羧酸和醇类酯化反应的高分子载体催化剂

用ＳｎＣｌ４处理过的Ｈ型大孔强酸性阳离子交换树脂作为羧酸和醇类酯化的高分子载体催化剂，在正丁醇与乙酸摩尔比１∶１和９７～１０４℃、１．５ｈ条件下，酯化率为９３０１％和选择性为１００％。讨论了催化剂用量、原料摩尔比和不同醇类对酯化率的影响     

溶胀剂对黏胶纤维催化脱水的影响

主要研究了不同浓度的乙二胺、尿素水溶液对黏胶纤维的溶胀作用,以及溶胀对催化剂催化效果的影响。通过保水值、吸碘值、~(13)C NMR和热失重分析等测试手段,对溶胀后的纤维性能进行了表征。结果发现:溶胀破坏了纤维内部的氢键结构,使分子链间距加大,催化剂分子更容易进入到纤维内部起到更好的催化效果。通过测定纤维的保水值和吸碘值,对比了乙二胺和尿素水溶液对黏胶纤维的溶胀效果,发现乙二胺对黏胶纤维的溶胀作用更强。~(13)C NMR结果表明,乙二胺对黏胶纤维有更大的消晶作用。热失重曲线表明:经乙二胺溶胀后的纤维的初始热失重温度进一步降低,有利于纤维在更低的温度下进行热处理,节约能耗。纤维强度测试结果表明,溶胀处理可以有效提高催化剂的催化效率。     

催化合成L-吡咯烷酮羧酸月桂酯

以L-吡咯烷酮羧酸和月桂醇为原料,固载催化剂A,通过酸醇酯化反应直接合成L-吡咯烷酮羧酸月桂酯。探讨催化剂种类、用量、物料比、反应时间和温度对酯化反应影响,确定适宜合成工艺条件:n(月桂醇)∶n(L-吡咯烷酮羧酸)=1.0∶1.3,环己烷为带水剂,每0.1 mol月桂醇加入催化剂A 3.5 g,170℃反应4 h,酯化率达98.6%。固载催化剂A具有较好的活性,重复使用9次时酯化率仍可达93.4%。     

聚甘油酯化改性PMVE/MAH的合成及吸水性能研究

以甲基乙烯基醚/马来酸酐共聚物(PMVE/MAH)与十聚甘油为原料,采用溶剂接枝法,制得聚甘油酯化改性PMVE/MAH。采用红外光谱和热分析仪对酯化产物进行了结构表征。研究了反应酯化率对产物性能的影响,考察了产物的热稳定性、保水性能、耐电解质性和重复吸水性能。结果表明,酯化率12.5%的共聚物吸水性最强,pH=7时吸水倍率为353 g/g,最适宜酸碱性条件为pH=8,此时酯化改性共聚物吸水倍率可达719 g/g,耐盐性良好,50℃环境温度下16 h仍有67.2%的保水率。     

聚羧酸酯类减水剂酯化率的研究

通过核磁共振方法研究了聚羧酸酯类减水剂的酯化工艺。讨论了酯化时间、酸醚比对酯化率的影响,确定最佳酯化工艺:酯化时间9 h、酸醚摩尔比2.5∶1。通过该方法能精确计算物料损失,提高原料利用率,为聚合工艺奠定基础。     

马来酸类聚羧酸减水剂的合成及其对水泥净浆流动性的影响研究

以马来酸酐、聚乙二醇、丙烯酸等为原料,采用先酯化再共聚的方法,合成了一系列侧链结构不同的聚羧酸减水剂,研究了反应温度、单体摩尔比对酯化率的影响,以及聚氧乙烯侧链类型、侧链含量对水泥净浆流动性的影响。通过1HNMR表征了酯化物和共聚物的结构,采用酸碱滴定法测定其酯化率。     

含硅二烃基锡二芳香羧酸酯的催化性能研究

通过酯化反应和缩醛化反应,考察了含硅二烃基锡二芳香羧酸酯在有机反应中的催化活性,讨论了催化剂用量、反应时间和溶剂等因素对催化反应的影响。实验结果表明,在酯化与缩醛化两类反应中,4种含硅二烃基锡二芳香羧酸酯均表现出良好的催化活性,其中[(CH3)3SiCH2]2Sn(OCOC6H4NO2-p)2的催化活性较高,在一定条件下酯化率可达96.3%,缩醛化率达90.6%。     

