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.     

PAAM高吸水树脂反相悬浮聚合

采用反相悬浮聚合法,通过部分中和丙烯酸与丙烯酰胺共聚制备了聚(丙烯酸-丙烯酰胺)(PAAM)高吸水树脂,讨论了聚合过程主要影响因素对其吸液性能的影响,并对其进行了FTIR、TGA测试,得到最佳的合成工艺配方:单体质量浓度为30%,中和度N为75%,丙烯酸与丙烯酰胺的摩尔比为7∶3,交联剂、引发剂和分散剂质量浓度分别为0.065%、0.7%和0.5%(相对于单体总质量),单体溶液的滴加速度为2～3mL/min,聚合温度和时间分别为70℃和1.5h。此时在蒸馏水、0.9%NaCl溶液%(wt)中最大吸水倍率分别为Qw=1300g/g、Qs=93g/g(Qw为蒸馏水中吸水倍率,Qs为0.9%NaCl溶液中的吸水倍率,下同),树脂在320℃之前都是比较稳定的,可以适应较高的使用温度。     

淀粉接枝丙烯酸/醋酸乙烯酯高吸水性树脂的制备

以过硫酸铵为引发剂,N,N-亚甲基双丙烯酰胺为交联剂,淀粉与丙烯酸/醋酸乙烯酯混合单体通过接枝共聚,制备了吸水及耐盐性能均较好的淀粉接枝丙烯酸/醋酸乙烯酯高吸水性树脂(CGAV)。最佳工艺条件为:淀粉10.0 g,m(混合单体)∶m(淀粉)=4∶1,w(引发剂)=0.3%,w(交联剂)=0.05%,于45℃反应2h~3 h。在最佳工艺条件下制得的CGAV吸去离子水率760 g.g-1,吸0.9%NaC l水溶液率68 g.g-1。     

丙烯酸稀土接枝剑麻纤维及性能研究

为改善剑麻纤维(SF)与聚合物基界面的相容性,制备了丙烯酸稀土接枝剑麻纤维,并对其结构进行表征。用过硫酸铵作为引发剂,把丙烯酸稀土接枝到剑麻纤维表面上。利用红外光谱仪、扫描电子显微镜、X射线粉末衍射仪对接枝剑麻纤维结构进行表征,结果表明丙烯酸稀土已成功接枝到剑麻纤维表面上。考察了接枝剑麻纤维热稳定性和吸油性能,结果表明接枝剑麻纤维的热稳定性、吸油性能优于剑麻纤维,饱和吸油量(24 h)达5.957 g.g-1,吸油倍率达4.727%。     

两性纳米复合高吸水性树脂的结构与性能

通过丙烯酸钠、阳离子单体丙烯酰氧乙基三甲基氯化铵(DAC)与钠蒙脱土原位溶液聚合成功地制备了具有插层结构的两性纳米复合高吸水性树脂. 其吸水性树脂吸水倍率和凝胶的抗压强度相对于聚丙烯酸钠基质均有较大提高. 吸水倍率最高可达2 380 g/g, 而凝胶的抗压强度提高到基质的180%左右. 由于复合材料结构上具有两性基团, 表现出对环境pH值特殊的应答性. 同时, 阳离子单体DAC的加入影响体系纳米结构的形成.     

部分水解聚(丙烯酸甲酯-乙酸乙烯酯-甲基丙烯酸甲酯)高吸水性树脂的合成及结构研究

研究了部分水解聚(丙烯酸甲酯-乙酸乙烯酯-甲基丙烯酸甲酯)高吸水性树脂-HP(MA-VAc-MMA)的合成,讨论了聚合,水解工艺条件对该树脂吸水(液)性能的影响,用红外,X-射线衍射和电子衍射等方法测定了共聚物的结构。结果表明,HP(MA-VAc-MMA)树脂的吸水能力为:去离子水837ml/g、自来水440ml/g、0.9%NaCl溶液ml/g、合成血119ml/g、合成尿73ml/g;该树脂具有结晶结构,与PVC树脂共混可制备吸水膨胀性材料。     

