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1.
Vahid Najafi Farshid Ziaee Kourosh Kabiri Mohammad Jalal Zohouriaan Mehr Hossein Abdollahi Pezhman Mosalla Nezhad Seyed Mehrdad Jalilian Arezu Nouri 《Iranian Polymer Journal》2012,21(10):683-688
Free-radical polymerization of polyethylene glycol methyl ether methacrylate macromer (PEGMEMA) was studied in aqueous media and in the presence of potassium persulfate (KPS) as water soluble initiator. An on-line nuclear magnetic resonance (NMR) method was applied to record the reaction data and determine the monomer conversion at various times during the polymerization reaction progress. 1H NMR spectrum of reaction mixture containing monomer, initiator and resultant polymer was continuously recorded in NMR instrument with the increase of reaction time. By processing the obtained data from NMR spectrum, the rate equation can be derived and reaction order can be determined with regard to monomer and initiator concentration. In other words, to determine the order of polymerization with regard to the concentration of reactants in free-radical polymerization of PEGMEMA, macromer samples with different amounts of monomer and KPS were prepared and polymerized at 50?°C. Orders of reaction with respect to monomer and initiator molar concentrations were equal to 1.025 and 0.480, respectively. The obtained values for reaction orders in this study were consistent with the classical kinetic rate equation in which the dependency of polymerization rate (R p) on monomer and initiator concentrations was equal to 1 and 0.5, respectively. To measure polymerization activation energy (E a), the effect of reaction temperature on the polymerization rate was investigated and E a?=?37.08?kJ/mol was obtained at the temperature range of 40?C50?°C. 相似文献
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采用离子液体1-丁基-3-甲基咪唑四氟硼酸盐([BMIM]BF4)为溶剂,进行了丙烯腈(AN)、丙烯酸甲酯(MA)、衣康酸(ITA)的自由基三元共聚反应的研究。讨论了总单体浓度、引发剂含量、聚合时间、MA含量、ITA含量对共聚物相对分子质量和转化率的影响。结果表明:以离子液体[BMIM]BF4为溶剂,AN、MA和ITA可发生三元共聚,聚合物相对分子质量可达10万以上;且MA的含量可以很低直至为0,对聚合物相对分子质量影响不大;以离子液体为溶剂的共聚物的化学结构与以NaSCN水溶液为溶剂的聚合物的结构相似。 相似文献
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The graft polymerization of acrylic acid (AA) onto corn starch well-swollen in aqueous isopropanol (IPA) was carried out by controlling reaction variables such as the concentrations of AA, initiator (a mixture of ammonium persulfate and sodium metabisulfite) and IPA as well as the temperature and time of reaction for the acquirement of products with good efficiency. Homopoly(acrylic acid) existing in the product mixture was removed by extraction with aqueous ethanol. In the temperature range of 30°C to 60°C the conversion gradually increased with increasing both reaction temperature and reaction time. The graft reaction showed a tendency to give high conversions even at reaction temperatures above 40°C. The reaction in aqueous IPA solution was more homogeneous and efficient than that in water. In addition, even though an equivalent quantity of initiator was used, the reaction conversion increased with increasing the concentration ratio of AA to corn starch. It was also found that the average distance between grafted sites decreased as the quantity of initiator and reaction temperature were increased. 相似文献
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Graft copolymerization of hydroxyethyl methacrylate (HEMA) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (BP) as initiator was carried out in water and in water/organic solvent as a reaction medium. The effect of initiator concentration, reaction time, temperature, and reaction medium as well as addition of FeSO4 to the polymerization medium was studied. Percent grafting was enhanced significantly by increasing BP concentration up to 0.016 mol/L and then decreased upon further increase in initiator concentration. Increasing the monomer (HEMA) concentration up to 0.48 mol/L improves significantly the graft yield. Raising the polymerization temperature up to 85°C causes a significant increase in grafting yield; further increase in temperature leads to decrease in graft yield. Incorporation of Fe+2 ions in the polymerization system decrease the graft yield. The same situation is encountered when water/solvent mixture is used as reaction medium. Solvent employed were methanol, toluene, and benzene. 相似文献