BTCA/Coll/PVA复合体系的交联动力学研究

以丁烷四羧酸(BTCA)为交联剂对胶原蛋白(Coll)/聚乙烯醇(PVA)复合体系进行化学交联处理;利用红外光谱分析了交联前后体系的化学变化;根据常见动力学机理函数,结合凝胶含量(α)研究复合体系的交联动力学。结果表明:BTCA对Coll/PVA体系有明显的交联作用,交联反应主要以酯化反应和酰胺化反应为主;BTCA/PVA和BTCA/Coll的表观凝胶反应活化能(E)分别为100.29,77.42 kJ/mol,表明BTCA较易与Coll反应;BTCA/Coll/PVA复合体系的最佳动力学函数G(α)为[-ln(1-α)]2/5,E为40.88 kJ/mol,比Coll/PVA复合体系的E(86.99 kJ/mol)明显减小,说明BTCA的加入降低了体系的E,有利于促进交联反应,可提高蛋白存留率。     

棉织物无甲醛抗皱整理中DMSO对BTCA交联性能的影响

1,2,3,4-丁烷四羧酸（BTCA）和棉纤维素的酯化交联反应活性因氢键作用而降低,因此在工业整理中存在烘焙温度过高的问题。研究了二甲基亚砜（DMSO）对BTCA整理工艺的影响,测试了织物中接枝和交联的BTCA含量以及其折皱回复角,同时借助傅利叶红外光谱对DMSO的作用机制进行研究。结果表明,当整理液中DMSO的含量为6%时,可以有效降低BTCA的烘焙温度,在160℃下烘焙3min后的棉织物折皱回复角为263.8°,其防皱效果优于经传统工艺（170℃下烘焙3min）整理后织物（259°）。DMSO因可以削弱BTCA与棉纤维交联体系中的氢键作用,不仅减弱了BTCA在纤维内部的聚集,有利于其扩散和成酐,还加剧了纤维素大分子链的热振动,从而有效提高了BTCA在棉纤维中的接枝率和交联率以及整理后织物的防皱性能。     

酯化改性苯乙烯马来酸酐共聚物及其盐的制备与应用

采用聚醚对苯乙烯马来酸酐共聚物(SMA)进行酯化改性,再使用胺中和部分剩余羧酸得到苯乙烯马来酸酐酯化及中和产物(SMAE-N)。并对不同的催化剂种类及其用量、不同的溶剂种类以及不同的反应温度、时间等因素对酯化率的影响进行探究。考察了反应过程中酸值变化,对酯化产物使用核磁共振氢谱(H-NMR)与傅里叶红外光谱(FT-IR)进行结构表征。同时探索了不同种类的聚醚和胺对钛白粉、炭黑等颜料分散性能的影响。结果表明,当溶剂使用乙酸丁酯、固体酸催化剂DP91,且用量为反应物质量分数的1%,苯乙烯马来酸与聚醚1007投料物质的量比为1∶4,115℃情况下反应5 h,酯化率可达到62.84%,再用三乙胺中和剩余羧酸的70%。颜料分散应用结果表明,SMAE-N对钛白粉、炭黑等颜料具有显著的分散效果。     

Crosslinking reactions of oxidized cellulose fiber. I. Reactions between dialdehyde cellulose and multifunctional amines on lyocell fabric

Fibrillation‐controlled lyocell fibers were developed by crosslinking reactions between dialdehyde cellulose (DAC) and multifunctional amines. DAC lyocell fibers were manufactured by partial oxidation with sodium metaperiodate and were successfully crosslinked with two multifunctional amines by Schiff‐base formation. The amorphous regions and the char formations, which were characterized by differential scanning calorimetry and thermogravimetric analysis, increased with the degree of oxidation. After the crosslinking reactions, an increase in the amorphous regions also appeared, whereas the thermal stability was somewhat improved by the chain crosslinking. These results were in good agreement with viscosity‐average degree of polymerization values in that they diminished with oxidation level and increased with the crosslinking reactions. The water retention value and moisture regain value decreased with the oxidation and crosslinking levels, which implied that the swellability of fibers and the water absorbency in characteristic sites decreased with them. The increase in the dry crease recovery angle also confirmed the presence of hemiacetal crosslinks in the DAC and amine crosslinks between the DAC and the amines. The fibrillation grade of the crosslinked fibers diminished with oxidation level and the amine concentration. In particular, the fibrillation properties of the crosslinked fibers with 4‐hydroxy‐2,4,6‐triaminopyrimidine sulfate salt were more easily controlled than those of the crosslinked fibers with 2,4,6‐triamino‐1,3,5‐triazine. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Hydrophilic polystyrene/maleic anhydride ultrafine fibrous membranes

