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1.
Graft copolymerization of granular allyl starch with carboxyl-containing vinyl monomers using H2O2/Fe2+ initiator in aqueous dispersion was investigated for enhancing grafting efficiency of the copolymerization. The graft copolymerization was evaluated in terms of grafting efficiency, grafting ratio, and conversion of monomer to polymer. Influences of both allyl etherification of starch and structures of vinyl monomers used on the copolymerization were revealed. Variables such as molar ratio of Fe2+ to H2O2, initiator concentration, monomer concentration, polymerization temperature, and time of the graft copolymerization were also studied. It was found that allyl etherification of starch enhanced the grafting efficiency and grafting ratio evidently. Acrylic acid exhibited the greatest grafting efficiency and ratio for the copolymerization after starch was allyl-etherified. The copolymerization should be carried out under the protection of nitrogen gas at 30–35 °C for 3 h by using H2O2/Fe(NH4)2(SO4)2 as initiator. Preferred molar ratio of H2O2/Fe(NH4)2(SO4)2/anhydroglucose was in a range of 20/1/1000 to 60/3/2000.  相似文献   

2.
In this study, poly[2-(N, N-dimethyl amino)ethyl methacrylate] (PDMAEMA) was prepared by bulk polymerization using AIBN as an initiator. Aqueous PDMAEMA solution was then purified by hollow fiber ultrafiltration membrane technology to remove oligomers. PDMAEMA/polysulfone (PSF) positively charged nanofiltration (NF) membrane was developed by interfacial polymerization by using PSF ultrafiltration membrane as the substrate, PDMAEMA aqueous solution as the coating solution and p-xylylene dichloride dissolved in n-heptane as the organic crosslinker. Effects of substrate material, concentration of monomer, pH value of PDMAEMA, coating time and crosslinking time were then carefully examined on the separation properties of the prepared NF membrane. Data suggested that the rejection rate of the composite NF membrane to 1 g/l of MgSO4 was around 86.7 %, and the water flux was about 18.4 L·m−2·h−1. Therefore, the developed NF membrane is suitable for rejection and desalination of alkaline dyes.  相似文献   

3.
Functionalized poly(ethylene terephthalate) (PET) fibers were synthesized by grafting of maleic acidmethacrylamide (MAA-MAAm) monomer mixtures by using benzoylperoxide as initiator onto PET fibers in an aqueous medium. The functionalized fibers were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimeter, and scanning electron microscopy. The effects of reaction conditions, such as monomer mixture ratio, monomer mixture and initiator concentration, polymerization time, and temperature on grafting were investigated. In alone grafting of MAA, grafting was not observed. However, the use of MAAm as a comonomer increased the amount of MAA inserted to the PET fiber up to 40.7 %. An increase in the temperature between 75 and 95 °C and also, increase in monomer mixture concentration between 0.50 and 1.00 M increased the grafting rate and saturation graft yield. The graft yield has shown an increase up to an initiator concentration of 1.0×10−2 M and decreased afterwards. The grafting increased the dyeability with disperse, acidic and basic dyes, and water absorption capacity but decreased the thermal stability of the fibers.  相似文献   

4.
Living nature of photoinduced cationic polymerization of isobutyl vinyl ether (IBVE) in the presence of various combinations of diphenyliodonium halide (DPIX), a photocationic initiator and zinc halide (ZnX2) in methylene chloride has been investigated. Attainment of 100 % conversion and a linear relationship between % conversion and number average molar mass of the resulting polymer, strongly suggests the living nature of this system. Livingness of the polymerization system was observed irrespective to the type of halide anion of the initiator and zinc salts unless the reaction temperature is not higher than −30°C. The rate of polymerization decreases in the order of iodide > bromide > chloride when halide salt of DPIX and ZnX2 are used. It is postulated that the cationic initiation is started by the insertion of weakly basic monomer in to the activated C-X terminal of the monomer adduct which is a reaction product of monomer and HX, a photolytic product of DPIX, formed in situ during the photo-irradiation process. It was concluded that polymerization is initiated by the insertion of weakly basic monomer into activated C-X terminal of monomer adduct due to the pulling action of ZnX2, which successively producing a new polarized C-X terminal for the propagation in cationic nature. This led us to a conclusion that the living nature of this cationic polymerization is ascribable to the polarized C-X growing terminal, which is stable enough to depress the processes of chain transfer or termination process.  相似文献   

