不同引发剂引发纤维素和丙烯酰胺接枝共聚的研究

本文研究了硫酸铈铵,硫酸亚铁/过氧化氢,硫脲/过氧化氢,高锰酸钾引发蔗渣微晶纤维素与丙烯酰胺的接枝聚合。通过上述引发剂的比较,发现高锰酸钾是一种优良的引发剂。探讨了高锰酸钾引发微晶纤维素接枝聚合的反应机理。     

羧甲基纤维素—丙烯酰胺接枝共聚最佳条件的研究

研究了羧甲基纤维素—丙烯酰胺接枝共聚反应,对初始pH值、引发剂用量、单体浓度、初始温度等因素对反应的影响进行了探讨,得到了最佳引发体系:H2SO4-KMnO4以及最佳反应条件:单体浓度30%、引发剂浓度500mg/L、初始温度30℃、初始pH值9。     

糠醛渣纤维素接枝丙烯酰胺的工艺研究

以糠醛渣纤维素为接枝底物,丙烯酰胺(AM)为接枝单体,过硫酸钾(KPS)-亚硫酸氢钠(SBS)为氧化还原引収剂,N,N’-亚甲基双丙烯酰胺(MBAM)为交联剂,制备糠醛渣纤维素/丙烯酰胺接枝共聚物。探讨了反应温度、引収剂用量、丙烯酰胺与糠醛渣纤维素质量比、反应时间对糠醛渣纤维素/丙烯酰胺接枝共聚物接枝率的影响。结果表明,当MBAM用量为0.03 g,丙烯酰胺与糠醛渣纤维素质量比为7∶1,引収剂KPS与SBS的质量比为2∶1,引収剂的用量为0.45 g,反应时间为3.5 h,反应温度为40℃时,接枝率可达到700%。     

淀粉与丙烯酰胺的接枝共聚

本文研究了在硝酸铈铵作用下，淀粉和丙烯酰胺接枝共聚合的反应规律，探讨了引发剂浓度、单体浓度、ｐＨ值、反应时间和反应温度对接枝聚合的影响，并对不同的引发体系引发淀粉—丙烯酰胺接枝聚合进行了比较，结果表明，以硝酸铈铵引发的淀粉—丙烯酰胺接枝聚合所产生的均聚物少，引发效率高。     

纤维素接枝共聚改性的若干途径

纤维素接枝共聚是对纤维素进行改性的重要方法之一。本文综述了迄今用于纤维素接枝共聚改性的若干主要途径，其中包括自由基型接枝共聚，离子型接枝共聚以及缩聚型接枝共聚三大类。     

均相制备纤维素/丙烯酰胺/甲基丙烯酸丁酯接枝共聚物的研究

以氢氧化钠/硫脲/尿素新型溶液溶解纤维素,在均相条件下以丙烯酰胺(AM)、甲基丙烯酸丁酯(BMA)为接枝单体,过硫酸铵为引发剂,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,通过自由基聚合法制备出了纤维素/AM/BMA接枝共聚物。考察了聚合温度、时间以及(NH4)2S2O8、AM、BMA、MBA的用量对接枝效果的影响。利用红外光谱(FT-IR)、X射线衍射(XRD)和扫描电镜(SEM)对接枝产物进行了结构表征。实验结果表明,纤维素/AM/BMA接枝共聚物的最佳合成条件为:m(纤维素)∶m(AM)∶m(BMA)∶m[(NH4)2S2O8]∶m(MBA)=1∶4∶2∶0.05∶0.006,反应温度为65℃,反应时间为2h,在此条件下接枝率可达87%,接枝效率为36%。制备的纤维素/AM/BMA接枝共聚物的吸水倍率为583g/g。     