Polystyrene/maleic anhydride (PSMA) was synthesized to reach a viscosity‐average molecular weight of 700 kDa and fabricated into ultrafine fibrous membranes consisting of fibers with an average diameter of 300 nm. These ultrafine PSMA fibers were rendered insoluble in organic solvents by reactions with hydrazine and ethylenediamine (ED). The highly efficient incorporation of diamines into the fibrous membranes was easily achieved by brief immersions in either dilute (0.5 wt %) hydrazine for 1 min or ED ether solution for 2 min. Heating at 150°C for 5 min produced crosslinked PSMA with very little or no solubility in acetone with the retention of the fibrous membrane structure. The ED‐crosslinked membranes were particularly stable to both bases and acids as well as hydrophilic solvents, had a 46° water contact angle, and absorbed 22 times the amount of water as the as‐spun fibrous membrane. This post‐fiber‐formation crosslinking approach was robust, highly efficient, and fast and required very little crosslinking reagent. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of chitosan/poly(vinyl alcohol) blend fibers

Chitosan and poly(vinyl alcohol) blend fibers were prepared by spinning their solution through a viscose‐type spinneret at 25°C into a coagulating bath containing aqueous NaOH and ethanol. The influence of coagulation solution composition on the spinning performance was discussed, and the intermolecular interactions of blend fibers were studied by infrared analysis (IR), X‐ray diffraction (XRD), and scanning electron micrograph (SEM) and by measurements of mechanical properties and water‐retention properties. The results demonstrated that the water‐retention properties and mechanical properties of the blend fibers increase due to the presence of PVA in the chitosan substract, and the mechanical strength of the blends is also related to PVA content and the degree of deacetylation of chitosan. The best mechanical strength values of the blend fibers, 1.82 cN/d (dry state) and 0.81 cN/d (wet state), were obtained when PVA content was 20 wt % and the degree of deacetylation of chitosan was 90.2%. The strength of the blend fibers, especially wet tenacity could be improved further by crosslinking with glutaraldehyde. The water‐retention values (WRV) of the blend fibers were between 170 and 241%, obviously higher than pure chitosan fiber (120%). The structure analysis indicated that there are strong interaction and good miscibility between chitosan and poly(vinyl alcohol) molecular resulted from intermolecular hydrogen bonds. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2558–2565, 2001     

Preparation and characterization of chitosan coatings onto regular cellulose fibers with ultrasound technique

Regenerated cellulose fibers—viscose fibers—were coated with chitosan using an ultrasound technique to improve their accessibility, reactivity and sorption properties. The main purpose of our research was to study the modification of viscose fibers and to determine the effect of the application of chitosan onto viscose fibers. Samples were obtained by treating the fibers with chitosan in a dilute acetic acid solution in an ultrasonic bath. The influences of the chitosan coating on the changes in morphology, supramolecular structure, sorption and tensile properties were studied. The spectra (FTIR analysis) of the treated viscose fibers showed changes and new absorption bands that revealed the existence of the chemical interactions with the chitosan. The scanning electron microscope images confirmed that the surface of the fibers was covered with the chitosan. A decrease in the water retention value and increase in the absorption and moisture content with an increasing concentration of chitosan was noted. Furthermore, the differences in tensile behavior were analyzed using an Instron tensile testing machine. The chitosan coating had no effect on the tensile strength of the viscose fibers, but influenced the tensile strain. Some changes, though not significant, were noted in the structure (crystallinity, orientation) of the treated viscose fibers.     

Preparation and properties of alginate superabsorbent filament fibers crosslinked with glutaraldehyde

Superabsorbent filament fibers based on sodium alginate were prepared using glutaraldehyde as a crosslinking agent. Alginate was extruded into an aqueous hydrochloric acid coagulation bath to form continuous alginic acid gel fibers via a wet‐spinning method. The alginic acid gel fibers were dehydrated by exchanging water with dioxane, crosslinked, then neutralized for better absorbency. Crosslinked alginate filaments exhibited a high saline solution and synthetic urine absorbencies, maintaining the integrity of the fiber structure. Maximum synthetic urine absorbency was obtained with the fiber crosslinked at a lower glutaraldehyde concentration compared with that required for maximum saline solution absorbency. This appears to be due to the crosslinking effect of calcium ions in the synthetic urine solution being absorbed. Strain and tenacity of the crosslinked alginate fibers decreased with an increasing amount of glutaraldehyde used in the crosslinking reaction. The decrease in tenacity was not significant while the strain showed an extensive decrease. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1797–1804, 2000     

A new crosslinked protein fiber from gliadin and the effect of crosslinking parameters on its mechanical properties and water stability