多孔壳聚糖接枝聚丙烯酸/钠基蒙脱土复合高吸水凝胶的制备及其对Pb2+的吸附

以十二烷基苯磺酸钠(SDS)胶束为孔模板,过硫酸铵(APS)引发,N,N'-亚甲基双丙烯酰胺(MBA)交联,壳聚糖(CS)与丙烯酸(AA)、钠基蒙脱土(Na-MMT)在水溶液中接枝共聚,成功制备了多孔壳聚糖接枝聚丙烯酸/钠基蒙脱土(CS-g-PAA/Na-MMT)复合高吸水凝胶,提出了SDS胶束致孔机理。扫描电子显微镜(SEM)分析表明,添加SDS的样品,凝胶表面出现多孔结构。通过考察SDS浓度对复合高吸水凝胶平衡吸水倍率和吸水速率的影响,发现当SDS浓度为1.5 mmol/L时,复合凝胶在蒸馏水和生理盐水中的平衡吸水倍率相对于空白样分别提高53.9%和35.3%,初始溶胀速率常数K_is也由空白样的1.2652 g/(g·s) 提高到5.1680 g/(g·s)。多孔结构也使复合凝胶对Pb²⁺的吸附速率加快,在10 min内即可达到饱和吸附量的95%,30 min完全达到吸附平衡。     

DSC研究高吸水树脂吸水性能与分子结构的关系

以丙烯酸(AA)、丙烯酰胺(AM)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为共聚单体合成了聚丙烯酸-丙烯酰胺-2-丙烯酰胺基-2-甲基丙磺酸(PAA-AM-AMPS)三元共聚物高吸水树脂.利用茶叶袋法测定了其最大吸水倍率,通过差示扫描量热仪(DSC)测定并比较了含水量为50%,75%和91%的各种水凝胶的自由水和结合水含量.结果表明在蒸馏水和生理盐水中高吸水树脂的最大吸水倍率分别为1900g/g和185g/g,共聚物的结合水含量随着AMPS和AA含量增加及AM含量的减少而增大;在0.9%生理盐水中,结合水含量随着AMPS和AM含量增加及AA含量的减少而增大,共聚物和均聚物高吸水树脂的最大吸水倍率呈现出与结合水含量相同的变化规律.     

丙烯酸与纤维素在60Co辐照下的接枝聚合反应

高吸水性树脂是一类高分子功能材料，吸水量大、保水性强，可以吸收比自身重量高几百到几千倍的水，而且所吸人的水在适当的压力下也不会被挤出。60年代初美国最早开始淀粉接枝丙烯腈研究，随后国内外学者又用纤维素或其衍生物与丙烯腈、丙烯酸酯等单体接枝聚合，经碱液水解后而得。纤维素类高吸水树脂虽然吸水倍率不很高，但吸水速度较快，吸水后形成的凝胶强度较大，其单体制备严格条件下，纤维素要经过活化，要有引发剂诱导，还要通氮气，在一定温度下反应才能进行。本文采用纤维素与丙烯酸在常温和辐照条件下，无需活化、引发剂和氮气保护，即可进行接枝聚合而制备高吸水材料。     

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%。     

Characterization of Starch/Acrylic Acid Super‐Absorbent Hydrogels Prepared by Ionizing Radiation

Copolymerization of acrylic acid (AAc) and gelatinized maize starch in aqueous medium using γ‐irradiation, followed by neutralization with alkali solution was carried out. The preparation conditions, such as irradiation dose and starch/AAc compositions were investigated. The higher the irradiation dose, as well as the AAc content in the feed solution, the higher the gel content. The copolymers were characterized by FTIR spectroscopy, thermo‐gravimetric analysis (TGA) and scanning electron microscopy (SEM). SEM revealed that the higher the dose, the lower the copolymer pore size. Starch/AAc copolymers have thermal stability higher than that for starch and poly acrylic acid individually. The swelling of starch/AAc hydrogels reduced as the gel content increases. The maximum water absorption obtained for starch/AAc hydrogels in distilled water was 200 g/g, and for neutralized starch/AAc hydrogels was 350 g/g. The swelling ratio of starch/AAc hydrogels of different compositions in NaCl solution is lower than that obtained in distilled water. The results suggest that the neutralized starch/AAc hydrogels have a high swelling property, and can be used in a variety of commercial applications.     