5.
Statistical copolymers of 2-hydroxy-3-benzophenoxy propyl methacrylate (HBPPMA) and benzyl methacrylate (BzMA) in different feed ratios were synthesized by free radical copolymerization method at 60 °C in presence of AIBN initiator. The compositions of copolymer were estimated from 1H-NMR technique. The monomer reactivity ratios of HBPPMA and BzMA were calculated as r1 (rHBPPMA)=0.51±0.076 and r2 (rBzMA)=1.07±0.140 for Kelen-Tüdos method, and was estimated as r1=0.37±0.0006 and r2=0.64±0.0485 according to Fineman Ross equation. The average values estimated from the two methods showed that monomer reactivity ratio of benzyl methacrylate was a slightly high in comparison to HBPPMA. The copolymer system showed an azeotropic point, which is equal to M BzMA =m BzMA =0.43. DSC measurements showed that the Tg’s of poly(HBPPMA) and poly(BzMA) were 84 °C and 73 °C, respectively. The Tg in the copolymer system decreased with increase in benzyl methacrylate content. The decomposition temperature of poly(BzMA) and poly(HBPPMA) occurs in a single stage at about 207 °C and 260 °C, respectively. Those of HBPPMA-BzMA copolymer systems are between decomposition temperatures of two homopolymers. The dielectric constant, dielectric loss factor and electrical conductivity were investigated depend on the frequency of the copolymers. The highest dielectric constants depending on all the studied frequencies were recorded for the poly(HBPPMA) and the copolymer containing the highest HBPPMA unit. The dielectric constant for P(HBPPMA) and P(BzMA) at 1 kHz are 6.56 and 3.22, respectively. Also, those of copolymer systems were estimated between these two values. Similarly, poly(HBPPMA) and copolymers, which are prepared under the same conditions show the dissipation factor and conductivity as well.  相似文献   

6.
The free radical solution polymerization of acrylonitrile (AN) with itaconic acid (IA) or methyl acrylate (MA) was carried out in dimethylsulfoxide (DMSO) using 2 2'-azobisisobutyronitrile (AIBN) as the initiator. Based on the monomer conversion versus time data, the copolymerization rate was retarded by IA but promoted by MA. The monomer sequence distribution was characterized by 13C NMR to explain the significant difference in the copolymerization kinetics of the ANIA and AN-MA copolymers. The results of the copolymer composition curves and 13C NMR spectral analysis illustrated that the penultimate model was suitable for describing the copolymerization behavior of AN-IA, and the terminal and penultimate models were adequate for AN-MA. The penultimate reactivity ratios, r MA , were ~2 times higher than r IA , indicating that the reactivity of AN-terminated radical having MA as the preceding group was higher than that with IA. Then, the corresponding content of triads sequence AN-AN-AN (AAA) in the AN-MA copolymers was higher than those in the AN-IA copolymers. The appearance of new resonance signals of the quaternary and methyl carbon indicated a higher content of IA in copolymers. The higher IA concentrations the lower viscosity-average molecular weight of the polymers. The decrease in the molecular weight was correlated to the formation of the oligomers.  相似文献   

7.
Polyacrylonitrile copolymer (CPAN) was obtained by water-deposit polymerization, using acrylonitrile (AN), vinyl acetate (VAc), potential crosslinking moiety (hydropropyl acrylate, HQ) as monomer, NaClO3 as initiator. CPAN was blended with cellulose acetate (CA) to prepare CPAN/CA blending fiber via wet spinning. The fiber was post-crosslinked and hydrolyzed to get water absorbency fiber. The structures and properties of the fibers were studied and the results showed that potential crosslinking moiety was necessary in making CPAN/CA blending water absorbency fiber. The saponification reaction was accelerated after blended with CA and the interfacial microvoids enhanced the water absorbency ability.  相似文献   

