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1.
The feasibility of a cellulose thiocarbonate–azobisisobutyronitrile (AIBN) initiation system to induce graft copolymerization of methyl methacrylate (MMA) and other acrylic monomers onto cotton fabric was investigated. Other acrylic monomers were acrylic acid, acrylonitrile, and methyl acrylate. The initiation system under investigation was highly activated in the presence of a metal‐ion reductant or a metal‐ion oxidant in the polymerization medium. A number of variables in the grafting reaction were studied, including AIBN concentration, pH of the polymerization medium, nature of substrate, monomer concentration, duration and temperature of polymerization, and composition of the solvent/water polymerization medium. The solvents used were methanol, isopropanol, 1,4‐dioxane, cyclohexane, benzene, dimethyl formamide, and dimethyl sulfoxide. There were optimal concentrations of AIBN (5 mmol/L), MMA (8%), Fe2+ (0.1 mmol/L), Mn2+ (8 mmol/L), and Fe3+ (2 mmol/L). A polymerization medium of pH 2 and temperature of 70°C constituted the optimal conditions for grafting. The methanol/water mixture constituted the most favorable reaction medium for grafting MMA onto cotton fabric by using the Fe2+–cellulose thiocarbonate–AIBN redox system. MMA was superior to other monomers for grafting. The unmodified cotton cellulose showed very little tendency to be grafted with MMA compared with the chemically modified cellulosic substrate. A tentative mechanism for the grafting reaction was proposed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1261–1274, 2004  相似文献   

2.
The ability of the cupric sulphate-hydrazine hydrate redox system to induce vinyl graft polymerization onto wool fibres was studied under different conditions. The magnitude of grafting is governed by concentrations of cupric ions, hydrazine hydrate and monomer as well as pH and temperature of the polymerization medium. Detailed studies were carried out on grafting of wool with methyl methacrylate though ethyl acrylate and styrene were also used. Cupric ions were also replaced by ferric ions in some experiments. Main conclusions arrived at from these studies are: (a) there are optimal concentrations of cupric ion and hydrazine hydrate, (b) the grafting reaction is more favoured at higher (pH higher than 7) than that at lower pH's (pH less than 5), (c) 70°C constitutes the optimal temperature for grafting, (d) the graft yield increases by increasing methyl methacrylate concentration, (e) replacement of cupric ion by ferric ion lowers the rate of grafting and (f) the highest graft yield is obtained with methyl methacrylate and the lowest with styrene.  相似文献   

3.
Dimethylaniline (DMA)/CuII-induced grafting of methyl methacrylate (MMA) onto wool fibres was studied under different conditions. The grafting reaction was found to be influenced by CuII, DMA, and MMA concentrations as well as polymerization temperature, reaction time, and polymerization medium. While the graft yield increased by increasing the amount of MMA from 100 to 500 mmol/L, maximum grafting occurred at 0.5 mmol/L CuSO4, 10 mmol/L DMA. The graft yield increased by increasing the reaction time from 15 to 150 min and by raising the polymerization temperature from 60 to 80°C. Using dimethylformamide/water and ethyl alcohol/water mixture as a medium for grafting decreased the graft yield, while using isopropyl alcohol/water mixtures increased the graft yield as compared to pure aqueous medium.  相似文献   

4.
The cellulose thiocarbonate, in the fabric from, was treated first with a freshly prepared ferrous ammonium sulphate (FAS) solution. The sotreated fabric formed, with N-bromosuccinimide (NBS), an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other vinyl monomers onto the cotton fabric. The effect of the polymerization conditions the polymer criteria, namely, graft yeild, homopolymer, total conversion, and grafting efficiency, was studied. These polymer criteria were found to depend extensively upon concentrations of the Fe2+ ion (activator), NBS (initiator), and MMA; pH of the polymerization medium, and duration and temperature of polymerization. Based on detailed investigation of these factors, the optimal conditions for grafting were as follows: Fe2+, 1 × 10−3 mol/L; NBS, 1 × 10−2 mol/L; MMA, 4%; pH, 2: polymerization time, 150 min; polymerization temperature, 60°C; material/liquor ratio, 1: 100. Under these optimal conditions, the rates of grafting of different vinyl monomers were in the following sequence: methyl methacrylate ≫ methyl acrylate > acrylonitrile. Other vinyl monomers namely, acrylic acid, and methacrylic acid have no ability to be grafted to the cellulosic fabric using the said redox system. A tentative mechanism for the polymerization reaction is suggested. © 1996 John Wiley & Sons, Inc.  相似文献   