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For free radical oligomerization of styrene, a scheme for calculating the molecular weight distribution and conversion in a continuous-stirred tank reactor (CSTR) train is developed, which also allows the calculation of molecular weight distribution (MWD) for batch reaction. Calculations show that under conventional or near dead-end condition: (1) increasing initial initiator concentration, reaction time and reaction temperature, and decreasing initial monomer concentration cause P?n and P?w to decrease and MWD to narrow; (2) increasing initial initiator concentration, reaction time and reaction temperature, and increasing monomer concentration cause monomer conversion to increase; (3) a single CSTR gives a lower rate of oligomer production, but a narrower MWD than does a batch reactor. 相似文献
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Methyl methacrylate has been polymerized in three-component o/w microemulsions made with the cationic surfactant dodecyltrimethylammonium bromide (DTAB). The effects of temperature type and concentration of initiator (AIBN or potassium persulfate), and surfactant and monomer concentration on polymerization kinetics are investigated. Final conversions and reaction rates increase with increasing monomer and initiator concentrations and with higher reaction temperatures. The rate of polymerization shows initiation and termination intervals, but no constant rate interval is observed. Both molecular weight and particle size decrease as the concentration of initiator increases, regardless of type of initiator. Latexes with small particle size (< 70 nm) and high molecular weights (>106) were obtained in all cases. Activation energies for the microemulsion polymerization of MMA with AIBN (10.3 kcal/mol) and KPS (13.4 kcal/mol) are smaller than that of bulk polymerization using AIBN (20 kcal/mol). © 1993 John Wiley & Sons, Inc. 相似文献
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Poly(methyl methacrylate) in the brush form is grown from the surface of magnetite nanoparticles by ambient temperature atom
transfer radical polymerization (ATATRP) using a phosphonic acid based initiator. The surface initiator was prepared by the
reaction of ethylene glycol with 2-bromoisobutyrl bromide, followed by the reaction with phosphorus oxychloride and hydrolysis.
This initiator is anchored to magnetite nanoparticles via physisorption. The ATATRP of methyl methacrylate was carried out
in the presence of CuBr/PMDETA complex, without a sacrificial initiator, and the grafting density is found to be as high as
0.90 molecules/nm2. The organic–inorganic hybrid material thus prepared shows exceptional stability in organic solvents unlike unfunctionalized
magnetite nanoparticles which tend to flocculate. The polymer brushes of various number average molecular weights were prepared
and the molecular weight was determined using size exclusion chromatography, after degrafting the polymer from the magnetite
core. Thermogravimetric analysis, X-ray photoelectron spectra and diffused reflection FT-IR were used to confirm the grafting
reaction. 相似文献
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Poly(vinylidene fluoride) was grafted with maleic anhydride monomer via a free‐radical mechanism in supercritical carbon dioxide medium. The free‐radical initiator chosen for this study was benzoyl peroxide. The structure of the resultant copolymer pendant groups was determined by 1H NMR spectroscopy to consist of individual succinyl anhydride functional groups. The degree of functionalization (graft level) was obtained by FTIR spectroscopy through the correlation of absorbance bands using standard samples. The FTIR analysis indicated increased graft level with monomer loading, reaction temperature, and treatment time; however, initiator loading and reaction temperature showed more‐complex behavior. Graft levels increased at moderate benzoyl peroxide initiator loadings (5.0 wt%) and decreased at the highest initiator loadings (10.0 wt%). POLYM. ENG. SCI., 45:631–639, 2005. © 2005 Society of Plastics Engineers 相似文献
11.