LiCl/DMAc非水溶液中纤维素均相接枝制备絮凝剂材料

为了使纤维素改性制备表面活性剂,采用LiCl/DMAc溶剂体系,以丙烯酰胺和木材纤维素为原料,进行接枝共聚及阳离子化,合成阳离子型天然高分子改性絮凝剂。讨论了LiCl用量、纤维素用量、单体浓度等因素对接枝产物絮凝性能的影响。通过正交实验确定最佳合成条件为:LiCl用量为6g/50mL,纤维素用量为0·50g/50mL,丙烯酰胺量为2·0g/50mL。产物接枝产率可达到62·74%。     

纤维素接枝共聚研究

本文论述了天然纤维素纤维的生产方法包括铜氨溶液、NMMO及LiCl/极性溶剂等对生态环境和纤维性能的影响 ,重点介绍了纤维素在LiCl/极性溶剂体系中溶解机理及各种溶解条件对溶解性能的影响。对纤维素接枝共聚及其产物也作了相应介绍。     

引发剂对纤维素接枝丙烯酰胺反应的影响

分别以硝酸铈铵、过硫酸钾和过硫酸钾/亚硫酸钠为引发剂,以马尾松漂白硫酸盐浆纸浆纤维素为骨架接枝丙烯酰胺,在单体浓度为0.75 mol/L、温度为45℃、反应时间为3 h时,得到硝酸铈铵和过硫酸钾的最佳浓度为3.0 mmol/L和5.0 mmol/L,过硫酸钾/亚硫酸钠在用量为6%时的最佳质量比为1.5,三者相应的接枝率分别为40%、48%和60%。同时比较了不同条件下三种引发剂的接枝效果,结果表明,过硫酸钾/亚硫酸钠的接枝效果最好,但均聚物含量高;硝酸铈铵作为引发剂虽然接枝效果不及前两者,但均聚物含量很低。     

纤维素接枝反应的研究进展

纤维素是世界上最丰富的天然可再生资源。离子液体是一种新型的绿色溶剂,在纤维素的均相接枝研究中正起着越来越重要的作用。文章介绍了纤维素接枝反应尤其是均相接枝反应的研究进展。     

Graft copolymerization of acrylamide onto cellulose in presence of comonomer using ceric ammonium nitrate as initiator

The graft copolymerization of acrylamide (AAm) and ethylmethacrylate (EMA) monomers onto cellulose has been carried out using ceric ammonium nitrate (CAN) as initiator in presence of nitric acid at (25 ± 1)°C and varying feed molarity from 7.5 × 10^?2 mol dm^?3 to 60.0 × 10^?2 mol dm^?3 at fixed feed composition (f_AAm = 0.6). The graft yield (%G_Y) has shown a linear increasing trend upto a feed molarity of 37.5 × 10^?2 mol dm^?3. The composition of grafted copolymer chains was found to be constant (F_AAm = 0.56) during feed molarity variation but shown variations with feed composition (f_AAm) and reaction temperature. The grafting parameters have shown increasing trends up to 7.5 × 10^?3 mol dm^?3 concentration of ceric (IV) ions and decreased on further increasing the concentration of ceric (IV) ions beyond 7.5 × 10^?3 mol dm^?3. The IR and elemental analysis data were used to determine the composition of grafted chains (F_AAm) and reactivity ratio of acrylamide (r₁) and ethylmethacrylate (r₂) comonomers. The reactivity ratio for acrylamide (r₁) and ethylmethacrylate (r₂) has been found to be 0.7 and 1.0 respectively, which suggested for an alternate arrangement of average sequence length of acrylamide (mM?₁) and ethylmethacrylate (mM?₂) in grafted chains. The rate of graft copolymerization of comonomers onto cellulose was found to be proportional to square concentration of comonomers and square root to the concentration of ceric (IV) ions. The energy of activation (ΔEa) of graft copolymerization was found to be 9.57 kJ mol^?1 within the temperature range of 20–50°C. On the basis of experimental findings, suitable reaction steps have been proposed for graft copolymerization of selected comonomers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2546–2558, 2006     