5.
Graft copolymerization of N-methylolacrylamide onto flax/polyester blend fabric using ferrous cellulose thiocarbonate/H2O2 redox system was investigated under different conditions including hydrogen peroxide concentration (1?60 mmol/l), ferrous ammonium sulphate concentration (1?50 mmol/l), N-methylolacrylamide concentration (5?200%, based on weight of sample), polymerization time (10?90 min), temperature (20?50°C), and pH of the medium (1.1?11). The nitrogen content and/or the methylol content were used for calculation of graft yields. Results obtained indicated that graft yields, derived from nitrogen analysis, are higher the greater the H2O2 concentration increases till 40 mmol/l, then level off. On the other hand, graft yields derived from methylol content exhibit maximum value at 10 mmol/l H2O2. The results indicate also that grafting was highly favoured when it was carried out using 1 mmol/l ferrous ammonium sulphate and pH 4.4 at 30°C for 60 min. The apparent activation energy of the copolymerization reaction amounts to 9.74 kJ/mol. Furthermore, the graft yield increases by increasing N-methylolacrylamide concentration within the range studied. The work was further extended to include a comparison between the polymerization efficiencies of the ferrous cellulose thiocarbonate/H2O2 redox system and the ferrous/H2O2 redox system in inducing grafting of N-methylolacrylamide onto flax/polyester blend fabric. For this reason, the two systems were studied with respect to graft yield, homopolymer proportion, total conversion, graft efficiency, and homopolymer efficiency.  相似文献   

6.
The presence of poly(ethylene terephthalate) (PET) fibers during polymerization of methyl methacrylate (MMA) using H2O2 as initiator resulted in a substantial, constant increase in the weight of the fibers after repeated extraction with acetone. Fractional precipitation curves of the extracted PET—MMA polymerization product and a physical mixture of PET and PMMA were different, indicating that the interaction of MMA with PET involved grafting. The magnitude of the latter enhanced considerably by increasing H2O2 concentration up to 30 mequiv/L, then decreased by further increasing H2O2 concentration. There was also an optimal temperature (80°C) for grafting; below or above this temperature, lower grafting was obtained. Similarly, carrying out the polymerization reaction at different pH values revealed that pH7 constituted the optimal. On the other hand, grafting increased upon increase of the methyl methacrylate concentration within the range studied (8–20%). Incorporation of Cu2+ or Fe3+ ions in the polymerization medium caused a decrement in grafting, irrespective of the metallic ion concentrations. Using methylene chloride as a swelling agent for the fibers failed to enhance the susceptibility of the latter toward grafting. On the contrary, tetrachloroethane was quite promising in this regard. The homopolymer formed during grafting was also reported.  相似文献   

7.
The grafting of methacrylic acid (MAA) and other vinyl monomers onto cotton cellulose in fabric form was investigated in an aqueous medium with a potassium peroxydiphosphate–metal ion–cellulose thiocarbonate redox initiation system. The graft copolymerization reaction was influenced by peroxydiphosphate (PP) concentration, the pH of the reaction medium, monomer concentration, the duration and temperature of polymerization, the nature of vinyl monomers, and the nature and concentration of metallic ions (activators). On the basis of a detailed investigation of these factors, the optimal conditions for the grafting of MAA onto cotton fabric with the said redox system were as follows: [Fe2+] = 0.1 mmol/L, [PP] = 2 mmol/L, [MAA] = 4%, pH‐2, grafting time = 2 h, grafting temperature = 70°C, and material/liquor ratio = 1 : 50. Under these optimal conditions, the graft yields of different monomers were in the following sequence: MAA ? acrylonitrile > acrylic acid > methyl acrylate > methyl methacrylate. The unmodified cellulosic fabric (the control) had no ability to be grafted with MAA with the PP–Fe2+ redox system. The percentage of grafting onto the thiocarbonated cellulosic fabric was more greatly enhanced in the presence of iron salts than in their absence. This held true when the lowest concentrations of these salts were used separately. A suitable mechanism for the grafting processes is suggested, in accordance with the experimental results. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1879–1889, 2003  相似文献   

