higher vibrational frequency of the TbO bond in RE2Hf2O7 (RE = Tb, Gd and Sm) and the transformation of Tb3+ into Tb4+ in the Tb4O7-HfO2 system. In addition, the REO-HfO2 ceramic coatings exhibited excellent thermal resistance, which could withstand high-temperature treatment at 1600 °C for at least 50 h without undergoing a phase change and exfoliation, and the infrared emissivity at different temperatures hardly changed after thermal treatment.  相似文献   

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