Atom transfer radical polymerization (ATRP) was used to grow polyacrylamide from the surface of ethylene–acrylic acid copolymer (EAA) film. The surface functionalization constituted initiator immobilization and surface graft polymerization. All reaction steps were conducted at 24 ± 3°C; polymerization was done in aqueous solution. For initiator immobilization, the carboxylic acid groups on EAA film were converted to acid chloride groups; further reaction with ethanolamines gave hydroxyl groups onto which 2‐bromoisobutyryl bromide initiator was attached. ATR‐FTIR data indicated that 1.64 ± 0.09 times higher initiator density was achieved by using diethanolamine, relative to ethanolamine. Acrylamide monomer was polymerized from the initiator by ATRP to yield nondistorted, transparent films with polymerization times of up to 1 h. For films prepared using diethanolamine, 1 h polymerization time reduced the static water contact angle by more than 50°, significantly increasing the hydrophilicity of the film surface. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1589–1595, 2004 相似文献
12.
Mark E. Van Dyke Stephen J. Clarson 《Journal of Inorganic and Organometallic Polymers》1998,8(2):111-117
It is well known that the rate of polymerization for an anionic mechanism is dependent on the ability of the bulk material or solvent system to disassociate the ion pair at the propagating chain end. In the anionic ring-opening polymerization of cyclic organosiloxanes in particular, the larger and softer the counter ion, the more rapidly the reaction proceeds. A recently developed phosphazene initiator system provides a large, soft counter ion relative to other traditional initiators used for the polymerization of poly(dimethylsiloxane) (PDMS). This novel initiator system was used in this investigation for the ring-opening polymerization of tetraphenyltetramethylcyclotetrasiloxane (P4) and the reaction kinetics under bulk and solution conditions were investigated. The new initiator system showed a dramatic increase in the rate of polymerization over the conventional potassium hydroxide-catalyzed system. Furthermore, this initiator was sufficiently reactive to be useful for the ring-opening polymerization of P4 at 293 K. 相似文献
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The free‐radical polymerization of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid (AMPS) in aqueous media and in the presence of potassium persulfate (KPS) as a thermal initiator was studied. The 1H‐NMR method was applied to record the reaction data in online gain. The effects of the monomer and initiator concentrations and also the reaction temperature were studied. The order of reaction with respect to the monomer was much greater than unity (1.94). None of the three theories describing an order of reaction higher than unity could predict the AMPS polymerization mechanism in this study. So, a new mechanism is presented. It is suggested that initiation took place through the formation of a complex between the initiator and monomer, and termination occurred not only by a bimolecular reaction but also by a monomolecular reaction. The order with respect to KPS was 0.49; this was consistent with classical kinetic theory. The determined activation energy at the overall rate of reaction was 92.7 kJ mol?1 K?1. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
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反相乳液共聚淀粉-丙烯酰胺-丙烯酰氧乙基三甲基氯化铵的合成及应用 总被引:1,自引:0,他引:1
以无水亚硫酸钠(Na2SO3)和过硫酸铵【(NH4)2S2O8】为51发剂,通过反相乳液聚合制备了淀粉/丙烯酰胺(AM)/丙烯酰氧乙基三甲基氯化铵(DAC)三元共聚物,讨论了乳化剂种类、引发剂用量、反应温度和反应时间对反应产物的影响,确定了最佳反应条件:选用OP-10与Span-80复配乳化剂,51发剂用量为0.15%,反应温度为35℃,反应时间为5h,在此条件下得到的产物特性粘数为465mL/g。用红外光谱对接枝共聚物的结构进行了表征。对生活污水的应用实验表明,该接枝共聚物有很好的絮凝效果。 相似文献
16.