8.
The radiation-induced graft copolymerization of vinyl acetate (VAc) onto ethylene-copropylene rubber (EPR) has been studied in methanol with radiation of cobalt-60. The effects of irradiation dose, dose rate, concentration of monomer, Cu++ concentration, and temperature on the degree of grafting were investigated. The dependence of the initial grafting rate on dose rate, monome, and Cu++ concentration were found to be 1.0, 1.95, and 0.5 order, respectively. The apparent activation energy was calculated to be 49 kJ/mol. Mechanical properties of the grafted polymer were investigated as a function of the grafting percentage. The tensile strength increases and elongation of break decreases with the increase of the degree of grafting in the region of low grafting percentage (≅ 10%). © 1996 John Wiley & Sons, Inc.  相似文献   

9.
Polymerization of allyl methacrylate with nylon 6 using benzoyl peroxide as initiator was carried out under different conditions. The polymer add-on was dependent upon allyl methacrylate and benzoyl peroxide concentrations, polymerization time and temperature as well as addition of metallic salts or organic solvents. The polymer add-on increased by increasing benzoyl peroxide concentration up to 0.5 mmol/l then decreased by further increase in peroxide concentration, whereas it increased as the allyl methacrylate concentration increased from 80 – 300 mmol/l. A polymerization temperature of 85°C constituted the optimal temperature, below or above this temperature resulted in lower polymer add-on. The effect of polymerization time was related to the polymerization temperature, no induction period occured at 95°C in contrast to 15 and 30 minutes at 85°C and 75°C, respectively. The incorporation of Cu+ +ions in the polymerization system improved the magnitude of polymer add-on. A similar situation was encountered with Fe+ + + and Li+ ions. Using a water/organic solvent mixture as a polymerization medium was advantageous in enhancing polymer add-on provided that the organic solvent did not exceed 1% in case of ethanol and isopropanol and 4% in case of methanol.  相似文献   

10.
Graft polymerization of acrylic acid/styrene mixtures on poly(ethylene terephthalate) fibers using H2O2 as initiator was investigated under different conditions including acrylic acid/styrene ratio, monomer mixtures concentration, initiator concentration, polymerization temperature, pH of polymerization medium, addition of metallic salts, and use of solvent/water mixture instead of aqueous medium. It was found that the rate and extent of grafting for acrylic acid/styrene mixtures were much higher than those of single monomers, indicating a synergestic effect. Maximum percent grafting occurred when acrylic acid/styrene mixture at a ratio of 30:70 was used. Increasing the monomer mixture concentration from 2% to 40% was accompanied by a significant enhancement in percent grafting. The latter increased also significantly as the H2O2 concentration increased from 10 to 150 meq/L; a further increase in H2O2 concentration decreased grafting. No grafting took place at 65°C even after 4 h. Raising the polymerization temperature to 75°C expedited grafting; the magnitude of the latter increased by increasing the temperature up to 95°C. Addition of copper sulphate and ferrous ammonium sulphate to the polymerization system offset grafting, the opposite holds true for lithium chloride provided that its concentration does not exceed 15 mmole/L. Methyl alchol/water mixture (20:80) constituted the optimal medium for polymerization. Grafting of acrylic acid/styrene mixtures to poly(ethylene terephtalate) fibers resulted in considerable improvement in moisture regain of the latter.  相似文献   

