Structural changes of regenerated cellulose dissolved in FeTNa,NaOH/thiourea,and NMMO systems

Regenerated cellulose was prepared from microcrystalline cellulose (MCC) via dissolution in three well‐known nonderivatizing systems: ferric chloride/sodium tartarate/sodium hydroxide (FeTNa), sodium hydroxide/thiourea (NaOH/thiourea), and N‐methylmorpholine‐N‐oxide (NMMO) systems. The effect of regeneration using the different systems on the supramolecular structure of the regenerated celluloses was studied using X‐ray diffraction and Fourier transform infrared (FTIR). The effect of regeneration on supermolecular structure, morphology, and thermal stability of regenerated celluloses were studied using scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The effect of regeneration systems used on the chemical reactivity of cellulose toward carboxymethylation, acetylation, and cyanoethylation reactions was briefly studied. The results showed dependence of all the aforementioned properties on the dissolution reagent used in spite of that all studied reagents cause the same change in cellulose crystalline structure (from cellulose I to cellulose II). The degree of polymerization, crystallinity, and thermal stability of the regenerated cellulose (RC) samples were in the following order: NaOH/thiourea RC > FeTNa RC > NMMO RC. SEM micrograph showed unique surface for the NMMO RC sample. The reactivity of the different regenerated cellulose samples toward carboxymethylation, cyanoethylation, and acetylation depended mainly on the reaction system and conditions used rather than on crystallinity of regenerated cellulose. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Isolation and Characterization of Microcrystalline Cellulose from Bamboo Pulp Through Extremely Low Acid Hydrolysis

Microcrystalline cellulose (MCC) has a wide range of applications in food, chemical, pharmaceutical industries, etc. In this study, the one-step preparation of MCC from bleached Kraft bamboo pulp (BKBP) by extremely low acid (ELA; acid concentration ≤0.1?wt %) was demonstrated. The experimental data indicate that the crystallinity, degree of polymerization (DP), and yield of MCC were strongly affected by the time and temperature of hydrolysis, as well as the concentration of hydrochloric acid (HCl). Rod-like MCC was obtained with a yield of 76.4% (based on the mass of original BKBP) and exhibited high crystallinity and narrow particle diameter distribution (78.7%, 30–70?μm) under optimal conditions (acid concentration of 0.08?wt%, 165?°C, 40?min). The Fourier transform-infrared spectroscopy (FTIR) and X-ray diffraction (XRD) measurements showed that the resulted MCC maintained cellulose I structure. Thermal analysis demonstrated that the as-prepared MCC exhibited good thermal stability. The ELA hydrolysis process may provide a green alternative for the manufacture of MCC from bleached Kraft bamboo pulp.     

New multifunctional poly(lactide acid) composites: Mechanical,antibacterial, and degradation properties

The aim of this work was to study the effect of the innovative combination of microcrystalline cellulose (MCC) and silver nanoparticles (Ag) on the poly (lactide acid) (PLA) composite properties, to modulate the PLA mechanical response and induce an antibacterial effect. The preparation and characterization of PLA‐based composites with MCC and Ag nanoparticles by twin‐screw extrusion followed by injection molding is reported. A film procedure was also performed to obtain PLA and PLA composite films with a thickness ranged between 20 and 60 μm. The analysis of disintegrability in composting conditions by means of visual, morphological, thermal, and chemical investigations was done to gain insights into the post‐use degradation processes. Tensile test demonstrated the MCC reinforcing effect, while a bactericidal activity of silver‐based composites against a Gram‐negative bacteria (Escherichia coli) and a Gram‐positive bacteria (Staphylococcus aureus) was detected at any time points and temperatures analyzed. Moreover, the disintegrability in composting showed that MCC is able to promote the degradation process. The combination of MCC and Ag nanoparticles in PLA polymer matrix offers promising perspectives to realize multifunctional ternary composites with good mechanical response and antibacterial effect, maintaining the optical transparency and the disintegrability, hence suitable for packaging applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

