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1.
Titanium oxide (TiO2) and zinc oxide (ZnO) composite structured nanoparticles were prepared by combining a sol-gel process and a solvothermal method. Titanium (IV) isoproxide (TTIP), used as a TiO2 precursor, was dissolved in a colloidal ZnO nanoparticle solution synthesized by the sol-gel method, and TiO2 was synthesized via solvothermal synthesis onto the ZnO nanoparticles. The effects of reaction conditions such as pH, reaction temperature, and reaction time on the morphology of the composite nanoparticles and the ultraviolet (UV) absorbance of their polymer composite films were investigated. The UV absorption of the poly(vinyl alcohol) (PVA) composite film with TiO2-coated ZnO nanoparticles was higher than that of the TiO2, ZnO, and ZnO-coated TiO2 composite films. The reaction pH was found to have the strongest influence on the UV absorbance of the PVA/(TiO2/ZnO) composite film. A pH of 7.0, reaction temperature of 250 °C, and reaction time of 24 h were the optimum conditions for UV absorption.  相似文献   

2.
A series of waterborne polyurethanes (WBPU) were prepared from 4,4-dicyclohexylmethane diisocyanate (H12MDI), 2,2-bis(hydroxylmethyl) propionic acid (DMPA), ethylenediamine (EDA), triethylamine (TEA), and triblock glycol [TBG, (ε-caprolactone)4.5-poly(tetramethylene ether) glycol (MW=2000)-(ε-caprolactone)4.5: (CL)4.5-PTMG-(CL)4.5, MW=3000] as a soft segment. Two melting peaks of TBG at about 14°C and 38°C were observed indicating the presence of two different crystalline domains composed of CL and PTMG dominant component. The effect of soft segment content (60–75 wt%) on the colloidal properties of dispersion, and thermal and mechanical properties of WBPU films, the water vapor permeability (WVP) and water resistance (WR) of WBPU-coated Nylon fabrics, and the adhesive strength of WBPU-coated layer and Nylon fabrics was investigated. As soft segment contents increased, the water vapor permeability of WBPU-coated Nylon fabrics increased from 3615 to 4502 g/m2day, however, the water resistances decreased from 1300 to 500 mmH2O.  相似文献   

3.
The inherent properties of rayon fibre have been changed with additional properties through graft copolymerization of acrylamide, AAm, by chemical method using ceric ammonium nitrate/nitric acid, (CAN/HNO3), as a redox initiator and γ-radiation induced mutual method. Reaction conditions such as monomer and initiator concentration, liquor ratio, temperature and time of reaction, amount of radiation dose have been optimized with respect to percentage of grafting. Maximum percentage of grafting (Pg), (40 %) using CAN/HNO3 was obtained at [CAN]=31.92×10?3 moles/l, [HNO3]=79.36×10?2 moles/l, [AAm]=14.07×102 moles/l in 20 ml of H2O at 45 °C within 120 min while in case of radiation induced method, maximum Pg (30 %) was obtained at higher monomer concentration (28.14×10?2 moles/l) and time (180 min) in 10 ml of H2O at room temperature with total dose exposure of 11.178 kGy. The graft copolymers were characterized by FTIR, thermogravimetric and scanning electron micrographic analysis. Swelling behaviour in water, methanol, ethanol, acetone and DMF and dyeing and flame retarding properties of rayon fibre and grafted rayon fibre were investigated. Percent dye uptake (71.8 %) was found to be higher than that observed for the pristine fibre (57.4 %) and the grafted fibre after post phosphorylation reaction showed excellent flame retarding properties.  相似文献   

4.
In the present work, thermogravimetric analysis of 17 organosolv lignin samples was carried out to determine their thermal stability and calculate the kinetic parameters of their pyrolysis. The thermal stability has been estimated by the measurement of the degradation temperature (Td), calculated according to the maximum reaction rate. In addition, degradation temperature at 10% of conversion (T10%) has been obtained in order to compare the initial stability of the samples with Td for all samples. The values of Td are comprised between 262 and 389 °C and the average value is 340 °C. The range for T10% is 251–320 °C and the average value is 270 °C. The ashes content of the samples has been analyzed and all the residues presented values lower than 4 wt%. Kinetic parameters of lignin pyrolysis were calculated by Borchardt–Daniels’ method assuming nth order reaction. The activation energy values obtained are comprised between 17.9 and 42.5 kJ/mol and the average value is 28.1 kJ/mol. These results are in agreement with the bibliography.  相似文献   