8.
The poly (8, 11-bis (3, 4-ethylenedioxythiophen-2-yl) acenaphtho [1, 2-b] quinoxaline) (PBEAQ), was synthesized by solid-state polymerization using ferric chloride (III) as an oxidant in high yield. The structure of the monomer and polymer was elucidated by FT-IR, UV-vis absorption spectrum and element analysis. PBEAQ has an [η] value of 0.42 dl g?1 at 25 °C in H2SO4 (w=98 %). The electrochemical performance of PBEAQ was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy with three-electrode cell configuration in acidic (1 M H2SO4), alkaline (6 M KOH) and organic (0.1 M tetraethylammoniumtetrafluoroborate (TEABF4) acetonitrile solution) electrolytic solutions and PBEAQ exhibits good performance in acidic medium.  相似文献   

9.
Poly(n-butyl methacrylate)/poly(methyl methacrylate) polymer networks were synthesized by two-step emulsion polymerization with sodium dodecylsulfonate and polyoxyethylene nonylphenolether as the emulsifier, distilled water as the continuous medium, and potassium persulfate as the initiator. The kinetics of two-step emulsion polymerization was studied. Effects of emulsifier concentration, initiator concentration, and polymerization temperature on monomer conversion and polymerization rate were investigated in detail. Experimental data indicate that both the steady state polymerization rate and monomer conversion increase with the augment of emulsifier concentration, initiator concentration, or reaction temperature.  相似文献   

10.
The new copolymers from different feed compositions of glycidyl methacrylate (GMA) and tetrahydrofurfuryl acrylate (THFA) were synthesized using free radical polymerization in toluene at 70±1 °C using benzoyl peroxide (BPO) as initiator. The polymers were characterized by 1H NMR, 13C NMR and FTIR spectroscopic techniques. The polydispersities of the copolymers suggest a strong tendency for chain termination by disproportionation. The glass transition temperature of the copolymers increases with increase in GMA content. The thermal stability of the copolymers increases with increase in THFA content. The copolymer compositions were determined using 1H NMR analysis. Reactivity ratios for GMA and THFA as determined by the Mao-Huglin method were r1=0.379 and r2=0.266. The results showed that all these copolymerizations are strictly linear systems describable by the Mayo-Lewis equation based on the terminal model and that accurate reactivity ratio data can be obtained.  相似文献   

11.
Graft copolymerization of acrylamide onto commercial acrylic fibers was carried out using benzoyl peroxide as a free-radical initiator in aqueous medium within the 75–95 °C temperature range. In this study, the effects of initiator and monomer concentration, the amount of fiber, polymerization time, and temperature on the graft yield were investigated. The optimum concentration for initiator was found to be 2.0×10−3 mol/l and the optimum temperature of 85 °C. The activation energy of the reaction was calculated to as 35.81 kJ/mol at the temperature interval of 75–95 °C. The structures and morphologies characterization of grafted fibers was investigated by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The thermogravimetric analysis data showed that the thermal stability of the acrylic fibers increased with graft yield. The scanning electron photographs showed that the homogeneous appearance of the fiber surface changed and a shell-like heterogeneous structure occurred at the surface with an increasing degree of grafting. The moisture content, water absorption, dyeability, and antimicrobial activity of grafted acrylic fibers were also reported. The results showed that grafting of polyAAm improved the moisture contain, water absorption, dyeability, and antimicrobial activity of fiber.  相似文献   

12.
The synthesis of poly(norbornene ester)s by using a (η 3-substituted allyl) palladium (N-heterocyclic carbene (NHC)) complex as catalyst was performed and the relationship between chemical structure and glass transition temperature or refractive index of poly(norbornene ester)s was investigated. Norbornene ester monomers were synthesized via esterification of 5-norbornene-2-methyl alcohol and aromatic carboxylic acids. The polymerization catalyst, (η 3-substituted allyl) palladium (NHC) complex, was synthesized according to a published procedure. 1H-NMR spectroscopy was performed to determine chemical structure of monomers and polymers. The molecular weight of the polymers was measured via gel permeation chromatography and the thermal properties were analyzed via thermogravimetric analysis and dynamic mechanical analysis. Refractive indices of polymer films were measured using a prism coupler. Polymers with the highest M n (between 100 kg/mol and 300 kg/mol) were synthesized when the ratio of monomer to catalyst was 2000:1. The glass transition temperature of synthesized polymers was about 100 °C lower than that of conventional norbornene polymers. Among the six polymers of different chemical structures, four polymers exhibited a refractive index of 1.6 or more at a wavelength in the visible light region.  相似文献   

