Rheology of Concentrated Cellulose Solutions in 1-Butyl-3-methylimidazolium Chloride

Rheological behavior of the concentrated cellulose/1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solutions was investigated. As polymeric fluid, solutions of cellulose in [BMIM]Cl display a marked elastic behavior under shear flow. The dependence of the shear viscosity η, and of the dynamic modulus, on concentration, average degree of polymerization (DP) and temperature is discussed. At lower concentrations and degrees of polymerization (DP), cellulose solutions show viscous, inelastic behavior at low frequencies and low shear rate. At higher concentration and DP, cellulose solutions are more elastic at higher frequencies and shear rate. Such solutions also have some usual rheological properties. The dynamic rheological responses revealed that the Cox–Merz rule did not hold for these cellulose solutions at high deformation rate. Plotting storage modulus G′ against loss modulus G″ gave almost a master curve which is independent of temperature and concentration, with the slope of about 1.651 for 10 wt% cellulose solutions. This value indicates the existence of microheterogeneity in the solution system.     

Nanocomposites of Cellulose Acetate Butyrate Reinforced with Cellulose Nanocrystals

Nanocrystals were prepared by acid hydrolysis of bacterial cellulose microfibrils. These were topochemically trimethylsilylated, in an attempt to reduce their hydrophilicity. Composites were made by dispersing either native or silylated crystals in cellulose acetatebutyrate matrixes and solution casting of the dispersions. Particles were characterized by transmission electron microscopy. The composites were characterized by differential scanning calorimetry and dynamic mechanical analysis. The unmodified cellulose crystals exhibited better reinforcement characteristics than the trimethylsilated crystals.     

Alkaline Degradation of Cellulose: Mechanisms and Kinetics

Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70–85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150–550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.     

Effect of Sequential Mixing and Compounding Conditions on Cellulose Acetate/Layered Silicate Nanocomposites

Injection molded nanocomposites have been successfully fabricated from cellulose acetate (CA), eco-friendly triethyl citrate (TEC) plasticizer, and organically modified clay with and without maleic anhydride grafted cellulose acetate butyrate (CAB-g-MA) as a compatibilizer. The effects of processing conditions such as mixing methods, pre-plasticizing times, extruder retention times (RT) and addition of compatibilizer on the performance of these nanocomposites have been evaluated. The cellulosic plastic with CA/TEC (80/20 wt%) was used as the polymer matrix for nanocomposite fabrication. The morphologies of these nanocomposites were evaluated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. The mechanical properties of the nanocomposites were measured and have been correlated with the XRD and TEM observations. From all of the sequential mixing methods used, powder–powder mixing leads to the most transparent nanocomposites. Cellulosic plastic-based nanocomposites obtained using increased pre-plasticizing times and RT showed better exfoliated structures. In the system containing compatibilizer, the minimum retention time required for obtaining almost completely exfoliated hybrid nanocomposites was shorter than in the system without compatibilizer.     

Preparation and Characterization of Cellulose/Polypropylene Composite Using an Oxidatively Degraded Polypropylene

In this work, an oxidatively degraded polypropylene (DgPP) was studied as a novel coupling agent for fibrous cellulose (FC)/polypropylene (PP) composite. An optimal preparation time of PP thermal oxidative degradation was 18 h at 130 °C, and the DgPP had functional groups such as γ-lactone and acid groups. The spherulite observation of the DgPP suggested miscibility for the undegraded PP. The addition of the DgPP presented the transparency improvement of FC/PP composite, and this behavior was found to be originated from the grafted DgPP, which was produced by the esterification reaction between the of FC and the DgPP. The scanning electron microscope (SEM) observation showed that the grafted DgPP coated the FC surface, and the tensile strength of the FC/PP composite increased by an appropriate amount of the DgPP addition. These results suggested that the DgPP was suitable for the coupling agent of FC/PP composite.     

球形纤维素吸附剂对Cr3+吸附和解吸的研究

用静态法和动态法研究了球形纤维素吸附剂对水中 Cr3+的吸附和解吸 ,包括静态等温吸附以及各种因素对吸附的影响等 ,并探讨了吸附机理。 Cr3+的吸附容量为 2 8mg/ g,采用浓度为 1.2 mol/ L 的 HCl溶液作解吸液回收 Cr3+的综合效果较好。静态法和动态法的吸附率均达 90 %左右 ,解吸率均达 85 %以上 ,且静态法的吸附率和解吸率分别略高于动态法的吸附率和解吸率 ,但动态法耗时短 ,更符合工业化要求。     

Evaluation of the Biodegradation of Starch and Cellulose Under Controlled Composting Conditions

