乙酸纤维素的应用及改性研究现状

随着污染问题及资源短缺问题的日益严重,乙酸纤维素作为纤维素的重要衍生物之一,具有良好的加工性能及可生物降解性能,近年来一直备受关注。本文系统介绍了乙酸纤维素在服装纺织、烟用滤嘴及膜材料等方面的应用,分析了目前乙酸纤维素应用中存在的问题。同时从共混改性、纳米及纳米复合改性、表面改性等方面对乙酸纤维素的改性技术的研究进展进行了综述,最后展望了乙酸纤维素的发展前景,指出开发简单易行能够工业化的改性技术及制备出可再生的生物降解材料研究是乙酸纤维素改性今后的主要发展方向。     

脂肪酶改性醋酸纤维的性能研究

采用脂肪酶Lipex 100L对醋酸纤维进行脱乙酰化处理,改善纤维的吸湿、染色等性能;通过脂肪酶处理残液的紫外光谱分析、反应液pH值变化以及染料对纤维的吸附量、回潮率、取代度测试等方法,分析酶处理后反应液中水解产物的产生和纤维表面官能团的变化.结果表明:脂肪酶处理醋酸纤维后,反应液中有水解产物乙酸存在,醋酸纤维的回潮率...     

Surface modification of cellulose nanocrystals by grafting with poly(lactic acid)

The use of biopolymers obtained from renewable resources is currently growing and they have found unique applications as matrices and/or nanofillers in ‘green’ nanocomposites. Grafting of polymer chains to the surface of cellulose nanofillers was also studied to promote the dispersion of cellulose nanocrystals in hydrophobic polymer matrices. The aim of this study was to modify the surface of cellulose nanocrystals by grafting from L‐lactide by ring‐opening polymerization in order to improve the compatibility of nanocrystals and hydrophobic polymer matrices. The effectiveness of the grafting was evidenced by the long‐term stability of a suspension of poly(lactic acid)‐grafted cellulose nanocrystals in chloroform, by the presence of the carbonyl peak in modified samples determined by Fourier transform infrared spectroscopy and by the modification in C1s contributions observed by X‐ray photoelectron spectroscopy. No modification in nanocrystal shape was observed in birefringence studies and transmission electron microscopy. © 2013 Society of Chemical Industry     

戊二醛交联改性再生纤维素纤维的研究

以氯化1-丁基-3-甲基咪唑离子液体为溶剂对木质纤维素进行溶解并纺丝,得到再生纤维素纤维,再使用戊二醛对再生纤维素纤维进行交联改性,研究其交联改性条件对再生纤维素纤维力学性能的影响。结果表明:经戊二醛交联后,再生纤维素纤维的断裂强度有明显的提高;在戊二醛质量分数为4%,反应温度为50℃,反应时间为30 min的交联条件下,所得再生纤维素纤维的断裂强度为3.2 cN/dtex。     

Robust hydrogel of regenerated cellulose by chemical crosslinking coupled with polyacrylamide network

Regenerated cellulose/polyacrylamide (RC/PAAm) double network (DN) hydrogels are composed of cellulose crosslinked by epichlorohydrin (ECH) and chemical-crosslinked PAAm. The prepared RC/PAAm DN hydrogels present enhanced strength, good shape recovery property, excellent energy dissipation properties, decreased equilibrium water content, and low equilibrium swelling ratio (SR). The compressive strength and modulus of RC/PAAm hydrogel are about 4.3 and 11.5 times compared to that of RC hydrogel, respectively. Intriguingly, the chemical crosslinking between ECH and cellulose chains could increase the distance between cellulose chains. Consequently, the increasing molar ratio of ECH to glucose leads to larger SRs and decreased mechanical strength of the hydrogels. Additionally, higher PAAm contents lead to more densely crosslinked networks, and thus decreasing the SRs and improving the mechanical strength of the hydrogels. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47811.     