11.
The effect of composition of graft chains of four types cellulose graft copolymers on the competitive removal of Pb2+, Cu2+, and Cd2+ ions from aqueous solution was investigated. The copolymers used were (1) cellulose‐g‐polyacrylic acid (cellulose‐g‐pAA) with grafting percentages of 7, 18, and 30%; (2) cellulose‐g‐p(AA–NMBA) prepared by grafting of AA onto cellulose in the presence of crosslinking agent of N,N′‐methylene bisacrylamide (NMBA); (3) cellulose‐g‐p(AA–AASO3H) prepared by grafting of a monomer mixture of acrylic acid (AA) and 2‐acrylamido‐2‐methyl propane sulphonic acid (AASO3H) containing 10% (in mole) AASO3H; and (4) cellulose‐g‐pAASO3H obtained by grafting of AASO3H onto cellulose. The concentrations of ions which were kept constant at 4 mmol/L in an aqueous solution of pH 4.5 were equal. Metal ion removal capacities and removal percentages of the copolymers was determined. Metal ion removal capacity of cellulose‐g‐pAA did not change with the increase in grafting percentages of the copolymer and determined to be 0.27 mmol metal ion/gcopolymer. Although the metal removal rate of cellulose‐g‐p(AA–NMBA) copolymer was lower than that of cellulose‐g‐pAA, removal capacities of both copolymers were the same which was equal to 0.24 mmol metal ion/gcopolymer. Cellulose did not remove any ion under the same conditions. In addition, cellulose‐g‐pAASO3H removed practically no ion from the aqueous solution (0.02 mmol metal ion/gcopolymer). The presence of AASO3H in the graft chains of cellulose‐g‐p(AA–AASO3H) created a synergistic effect with respect to metal removal and led to a slight increase in metal ion adsorption capability in comparison to that of cellulose‐g‐pAA. All types of cellulose copolymers were found to be selective for the removal of Pb2+ over Cu2+ and Cd2+. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2034–2039, 2003  相似文献   

12.
Treatment of cotton fabric with carbon disulphide in presence of NaOH resulted in cellulose thiocarbonate. The latter formed a complex when treated with ceric ammonium nitrate (CAN). After being thoroughly washed, the CeIV cellulose thiocarbonate was capable of initiating vinyl graft polymerization onto cotton fabric without homopolymer formation. The graft yield obtained with methyl methacrylate was found to increase by increasing CAN from zero to 50 mmol/l at temperatures from 60 to 80°C. Grafting was greatly favoured at pH 2; alkaline pH offset grafting. Incorporation of up to 7% of methanol, ethanol, or isopropanol in the aqueous polymerization medium enhanced grafting significantly with the certainty that the highest graft yield was obtained with isopropanol; using higher alcohol percentages decreased grafting. The rate of grafting showed an initial fast rate followed by a slower rate; 60 minutes reaction time proved appropriate for grafting irrespective of the condition used. In addition to methyl methacrylate the ability of CeIV-cellulose thiocarbonate to induce grafting of acrylonitrile and acrylamide was also examined. The rate of grafting followed the order methyl methacrylate > acrylonitrile > acrylamide.  相似文献   

13.
The ceric ion-cellulose redox system has been studied for grafting acrylonitrile on cotton fibers. Grafting yields are very high as compared to the persulfate-thiosulfate redox system reported earlier. Traces of copper sulfate in the reaction mixture do not increase grafting yields, unlike the persulfate-thiosulfate system. The high polymerization rate on cotton fibers is shown to be due to the reducing action of cellulose and not to the large surface area of cotton fibers. The Ce+4 consumption during grafting is higher than during oxidation of cellulose, indicating formation of homopolymer during the grafting reaction. Studies on the consumption of Ce+4 by model compounds such as D-glucose and α-methyl-D -glucoside show that the hemiacetal group in D -glucose is responsible for a faster rate of Ce+4 consumption. Formation of a Ce+4-alcohol complex also contributes to the initial fast rate of Ce+4 consumption. Studies on the oxidation of cellulose by Ce+4 indicate that the initial oxidative attack occurs on carbon atom 2, with the formation of a >C?O group. On further oxidation, cleavage of the C2-C3 bond occurs as shown by the presence of glycol aldehyde determined chromatographically. Cellulose-polyacrylonitrile grafts have been isolated by an acetolysis treatment followed by extraction with dimethylformamide. Number-average molecular weights of the isolated fractions are approximately 50,000–55,000. A theoretical method to calculate the number-average molecular weights, based on the PAN and the COOH contents of the grafted cellulose, is described.  相似文献   

