Pure Cellulose Fibers Research Articles

Flame Retardant Properties of Viscose Fibers Containing Talcum Powder

Cellulose-insoluble silicate (talcum powder) hybrid fibers with 10%, 20%, 30% silica contents were prepared by wet spinning. The flammabilities and combustion processes were evaluated by the limiting oxygen index (LOI) and cone calorimetry. The LOI results suggested that the hybrid fibers were flame retandant with the LOI value of 22, 25 and 27, as compared to 20 of pure cellulose fibers. Cone calorimetry showed that the rate of heat release value and total heat release value of hybrid fibers decreased. Hybrid fibers with 20% SiO2 loading is the best flame retardant sample. SEM studies of residues after cone calorimetry indicated that the hybrid fibers produced tight and hard residue crusts.

Reinforcing wood–plastic composites with macro- and micro-sized cellulosic fillers: Comparative analysis

The application area of wood–plastic composites is growing rapidly, which is reflected in massive research activity. In the present study, comparative analysis of cellulosic fillers of different macro- and micro-sized particles in reinforcing polypropylene-based wood–plastic composites is performed. The mechanical properties of composites manufactured with three different types of spruce wood flour (coarse, 20-mesh and Arbocel C320) particles are compared. The study shows that composites with 20-mesh wood flour have better tensile, flexural and impact properties. The possibility of using a microfibrillated cellulose as the reinforcing filler in wood–plastic composite is also studied. The combination of microfibrillated cellulose (10 wt%) with coarse wood flour resulted in improvement in almost all mechanical parameters of the wood–plastic composite. In addition, it is shown that a wood–plastic composite manufactured using pure cellulose fibres has the weakest mechanical properties. The water absorption and thickness swelling of the composite, as well as the durability of the composites exposed to three cycles of water immersion, freezing and thawing are observed. The microstructure of the composites is examined by scanning electron microscope. The superior properties of microfibrillated cellulose-containing wood–plastic composites are described for the first time.

Preparation and characterization of bionanocomposite fiber based on cellulose and nano-SiO2 using ionic liquid

Microcrystalline cellulose (MCC)/nano-SiO2 composite fibers were processed from solutions in 1-allyl-3-methylimidazolium chloride (AMIMCl) by the method of dry-jet wet spinning. The oscillatory shear measurements demonstrated that the gel network formed above 10wt% nano-SiO2 and the complex viscosity increased with increasing nano-SiO2. Remarkably, the shear viscosity of the nanofluids was even lower than solutions without nano-SiO2 under high shear rates. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images revealed that well-dispersed particles exhibit strong interfacial interactions with cellulose matrix. Measurements on wide-angle X-ray diffraction (WAXD) indicated that the regenerated cellulose and nanocomposite fibers were the typical cellulose II crystalline form, which was different from the native cellulose with the polymorph of Type I. The tensile strength of the nanocomposite fibers was larger than that of pure cellulose fiber and showed a tendency to increase and then decrease with increasing nano-SiO2. Furthermore, the nanocomposite fibers exhibited improved thermal stability.

Characteristics of regenerated nanocellulosic fibers from cellulose dissolution in aqueous solutions for wood fiber/polypropylene composites

The effects of aqueous solutions were evaluated on the properties of regenerated cellulosic nanofibers prepared from pure cellulose fibers in various formulations of aqueous solutions. Thermoplastic composites were prepared with reinforcement of the regenerated cellulosic nanofibers. The regenerated cellulosic fibers from cellulosic woody biomass were obtained from dissolved cellulose solutions by coagulating with sulfuric acid and water for phase separation. The properties of the regenerated cellulosic fibers were characterized using Fourier-transform infrared spectroscopy (FTIR), wide angle X-ray diffraction (WAXRD), thermogravimetric analysis (TGA), field emission scanning electron microscopy, and tensile testing. The TGA, WAXRD, and FTIR spectra indicated that the regenerated nanofibers possessed cellulosic crystal type II. The micrographs of regenerated cellulosic fibers showed a dense composite structure and lower crystallinity than controlled fibers. The tensile strength of regenerated cellulosic fiber-reinforced polymer composites reached 30 MPa, which was 70% higher than the control fiber-reinforced composites. The composites prepared from regenerated fibers with sodium hydroxide (NaOH)/urea and NaOH/urea/thiourea aqueous solutions provided the best results. This work also provides a potential promising method to efficiently obtain nanocellulosic fibers as reinforcement materials in bio-based nanocomposites.

