辉光放电电解等离子体引发合成聚丙烯酸钠/腐植酸复合高吸水性树脂

以丙烯酸和腐植酸为原料,N,N-亚甲基双丙烯酰胺为交联剂,在水溶液中采用辉光放电电解等离子体引发聚合反应制备聚丙烯酸钠/腐植酸复合高吸水性树脂。 考察了放电电压、交联剂、丙烯酸中和度、后聚合温度、腐植酸钠和丙烯酸的含量对树脂吸水率的影响,讨论了树脂在0.9%氯化钠溶液中的溶胀速率和不同pH值溶液中的溶胀行为。 用红外光谱和热重分析分别对产物进行了结构表征和稳定性测试,结果表明,最佳的合成条件为：放电电压470 V、交联剂质量分数为0.6%、腐植酸钠质量分数为4%、丙烯酸质量分数为10%、中和度60%、后聚合温度70 ℃。 所得复合树脂对蒸馏水的吸水率为1152 g/g,对0.9%NaCl溶液的吸水率为89 g/g,800 ℃后复合树脂残留率为44.3%。     

活性炭复合改善聚丙烯酸凝胶耐盐性及其溶胀机理

在活性炭(Ac)存在的情况下通过自由基溶液聚合,以过硫酸铵为引发剂,N,N′-亚甲基双丙烯酰胺为交联剂,制备了活性炭复合聚丙烯酸凝胶(PAA/AC)。 考察了凝胶在蒸馏水、生理盐水和不同pH值缓冲溶液中的平衡溶胀比以及溶胀动力学,结果表明,活性炭能有效提高凝胶的平衡溶胀比,在实验设计的pH值范围内复合凝胶具有比PAA凝胶更高的平衡溶胀比,蒸馏水和生理盐水中PAA/AC凝胶的平衡溶胀比分别可达到303和60 g/g,约为PAA凝胶的2.4倍。 讨论了凝胶的溶胀机理,结果表明,活性炭成分的介入破坏了聚合物链段之间的聚集态结构,减弱了聚合物链段之间的相互作用,提高了凝胶的溶胀能力。 示差扫描量热仪测定复合前后凝胶的玻璃化转变温度,扫描电子显微镜观察了复合前后凝胶的断面网络结构,结果进一步表明活性炭复合后聚合物链段之间的作用力减弱。     

聚丙烯酸(钾)/凹凸棒吸水剂的制备及性能研究

在凹凸棒存在的情况下,以丙烯酸为单体,以N,N-亚甲基双丙烯酰胺(MBA)为交联剂,过硫酸钾(KPS)为引发剂,采用水溶液聚合法合成了聚丙烯酸(钾)／凹凸棒吸水剂。用TGA和SEM对产物进行了表征。IR分析证实了凹凸棒与丙烯酸发生了接枝共聚反应。研究了引发剂的用量、交联剂的用量和粘土的用量等反应条件对复合吸水剂吸水性的影响。当凹凸棒w=0．10时,复合吸水材料在蒸馏水和生理盐水中的吸水倍数分别大于1200和100。     

P(AMPS-co-HEMA)凝胶的合成与吸银性能研究

以2-丙烯酰胺基-2-甲基丙磺酸(AMPS)和甲基丙烯酸羟乙酯(HEMA)为单体,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,过硫酸钾(KPS)为引发剂,采用自由基水溶液聚合法制备P(AMPS-co-HEMA)共聚凝胶,通过傅里叶红外光谱(FT-IR)对材料结构进行了表征.研究单体配比、交联剂的用量、引发剂的用量对共聚凝胶吸水性能的影响,并在此基础上对凝胶的溶胀、吸银及消溶胀性能进行研究.结果表明,当单体摩尔比n(AMPS)∶n(HEMA)=2∶1,交联剂用量ω(MBA)=0.6％,引发剂用量ω(KPS)=0.8％,所制得的凝胶吸水性能最好;凝胶在蒸馏水中的溶胀过程属于松弛平衡扩散;凝胶在AgNO3溶液中60min左右达到消溶胀平衡,且当AgNO3溶液的浓度为0.05mol/L时,银离子吸附量最大,为0.04g/g,消溶胀速率最快.     