5.
Ionic conductivity and mechanical properties of a mixed polymer matrix consisting of poly(ethylene glycol) (PEG) and cyanoresin type M (CRM) with various lithium salts and plasticizer were examined. The CRM used was a copolymer of cyanoethyl pullulan and cyanoethyl poly(vinyl alcohol) with a molar ratio of 1:1, mixed plasticizer was ethylene carbonate (EC) and propylene carbonate (PC) at a volume ratio of 1:1. The conductive behavior of polymer electrolytes in the temperature range of 298∼338 K was investigated. The PEG/LiClO4 complexes exhibited the highest ionic conductivity of ∼10−5 S/cm at 25°C with the salt concentration of 1.5 M. In addition, the plasticized PEG/LiClO4 complexes exhibited improvement of ionic conductivity. However, their complexes showed decreased mechanical properties. The improvement of ionic conductivity and mechanical properties could be obtained from the polymer electrolytes by using CRM. The highest ionic conductivity of PEG/CRM/LiClO4/(EC-PC) was 5.33×10−4 S/cm at 25°C.  相似文献   

6.
Response surface methodology was used to study the alkaline extraction of heteroxylans from maize bran. The ratio volume of alkali/weight of bran and the particle size had no effect on extraction yield, whereas the yield increased significantly with the temperature and time of extraction and the concentration of the alkali. The variation in the yield depended on the nature of the alkali, and empirical second-order models were built to fit the results obtained by extraction with KOH and Ca(OH)2. Comparison of the compositional and structural features of the heteroxylans obtained by extraction with 0·8 m KOH at 85 °C, saturated Ca(OH)2 at 95 °C and 0·5 m KOH at 65 °C with one obtained by industrial lime-cooking of maize kernels showed that all four samples were very similar and that a very high extraction yield (87 %) was achieved.  相似文献   

7.
Thermoplastic polyurethane, based on 4,4′-diphenylmethane diisocyanate and polyether polyol, was degraded by glycol and ethanolamine at 170 °C. Optimum conditions for the glycolysis of thermoplastic polyurethane were investigated by adjusting the ratio of polymer to degradation reagent, glycol to ethanolamine as well as the reaction temperature. The degradation reaction was conducted under nitrogen atmosphere and accelerated by catalysts such as lithium acetate, which was evidenced by lowering the degradation temperature as well as the amounts of degradation reagent. The decomposition products were completely separated into two layers. The upper liquid layer was a polyether polyol, which was characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The present glycolysis procedure allows a simple recycling of the hydroxyl terminated polyol in pure form.  相似文献   

8.
In the polycondensation reaction of polyethyleneterephthalate(PET), Sb2O3 can react effectively as a catalyst, if physically transformed. Sb2O3 powder is transformed into liquid solution by dissolving in ethylene glycol(EG). Homogeneous catalyst is made by mixing this liquid solution with glycols having different solubility. The efficient reaction of PET polymerization is expected by using homogeneous catalyst. PET was synthesized using homogeneous catalysts of 4 wt.% Sb2O3 solution dissolved in glycol[EG, 2,2-bis(4-(2-hydroxyethoxy)phenol)propane(BHPP), neopentyl glycol(NPG), and 1,3-propandiol(PD)]. PET using EG-BHPP(Sb2O3) catalysts shows the highest I.V. within a reaction time of 120 min. In the p-d analysis, PET using EG-BHPP(Sb2O3) catalysts has the fastest propagation rate and slowest degradation rate. EG-BHPP(Sb2O3) catalysts are more efficient than EG(Sb2O3) catalysts and Sb2O3 powder catalysts.  相似文献   