Influence of Homogenization Treatment on Physicochemical Properties and Enzymatic Hydrolysis Rate of Pure Cellulose Fibers

The aim of this study is to compare the effect of different homogenization treatments on the physicochemical properties and the hydrolysis rate of a pure bleached cellulose. Results obtained show that homogenization treatments improve the enzymatic hydrolysis rate of the cellulose fibers by 25 to 100%, depending of the homogenization treatment applied. Characterization of the samples showed also that homogenization had an impact on some physicochemical properties of the cellulose. For moderate treatment intensities (pressure below 500b and degree of homogenization below 25), an increase of water retention values (WRV) that correlated to the increase of the hydrolysis rate was highlighted. Result also showed that the overall crystallinity of the cellulose properties appeared not to be impacted by the homogenization treatment. For higher treatment intensities, homogenized cellulose samples developed a stable tridimentional network that contributes to decrease cellulase mobility and slowdown the hydrolysis process.

Influence of steam explosion on physicochemical properties and hydrolysis rate of pure cellulose fibers

The aim of this study is to compare the effect of different steam explosion treatments on the physicochemical properties and the hydrolysis rate of a pure bleached cellulose. The results showed that moderate steam explosion treatments (severity factor below 5.2) did not appear to improve the enzymatic hydrolysis rate of the cellulose fibers. However, characterization of the samples showed a modification of the physicochemical properties of the cellulose, resulting in an increase of the water retention values (WRV) coupled to an increase of the overall crystallinity. For higher treatment intensities, an important thermal degradation of the cellulose was highlighted. This thermal degradation caused an important modification of the cellulose composition which leads to a decrease of the hydrolysis rate.

Study on electrical transport and photoconductivity in iodine-doped cellulose fibers

The electrical transport and photoconductivity of pure and iodine-doped cellulose fibers have been studied. The studies were conducted in the temperature range 293–363 K, while the electric field was varied over the range 1–100 V cm−1. The conductivity of the iodine-doped cellulose fibers shows significant enhancement by more than four orders of magnitude as compared to undoped samples. The analysis reveals that the electrical conduction follows Ohm’s law for iodine-doped samples, while for the undoped samples the bulk-limited Pool–Frenkel conduction mechanism is likely to dominate for the steady state current. Especially, the clear photoconduction response at UV and visible region indicates that photoconduction is essential due to band-to-band electron–hole pair’s generation and that doped CF is a good conductor of photogenerated carriers.

Effects of process and source on elastic modulus of single cellulose fibrils evaluated by atomic force microscopy

A test method to measure cellulose fibril elastic modulus using atomic force microscopy was used to investigate the effects of process and source on the moduli of single cellulose fibrils. The cellulose fibrils were generated from cellulose by mechanical treatments. Individual fibrils were suspended over a micro scale groove etched on a silicon wafer. A nano-scale three-point bending test was performed to obtain the elastic moduli. The results indicated that the elastic moduli of cellulose fibrils were not significantly different between 30 min and 60 min of high intensity ultrasonic treatment for Lyocell fiber, between isolation methods of ultrasonic and homogenizer treatment for pure cellulose fiber, and between different cellulose sources of pulp fibers treated by homogenizer regardless the effects of sample size coupled with inherent variation in the raw material. The elastic modulus of Lyocell fibrils with diameters from 150 to 180 nm was evaluated to be 98 ± 6 GPa. Modulus values decreased dramatically when the diameter was more than 180 nm.

Rheological properties of cellulose/chitin xanthate blend solutions and properties of the prepared fibers