14.
Rat liver glutamine synthetase is activated by Mg++ and by Mn++. Optimal activity of the Mg++ activated synthetase occurred at about pH 7.8. The pH optimum of the Mn++ activated enzyme varied from 6.2 at low Mn++concentrations to 4.4 at high Mn++concentrations. α-N-Ethyl-L-glutamine inhibits the synthetase activity. The inhibition is of a mixed type. The synthetase is also inhibited, to a lesser degree, by α-N-propyl-L-glutamine but not by α-N-butyl-L-glutamine.  相似文献   

15.
A novel chelating fiber was prepared by the irradiation‐induced grafting copolymerization of glycidyl methacrylate on polypropylene fiber and consequent amination with diethylenetriamine. The effects of the reaction conditions, such as reaction time, temperature, and monomer concentration, on the degree of grafting were investigated. The optimal conditions for grafting were found to be 3 h, 100°C, and a 50% (v/v) glycidyl methacrylate concentration in tetrahydrofuran solution. This fiber showed good adsorption performance at different concentrations of Hg2+, in particular for trace Hg2+. Under the adsorption conditions of pH = 4, initial concentration = 1000 mg/L, and time = 20 h, the adsorption capacity of the chelating fiber for Hg2+ reached 785.28 mg/g. It completely adsorbed the Hg2+ ions in solution within a short contact time, showing a very high adsorption rate for Hg2+. Furthermore, the chelating fiber also had a high selectivity for mercury, whereas Cu2+ coexisted in different concentrations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

16.
Diethylaminoethyl (DEAE) cottons having different % N were prepared by reacting cotton cellulose in the fabric form with diethylamine hydrochloride at different concentrations in the presence of sodium hydroxide. The modified samples so obtained were subjected to the graft polymerization reaction using methacrylic acid (MAA) as the vinyl monomer and potassium permanganate-citric acid system as the initiator. The percentage of grafting (PG) was found to increase by increasing the % N, indicating that the presence of the DEAE groups in the molecular structure of the cellulose enhances the susceptibility of the latter to grafting. DEAE groups seem to act as additional sites for grafting; and/or, by virtue of their basicity, they interact with the citric acid, thereby creating primary free radicals in the vicinity of the cellulose. As a result, grafting increases, increasing the initiator and monomer concentration, as well as the polymerization time and temperature functions in favor of the PG. It was also disclosed that DEAE cotton-g-poly (methacrylic acid) serves as cationic and anionic ion exchanger by virtue of the presence of both DEAE and carboxylic groups. This was evidenced by the results of a detailed investigation on the ability of the exchanger to adsorb direct and basic dyes as well as Cu2+ ions. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 739–745, 1998  相似文献   

17.
To develop cost effective and eco friendly polymeric materials for enrichment and separation technologies, 1‐vinyl‐2‐pyrrolidone (N‐VP) was graft copolymerized onto cellulose, extracted from pine needles. Optimum conditions have been evaluated for the grafting of N‐VP onto cellulose and at these conditions it was also grafted onto cellulose phosphate, hydroxypropyl cellulose, cyanoethyl cellulose, and deoxyhydrazino cellulose. At the optimum grafting conditions for N‐VP, it was also cografted with maleic anhydride. Kinetics of radiochemical graft copolymerization has been studied and evaluation of the polymerization and grafting parameters as percent grafting, percent grafting efficiency, rate of polymerization, homopolymerization, and graft copolymerization have been evaluated. Graft copolymers have been characterized by elemental analysis, FTIR, and swelling studies. An attempt has been made to study sorption of some metal ions such as Fe2+ and Cu2+ and iodine on select graft copolymers to investigate selectivity in metal ion sorption and iodine sorption as a function of structural aspects of the functionalized graft copolymers to find their end uses in separation and enrichment technologies. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 373–382, 2005  相似文献   