改性微晶纤维素的制备及其对填充丁苯橡胶性能的影响II 改性棉纤维素对填充丁苯橡胶性能的影响

研究了微晶纤维素(MCC)和改性微晶纤维素(MMCC)的用量对丁苯橡胶(SBR)硫化胶物理机械性能的影响,以及分别填充20phrMCC和MMCC的SBR复合材料的耐磨性和动态力学性能分析。结果表明,当MCC和MMCC的用量都为20phr时,硫化胶有最大的拉伸强度,分别为15.3MPa和19.0MPa;填充MMCC的SBR复合材料的磨耗体积比填充MCC的降低了41%;填充20phr的MCC和MMCC的SBR具有相似的玻璃化温度。     

Preparation of Spherical Cellulose Nanocrystals from Microcrystalline Cellulose by Mixed Acid Hydrolysis with Different Pretreatment Routes

Spherical cellulose nanocrystal (CNC), as a high value cellulose derivative, shows an excellent application potential in biomedicine, food packaging, energy storage, and many other fields due to its special structure. CNC is usually prepared by the mixed acid hydrolysis method from numerous cellulose raw materials. However, the pretreatment route in preparing spherical CNC from cellulose fiber is still used when choosing microcrystalline cellulose (MCC) as the raw material, which is not rigorous and economical. In this work, pretreatment effects on the properties of spherical CNC produced from MCC by mixed acid hydrolysis were systematically studied. Firstly, the necessity of the swelling process in pretreatment was examined. Secondly, the form effects of pretreated MCC (slurry or powder form) before acid hydrolysis in the preparation of spherical CNC were carefully investigated. The results show that the swelling process is not indispensable. Furthermore, the form of pretreated MCC also has a certain influence on the morphology, crystallinity, and thermal stability of spherical CNC. Thus, spherical CNC with different properties can be economically prepared from MCC by selecting different pretreatment routes through mixed acid hydrolysis.     

Development and properties evaluation of bio‐based PLA/PLGA blend films reinforced with microcrystalline cellulose and organophilic silica

The preparation and properties of hybrid materials based on poly(lactic acid)/poly(lactic acid‐co‐glycolic acid) (PLA/PLGA) blends using microcrystalline cellulose (MCC) and organophilic silica (R972) as fillers have been investigated. Hybrid materials were manufactured by solution casting using chloroform as solvent to prepare films. R972 was incorporated in a ratio of 3 wt%, and MCC was added in ratios of 3, 5, or 7 wt% with respect to the weight of the polymeric matrix. Films were prepared with only MCC addition or with MCC and R972 combined. Properties of the films were evaluated by X‐ray diffraction (XRD), nuclear magnetic resonance, differential scanning calorimetry (DSC) and mechanical property measurements. The results show that each filler, when added individually or in combination, affects the structure and final properties of the films differently. MCC acts as a nucleating agent for the crystallization of the polymeric matrix. An increase in the MCC content increased the crystallinity of the films. This effect became more pronounced with silica addition. The domain distribution curves showed PLA/PLGA blends to be homogeneous, which was further confirmed by DSC. An improvement in the mechanical performance was observed with MCC addition, especially when silica was added together with cellulose. POLYM. ENG. SCI., 57:464–472, 2017. © 2016 Society of Plastics Engineers.     

微晶纤维素/聚乳酸复合材料的性能研究

以微晶纤维素为填充剂,聚乳酸为基体,采用熔融共混法制备PLA/MCC生物降解复合材料。考察了聚甲基丙烯酸甲酯(PMMA)表面处理的微晶纤维素对复合材料性能的影响。结果表明,PMMA包覆MCC增加了弯曲强度。表面改性处理提高了MCC的热稳定性,使其加工温度提高了。     

纳米SiO2包覆微晶纤维素对PBS/PLA复合材料性能的影响

以纳米二氧化硅(nano-SiO2)表面包覆的微晶纤维素(MCC)为填料,采用熔融共混的方法制备了聚乳酸/聚丁二酸丁二醇酯（PLA/PBS）复合材料。运用扫描电子显微镜、热重分析仪、差示扫描量热仪、动态热力学分析仪等方法研究了nano-SiO2对PLA/PBS/MCC复合材料的力学性能、热稳定性以及结晶行为的影响。结果表明,nano-SiO2包覆在MCC表面后与PLA/PBS熔融共混提高了nano-SiO2在聚合物材料中的分散性,改善了MCC与树脂基体的相容性;添加5 %（质量分数,下同）MCC的PLA/PBS/MCC复合材料,与同样添加量的PLA/PBS/nano-SiO2-MCC复合材料相比,其储能模量、冲击强度以及结晶度分别提高了13.04 %、11.70 %、71.92 %。     