AbstractThe focus of this article is the rheological properties of cellulose xanthate, chitin xanthate, and their blend solutions with cellulose/chitin blend weight ratios of 9.5 : 0.5, 9 : 1, 8 : 2, and 5 : 5 (mostly 9 : 1 blend solutions). The preparation and properties of fibers from 9 : 1 blend solutions and cellulose xanthate solutions are also discussed. The non‐Newtonian index of the investigated solutions was found to vary in the following order: chitin < cellulose < 9.5 : 0.5 blend < 9 : 1 blend < 8 : 2 blend < 5 : 5 blend. Showing a tendency contrary to that of the non‐Newtonian index, the structure viscosity index varies in the following order: chitin > cellulose > 9.5 : 0.5 blend > 9 : 1 blend > 8 : 2 blend > 5 : 5 blend. For 5–9 wt % 9 : 1 blend solutions, increasing the solution temperature aids the improvement of the fluidity of 9 : 1 blend solutions in the temperature range of 10–40°C. The zero shear viscosity decreases in an index manner with the solution temperature increasing. The 7–8 wt % 9 : 1 blend solutions have good filtering and rheological properties and are ideal for spinning fibers. The mechanical properties of blend fibers spun from 7% 9 : 1 blend solutions are lower than those of pure cellulose and are much higher than those of Crabyon fiber, and they still reach the national criteria and fit the need for further processing. This proves that the viscose method which we have developed here is an efficient way of preparing cellulose/chitin blend fibers with satisfactory mechanical properties and processing properties. Scanning electron microscopy photographs show that the surface of 9 : 1 blend fibers is coarser than that of pure cellulose fibers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Regenerated cellulose-silk fibroin blends fibers

Fibers made of cellulose and silk fibroin at different composition were wet spun from solutions by using N-methylmorpholine N-oxide hydrates (NMMO/H 2O) as solvent and ethanol as coagulant. Different spinning conditions were used. The fibers were characterized by different techniques: FTIR-Raman, scanning electron microscopy, wide-angle x-ray diffraction, DSC analysis. The results evidence a phase separation in the whole blends compositions. The tensile characterization, however, illustrates that the properties of the blends fibers are higher respect to a linear behaviour between the pure polymers, confirming a good compatibility between cellulose and silk fibroin. The fibers containing 75% of cellulose show better mechanical properties than pure cellulose fibers: modulus of about 23 GPa and strength to break of 307 MPa.

A preliminary study for fiber spinning of mixed solutions of polyrotaxane and cellulose in a dimethylacetamide/lithium chloride (DMAc/LiCl) solvent system

Polyrotaxane fiber and polyrotaxane/cellulose blend fibers were prepared by wet-spinning of the polyrotaxane or polyrotaxane/cellulose blend solution dissolved in the new solvent system, i.e. dimethylacetamide/lithium chloride (DMAc/LiCl), into methanol and a subsequent annealing. In the resultant polyrotaxane/cellulose fiber, some undissolved rodlike cellulose microcrystals were oriented along with the fiber axis, resulting in formation of nanocomposite-like structure. From tensile measurements, it was found that the Young's modulus and tensile strength of the fibers with polyrotaxane/cellulose ratio of 1:1 and 2:1 were higher than those of the pure cellulose fiber. Although the mechanical properties of the fiber with polyrotaxane/cellulose ratio of 4:1 and the pure polyrotaxane fiber were lower than those of the pure cellulose fiber, these fibers showed significantly large strain at break (up to 90% strain), presumably due to the sliding of the cyclodextrin rings of the polyrotaxane in the fibers.

Mechanical and electrical properties of composites based on thermoplastic matrices and conductive cellulose fibers

AbstractHighly pure cellulose fibers were coated with polypyrrole (PPy) and subsequently used for preparation of composites, which reached a certain level of electrical conductivity. The cellulose fibers surface was entirely covered when 20 wt % of pyrrole was used for the modification, as confirmed by scanning electron microscopy (SEM). The cellulose fibers covered with PPy were kneaded with thermoplastic matrices: linear low‐density polyethylene (LLDPE), high‐density polyethylene (HDPE), and polycaprolactone (PCL). The highest electrical conductivity achieved was for composites based on the PCL matrix. PCL filled with 50 wt % of conducting cellulose fibers reached an electrical conductivity of 6.5 × 10−4 S cm−1. This electrical conductivity falls within the range required for antistatic materials. The mechanical properties of HDPE, LLDPE, and PCL matrices loaded with both treated and untreated cellulose fibers were also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 133–142, 2006

The influence of camphorquinone on the photochemical stability of cellulose

The photochemical stability of pure cellulose fibres and cellulose fibres with camphorquinone (CQ) has been studied by Fourier transform infrared spectroscopy (FTIR), thermogravimetry analysis (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). The initial decomposition temperature T o, temperature of the maximum rate of the process T max and specific enthalpy Δ H were higher for cellulose fibres before UV irradiation than for those UV irradiated in either N 2 or air. The weight loss was higher for the samples after UV irradiation. In the presence of CQ the initial decomposition temperature T o for cellulose fibres was the same before and after UV irradiation, but much lower than for pure non-irradiated cellulose fibres. The specific enthalpy of the process is much lower after UV irradiation. The weight loss was smaller for the samples with CQ than for pure cellulose fibres. Comparison of the shape of the derivatographic, DSC and FTIR curves before and after UV irradiation suggests that photodegradation of cellulose occurs during irradiation of this biopolymer and that this process is faster in the presence of camphorquinone (CQ). The camphorquinone is photo-excited by UV light to the reactive triplet state and causes more efficient photodegradation of the cellulose.