氧化淀粉基高吸水性树脂的制备及表征

以过硫酸铵为引发剂,N,N’-亚甲基双丙烯酰胺为交联剂,制备氧化淀粉―丙烯酸―丙烯酰胺高吸水性树脂,并采用红外光谱、X射线衍射等手段对产品的结构进行表征。通过单因素实验优化其制备工艺,最佳工艺条件为:氧化淀粉基体用量为50%,丙烯酸/丙烯酰胺质量比为4∶1,丙烯酸中和度为70%,引发剂过硫酸铵用量为0.5%,交联剂N,N’-亚甲基双丙烯酸胺用量为0.15%,反应温度为80℃,反应时间为3 h。此条件下,氧化淀粉基高吸水性树脂的吸水率达到972.4 g/g。     

一步法合成大孔丙烯酸交联树脂

悬浮聚合;二乙烯苯;一步法合成大孔丙烯酸交联树脂     

钻井液用交联-接枝淀粉的制备及性能

以N,N′-亚甲基双丙烯酰胺为交联剂,过硫酸铵为引发剂,采用“溶剂法”工艺合成了高粘度抗剪切丙烯酸钠接枝淀粉(St),考察了单体、引发剂和交联剂用量、丙烯酸中和度、反应时间及反应温度对合成交联丙烯酸钠接枝淀粉糊液粘度的影响。 结果表明,其优化反应条件为：m(淀粉)∶m(丙烯酸）=1∶1.5,乙醇质量分数为80%,过硫酸铵的用量为单体总质量的1%,交联剂为单体总质量的0.6%,反应时间2.5 h,反应温度为55 ℃,丙烯酸中和度为70%。 该交联接枝淀粉糊液具有良好的触变性,在4%盐水泥浆中的添加量为14.0 g/L时,表观粘度为26.0 mPa·s,滤失量为7.2 mL;在饱和盐水泥浆中添加量为23.5 g/L时,表观粘度为54.5 mPa·s,滤失量为3.1 mL;在80 ℃高温下老化16 h其表观粘度及滤失量等性能基本保持不变,表现出良好的增粘、降失水作用和抗盐、抗老化性能。     

Coupled acid and enzyme mediated production of microcrystalline cellulose from corn cob and cotton gin waste

Microcrystalline cellulose has applications in food, pharmaceuticals, and other industries. Most microcrystalline cellulose (MCC) is produced from dissolving pulp using concentrated acids. We investigated steam explosion treatment of corn cobs and cotton gin waste for the production of microcrystalline cellulose. The corn cob was converted into a coarse brown powder after steam explosion and the lignin and residual hemicellulose fractions were extracted respectively with sodium hydroxide solution and water. The residual cellulose was readily bleached with hydrogen peroxide and converted to microcrystalline cellulose using hydrochloric acid, sulfuric acid and cellulase enzyme preparation. The resulting microcrystalline cellulose samples had properties that were similar to commercial microcrystalline cellulose. Similarly, cotton gin waste was steam exploded and converted into microcrystalline cellulose, but this material was more difficult to bleach using hydrogen peroxide. The degree of polymerization for the MCC samples ranged from 188.6 to 549.8 compared to 427.4 for Avicel PH101 MCC.     

Pretreatment and enzymatic saccharification of corn fiber

Corn fiber consists of about 20% starch, 14% cellulose, and 35% hemicellulose, and has the potential to serve as a low-cost feedstock for production of fuel ethanol. Several pretreatments (hot water, alkali, and dilute, acid) and enzymatic saccharification procedures were evaluated for the conversion of corn fiber starch, cellulose, and hemicellulose to monomeric sugars. Hot water pretreatment (121°C, 1 h) facilitated the enzymatic sacch arification of starch and cellulose but not hemicellulose. Hydrolysis of corn fiber pretreated with alkali un dersimilar conditions by enzymatic means gave similar results. Hemicellulose and starch components were converted to monomeric sugars by dilute H₂SO₄ pretreatment (0.5–1.0%, v/v) at 121°C. Based on these findings, a method for pretreatment and enzymatic saccharification of corn fiber is presented. It in volves the pretreatment of corn fiber (15% solid, w/v) with dilute acid (0.5% H₂SO₄, v/v) at 121°C for 1 h, neutralization to pH 5.0, then saccharification of the pretreated corn fiber material with commercial cellulase and β-glucosidase preparations The yield of monomeric sugars from corn fiber was typically 85–100% of the theoretical yield. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Reducing water absorption in compostable starch-based plastics