氨基硅油微乳液改性水性聚氨酯的合成和性能

合成了水性聚氨酯乳液和氨基硅油(AEAPS)微乳液改性水性聚氨酯乳液,研究了两种水性聚氨酯的性能及在织物上的涂层效果。结果表明,当氨基硅油相对于聚丙二醇的质量百分比为8.18%时,有机硅改性水性聚氨酯乳液的离心稳定性好,乳液胶膜表面硅原子的质量分数为0.92%;该有机硅改性水性聚氨酯软段相与硬段相的微观相分离增大,乳液胶膜的耐水性能和热稳定性提高;该有机硅改性水性聚氨酯乳液作为织物涂层剂时,可以赋予织物柔软、滑爽的风格。     

Surface modification of cellulose nanocrystals

In order to improve the dispersibility of cellulose nanocrystal (CNC) particles, three different grafted reactions of acetylation, hydroxyethylation and hydroxypropylation were introduced to modify the CNC surface. The main advantages of these methods were the simple and easily controlled reaction conditions, and the dispersibility of the resulting products was distinctly improved. The properties of the modified CNC were characterized by means of Fourier transform infrared spectroscopy (FT-IR), ¹³C nuclear magnetic resonance (NMR), transmission electron microscopy (TEM) and thermogravimetric analyses (TGA). The results indicated that after desiccation, the modification products could be dispersed again in the proper solvents by ultrasonic treatments, and the diameter of their particles had no obvious changes. However, their thermal degradation behaviors were quite different. The initial decomposition temperature of the modified products via hydroxyethylation or hydroxypropylation was lower than that of modified products via acetylation. Translated from Acta Polymerica Sinica, 2006, (8): 982–987 [译自: 高分子学报]     

Regioselective catalyzed modification of poly(methylhydro)siloxane using RuRh and RuPt bimetallic dendrimer‐encapsulated nanoparticles

RuRh and RuPt bimetallic dendrimer‐encapsulated nanoparticles (DENs) were successfully prepared by a two‐step process involving co‐complexation, using ruthenium and rhodium or ruthenium and platinum complex ions with partially quaternized fifth‐generation poly(amidoamine) (G5‐Q), and then coreduction with NaBH₄. UV–vis, transmission electron microscope, and laser scattering analyses were used to characterize the bimetallic alloy DENs. The regioselective synthesis of multifunctional hybrid poly(methylhydro)siloxane was achieved by the RuRh and RuPt alloy nanoparticle catalysts. The experimental results showed that the RuRh and RuPt bimetallic DENs presented higher catalytic activity than physical mixtures of their monometallic DENs, respectively. This should be due to synergistic electronic effect of RuRh and RuPt alloy catalysts. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Surface modification of nanocrystalline cellulose and its application in natural rubber composites

As a biopolymer with high mechanical strength, nanocellulose was generally considered as a green filler for reinforcing polymer. In this study, nanocrystalline cellulose (NCC) isolated from softwood pulp was successfully modified by cetyltrimethyl ammonium bromide (CTMAB), a cationic surfactant, and the modified nanocrystalline cellulose (m-NCC) was used to reinforce natural rubber (NR). In this composite architecture, it was found that when the filler content was 5 or 10 phr, the surface modification of NCC improved the dispersion state of NCC in NR matrix and the interfacial interaction between NR and NCC. Therefore, the NR/m-NCC composites exhibited outstanding mechanical properties, and its tensile strength, elongation at break and tear strength was increased by 132.8, 20, and 66.1%, respectively, compared to pristine NR composites. Besides, the modified NCC could accelerate the vulcanization and improve wet-skid resistance and aging resistance of NR composites. It is envisioned that the modified NCC has the potential to be generalized to manufacturing other polymer matrix composites strengthened with nanocellulose.     

Structure and mechanical properties of cellulose derivatives/soy protein isolate blends

Biodegradable and biocompatible composites based on soy protein isolate (SPI) and various cellulose derivatives have been prepared, and the dependence of structures and mechanical properties on the content and species of cellulose derivatives for the composites were investigated by X‐ray diffraction, differential scanning calorimetry, scanning electron microscope, and tensile test. The selected cellulose derivatives, such as methyl cellulose (MC), hydroxyethyl cellulose (HEC), and hydroxypropyl cellulose, were miscible with SPI when the content of cellulose derivatives was low, and then the isolated crystalline domains, shown as the structures of network and great aggregate, formed with an increase of cellulose derivative content. The miscible blends could produce the higher strength, and even result in the simultaneous enhancement of strength and elongation for the HEC/SPI and MC/SPI blends. Meanwhile, the moderate content of great MC domains also reinforced the materials. However, the damage of original ordered structure in SPI gave the decreased modulus. Since all the components, i.e., cellulose derivatives and soy protein, are biocompatible, the resultant composites are not only used as environment‐friendly material, but the biomedical application can be expected, especially for the tissue engineering scaffold. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Thermoplastic cellulose acetate and cellulose acetate compounds prepared by reactive processing