18.
Graft copolymerization of methacrylic acid (MAA) onto cotton fabric using tetravalent ceric ion (CeIV)–cellulose thiocarbonate redox system was investigated under different conditions including pH of the polymerization medium (1–4), ceric sulphate (CS) concentration (4–20 m mole/l), MAA concentration (1%–6%), polymerization time (1/4–2 h) and polymerization temperature (0–70°C). Results obtained indicated that the optimal conditions for MAA grafting onto cotton fabric using the said redox system consisted of: [CS], 20 m mole/l; [MAA], 4%; pH of the medium, 2; time, 2 h; temperature, 60 °C keeping a material-to-liquor ratio at 1:0. Applying optimized conditions to different monomers, namely, acrylic acid (AA), methacrylic acid (MAA), acrylamide (Aam), acrylonitrile (AN), butyl acrylate (BuA), methyl methacrylate (MMA), ethyl methacrylate (EMA) and glycidyl methacrylate (GMA) onto the same substrate, the rates of grafting followed the order:
A scheme for the mechanism of initiation, propagation and termination reactions was proposed.  相似文献   

19.
Cellulose thiocarbonate was prepared by reacting cotton cellulose fabric with carbon disulphide in the presence of sodium hydroxide. The treated fabric formed, with pentavalent vanadium ion, an effective redox system capable of initiating grafting of methyl methacrylate (MMA) and other monomers no+o the cotton fabric. The dependence of grafting on vanadium concentration, pH of the polymerization medium, temperature and duration of grafting, nature and concentration of monomer, and solvent/water ratio was studied. The results indicated that increasing the pentavalent vanadium (Vv) concentration up to 60 mmol/L was accompanied by enhancement in the rate of grafting; the latter was not affected by further increase in Vv concentration. Maximum grafting yield was achieved at pH 2; grafting fell greatly at higher pH. The rate of grafting followed the order: 70° > 60° > 50°C. The graft yield increased significantly by increasing the MMA concentration from 0.5 to 5%. Of the solvents studied, n-propanol and isopropanol enhanced the grafting rate provided that a solvent/water ratio of 5 : 95 was used; a higher solvent ratio decreased the magnitude of grafting. Other solvents, namely, methanol, ethanol, n-butanol, and acetone, in any proportion, decreased the rate of grafting. With the monomer used, the graft yield followed the order: methyl methacrylate > methyl acrylate > methacrylic acid > ethyl methacrylate > acrylic acid. Also reported was a tentative mechanism for vinyl-graft copolymerization onto cotton fabric using cellulose thiocarbonate-Vv. © 1993 John Wiley & Sons, Inc.  相似文献   

20.
The ability of dimethylaniline (DMA)/Cu2+ ion initiator to induce grafting of methyl methacrylate (MMA) onto nylon 6 was investigated under a variety of conditions. It was found that the graft yield is dependent on the concentration of the Cu2+ ion, of DMA, and of MMA. While the graft yield increases as the monomer concentration increases, there are optimal concentrations of DMA and Cu2+ ion. Below or above these concentrations, lower grafting occurred. The type of cupric salt also affects grafting to varying degrees. While the presence of CuSO4 and Cu(NO3)2 accelerates grafting, the presence of CuCl2 offsets the reaction. Increasing the reaction temperature and reaction time favorably influences grafting. Addition of acetic acid enhances grafting, whereas formic acid decreases grafting. Preswelling of nylon with formic acid leaves the susceptibility of nylon toward grafting practically unaltered. Studies of the copolymerization reaction was not confined to the graft yield but was extended to homopolymer formation and total conversion.  相似文献   

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