再生纤维素/壳聚糖/银纳米线抗菌复合膜制备及性能

以1-丁基-3甲基咪唑氯盐（[Bmim]Cl）为溶剂体系，通过微晶纤维素（MCC）溶解再生制备基膜，壳聚糖（CS）、银纳米线（AgNW）共混液包覆方法制备抗菌复合膜，通过FTIR、XRD、SEM和热重分析对复合膜的形貌和结构进行表征及对力学、光学、阻隔、抑菌等性能测试分析。结果表明，壳聚糖和银纳米线成功复合于纤维素基膜，与再生纤维素膜相比，当AgNW质量分数为0.5%时，复合膜的拉伸强度提升了12.2%，透光率保持在89.82%，氧气透过率下降了86.7%，且对大肠杆菌具有良好的抑制作用，制备出一种力学性能、光学性能、阻隔性能、抗菌性能优异的可降解纤维素/壳聚糖/银纳米线抗菌复合膜。     

Preparation of acylated microcrystalline cellulose using olive oil and its reinforcing effect on poly(lactic acid) films for packaging application

A novel poly(lactic acid) (PLA) based composite, reinforced by microcrystalline cellulose (MCC) was prepared. MCC was modified by esterification reaction using olive oil for improving the compatibility with PLA matrix. The acylated microcrystalline cellulose (AMCC) exhibited reduced polarity in comparison to unmodified MCC. AMCC/ PLA composite films were prepared using solvent casting technique. The effects of the MCC surface modification on morphological, mechanical, physical, thermal, biodegradability and barrier properties of the PLA based MCC composites were studied. FTIR analysis confirmed acylation reaction of MCC. Scanning electron microscopy analysis exhibited a uniform distribution of AMCC in PLA matrix. Barrier properties of AMCC based composites were improved as compared to MCC based composites. The tensile strength and tensile modulus of composite films (at 2 wt.% AMCC) were improved about 13% and 35% as much as those of the pure PLA films, respectively. These biodegradable composite films can be a sustainable utilization of olive oil and microcrystalline cellulose in the food packaging application.     

Controlling water permeability of composite films of polylactide acid,cellulose, and xyloglucan

To test the hypothesis that the introduction of a hydrophilic hemicellulose would affect viscoelastic properties and increase water permeability, xyloglucan (XG) was adsorbed onto the surface of microcrystalline cellulose (MCC) in water dispersion prior to the extrusion of 79–80 wt % polylactide acid (PLA), 20 wt % MCC, and 0–1 wt % XG. For comparison, composites of PLA, MCC, and non‐absorbed XG were produced. Analysis of thermal properties showed no differences for glass‐transition or melting temperatures, but the crystallinity of the films increased with the addition of MCC and XG. Storage modulus of the composite materials increased with XG content; however, at higher humidities storage modulus decreased, probably because of lower interfacial adhesion. Water permeability through the films increased more with the addition of XG adsorbed to the MCC than with the MCC and XG simply mixed in the same amounts. © 2014 The Authors. Journal of Applied Polymer Science Published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41219.     

Mechanical properties of biodegradable composites from poly lactic acid (PLA) and microcrystalline cellulose (MCC)

Biodegradable composites were prepared using microcrystalline cellulose (MCC) as the reinforcement and polylactic acid (PLA) as a matrix. PLA is polyester of lactic acid and MCC is cellulose derived from high quality wood pulp by acid hydrolysis to remove the amorphous regions. The composites were prepared with different MCC contents, up to 25 wt %, and wood flour (WF) and wood pulp (WP) were used as reference materials. Generally, the MCC/PLA composites showed lower mechanical properties compared to the reference materials. The dynamic mechanical thermal analysis (DMTA) showed that the storage modulus was increased with the addition of MCC. The X‐ray diffraction (XRD) studies on the materials showed that the composites were less crystalline than the pure components. However, the scanning electron microscopy (SEM) study of materials showed that the MCC was remaining as aggregates of crystalline cellulose fibrils, which explains the poor mechanical properties. Furthermore, the fracture surfaces of MCC composites were indicative of poor adhesion between MCC and the PLA matrix. Biodegradation studies in compost soil at 58°C showed that WF composites have better biodegradability compared to WP and MCC composites. The composite performances are expected to improve by separation of the cellulose aggregates to microfibrils and with improved adhesion. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2014–2025, 2005     