Novel families of thermoplastic polysaccharides such as cellulose-2,5-acetate were produced by means of reactive processing technology that grafted cyclic lactones simultaneously onto polysaccharide, hydroxyfunctional plasticizer, and optionally also onto hydroxyfunctional fillers. Organosolv lignin, cellulose, starch, and chitin were added to effect reinforcement of the polymer matrix. Mechanical and thermal properties depended upon molecular architecture of the components and process parameters such as temperature, feed ratios, and screw speed. Such blends and composites utilize renewable resources and are of interest in waste disposal via biodegradation. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 213–242, 1997     

Synthesis and properties of novel benzocyclobutene‐functionalized siloxane thermosets

Two kinds of novel benzocyclobutene (BCB) functionalized monomers were synthesized through imidization of siloxane‐containing dianhydride with 4‐aminobenzocyclobutene. The BCB monomers obtained exhibited good solubility in various organic solvents. They were converted into crosslinked polymer via ring opening and the following Diels–Alder reaction at proper temperature. The curing kinetics were studied by non‐isothermal differential scanning calorimetry. The BCB polymers showed good thermal stability, excellent dielectric properties, low water absorption and good planarization. Moreover, the thermal and mechanical properties of the BCB resins could be adjusted by the length of the siloxane unit. The BCB resins with a shorter siloxane chain exhibited higher glass transition temperature, higher modulus and lower coefficient of thermal expansion than BCB resins with longer chains. © 2013 Society of Chemical Industry     

Synthesis and properties of polyurethane modified with aminoethylaminopropyl poly(dimethyl siloxane)

A series of polyurethanes with different siloxane contents were synthesized, which were based on 4,4′‐methylene diphenyl diisocyanate (MDI), poly(tetramethylene oxide) (PTMO), aminoethylaminopropyl poly(dimethyl siloxane) (AEAPS), and butanediol (BD). The chemical compositions, structures, and bulk and surface properties were investigated using an infrared surface quantitative analysis technique (FTIR‐ATR), surface contact angle, electron spectroscopy for chemical analysis (ESCA), stress–strain analysis, and dynamic mechanical thermal analysis (DMTA). It was shown that siloxane concentration on the surface region of the elastormers was higher than that in the bulk for a resulting surface enrichment of the siloxane, and the tensile properties of these elastomers were not changed significantly with the AEAPS modification. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2552–2558, 1999     

Preparation of polyacrylonitrile and cellulose acetate blend fibers through wet‐spinning

Fibers containing both polyacrylonitrile (PAN) and cellulose acetate (CA) were prepared through wet‐spinning by using N,N‐dimethylformamide (DMF) as a solvent. Compatibility of PAN and cellulose acetate blend (PCB) fibers was investigated by means of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and infrared (IR) spectrophotometry. The absorptive capacity and mechanical properties of the fibers were measured. It was observed that the surface and the cross section of PAN fibers were quite smooth and free from voids and microcracks, whereas cracks and voids were present on the surface and cross section of blend fibers, which increased with the incorporation of CA in the blend. Moisture regains of blend fibers were quite high while their tensile properties showed a partial decrease. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2000–2005, 2007     

Viscoelastic properties of cellulose derivatives: 1. Cellulose acetate

The dynamic mechanical spectrum of cellulose acetate (CA) from −130°C to 240°C has been determined at different frequencies (from 0.1 to 30 Hz). Three relaxations, designated , β and γ in order of decreasing temperature, and one shoulder (β*) above room temperature were found. Comparison with calorimetric and thermogravimetric measurements yields the conclusion that the relaxation (197°C at 3 Hz) is related to the glass-to-rubber transition and the β* shoulder (50°C–100°C) is due to loss of moisture. The β relaxation (−38°C at 3 Hz, ΔH = 100 kJ mol⁻¹) is tentatively assigned to local motions of the main chain (glucopyranose rings). The low-temperature γ relaxation (−88°C at 3 Hz, ΔH = 46 kJ mol⁻¹), is humidity-dependent: its intensity decreases when the samples are dried to moisture contents lower than that obtained by normal room conditioning (about 3%). Higher water contents shift the relaxation to lower temperatures without increasing the intensity of the mechanical loss. It is suggested that water associated with the unesterified methylol groups of cellulose acetate is responsible of the dynamic mechanical γ dispersion.     