Interfaces in polyolefin/cellulosic fiber composites: Chemical coupling, morphology, correlation with adhesion and aging in moisture

AbstractThis paper details the characteristics of pure cellulose and wood fibers when associated with thermoplastic matrices for composite applications. Chemical modification of the cellulose is performed to allow a good compatibilization, and the most efficient compatibilizing agents must possess: (i) a function highly reactive with the OH groups of the cellulose and (ii) a non‐polar chain with preferably a polymeric structure. Polypropylenes grafted with maleic anhydride are thus efficient agents. Smaller compatibilizing agents, especially if reacted with cellulose in swelling media, react with the bulk of the fiber and lead to dimensional stability. All treatments, even when performed with low degrees of grafting or small alkyl chains, significantly modify the hydrophilicity of the cellulose surface and play a role in a better wettability of the fiber by the matrix leading to improved adherence. The global mechanical properties are then improved, but the effect is preferably studied at the scale of a single filament composite. The morphology of the matrix in the vicinity of the non‐treated fiber shows that, in some cases, the fiber acts as a nucleating agent involving the formation of a transcrystalline phase. Aging in moisture is generally detrimental to the mechanical properties. This phenomenon is limited by the chemical treatment performed on the fibers.

Effects of Several Ingredient Variables on Mechanical Properties of Wood Fiber-Polyolefin Composites Blended in a Thermokinetic Mixer

AbstractWe examined the influence of several variables on the mechanical properties of wood fiber-polyolefin composites blended in a thermokinetic mixer. A pure cellulose fiber and fibers from old newspaper provided similar performance in matrices of virgin polypropylene or recycled milk bottles (high density polyethylene). Relative to wood flour, these fibrous fillers led to greater strength and modulus with both plastics, to lower impact energy with polyethylene, and to similar impact energy with polypropylene. Compared with the existing commercial wood flour-polypropylene system, the totally recycled polyethylene-newspaper composite provided equivalent strength and modulus, along with greater notched impact energy. Little difference was seen in composites containing a maleated polypropylene additive in the form of the solid anhydride or the emulsified potassium salt, indicating that the additive acted as a dispersing agent and not as a strong coupling agent.

An X-Ray Study of Acetylated Jute

X-ray results for progressively acetylated jute fibers are described. The diffraction pattern of partially acetylated jute has certain features in common with that of a similarly treated pure cellulose fiber such as ramie or cotton, but the intense equatorial reflection characteristic of the acetyl cellulose appears to be absent in it. At highest acetyl content, the x-ray photograph of jute is closely similar to that of cellulose triacetate I, and the transformation to the new lattice appears as complete as in a pure cellulose fiber. The two large spacing equatorial reflections Ax and Ay show improved sharpness and in tensity as well as increased spacing on the partially acetylated jute diagram but are absent in the fully substituted one. The results are discussed in the light of the structure of jute.

THE EFFECT OF WATER REMOVAL ON THE CRYSTALLINITY OF CELLULOSE

The effect of various modes of drying upon the crystallinity of cellulose has been determined by X-ray diffraction.No change in the crystallinity index was observed when previously undried pure cellulose fibers from softwood were dried from water under a wide range of conditions, but a lower value was obtained when they were dried from benzene to which the fibers were accommodated by a series of solvent exchanges. Heat of wetting determinations on the same samples indicated changes in the accessibility with different drying methods. Qualitative variations in the degree of intrafiber bonding were also detected by a differential staining method. The X-ray measurements suggested that drying from water either produces no change in lateral order or that such changes are too small to be detectable by X-rays.The crystallinity of cellulose prepared by dry-milling whole fibers was studied. The crystallinity was substantially reduced in a Wiley mill and obliterated in a ball mill. X-Ray diffraction showed that wetting with water and then drying restored the crystallinity, while similar treatment with other liquids yielded less definite results. However, by following the destruction of the lattice with progressive periods of milling, it was concluded that alcohols reform this lattice to a limited extent depending, among other factors, upon the swelling capacity.