Two methacrylate-type resin including cyclohexane moiety were synthesized and characterized. The curing characteristics of these resins were investigated according to the change of thermal initiator. An autocatalytic kinetic reaction occurs in these systems, and the kinetic parameters of all systems were reported in terms of generalized kinetic equation that considered the diffusion term. It can be shown that the reaction conversion rate of one methacrylate-type resin (NC-9110-MA) is faster than another resin (EHPE-3150-MA), regardless of the kinds of thermal initiator, which is attributed to the reaction rate constant increases of NC-9110-MA with lower activation energy compared with EHPE-3150-MA. It can be seen that the conversion reaction rate of these resin systems with BPO as thermal initiator at low temperature is higher than those with AIBN. A main factor of reaction conversion rate increase for the NC-9110-MA resin system is a reaction rate constant; however, that for the EHPE-3150-MA resin system is a total reaction order. These resin with BPO as thermal initiator represent a lower cure reaction activation energy and collision frequency factor than those with AIBN. 相似文献
17.
多单体固相接枝聚丙烯 总被引:1,自引:0,他引:1
用乙醚作分散剂,将接枝单体和引发剂均匀分布到聚丙烯(PP)粒子表面,改善相间传质;以偶氮二异丁腈为引发剂,用固相接枝方法制备了丙烯酸丁酯(BA)-马来酸酐(MAH)-苯乙烯(St)接枝PP。考察了接枝单体用量、引发剂用量、反应温度及时间、界面剂用量等对接枝的影响,用傅里叶变换红外光谱仪、热重分析仪和扫描电子显微镜等对接枝产物进行了表征。结果表明:使用分散剂消除了普通固相反应出现的结块现象,接枝单体分布比较均匀;PP为20.0 g时,n(BA)/n(MAH)/n(St)为2:1:1,接枝单体质量分数为6%,引发剂质量分数为0.3%,在80℃反应1.5 h,得到了接枝率为3.48%的接枝产物;产物的拉伸强度没有变化,但极性和热稳定性得到提高。 相似文献
18.
Graft copolymerization of acrylonitrile onto bagasse and wood pulps has been studied using ceric ammonium nitrate as initiator. The effect of order of reactants addition on grafting was examined: three methods were studied. Addition of the pulp to a mixture of initiator and monomer (method A) resulted in more efficient grafting than the other two methods. The reaction produced more grafting at 50°C than at 30°C or at 40°C. The results showed that the monomer and initiator concentrations are the major factors influencing the grafting rate of acrylonitrile. Increasing the acrylonitrile or initiator concentration was accompanied by a substantial increase in graft yields. Increasing the initiator concentration is more effective on polymerization rate than the increase in monomer concentration. The extent of grafting of this monomer can best be controlled by reaction time. Water swelling of pulps significantly affected the grafting rate of acrylonitrile as well as the ceric consumption during grafting. The reactivity of bagasse pulp towards grafting of acrylonitrile is higher than that of wood pulp due to a more open structure of cellulose in bagasse pulp as well as the presence of some lignin which accelerates grafting. Ceric consumption during grafting depends on the nature of the pulp as well as the monomer and initiator concentrations, time, temperature, and the method of grafting. More Ce(IV) is consumed during grafting than during oxidation of the pulps under identical reaction conditions, due to homopolymer formation which accompanied grafting. The ceric consumption by bagasse during grafting or oxidation is somewhat greater than that consumed by wood pulp under similar reaction conditions. 相似文献
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The polymerization of methyl isopropenyl ketone (MIPK) inside low-density polyethylene beads has been studied with lauroyl peroxide as the initiator. The reaction was carried out by first immersing the polymer beads in a liquid solution of MIPK monomer and initiator for 5 h at 55°C and then draining the excess liquid. The temperature of these monomersoaked beads was increased to a reaction temperature (85°C) and the monomer was polymerized in the solid resins. The bulk polymerization of MIPK and the sorption characteristics of MIPK and initiator were also investigated through experimentation and model simulation. It has been observed that the monomer uptake in the solid polymer increased considerably in the presence of the lauroyl peroxide initiator in the liquid phase during the sorption stage. The differential scanning calorimetry study also indicated that some changes in the polymer morphology have occurred due to the incorporation of poly-MIPK into the polyethylene resins. © 1995 John Wiley & Sons, Inc. 相似文献