纤维素的改性及应用研究进展

植物纤维素是天然的可再生资源, 对纤维素的改性利用一直是研究的热点。本文简要介绍了纤维素的结构与性质, 综述了纤维素的改性方法, 包括物理改性、化学改性和生物改性等, 其中化学改性是最主要的方法, 包括酯化、磺化、醚化、醚酯化、交联和接枝共聚等, 通常涉及其结构中羟基的一系列反应。通过改性, 引进了一系列离子型基团, 有利于增强纤维素的亲水性。经改性后的纤维素与之前相比, 结晶度和聚合度明显降低, 可及度明显提高, 无论物理性质还是化学性质都表现出更大的优越性。其后回顾了纤维素衍生物在食品、造纸以及建筑行业中的一些研究应用成果, 阐述了其在医药及废水处理等方面的研究进展, 并展望了纤维素衍生物的发展前景。     

Determination of crosslinking density of hydrogels prepared from microcrystalline cellulose

Hydrogels with four different plant‐based microcrystalline cellulose concentrations were prepared using the self‐assembly technique. The interaction parameter between cellulose and water was determined by the classical Flory‐Huggins theory, and was found to be around 0.44 with weak concentration dependence. The crosslinking density in these hydrogels was measured by both the Mooney‐Rivlin equation and the Flory‐Rehner theory. Reasonable consistency was found between the two methods albeit results from the Flory‐Rehner theory were slightly higher due to the contribution from the physical crosslinks. The crosslinking density values for all four hydrogels determined from both methods were found to range from 19 to 56 mol/m³. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

聚醚与甲基丙烯酸十二烷基酯共改性硅油的制备与表征

以氯铂酸为催化剂,烯丙醇聚氧乙烯聚氧丙烯醚(F-6)、甲基丙烯酸十二烷基酯(LMA)和含氢硅油(PHMS)为原料,通过硅氢加成制备了聚醚与甲基丙烯酸十二烷基酯共改性硅油(PMS),并用红外光谱和核磁共振氢谱对其结构进行了表征。考察了硅氢键与碳碳双键的量之比、反应温度、反应时间、催化剂用量对Si—H转化率的影响,确定了最佳工艺为:甲苯的质量分数30%～40%,Si—H与CC的量之比1.00∶1.20,催化剂用量为30×10-6,反应温度为90℃,反应时间为6 h,Si—H转化率达到92.35%。产物水溶液的临界胶束浓度为0.6 g/L,PMS的临界表面张力为22.236 mN/m,表现出低表面能的特点。     

Morphological and grafting modification of natural cellulose fibers

Crystal structure and mechanical properties of cellulose fibers were studied to investigate the effect of chemical treatment on the fiber. Pretreatment by acetone extraction, mercerization with 3–20% wt/v sodium hydroxide (NaOH), and acrylonitrile (AN) grafting initiated by azo‐bis‐isobutylonitrile were performed. From Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction quantitative measurements, the pretreated fibers showed an induced slight decrease of crystallinity index. The structural transformation of the fibers from cellulose I to cellulose II was observed at high NaOH concentration of 10–20% wt/v. The amount of grafting, 1.56, 2.94, 6.04, 8.34, or 10.46%, was dependent upon the initiator concentration and the volume of monomer in the reactor. The AN grafted fibers had no transformation of crystalline structure as observed after mercerization. Only a variation of X‐ray crystallinity index with grafting amount was observed. Moisture regain of pretreated and modified fibers depended on the structure of the fiber and the amount of grafting. The mechanical properties performed by a single fiber test method were strongly influenced by the cellulose structure, lateral index of crystallinity, and fraction of grafting. Scanning electron microscopy was used for analysis of surface morphologies of treated fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2456–2465, 2004     

The effect of plasticizer and cellulose nanowhisker content on the dispersion and properties of cellulose acetate butyrate nanocomposites

We studied the effects of plasticizer and cellulose nanowhisker content on the dispersion and properties of cellulose acetate butyrate (CAB)‐based bionanocomposites. The cellulose nanowhiskers in an aqueous medium were solvent‐exchanged to nonaqueous polar solvent (acetone) and used for nanocomposite processing by solution casting. The plasticized and unplasticized nanocomposites with 5 and 10 wt % cellulose nanowhisker content were prepared. Atomic force microscopy indicated nanoscale dispersion of whiskers in the CAB matrix. The dynamic mechanical analysis showed an increase in storage modulus with addition of cellulose nanowhiskers, especially above the glassy‐rubbery transition region. Thermogravimetric analysis showed an improvement in thermal stability with increased whisker content for both unplasticized and plasticized nanocomposites. The plasticized nanocomposites showed better transparency than the unplasticized composites, indicating a better dispersion of cellulose nanowhiskers in CAB, in the presence of a plasticizer. The dynamic mechanical properties and thermal stability increased, whereas transparency decreased with increased CNW content. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009