13.
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   

14.
In this study, anionic hydrogels were prepared using a crosslinker (N,N′-methylenebisacrylamide) through a free radical addition reaction in aqueous solutions of neutral acrylamide or 2-hydroxyethyl methacrylate monomer and anionic monomers, mesaconic acid or aconitic acid. Cationic dyes along with safranine (azine-), nile blue (oxazine-) and methylene blue (thiazine-) were selected as models of pollutants, and adsorption of these dyes onto the hydrogels was investigated. To examine the effect of concentration on adsorption, dye solutions prepared with a concentration range of 5–50 mg l?1 and 0.1 g hydrogel at 25 °C were exposed to the hydrogels until equilibrium was established. Dye adsorption onto the hydrogels was found to be an L type Giles adsorption isotherm. Monolayer sorption capacity and adsorption constant values were calculated from the Langmuir plots. To calculate RL values, a non-dimensional analysis was used and they were always found to be 0<R<1. In other words, the hydrogels were favorable for adsorption of these dyes. Aqueous solutions of dyes were observed to interact with hydrogels in the following order: oxazine > azine > thiazine. Furthermore, the higher the number of carboxyl groups in the hydrogel composition, the higher the adsorbed amount of substance.  相似文献   

15.
Yellow mosaic disease (YMD) has been a serious threat to blackgram cultivation especially during post-monsoon season. Visual assessment of disease severity is qualitative and time consuming. Rapid and non-destructive estimation of YMD by hyperspectral remote sensing has not been attempted so far on any of its hosts. Field studies were conducted for two seasons with eight blackgram genotypes having differential response to YMD. Comparison of mean reflectance spectra of the healthy and YMD infested leaves showed changes in all the broad band regions. However, reflectance sensitivity analysis of the narrow-band hyperspectral data revealed a sharp increase in reflectance from the diseased leaves compare to healthy at 669 (red), 505 and 510 nm (blue). ANOVA showed a significant decrease in leaf chlorophyll (p < 0.0001) with increase in disease severity, while no such relationship was observed for relative water content. By plotting coefficients of determination (R2) between leaf chlorophyll and percent reflectance at one nm wavelength interval, two individual bands (R571; R705) and two band ratios (R571/R721; R705/R593) with highest R2 values were selected. These bands showed a significant linear relationship with SPAD chlorophyll readings (R2 range 0.781–0.814) and spectrometric estimates of total chlorophyll content (R2 range 0.477–0.565). Further, the relationship was stronger for band ratios compared to single bands. With optimal spectral reflectance ratios as inputs, disease prediction models were built using multinomial logistic regression (MLR) technique. Based on model fit statistics, reflectance ratios R571/R721 and R705/R593 were found better than the individual bands R571 and R705. Validation of MLR models using an independent test data set showed that the overall percentage of correct classification of the plant into one of the diseased categories was essentially same for both the ratios (68.75%). However, the MLR model using R705/R593 as dependent variable was of greater accuracy as it gave lower values of standard errors for slopes (βG range 9.79–36.73) and highly significant estimates of intercept and slope (p < 0.05). Thus the models developed in this study have potential use for rapid and non-destructive estimation of leaf chlorophyll and yellow mosaic disease severity in blackgram.  相似文献   

16.
An attempt was made to correlate the polymerization temperature and rheological and thermal properties of acrylonitrile (AN)-acrylamide (AM) copolymers. The copolymers were synthesized at different polymerization temperature. The copolymer structure was characterized by gel permeation chromatography (GPC) and Infrared spectrum (IR). The rheological and thermal properties were investigated by a viscometer and differential scanning calorimeter-thermogrametric (DSCTG) analysis, respectively. When the polymerization temperature increased from 41 °C to 65 °C, the molecular weight ([`(M)] w )(\overline M _w ) of copolymers decreased from 1,090,000 to 250,000, while its conversion increased from 18% to 63%, and the polymer composition changed slightly. To meet the requirements of carbon fibers, the rheological and thermal properties of products were also investigated. It was found that the relationship between viscosity and [`(M)] w\overline M _w was nonlinear and the viscosity index (n) decreased from 3.13 to 2.69, when the solution temperature increased from 30 °C to 65 °C. This suggests the dependence of viscosity upon [`(M)] w\overline M _w is higher at lower solution temperature. According to the result of activation energy, the sensivity of viscosity to solution temperature is higher for AN-AM copolymers synthesized at higher polymerization temperature. The result of thermal analysis shows that the copolymers obtained at higher polymerization temperature are easier to cyclization evidenced from lower initiation temperature. The weight loss behavior changed irregularly with polymerization temperature due to irregular change of liberation heat.  相似文献   