9.
The color degradation of aqueous solutions of six natural red pigment extracts (elderberry, red cabbage, hibiscus, red beet, Opuntia fruits and red cochineal) used commercially as food colorants was investigated at temperatures between 50 and 90 °C. Color degradation was studied in respect to both spectral properties and visual color. The remaining absorbance at 535 nm as a function of the incubation time and temperature was used to quantify the degradation process. Red cochineal was the most thermoresistant extract with a remaining absorbance of 95 % after 6 h at 90 °C. Anthocyanin extracts (elderberry, red cabbage, hibiscus) showed remaining absorbance percentages of 63.8, 46.1 and 26.7, respectively. Betacyanin extracts (red beet, Opuntia fruits) were the most thermosensitive maintaining only 12.5 and 1.7 %, respectively, of the initial absorbance at 535 nm. Applying a first-order kinetic model to the degradation processes, reaction rate constants (k) and half-life periods (t 1/2 ) were calculated. The temperature dependence of the degradation rate constant obeyed the Arrhenius relationship, with activation energies (E a ) ranging between 3.02 and 53.37 kJ?mol?1. The higher activation energy values indicated greater temperature sensitivity. Changes in visual color attributes corroborated the high thermal stability of the red cochineal extract.  相似文献   

10.
A new approach for the synthesis of polymer precursor for quaternary SiBNC fibers is presented. The inexpensive, commercially available reactants n-propylamine (C3H7NH2), trichlorosilane (SiHCl3) and boron trichloride (BCl3) were used in a simple one-step reaction. The reaction mainly involved the co-polymerization between Si-Cl, B-Cl and N-CH2CH2CH3 with C3H7NH2 evaporation. Characterization of synthesized polymer was performed by FT-IR and NMR. The polymer has a relatively linear-chain chemical structure, and could be easily converted into flexible green fibers by melt-spun with diameter of 24 μm. After pyrolysis process at 1000 °C under nitrogen atmosphere, SiBNC ceramic fibers were obtained with a diameter of about 19 μm. Those fibers showed average tensile strength of 1.05 GPa and it remained in the amorphous state up to 1600 °C, which made them as the promising candidates for reinforcements in ceramic matrix composites for hightemperature application.  相似文献   

11.
Jatropha curcas oil (JCO) has a high content of free fatty acids and has been used extensively as a feedstock in biodiesel production. In the present study, the transesterification reaction of JCO to Jatropha curcas methyl ester (biodiesel) was performed in a continuous pulsed loop reactor under atmospheric conditions. The JCO was pre-treated prior to the reaction to reduce the free fatty acid content to below 1% (w/w). The operating parameters of the loop reactor were optimised based on the conversion of the JCO to Jatropha curcas biodiesel and included reaction temperature, molar ratio of oil to MeOH, reaction time and oscillation frequency. The findings show that the highest reaction conversion of 99.7% (w/w) was achieved using KOH catalyst and 98.8% conversion was obtained using NaOCH3 catalyst. The optimal operating conditions were a molar ratio of 6:1, an oscillation frequency of 6 Hz, temperature of 60 °C, feedstock FFA content of 0.5% (w/w) and only 10 min of reaction time. As a commercial commodity, the physical properties of biodiesel were analysed, and they compared well with the characteristics of fossil-based diesel fuel.  相似文献   

12.
For thermal adaptable fabrics, the polyurethane-urea microcapsules containing phase-change materials (PCMs: hexadecane, octadecane and eicosane) were successfully synthesized by interfacial polycondensation using 2,4-toluene diisocyanate (TDI)/poly(ethylene glycol) (PEG400)/ethylene diamine (EDA) as shell monomers and nonionic surfactant NP-12 in an emulsion system under stirring rates of 3,000～13,000 rpm. The mean particle size of microcapsule decreased significantly with increasing the stirring rate up to 11,000 rpm, and then leveled off. The mean particle size increased with increasing the content and molecular weight (eicosane > octadecane > hexadecane) of PCMs at the same stirring rate. The mean particle sizes of microcapsules were found to decrease with increasing the NP-12 content up to 1.5 wt%, and thereafter increased a little. It was found that the melting temperature (Tm) and crystallization temperature (Tc) of three kinds of encapsulated PCMs and their enthalpy changes (ΔHm, ΔHc) increased with increasing PCM contents. The encapsulation efficiencies (Ee) of hexadecane microcapsule linearly increased with increasing the content of hexadecane. It was found that the stable microcapsule containing 50 wt% of hexadecane could be obtained in this study. However, Ee of octadecane and eicosane microcapsules increased with increasing PCM’s contents up to 40 wt%, and then decreased a little. By considering the encapsulation efficiency, it was found that the maximum/optimum contents of octadecane and eicosane microcapsules were about 40 wt%. By the dynamic thermal performance test, it was found that the maximum buffering levels of Nylon fabrics coated with hexadecane, octadecane, and eicosane microcapsules were about ?2.4/+2.9°C, ?3.6/+3.6°C and ?4.0/+4.7°C, respectively.  相似文献   