基于溶胶-凝胶技术制备纳米纤维素的表征

通过傅里叶变换红外光谱、X射线衍射、热重、透射电子显微镜分析及激光粒度分析对基于溶胶-凝胶技术制备的纳米纤维素进行表征,结果表明原料微晶纤维素超分子结构为纤维素Ⅰ型,制备的纳米纤维素为纤维素Ⅱ型;微晶纤维素的结晶度为87.54%,纳米纤维素的结晶度为73.49%,纳米纤维素结晶度较微晶纤维素有所下降;制备的纳米纤维素热稳定性低于微晶纤维素;纳米纤维素平均粒度425 nm,粒度分布呈现正态分布;纳米纤维素长径比为5∶1～40∶1。     

Structural changes of starch/polyvinyl alcohol biocomposite films reinforced with microcrystalline cellulose due to biodegradation in simulated aerobic compost environment

Starch/Polyvinyl alcohol (PVA) based biocomposite films reinforced with micro crystalline cellulose (MCC) (10 wt %) particles were prepared by solution casting method, incorporating glycerol as plasticizer. These biocomposite films were subjected to biodegradation at ambient temperature in a simulated aerobic compost pit. The extent of biodegradation of these films was studied in terms of weight loss. The corresponding changes in the structure of the films were observed using scanning electron microscopy, X‐Ray diffraction study, and differential scanning calorimetry. The melting point of PVA component of the biocomposite film shifted from 204 to 223°C with increase in biodegradation time and a remarkable difference was observed in their melt crystallization behavior. The unreinforced films also showed a similar trend, but the increase in the crystallinity of PVA was more pronounced in MCC reinforced films than that observed in the unreinforced ones. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Crystallisation,mechanical properties and rheological behaviour of PLA composites reinforced by surface modified microcrystalline cellulose

Microcrystalline cellulose chemically modified by 3-isocyanatopropyl triethoxysilane (K-MCC) was incorporated as reinforcement into a polylactic acid (PLA) matrix to prepare PLA/K-MCC composites by melt blending. X-ray diffraction showed that PLA's crystalline structure was not affected by the added K-MCC, but its degree of crystallinity increased somewhat. Differential scanning calorimetry indicated that, when 5?wt-%K-MCC was added to PLA, the crystallisation of PLA improved greatly, and the degree of crystallinity reached a maximum of 39.4%, which exceeded that of pure PLA. Mechanical testing revealed that the tensile strength, modulus and heat distortion temperature of PLA also increased significantly after modified MCC was added, and the optimum mechanical properties of the composite were obtained. Dynamic rheological tests revealed shear thinning behaviour in the PLA/K-MCC composites. With increasing shear rate, more obvious shear thinning was observed because of more homogeneous dispersion of K-MCC with fewer hydroxyl groups in the PLA matrix.     

Extraction and characterization of cellulose nanocrystals from cotton fiber by enzymatic hydrolysis-assisted high-pressure homogenization

Cellulose nanocrystals (CNCs) have attracted increasing attention in the field of nanomaterials because of its high aspect ratio, good structure, and high thermal stability. In this study, enzymatic hydrolysis-assisted high-pressure homogenization was applied as an environmentally friendly technique to extract CNCs from cotton-derived microcrystalline cellulose (MCC). The overall optimization of enzymatic pretreatment was conducted by response surface methodology, and the maximum CNCs yield was 40.09% under the optimized experimental conditions. The extracted CNCs under the optimal conditions showed needle-like shape with a length of 100–250 nm and a width of 5–10 nm and exhibited an overall particle size range of 3–80 nm. The basic chemical structure of cellulose was not changed after enzymatic hydrolysis and high-pressure homogenization. The CNCs exhibited slightly lower crystallinity and higher thermal stability than MCC. High aspect ratio CNCs extracted in this present study have great potential as a reinforcing agent in biodegradable packaging materials.     