BACKGROUND: Although several cereal proteins have been used to develop fibers and films, it has not been possible to obtain protein materials with good mechanical properties and water stability, even after crosslinking. Previously, high concentrations of glutaraldehyde were used to improve the mechanical properties of protein fibers but the effect of crosslinking conditions on the properties of the crosslinked materials has not been studied in detail. RESULTS: Low concentrations of glutaraldehyde can be used to improve the mechanical properties and water stability of gliadin fibers. Quantitative relationships that can predict the breaking tenacity of the fibers at various crosslinking conditions are developed. Glutaraldehyde crosslinking is more resistant to hydrolysis in neutral pH than under acidic conditions in terms of increasing and retaining the breaking tenacity. The crosslinked fibers show improved resistance to hydrolysis over poly(lactic acid) fibers in aqueous dispersions at pH = 4 and 7 at 50 and 90 °C, respectively. CONCLUSIONS: This study shows that low concentrations of glutaraldehyde can impart excellent mechanical properties to gliadin fibers. The quantitative relationships developed can be used to select the crosslinking conditions such low glutaraldehyde concentration and high temperature or vice versa to obtain the desired improvement in mechanical properties or water stability. Copyright © 2008 Society of Chemical Industry     

Comparative study of the properties of differently decrystallized and crosslinked cotton fibers

The physical, structural, and mechanical properties of decrystallized cotton fibers prepared by preswelling in different concentrations of alkali followed by partial substitution—to nearly the same extent irrespective of the preswelling alkali concentration—by acetylation or cyanoethylation have been compared. The decrystallized fibers have been crosslinked with dimethylol dihydroxy ethylene urea (DMDHEU), along with the swollen controls, and the mechanical properties have been measured on these samples. It was found that preswelling in NaOH solution of lower concentration (12–15%) prior to cyancethylation results in better decrystallized fibers which also possess better strength uniformity, whereas a higher concentration of NaOH (15% or above) is necessary for acetylation to obtain fibers with nearly similar characteristics. On crosslinking, the swollen and substituted fibers show a better strength retention and a higher strength uniformity than the swollen control, for the same degree of crosslinking.     

Elastomers based on cellulose fibers. II. Ethyl acrylate grafting onto disulfide-crosslinked cellulose

Partially disulfide-crosslinked viscose rayon fibers (? S? S? 2.3 mole/10⁴ g. cellulose) were prepared by means of mercaptoethylation and successive oxidation and then grafted to the extent of 200–1200% graft-on of ethyl acrylate with or without preswelling by zinc chloride, by using the ceric ion method. The tensile strength, breaking elongation, initial modulus, elastic recovery, and extension energy loss of the modified fibers were measured. In the disulfide-crosslinked, about 1000% ethyl acrylate-grafted fibers with preswelling, typical rubber elasticity was found. The disulfide crosslinkage in the grafted fibers was found generally to be capable of cleaving and re-forming by the reduction and successive oxidation treatments, and the properties were also well reversible. Therefrom, it was confirmed that intermolecular crosslinking between cellulose molecules plays an important role for developing of elastomeric properties, as was found for the methylene-crosslinked and grafted fiber reported previously. Most of elastomeric properties in our grafted fibers seem to be essentially attributable to the random conformation of the decrystallized, disoriented, and weakly crosslinked cellulose chains which are embedded in a matrix of flexible graft polymers.     

Hydrogels based on graft copolymers of collagen synthesis

Graft copolymerization of 2-hydroxyethyl methacrylate in combination with hydrophobic monomers onto soluble collagen was employed in the synthesis of hydrogels. The hydrogels were formed by simultaneous graft copolymerization and crosslinking. In order to study the effect of various crosslinking agents on the water retention character of the hydrogels, three different crosslinking agents, namely, N,N′-methylene bis acrylamide, 1,4-butanediol dimethacrylate, and hexamethylene urethanediacrylate were used. Hexamethylene urethanediacrylate crosslinked systems require a minimum amount of crosslinking agent to attain maximum water content in comparison to the other systems.     

Reactive electrospinning of poly(vinyl alcohol) nanofibers

We aim to couple the electrospinning in‐line with solution chemistry to fabricate novel crosslinked polymer nanofibers. Poly(vinyl alcohol) (PVA) was used as a model polymer due to its high amount of hydroxyl groups. To obtain ideal parameters for electrospinning, pure PVA was explored primarily. To gain crosslinked fibers, PVA was first crosslinked partially with glutaraldehyde (GA) followed by transferring this precursor to a long hot tube which was used as reactor and then electrospun right before gelation. The preheating time and tube‐passing time were determined with viscometer and rheometer. The reactive as‐spun fibers could maintain their original morphology after water immersion due to their high crosslinking degree. The thermal stability and mechanical property of reactive as‐spun fibers were improved drastically compared with pure and GA vapor crosslinked PVA fibers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012