Ceric(IV) ion‐induced graft copolymerization of acrylamide and ethyl acrylate onto cellulose

Graft copolymerization of acrylamide (AAm) and ethyl acrylate (EA) onto cellulose has been carried out from their binary mixtures using ceric ammonium nitrate (CAN) as an initiator in the presence of nitric acid at 25 ± 1 °C. The extent of acrylamide grafting increased in the presence of the EA comonomer. The composition of the grafted chains (F_AAm = 0.52) was found to be constant during the feed molarity variation from 7.5 × 10^?2 to 60.0 × 10^?2 mol L^?1, whereas the composition of the grafted chains (F_AAm) was found to be dependent on feed composition (f_AAm) and reaction temperature. The effects of ceric(IV ) ion concentration, reaction time and temperature on the grafting parameters have been studied. The grafting parameters showed an increasing trend up to 6.0 × 10^?3 mol L^?1 concentration of CAN at a feed molarity of 30.0 × 10^?2 mol L^?1 and showed a decreasing trend on further increasing the concentration of CAN (>6.0 × 10^?3 mol L^?1) at a constant concentration of nitric acid (5.0 × 10^?2 mol L^?1). The composition of the grafted chains (F_AAm) was determined by IR spectroscopy and nitrogen content and the data obtained then used to determine the reactivity ratios of the acrylamide (r₁) and ethyl acrylate (r₂) comonomers by using a Mayo and Lewis plot. The reactivity ratios of acrylamide and ethyl acrylate were found to be r₁ = 0.54 and r₂ = 1.10, respectively, and hence the sequence lengths of acrylamide (m?M₁) and ethyl acrylate (m?M₂) in the grafted chains are arranged in an alternating form, as the product of the reactivity ratios of acrylamide and ethyl acrylate (r₁ × r₂) is less than unity. The rate of graft copolymerization of the comonomers onto cellulose was found to be dependant on the ‘squares’ of the concentrations of the comonomers and on the ‘square root’ of the concentration of ceric ammonium nitrate. The energy of activation (ΔE_a) of graft copolymerzation was found to be 5.57 kJ mol^?1 within the temperature range from 15 to 50 °C. On the basis of the results, suitable reaction steps have been proposed for the graft copolymerzation of acrylamide and ethyl acrylate comonomers from their mixtures. Copyright © 2005 Society of Chemical Industry     

黄原胶与丙烯酰胺接枝共聚反应的研究

以过硫酸铵为引发剂,在氮气保护下,研究了黄原胶与丙烯酰胺的接枝共聚反应。考察了单体浓度、引发剂浓度、反应温度和反应时间等因素对接枝率及接枝效率的影响,探讨了过硫酸铵引发黄原胶接枝丙烯酰胺共聚反应的基本规律。采用红外光谱、X射线粉末衍射对接枝共聚物的结构进行研究,用热重分析法表征了产物的热性能,并初步探讨了接枝机理。结果表明,过硫酸铵能有效地引发黄原胶与丙烯酰胺的接枝共聚反应,并且接枝率和接枝效率随单体浓度、引发剂浓度、反应温度的变化出现极大值,随反应时间的延长不断上升,直至基本不变。     

微晶纤维素胶体的流变性研究

本文研究了微晶纤维素肢体的流变性质．微晶纤维素肢体为触变性流体，它的贮存稳定性、热稳定性和酸碱稳定性优于羧甲基纤维素．按Ostwade幂方程式算出它的触变系数及按Green－Weltmann方程式算出它的时间融变系数和拆散触变系数都比较大。     

PAE与丙烯酰胺接枝共聚改性的研究

利用溶液聚合的方法，使丙烯酰胺单体与不饱和聚酰胺多胺环氧氯丙烷树脂接枝共聚。在实验过程中，运用单体因素分析的方法，讨论了反应时间、引发剂用量、聚合单体丙烯酰胺的用量等主要因素对接枝共聚反应的影响。接枝后的聚丙烯酰胺树脂除了具有良好的湿拉伸强度性能外，还可以大幅度地提高纸张的干拉伸强度。     