13.
Cotton fabrics were coated with conducting polypyrrole (PPy) by mist polymerization derived from aqueous solution of pyrrole (Py) with ferric chloride (FeCl3) as oxidant. The polymerization conditions, such as the reaction time and the concentrations of monomer and oxidant, were systematically investigated. The prepared PPy-coated fabrics could keep their temperature at about 24–44 °C when charged by a fixed DC voltage of 1–3 V. The results indicate that these PPy-coated fabrics can be used potentially as heating pads and integrated into the apparel to make the wearer warm enough using a portable battery. Furthermore, such fabrics are more comfortable than the conventional heating pads due to their flexibility and breathability.  相似文献   

14.
The present study investigated the effects of elevated carbon dioxide concentration ([CO2]) and air temperature on the germination of seed bulbils and the seedling vigour of two Chinese yam lines. Plants were grown under two [CO2] levels, ambient and elevated (ambient + 200 μmol mol?1), and two mean air temperature regimes, 22.2 °C (ambient + 1.4 °C) and 25.6 °C (ambient + 5.2 °C). Elevated [CO2] did not affect bulbil germination under both air temperature regimes. During the early growth stage, the dry weight (DW) of leaves, vines, shoots, roots, belowground parts (roots + tubers) and whole plants were higher under elevated [CO2] than ambient [CO2] for both lines under the low- and high-temperature regimes. The values of vigour indexes (index I = germination % × seedling length and index II = germination % × seedling DW) were also higher under elevated [CO2] than ambient [CO2] for both lines. These results indicated that Chinese yam seedlings respond positively to elevated [CO2] during the early growth stage. The above:belowground DW ratios were lower under elevated [CO2] than ambient [CO2] in seedlings with very small new tubers for both yam lines, indicating that elevated [CO2] strongly affected the root growth in the early growth stage. The DWs of post-treatment seed bulbils were higher in the elevated [CO2] under both air temperature regimes. The results showed that Chinese yam used a smaller amount of the reserves in seed bulbils under elevated [CO2] than under ambient [CO2].  相似文献   

15.
The present field experiment was conducted during two consecutive cropping seasons in central Portugal to study the effects of simultaneous elevation of carbon dioxide concentration ([CO2]) (550 μmol mol?1) and air temperature (+2–3 °C) on japonica rice (Oryza sativa L. “Ariete”) yield, crop duration, and SPAD-values across the seasons compared with the open-field condition. Open-top chambers were used in the field to assess the effect of elevated air temperature alone or the combined effect of elevated air temperature and atmospheric [CO2]. Open-field condition was assessed with randomized plots under ambient air temperature and actual atmospheric [CO2] (average 382 μmol mol?1). Results obtained showed that the rice “Ariete” had a moderate high yielding under open-field condition, but was susceptible to air temperature rise of +2–3 °C under controlled conditions resulting in reduction of grain yield. The combined increase of atmospheric [CO2] with elevated air temperature compensated for the negative effect of temperature rise alone and crop yield was higher than in the open-field. SPAD-readings at reproductive stage explained by more than 60 % variation the straw dry matter, but this finding requires further studies for consolidation. It can be concluded that potential increase in air temperature may limit rice yield in the near future under Mediterranean areas where climate change scenario poses a serious threat, but long term field experiments are required.  相似文献   