To improve the mechanical and physical properties of corn starch-based bioplastics the addition of natural polymers was investigated. Thermoplastic starch (TPS) was made of 70 g corn starch and 30 g glycerol. To this mixture 10–10 g of cellulose, hemicellulose and zein (protein) were added. Mechanical strength, water absorption and enzymatic degradation of composite materials were measured. Unfilled TPS and 10 w/w% polycaprolactone filled TPS were used as controls in the experiments. All the samples were biodegradable by enzymes. The tensile strength of unfilled and biopolymer filled TPS samples were significantly higher than that of the polycaprolactone filled one. Hemicellulose and zein composites had the best mechanical strength (10.4 and 11.5 MPa). Water uptake of each sample was measured using five different relative humidities. There were slight differences in water uptake of polycaprolactone, hemicellulose and zein filled TPS, however unfilled and cellulose filled samples absorbed more moisture than the polycaprolactone control in all the relative humidities used.     

Preparation and properties of superabsorbent containing starch and sodium humate

Starch and sodium humate were utilized as raw material for synthesizing starch‐g‐poly(acrylic acid)/sodium humate (St‐g‐PAA/SH) superabsorbent by graft copolymerization reaction of starch (St) and acrylic acid (AA) in the presence of sodium humate (SH) in aqueous solution. The effect of weight ratio of AA to St, initial monomer concentration, neutralization degree of AA, amount of crosslinker, initiator and SH on water absorbency of the superabsorbent were studied. The swelling rate and swelling behavior in NaCl solution as well as reswelling ability of the superabsorbent were systematically investigated. The results showed that the superabsorbent synthesized under optimal conditions with SH content of 7.7 wt% and St content of 11.5 wt% exhibits water absorbency of 1100 g/g in distilled water and 86 g/g in 0.9 wt% NaCl solution, respectively. Introducing SH into the St‐g‐PAA polymeric network can improved the swelling rate and reswelling capability of the superabsorbent. Copyright © 2008 John Wiley & Sons, Ltd.     

氧化锌催化淀粉/乳酸接枝共聚物的制备与表征

以氧化锌为催化剂,采用原位聚合法制备了淀粉/乳酸接枝共聚物。由FT-IR、1H NMR、XRD和SEM对接枝产物进行了表征,且讨论了反应温度、淀粉与乳酸质量比、催化剂用量和反应时间对淀粉接枝率的影响,结果表明,当反应温度为95℃,淀粉与乳酸质量比为1∶5,催化剂用量为乳酸质量的1.0%,反应时间11 h时,产物的接枝率可达到14.20%。     

Novel approach of corn fiber utilization

The corn wet milling process produces a 10% (w/w of the processed corn) byproduct called corn fiber, which is utilized worldwide as a low-value feedstock for cattle. The aim of this study was to find a higher value use of corn fiber. The main fractions of corn fiber are: 20% starch, 40% hemicellulose, 14% cellulose, and 14% protein. Extraction of the highly valuable, cholesterol-lowering corn fiber oil is not feasible owing to its low (2% w/w) concentration in the fiber. The developed technology is based on simple and inexpensive procedures, like washing with hot water, dilute acid hydrolysis at 120°C, enzymatic hydrolysis of cellulose, screening, drying, and extraction. The main fractions are sharply separated in the order of starch, hemicellulose, cellulose, lipoprotein, and lignin). The lipoprotein fraction adds up to 10% of the original dry corn fiber, and contains 45% corn fiber oil, thus yielding more oil than direct extraction of the fiber. It is concluded that the defined method makes the extraction of the corn fiber oil economically feasible. The fractionation process also significantly increases the yield of cholesterol-lowering substances (sterols and sterolesters). At the same time clear and utilizable fractions of monosaccharides, protein, and lignin are produced.