双重交联VSNPs-PAA纳米复合水凝胶的制备及其溶胀性能的研究

采用自由基聚合法合成了乙烯基硅纳米粒子-聚丙烯酸(VSNPs-PAA)双重交联复合水凝胶,考察了交联剂、引发剂、单体以及p H值、温度、盐溶液等对水凝胶溶胀行为的影响。结果表明,引发剂浓度为0.08%,交联剂浓度为0.1%,单体浓度为80%时,合成的水凝胶溶胀性能最大,吸水率达到5000%以上;该水凝胶不仅具有p H值敏感性和p H值变化下良好的反复性,而且在p H4的酸性溶液中表现出温度敏感性,其溶胀率随温度的升高而增大;水凝胶的溶胀率随着盐溶液浓度的增大而减小。     

紫外光聚合法制备棉秆纤维素接枝丙烯酸-腐植酸高吸水树脂及其性能

以丙烯酸(AA)、改性棉秆纤维素(MCSC)和腐植酸(HA)为原料,2,2-二甲氧基-苯基甲酮为引发剂,采用紫外光聚合法制备了降解性复合高吸水树脂(MCSC-g-PAA/HA)。用红外光谱和扫描电镜对产物进行了表征。研究了AA的浓度、MCSC和HA的含量、反应时间和光引发剂的添加量等因素对该树脂溶胀性能的影响。通过测定该树脂的吸水速率和土壤中的保水率及降解性,研究了盐溶液浓度对树脂吸液率的影响。结果表明,在优化条件下,所得树脂在蒸馏水和食盐水(w(NaCl)=0.9%)中的吸液率分别达到870 g/g与94 g/g。     

均相条件下甲壳素基高吸水树脂的制备及性能研究

利用冻融循环处理破坏甲壳素致密的晶体结构和氢键相互作用,使甲壳素溶解在8 wt%NaOH/4wt%urea水溶液中,制备了碱-甲壳素均相溶液.采用静态溶液聚合法,以过硫酸铵(APS)为引发剂、甲叉双丙烯酰胺(MBA)为交联剂,在均相条件下制备了甲壳素接枝聚丙烯酸钠高吸水树脂.研究了丙烯酸、NaOH、MBA和APS用量以及反应温度和时间对产物吸水性能和得率的影响.在最优化条件下制备的树脂的最大吸蒸馏水、自来水、生理盐水和人工尿液倍率分别可达1251,455,84和77 g.g-1.采用FTIR和XRD对合成的树脂进行初步结构表征,证明反应过程中甲壳素与丙烯酸发生了接枝共聚反应,而不是甲壳素与聚丙烯酸钠的简单物理共混.     

超大孔P(AA-co-AM)/PVA水凝胶的制备及吸附性能研究

采用泡沫分散聚合法,以饱和Na2CO3水溶液为发泡剂,过硫酸铵(APS)及NaHSO3为引发剂,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,聚(氧化乙烯/氧化丙烯)(PF127)为泡沫稳定剂,丙烯酸(AA)和丙烯酰胺(AM)为单体,聚乙烯醇(PVA)为第二网络,制备超大孔半互穿水凝胶P(AA-co-AM)/PVA,并研究其对阳离子兰染料的吸附性能。研究表明,P(AA-co-AM)/PVA具有相互贯穿的超大孔结构;当n(AM):n(AA)=1.5:1,w(PVA)=1.6%时凝胶的平衡溶胀度达186.56g/g;凝胶具有很好的离子响应性,在蒸馏水中的平衡溶胀度为129.16g/g时,在0.1mol/L NaCl溶液中只有31.07g/g;对阳离子兰染料溶液的脱色率达92.17%,吸附容量达17.16mg/g。     

PVP-P(AAEA-co-AA)/纳米金温度-电场双重敏感性凝胶的制备及性能

采用溶液聚合法以聚乙烯吡咯烷酮(PVP)为第二网络,以丙烯酸(AA)、4-乙酰基丙烯酰乙酸乙酯(AAEA)为单体制备PVP-P(AAEA-co-AA)半互穿水凝胶(PVP-SIPN),再通过原位还原法合成PVP-P(AAEA-co-AA)/纳米金复合凝胶(GNPs gel),探讨凝胶的溶胀/消溶胀性能、温度及电场敏感性。研究表明,随PVP用量的增加PVP-SIPN溶胀速率减小,平衡溶胀度降低;当PVP用量低于5%凝胶保水率随PVP用量增加而降低,高于5%时保水率随PVP用量增加而增加;PVP-SIPN相转变温度升高,且凝胶温度敏感性随之减弱。纳米金的加入导致凝胶平衡溶胀度从82.3g/g降低至22.66g/g,在电场作用下,外界离子浓度小于0.2mol/L时,GNPs gel发生溶胀;反之,消溶胀,凝胶消溶胀速率随外界电压增大而增大。     