17.
以33个不同玉米基因型为材料,在低磷和高磷两个供磷水平下,分析玉米基因型磷效率与多个相对根系性状的关系,建立最优回归方程。结果表明,相对总根重和相对须根数对磷效率的回归系数显著,建立磷效率与相对总根重和相对须根数二者的最优回归模型为Y=-0.224-0.576X2+1.780X3,R2=0.880(p<0.05);相对表层根重对磷效率的回归系数显著,建立磷效率与相对表层根重的最优回归模型为Y=-0.235+1.136X1,R2=0.653(p<0.05);相对须根数和相对表层根重可以作为培育高磷效率玉米基因型的改良目标性状。  相似文献   

18.
In this paper, the morphological transformations in Hibiscus sabdariffa stem fiber on graft copolymerization with acrylonitrile (AN) and its binary mixture with methyl acrylate (MA) and acrylamide (Aam), using ceric ammonium nitrate — nitric acid initiator system has been reported. Different reaction parameters such as temperature, time, initiator concentration, monomer concentration and pH were optimized to get the maximum graft yield (Pg:28.0) and used in binary monomeric mixture to further improve the properties. The graft copolymer thus formed were characterized by FTIR, SEM, XRD, TGA, and DTA techniques. The percentage crystallinity and crystallinity index were found to decrease with increase in percentage grafting. The graft copolymer were found to be moisture, chemical and thermal resistant for various advanced applications.  相似文献   

19.
Polyurethane-poly(2,2,3,3-tetrafluoropropyl acrylate) (PU-PTFPA) triblock copolymer aqueous dispersions were synthesized by three-step polymerization. Infra-red (IR) data verify the copolymerization between PU and TFPA. The properties of copolymer aqueous dispersion and its film cast from the dispersion have been investigated by transmission electron microscopy (TEM), dynamic light scattering (DLS), and some other physical testing methods. TEM observations indicate that the morphologies of copolymer particles formed in water are almost irregular spherical shape with core-shell structure. DLS results verify that the introduction of TFPA monomer changes the average particle size of copolymer particles. The experimental data demonstrate that the factors influencing the properties of PU-PTFPA triblock copolymer aqueous dispersion and its film cast from the dispersion mainly involve PU content, DMPA content and PTFPA content.  相似文献   

20.
Low molecular weight copolymers of maleic anhydride and vinyl acetate were prepared to develop formaldehyde free cross-linking agents. Since lower molecular weight is favorable for efficient penetration of the finishing agent into the cotton fibers in the padding process, the concentration of the initiator, chain transfer agent and the monomer ratios were varied to obtain copolymers of low molecular weights. The prepared polymers were characterized by GPC,1H-NMR, FTIR, DSC and TGA. Copolymers of molecular weights of 2 000 to 10 000 were obtained and it was found that the most efficient method of controlling the molecular weight was by varying the monomer ratios. Poly(maleic anhydride-co-vinyl acetate) did not dissolve in water, but the maleic anhydride residue hydrolyzed within a few minutes to form poly(maleic acid-co-vinyl acetate) and dissolved in water. However, the maleic acid units undergo dehydration to form anhydride groups on heating above 160 °C to some extent even in the absence of catalysts. The possibility of using the copolymers as durable press finishing agent for cotton fabric was investigated. Lower molecular weight poly(maleic anhydride-co-vinyl acetate) copolymers were more efficient in introducing crease resistance, which appears to be due to the more efficient penetration of the crosslinking agent into cotton fabrics. The wrinkle recovery angles of cotton fabrics treated with poly(maleic anhydride-co-vinyl acetate) copolymers were slightly lower than those treated with DMDHEU and were higher when higher curing temperatures or higher concentrations of copolymer were used, and when catalyst, NaH2PO2, was added. The strength retention of the poly(maleic anhydride-co-vinyl acetate) treated cotton fabrics was excellent.  相似文献   

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