In order to verify the response of the controlled composting test method (i.e., the ISO/DIS 14855:1997, the ASTM D 5338-92, or the CEN counterpart) to starch at different concentrations, the maximum amount prescribed by the test method (100 g) and lower amounts (60 and 30 g), as if starch were a coingredient in a blend, were tested. After 44 days of incubation (at a constant temperature of 58°C) the biodegradation curves were in a plateau phase, displaying the following final values (referred to a nominal starch initial amount of 100 g): starch 100 g, 97.5%; starch 60 g, 63.7%; and starch 30 g, 32.5%. The data show a CO₂ evolution roughly equal, in each case, to the theoretical maximum, indicating a complete starch mineralization. We cannot discern whether the deviations found at lower concentrations are caused by a priming effect. In any case, the extent of the deviations is not high and is acceptable in biodegradation studies. The average biodegradation of cellulose, obtained gathering four independent experiments with 11 biodegradation curves, turned out to be 96.8 ± 6.7% (SD) after 47 ± 1 days. The data indicate that the controlled composting is a reliable test method also for starch and cellulose and, consequently, for starch-based and cellulose-based materials.     

Cellulose acetate biodegradability upon exposure to simulated aerobic composting and anaerobic bioreactor environments

Cellulose acetate (CA) films with degree of substitution (d.s.) values of 1.7 and 2.5 were exposed to biologically active in-laboratory composting test vessels maintained at approximately 53 °C. The CA 1.7- and 2.5-d.s. films (thickness values of 0.5–1.0 and 2.0 mil, respectively) had completely disappeared by the end of 7- and 18-day exposure time periods in the biologically active bioreactors, respectively. The relatively small CA film weight loss observed in the poisoned control test vessels allows the conclusion that CA film erosion during the composting exposures resulted, at least in part, from biologically mediated processes. Under strictly anaerobic conditions, an active methanogenic inoculum was developed by acclimation of a sewage sludge to a synthetic municipal solid waste (SMSW) mixture at 42°C. The CA 1.7-d.s. film samples (0.5- to 1.0-mil thickness) were exposed in anaerobic serum bottles containing a 25% solids loading of SMSW in which methanogenic activity was rapidly established after introducing of the developed inoculum. For exposures of 30 days only small visually distinguishable fragments of the CA 1.7-d.s. films were recovered. In contrast, exposure of the CA 1.7-d.s. film to a poisoned control test vessel resulted in negligible weight loss. Therefore, degradation of the CA 1.7-d.s. films upon exposure to the anaerobic bioreactors was due, at least in part, to biologically mediated processes.Guest Editor: Dr. Graham Swift, Rohm & Haas.     

Extraction of Cellulose Nanocrystals from Phormium tenax Fibres

Cellulose nanocrystals with an acicular structure ranged from 100 to 200 nm in length and 15 nm in width were extracted from Phormium tenax leaf fibres by acid hydrolysis. A two-step procedure for the extraction of nano-sized cellulose was studied and the obtained nanocrystals were characterized using morphological investigations (optical, scanning electron and atomic force microscopy), as well as physico-chemical characterization by Wide Angle X-ray Scattering, infrared spectroscopy and thermogravimetric analysis. A study of birefringence properties was also performed. The first chemical treatment leads to the production of holocellulose by the gradual removal of lignin, while the subsequent sulphuric acid hydrolysis process allows obtaining cellulose nanocrystals in an aqueous suspension. The results reported support the repeatability and the effectiveness of the procedure performed. Moreover, the high cellulose content of P. tenax fibre and their declining market interest, suggest the interest of this investigation and the possibility to use natural fibres for the production of a reinforcement phase to involve in the nanocomposite approach for industrial applications.     

Marine Debris &; Plastics: Environmental Concerns,Sources, Impacts and Solutions

Marine debris (marine litter) is one of the most pervasive and solvable pollution problems plaguing the world’s oceans and waterways. Nets, food wrappers, cigarette filters, bottles, resin pellets, and other debris items can have serious impacts on wildlife, habitat, and human safety. Successful management of the problem requires a comprehensive understanding of both marine debris and human behavior. Knowledge is key for consumers to make appropriate choices when it comes to using and disposing of waste items. Education and outreach programs, strong laws and policies, and governmental and private enforcement are the building blocks for a successful marine pollution prevention initiative. The plastic industry also has a role to play in educating its employees and customers, and searching for technological mitigation strategies.     

Thermo-mechanical Characterization of New Natural Cellulose Fiber from Zmioculus Zamiifolia

Journal of Polymers and the Environment - The environmental impact on pollution has attracted the use of natural cellulose fibers as a replacement for synthetic materials due its ecofriendly nature...     

Nanocomposites of Waterborne Polyurethane Reinforced with Cellulose Nanocrystals from Sisal Fibres

Cellulose nanocrystals (CNC) were isolated from sisal fibres and were incorporated in the form of an aqueous suspension to a waterborne polyurethane (WBPU) synthesized from components derived from natural sources using an aliphatic diisocyanate. Transparent nanocomposite films with different CNC contents were prepared using a casting method. The morphology, thermal behaviour and mechanical properties of the nanocomposite films were characterized. Homogeneous distribution of CNC in the WBPU, even at high CNC contents was observed, resulting in an increase of 100% in modulus for systems with 5 and 10 wt% of CNC, with high elongations around 650%.     