碳纳米管复合聚丙烯酸钠的制备及吸水性能

以过硫酸铵(APS)为引发剂,N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,采用水溶液聚合法制备了碳纳米管/聚丙烯酸钠高吸水树脂。系统考察了碳纳米管质量分数、引发剂、交联剂和聚合温度对树脂吸水性能的影响。结果表明,以单体丙烯酸质量为基准,当交联剂,引发剂和碳纳米管质量分数分别为0.04%、0.3%和0.3%,聚合温度75℃时,所合成树脂的吸水性能最佳。添加碳纳米管后树脂表面粗糙和形成孔结构导致了其吸水性能的变化,使得碳纳米管/聚丙烯酸钠的吸水量和吸水速率明显提高,其吸去离子水和生理盐水能力分别达到1423和104g/g。该树脂重复吸水5次后,其吸水能力为1081.5g/g,达到最大吸水倍数的76.0%。     

Modified chitosan 4. Superabsorbent hydrogels from poly(acrylic acid-co-acrylamide) grafted chitosan with salt- and pH-responsiveness properties

Graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto chitosan was carried out by using potassium persulfate (KPS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The effect of reaction variables, such as MBA concentration and AA/AAm ratio on the water absorbency capacity have been investigated. The polymer structures were confirmed by FTIR spectroscopy. Water absorbencies were compared for the hydrogels before and after alkaline hydrolysis. In the non-hydrolyzed hydrogel, enhanced water absorbency was obtained with increasing AA in monomer feed. However, after saponification, the sample with high AAm ratio exhibited more water absorbency. These behaviors were discussed according to structural parameters. The swelling kinetics of the superabsorbing hydrogels was studied as well. The hydrogels exhibited ampholytic and reversible pH-responsiveness characteristics. The swelling variations were explained according to swelling theory based on the hydrogel chemical structure. The hydrogels exhibited salt-sensitivity and cation exchange properties. The pH-reversibility and on-off switching properties of the hydrogels make the intelligent polymers as good candidates for considering as potential carriers for bioactive agents, e.g. drugs.     

Synthesis and properties of clay-based superabsorbent composite

A novel superabsorbent composites based on acrylic acid, acrylamide, and inorganic clay mineral-attapulgite were synthesized through a solution polymerization to improve water and saline absorbencies. The superabsorbent composite was characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The effects of saline solutions, amount of initiator, crosslinker and attapulgite on the water absorbency of superabsorbent composites were investigated. The water retention test of superabsorbent composites were also carried out. The superabsorbent composite exhibited improved water and saline absorbencies compared with that of crosslinked poly(acrylic acid-co-acrylamide) superabsorbent polymer. The water absorbency of the superabsorbent composite synthesized under optimal synthesis conditions with an attapulgite content of 10% reaches more than 1400 g H₂O/g and 110 g H₂O/g in distilled water and 0.9% NaCl solution, respectively.     

Synthesis,characterization, and swelling behaviors of chitosan‐g‐poly(acrylic acid)/poly(vinyl alcohol) semi‐IPN superabsorbent hydrogels

A series of granulated semi‐interpenetrating polymer network (semi‐IPN) superabsorbent hydrogels composed of chitosan‐g‐poly(acrylic acid) (CTS‐g‐PAA) and poly(vinyl alcohol) (PVA) were prepared by solution polymerization using ammonium persulfate (APS) as an initiator and N,N′‐methylenebisacrylamide (MBA) as a crosslinker. The effects of reaction conditions such as the concentration of MBA, the weight ratio of AA to CTS, and the content of PVA on water absorbency were investigated. Infrared (IR) spectra and differential scanning calorimetry (DSC) analyses confirmed that AA had been grafted onto CTS backbone, and PVA semi‐interpenetrating into CTS‐g‐PAA networks. SEM analyses indicated that CTS‐g‐PAA/PVA has improved porous surface and PVA was uniformly dispersed in CTS‐g‐PAA network. The semi‐IPN hydrogel containing 10 wt% PVA shows the highest water absorbency of 353 and 53 g g^?1 in distilled water and 0.9 wt% NaCl solution, respectively. Swelling behaviors revealed that the introduction of PVA could improve the swelling rate and enhance the pH stability of the superabsorbent hydrogel. Copyright © 2009 John Wiley & Sons, Ltd.     