Shear‐induced crystallization of injection molded vetiver grass‐polypropylene composites

Vetiver grass was used as an alternative filler in polypropylene (PP) composites in this study. Chemical treatment of vetiver grass by alkalization was carried out to obtain alkali‐treated vetiver grass. It was shown that alkali‐treated vetiver grass exhibited higher thermal stability than untreated vetiver grass. Injection molding was used to prepare the composites. The microstructure of injection molded samples showed a distinct skin layer due to shear‐induced crystallization. It was found that normalized thickness of shear‐induced crystallization layer of the composite was lower than that of neat PP. The effect of vetiver particle sizes on shear‐induced crystallization and physical properties of the composites were elucidated. Furthermore, the effect of processing conditions on shear‐induced crystallization, degree of crystallinity, gapwise crystallinity distribution, and mechanical properties of the composite were investigated. It was shown that injection speed and mold temperature affected the normalized thickness of shear‐induced crystallization layer and degree of crystallinity of the composites. However, processing conditions showed insignificant effect on the mechanical properties of vetiver fiber‐PP composites. The degree of crystallinity showed no distribution throughout the thickness direction of the composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

纤维素的酸处理及醋酸酯化表面改性研究

分别用HCl和H2SO4处理从棉纤维中提取的纤维素,100℃下回流水解30～60 min得到微晶纤维素(MCC),并对其进行醋酸酯化表面改性.采用X-射线衍射(XRD)、热重分析(TG)、红外光谱(IR)技术研究酸处理对MCC的聚合度、结晶度和热稳定性的影响,探讨了改性方法对产物性能的影响.结果表明,纤维素微晶化后仍保持原来的晶型以及晶区和非晶区共存的微细结构,结晶度不能达到100%.扫描电子显微镜(SEM)测试结果表明,不同酸处理后所得产物的形态和热性能有所不同,MCC的最高适用温度不宜超过270℃.适宜的醋酸酯化改性条件为:硫酸和水体积比1∶8、温度60～70℃、改性处理3～5 h.改性后微晶纤维素的内部结晶区结构没有变化,在有机溶剂中的分散性得到良好的改善.     

Effect of surface modification of microcrystalline cellulose with ionic liquids on natural latex composites

As an environmentally friendly biomacromolecular material, microcrystalline cellulose (MCC) enhances the performance of natural rubber latex (NRL) composites. However, MCC has strong polarity, which weakens the interfacial interaction between MCC and the non-polar NRL matrix and reduces the reinforcing performance due to the many hydroxyl groups on its surface. In this paper, the ionic liquid (IL) modified MCC/IL material was prepared, and AIR-FTIR, x-ray diffraction, and XPS photoelectron spectroscopy were performed to detect it from the perspective of environmental protection. And natural latex/microcrystalline cellulose/ionic liquid (NRL/MCC/IL) composites with excellent properties were prepared by latex blending. The activation energy, vulcanization characteristics, basic mechanical properties, dynamic mechanical properties, and filler-rubber interfacial interactions of NRL/MCC/IL composites were investigated. The results showed that the vulcanization rate constant of NRL/MCC/IL composites increase, the activation energy decreases and the mechanical properties were significantly improved. At the same time, the matrix interface interaction of composites was quantitatively calculated using Ayala parameters. The results showed that the interfacial interaction force of the composite was stronger after an appropriate amount of IL pretreatment. The whole process is not only conformed to the concept of green development, but also broadens the application of MCC in rubber materials.     

Application of ultrasonic waves in activation of microcrystalline cellulose

In this work, microcrystalline cellulose (MCC) was activated with ultrasonic waves. The influences of ultrasonic treatment on the changes of supramolecular structures and morphology structure were studied by WAXS and SEM. The accessibility of the MCC was characterized by water retention value (WRV) and specific surficial area. The influence of ultrasonic treatment on the reactivity of MCC was investigated through the reaction of MCC being oxidized into 2,3‐diadehyde cellulose (DAC) by periodate sodium. The mechanism of the reactivity change of ultrasonically treated MCC was examined. The results showed that the degree of crystallinity of MCC decreased and the degree of polymerization showed little change after treatment with ultrasonic waves. The morphologial variation of the treated MCC was significant when compared with the untreated MCC, which contribute to the improvement of accessibility. The aldehyde content of DAC prepared from ultrasonically treated MCC was improved from 64.19 to 85.00%, indicating that the regioselective oxidation reactivity of MCC was significantly improved. The aldehyde content was found to first increase with time of ultrasonic treatment to a point, and then decrease as time progressed. In addition, the aldehyde content was found to increase with an increase in ultrasonic power. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008