丙烯酰胺/甲基丙烯酸丁酯改性纤维素的研究

以纤维素为基体,丙烯酰胺(AM)、甲基丙烯酸丁酯(BMA)为接枝单体,过硫酸钾为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,聚乙烯吡咯烷酮为分散剂,通过悬浮接枝聚合法制备出了纤维素基吸水吸油材料;考察了单体用量、引发剂用量、反应时间、反应温度及交联剂用量等因素对接枝聚合物的吸水、吸油性能的影响。结果表明:在单体与纤维素的质量比为3.0∶1.0,AM∶BMA的质量比为2.0∶1.0,相对于单体,引发剂质量分数为6.0%,交联剂质量分数为0.5%,分散剂质量分数为0.5%,反应温度为70℃,反应时间为4 h的条件下,得到纤维素-AM-BMA接枝共聚物,其吸油倍率为11.55 g/g,吸水倍率为23.51 g/g,聚合度为534.6。     

Graft copolymerization of acrylic acid on cellulose: Reaction kinetics of copolymerization

Acrylic acid (AA) was grafted to cellulose by using ceric ammonium nitrate (CAN) initiator in aqueous nitric acid solution at 30, 50, 70, and 90°C during reaction periods of 30 to 180 minutes. About 45% of the AA was polymerized at 90°C after 180 minutes. The grafted polymer and homopolymer were isolated by acetone from the reaction mixture, dried, and subjected to Soxhlet extraction with dioxane to separate the homopolymer, poly(acrylic acid), from the graft copolymer. The water absorption capacities and grafting values of grafted cellulose were also determined. The maximum grafting yield was obtained at 30°C. It was also observed that polyacrylic acid-grafted cellulose produced at 30°C had the highest water retention capacity. The time dependence of AA conversion allowed calculation of first-order reaction rate constants. These rate constants were then used to determine apparent activation energies. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 929–934, 1997     

Studies of graft copolymerization of acrylamide onto guar gum using peroxydiphosphate–metabisulphite redox pair

The effect of reaction conditions on the grafting parameter during grafting of acrylamide onto guar gum has been studied using peroxydiphosphate–metabisulphite redox pair at 35 °C. Grafting ratio, efficiency and add‐on all increase as the concentrations of peroxydiphosphate and acrylamide increase up to 40.0 × 10⁻³ mol dm⁻³ and 40.0 × 10⁻² mol dm⁻³, respectively. It has been observed that the optimum concentrations of metabisulphite and guar gum for obtaining high grafting ratio, efficiency, add‐on and conversion are 6.0 × 10⁻³mol dm⁻³ and 91.7 × 10⁻² g dm⁻³, respectively. © 2000 Society of Chemical Industry     

Gamma ray induced graft copolymerization of N-vinylpyrrolidone,acrylamide and their mixtures onto polypropylene films

The radiation initiated grafting of N-vinylpyrrolidone (NVP) acryl-amide (AAm) and their mixtures onto polypropylene (PP) films using a direct radiation technique has been investigated. Different solvents were used for diluting the monomers and it was found that dioxane was suitable for this grafting system. The influence of other grafting parameters such as inhibitor, monomer concentration and dose rate on the rate of grafting and grafting yield was studied. The values of the coefficients relating the grafting rate to monomer concentration and dose rate were found to be 1·4 and 1·5 for (NVP), and 1·6 and 1·47 for (AAm), respectively. Also, the coefficients relating grafting rate to co-monomer concentration for 20/80 and 50/50 AAm/NVP mixtures were found to be 1·6 and 1·7. Some physicochemical properties such as swelling, thermal behaviour, mechanical and electrical conductivity were also investigated, and the possibility of some practical uses, e.g. the removal of heavy metals from solution, for the grafted membranes is discussed. © 1998 SCI.