Sodium alginate-g-poly(acrylic acid-co-2-hydroxyethyl methacrylate)/montmorillonite superabsorbent composite: Preparation,swelling investigation and its application as a slow-release fertilizer

Sodium alginate-g-poly(acrylic acid-co-2-hydroxyethyl methacrylate)/montmorillonite superabsorbent composites (SACs) were prepared by graft copolymerization of acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) onto sodium alginate (Na-Alg) in the presence of montmorillonite (MMT) using N,N′-methylenebisacrylamide (MBA) as a crosslinker and potassium persulfate (KPS) as an initiator in aqueous solution. The composite structures were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), Thermal Gravimetric Analysis (TGA) and Scanning Electron Microscope (SEM). The effect of % initiator, crosslinker amount and clay ratio on the swelling capacity was investigated. The results indicated that the highest swelling capacity of the composites in distilled water was 752 g/g by using 1.25% KPS and 0.06% MBA, 75% AA, 6.25% HEMA and 12.5% Na-Alg. Different samples were loaded with urea to evaluate their release potentials, and the release was studied by measuring the conductivity. The amount of urea release increased with increasing MMT amount.     

Preparation and swelling properties of hydrolysis-resistant superabsorbent composite based on acrylic acid and sodium bentonite

Abstract

A novel hydrolysis-resistant superabsorbent composite was prepared via the solution polymerization based on acrylic acid (AA) and sodium bentonite (SBT) as monomers, tetraallylammonium bromine (TAAB) as crosslinker and ammonium persulfate (APS) as initiator. The mechanism of polymerization and the structure of the superabsorbent polymer (SAP) were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (X-ray), and scanning electron microscopy (SEM). The reaction conditions such as different mass ratios of APS to AA, TAAB to AA, SBT to AA, neutralization degree of AA were optimized by orthogonal experiment, and the influence of each reaction condition on the capacity of water absorption at 150?°C was investigated via single-factor controlled experiment. The hydrolysis resistance and swelling kinetics of the SAP were studied in different solutions at 150?°C. Compared to traditional SAPs, the SAP synthesized with TAAB as crosslinker performed a more excellent hydrolysis resistance and water absorbency capacity at high temperatures. The water absorbency in distilled water or 0.1?mol L^?1 NaCl solution could reach 392.6 and 145.2?g g^?1at 150?°C, respectively. The SAP maintaining high swelling capacity in the pH range of 5–9 indicated its wide application values in the acidic or alkaline environment at high temperature. In addition, the SAP exhibited good reusability which could still retain about 73% of its initial water absorbency after reswelling six times at 150?°C.     

Modified carrageenan 3. Synthesis of a novel polysaccharide-based superabsorbent hydrogel via graft copolymerization of acrylic acid onto kappa-carrageenan in air

A novel biopolymer-based superabsorbent hydrogel was synthesized through chemically crosslinking graft copolymerization of acrylic acid (AA) onto kappa-carrageenan (κC), in the presence of a crosslinking agent and a free radical initiator. A proposed mechanism for κC-g-polyacrylic acid was suggested and the affecting variables onto graft polymerization (i.e. the crosslinker, the monomer and the initiator concentration, the neutralization percent and reaction temperature) were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. Maximum water absorbency of the optimized final product was found to be 789 g/g. The swelling capacity of the synthesized hydrogels was also measured in various salt solutions. The time-temperature profile of the polymerization reaction, in order to investigate the effect of molecular oxygen was conducted in terms of the absence and presence of the atmospheric oxygen. The overall activation energy (E_a) of the graft polymerization reaction was found to be 2.93 KJ/mol.     

丙烯酸与丙烯酰胺共聚制备高吸水性树脂

采用溶液聚合法,以N,N’-亚甲基双丙烯酰胺（NMBA）为交联剂,过硫酸钾（KPS）为引发剂合成了高吸水性树脂聚（丙烯酸-丙烯酰胺）（P（AA—AM））,研究了单体配比、丙烯酸中和度、引发剂及交联剂用量、反应温度对树脂在去离子水和0．9％盐水中吸水率的影响．最佳条件下制备的树脂在去离子水中吸水率为750g·g^-1,在0．9％盐水中吸水率为85g·g^-1．