Isolation and Characterization of Cellulose Micro/Nanofibrils from Douglas Fir

Cellulose micro/nanofibrils were successfully extracted from softwood Douglas fir in three distinct stages. Initially raw Douglas fir wood chips were subjected to a hot water extraction (HWE) treatment. Then HWE treated cellulosic fibers underwent a bleaching process followed by a mild ultrasonication. Chemical composition analysis according to ASTM standards confirmed that most of hemicelluloses and nearly all lignin were removed during the first two stages, respectively. Microscopy studies showed formation of nanofibrils during the ultrasonication process, and increasing ultrasonication time led to generation of greater percentage of nanofibrils. With the removal of the matrix materials, the crystallinity of the cellulosic fibers was increased, whereas thermal stability was maintained. HWE opened up the cell wall structure, thereby facilitating the subsequent fractionation into micro/nanofibrils. The obtained cellulose micro/nanofibrils could serve as reinforcing material in composite products or raw material for other applications, such as filtration membrane.     

Biodegradation of Waste Cellulose

Environmental issues such as the depletion of nonrenewable energy resources and pollution are very topical and would need more scientific attention in order to be addressed in a way beneficial to life. The extent of solid waste production is a global concern and development of its bioenergy potential can simultaneously address issues such as pollution control and renewable energy development. Various wastepaper materials, a major component of solid waste, have been treated with cellulase from Trichoderma viride to bioconvert its cellulose component into fermentable sugars that could be utilized as feedstock for bioproduct development. These paper materials exhibited different susceptibilities toward the cellulase and showed different sugarreleasing patterns when increasing amounts of each paper were treated with the enzyme. Bioconversion of paper with different enzyme concentrations and during various time intervals also resulted in nonsimilar sugar-releasing patterns. With all the paper materials, a general decline in efficiency was observed with increasing amounts of sugar produced during the different bioconversion variables investigated.     

Preparation and Fundamental Characterization of Cellulose Nanocrystal from Oil Palm Fronds Biomass

The objective of this work was to isolate cellulose nanocrystal (CNC) from oil palm fronds (Elaeis guineensis) and its subsequent characterization. Isolation involves sodium hydroxide/anthraquinone pulping with mechanical refining followed by total chlorine free bleaching (includes oxygen delignification, hydrogen peroxide oxidation and peracetic acid treatment) before acid hydrolysis. Bleaching significantly decreased kappa number and increased α-cellulose percentage of fibers as confirmed by Technical Association of the Pulp and Paper Industry standards. Transmission electron microscopy (TEM), X-ray diffraction, Fourier transform infrared spectroscopy and thermogravimetric analysis revealed that acid hydrolysis along with bleaching improved crystallinity index and thermal stability of the extracted nanocrystals. It was observed that CNC maintained its cellulose 1 polymorph despite hydrolysis treatment. Mean diameter as observed by TEM and average fiber aspect ratio of obtained CNC was 7.44 ± 0.17 nm and 16.53 ± 3.52, respectively making it suitable as a reinforcing material for nanocomposite.     

不同氧化法对模拟聚合物驱废水降黏效果的影响

分别采用UV-Fenton试剂氧化法、次氯酸钙氧化法和二氧化氯氧化法处理模拟聚合物驱废水,考察了各工艺条件对废水降黏效果的影响。实验结果表明:在初始废水pH为7、反应温度为50℃、反应时间为20 min的条件下,UV-Fenton试剂氧化法适宜的H2O2加入量为1 mmol/L,n(H2O2)∶n(Fe2+)=10,处理后废水降黏率达65.7%;次氯酸钙氧化法适宜的次氯酸钙加入量为500 mg/L,处理后废水降黏率达81.7%;二氧化氯氧化法适宜的二氧化氯加入量为100 mg/L,处理后废水降黏率为40.9%。3种氧化法对模拟聚合物驱废水的降黏率大小顺序为:次氯酸钙氧化法>UV-Fenton试剂氧化法>二氧化氯氧化法。     

Extraction and Characterization of Microcrystalline Cellulose from Date Palm Fibers using Successive Chemical Treatments

Journal of Polymers and the Environment - The aim of present study is to extract microcrystalline cellulose (MCC) from fruit bunch branches fibers of Algerian date palm trees (phoenix dactylifera...     

巴氏醋酸杆菌发酵处理甲醇废水合成细菌纤维素的研究

介绍了巴氏醋酸杆菌以甲醇为唯一碳源、以酵母膏或蛋白胨为氮源合成细菌纤维素,同时净化甲醇废水的方法,并对合成细菌纤维素的培养条件进行了研究。试验得出巴氏醋酸杆菌的适宜发酵条件为：发酵培养基中甲醇质量分数为3．5％左右,发酵培养基初始pH为5．0～6．0。接种量为5％,发酵培养温度为30℃,振荡器转速为100r／min。