16.
The hydrolysis of polycarbonate (PC) was studied using ionic liquid [Bmim][Cl] as solvent and catalyst. The effects of reaction temperature, water dosage and [Bmim][Cl] dosage on reaction results were examined. It was showed that the hydrolysis conversion of PC was almost 100 % and the yield of bisphenol A (BPA) was over 95 % under the reaction conditions of temperature 165 °C, time 3.0 h, m([Bmim][Cl]):m(PC)=1.5:1 and n(H2O):n(PC)=10:1. The ionic liquid could be reused for 8 times without obvious decrease in the conversion of PC and yield of BPA. Therefore, an environmental friendly strategy for chemical recycling of PC was developed.  相似文献   

17.
The effect of water activity (aw, 0·85–0·95), temperature (15–30 °C) and incubation period (2–4 weeks) on growth and calorific losses in relation to colonisation by three mycotoxigenic isolates ofAspergillus ochraceuswas studied on maize-based substrates. The calorific losses (kJ) of maize flour due to fungal growth in relation to temperature andawwere quantified and found to be maximal at 20–30 °C (10·52–16·18%, after 4 weeks at 0·95aw), with only slight losses at 0·85aw(0–7·14%), at both 15 and 20 °C. This suggests that growth of mycotoxigenicAspergillusspp. can significantly contribute to nutritional losses of this staple agricultural food. Calorific values correlated inversely with fungal biomass, with the latter being greatest at 0·95awafter both two and four weeks, and maximal at 30 °C. Most of the single, two-, three- and four-way interactions ofaw, temperature, time and isolate had a statistically significant (p<0·01) influence on calorific losses and fungal biomass.  相似文献   

18.
Liquefaction of bagasse and cotton stalks was conducted by using polyhydric alcohols (polyethylene glycol PEG#400 and glycerin) in the presence of sulfuric acid (SA) as a catalyst. The effects of different liquefaction conditions, such as ratio raw material/liquefying solvent, effect of PEG#400/glycerin, acid concentration, liquefaction temperature and time on the liquefaction yield have been investigated. The hydroxyl and acid numbers for some liquefied samples were also determined. The results showed that the minimum residue content was obtained at 1/5 raw material to liquefying solvent. PEG#400 alone is not favoured as liquefying solvent as it gives ∼19% residual content for bagasse and ∼22% for cotton stalks at the optimum studied reaction conditions. Replacing 10% of PEG#400 with glycerin as well as increasing the SA concentration, liquefaction temperature or time, decreased the amount of residue for both bagasse and cotton stalks to less than 10%. The hydroxyl number of the produced polyols slowly decreased from 253 to 223 mg KOH/g on extending the reaction time till 120 min and the residual polyols prevented re-condensation of the liquefied components. It seems that this system can be applied on various types of lignocellulosic agricultural residues.  相似文献   

19.

In this study, the effect of climate change on planting date and growth duration of rainfed wheat in the west and northwest parts of Iran has been investigated. The occurrence of climate change in the region was first evaluated for the base period (1992–2018) using two nonparametric tests of Mann–Kendall and Sen's slope estimator. Then, the climatic parameters of maximum temperature, minimum temperature and precipitation were simulated under RCP4.5 scenario for the period 2019–2039 based on downscaled output data of the Community Climate System Model (CCSM4) using LARS WG software. The growth period was obtained using a linear multiple regression model, which was selected based on R-square and accounted for 87% of its total variation. The results predicted that the average annual temperature will increase by 2 °C, while the average annual precipitation will increase by 30% by the end of 2039. Planting dates were determined based on two indices combining temperature and precipitation for the base and future periods. The results showed that climate change effects at the 2039 horizon will shorten by 18 days the wheat growth period and the appropriate planting time for rainfed wheat will be reduced by 2–19 days.

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20.
低温冷凉区覆膜玉米子粒灌浆速率和产量特征分析   总被引：3，自引：0，他引：3  
在吉林省东部低温冷凉区,通过logistic方程比较覆膜和不覆膜玉米子粒灌浆过程,探讨不同种植方式对玉米子粒灌浆和产量的影响。结果表明,通过覆膜可有效提高地温,促进玉米生育进程,提高玉米灌浆速率,延长灌浆持续时间,显著增加玉米百粒重和产量。通过覆膜,3个品种两年平均产量最高可达11 571 kg/hm~2。平均灌浆速率(R_(mean))和灌浆速率达到最大时的玉米生长量(W_(max)),与玉米百粒重和产量存在显著的正相关关系。  相似文献   

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