Thermochromic and/or photochromic properties of electrospun cellulose acetate microfibers for application as sensors in smart packing

There is growing demand for smart materials whose chemical structure, shape, and/or color, among other properties could be modified for use in applied packaging in the food industry, pharmacy, textiles, and so forth. These variations results from external stimuli, whether chemical, physical, and/or environmental (humidity, heat, light, and so forth), which has created promising materials for use in various areas of engineering, such as the production of ultrasensitive sensors with the capacity that the said variations are perceptible to the naked eye. The production of nanostructured sensor membranes obtained by electrospinning is one interesting alternative that has been attracting the attention of researchers in recent years. However, many studies related to the application of photosensors supported in electrospun cellulose acetate (CA) have not been found in the literature. Among the most used materials in electrospinning, CA stands out due to its wide availability and low cost that reflects in several applications. Two commercial sensitive pigments were used, a thermosensitive and a photosensitive one, in concentrations between 0 and 10% (m/v), to evaluate the best amount in the nanosensors they could be seen through naked eye. Variation on the fibers morphology was characterized by scanning electron microscopy. The stability and thermal transitions were evaluated using thermogravimetric analysis/differential thermogravimetric analysis and differential scanning calorimetry. The composition of chemical fibers was studied using FTIR-ATR. Finally, the thermal and/or UV light response was performed by qualitative test.     

Influence of water on phase transition and rheological behavior of cellulose/ionic liquid/water ternary systems

The influence of water content on liquid crystalline (LC) gel formation and the rheological behavior of a ternary microcrystalline cellulose (MCC)/1‐ehtyl‐3‐methylimidazolium acetate (EmimAc)/water system was investigated using polarized optical microscopy (POM) and rheometry. POM indicated that the distinct water content range for forming a fully anisotropic LC gel with 14 wt % MCC was 4–10 wt %. Adding water to the MCC/EmimAc system resulted in enhanced complex viscosity and storage and loss moduli, and ultimately LC gel formation. Comparison of creep compliance vs. time revealed that the system without water showed representative viscoelastic behavior, while the time dependence of creep compliance disappeared as the water content increased, suggesting elastic‐solid behavior. Additionally, hydrogen bonding between cellulose and EmimAc weakened as water content increased, whereas the intra‐ and intermolecular hydrogen bonds of cellulose became stronger because of strong self‐association. This strong bonding caused aggregation, chain entanglement, and self‐supporting LC gel network formation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44658.     

Influence of wood pulp quality on the structure of carboxymethyl cellulose

The quality of carboxymethyl cellulose (CMC) prepared from different wood-derived market pulps is examined. The pulps represent kraft and sulfite qualities with different levels of hemicellulose (1.5–22.8 wt %), intrinsic viscosity (391–780 mL g⁻¹), and content of extractives (0.04–0.13 wt %). The pulps are carboxymethylated in aqueous medium at three different levels of sodium hydroxide concentration, resulting in three levels of degree of substitution (DS), 0.3, 0.7–0.8, and 1.3–1.4 (according to nuclear magnetic resonance spectroscopy and high-performance liquid chromatography). CMC with DS 0.7–0.8 is found to be near the limit for water solubility and the resulting ranking for that solubility is shown to be correlated to DS. The DS is found to be impaired by a high content of impurities and high degree of Cellulose II in the pulp. The sulfite pulps yield CMC with the best solubility in water. A high level of extractives does not interfere with reactivity. Moreover, it is found that impurities, such as lignin and xylan, inhibit thickening behavior even at high DS, and that the ratio of substitution on Position 3 is a measure of the xylan content, which suggests that this position in xylan has extremely high reactivity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47862.     

Fabrication of natural cellulose microspheres via electrospraying from NaOH/Urea aqueous system

Regenerated cellulose microspheres (RCM) with controllable sizes and architectures are prepared via electrospraying from environmental‐friendly NaOH/Urea aqueous system. The particle size and shape of RCM is mainly dependent on the interplay among the electrical force, surface tension, and viscous force. Particle size can be reduced to a certain extent by increasing voltage and decreasing surface tension, electrode spacing, solution concentration, degree of polymerization, and flow rate. The deformation of droplets, which is peculiarly prone to occur for low viscosity and long electrode spacing, results in elongated spheres, tear‐shaped particles, wedge‐shaped particles, and banding shaped particles besides micorspheres. The sophericity and uniformity of particles generally become worse as a result of the deformation of droplets. RCM possess good porosity and large specific surface area after regeneration. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40656.     

Effect of solvent on morphology of electrospinning ethyl cellulose fibers

The influence of the composition of a multicomponent solvent on the surface morphology and diameter distribution of ethyl cellulose fibers produced by electrospinning technology was investigated. The results showed that the average diameter of the fibers using the multicomponent solvent was thinner than when using either of the two components and the diameter distribution of the fibers became narrower. Tiny tubercles formed on the fiber surface, which may improve the specific surface area and broaden the applications. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1292–1297, 2005     

Fiber and film developments from immiscible blends of cellulose acetate propionate and poly(butylene terephthalate)

Binary blends of cellulose acetate propionate (CAP) and poly(butylene terephthalate) (PBT) in the composition range of 5–15 wt % for CAP were prepared in the form of films and fibers by compression molding and spinning, respectively. The presence of two invariant glass‐transition temperatures corresponding to the CAP and PBT components and viscosities lower than those of the neat PBT of the CAP–PBT blends implied that the CAP–PBT blends were immiscible. Moreover, the crystallinity of the PBT component was higher in the spun fibers than in the films; this was possibly due to the different cooling methods or the chain orientation in the spinning process. In the meantime, the CAP component could not undergo crystallization because of its rigid structure and alkyl substituents. For the CAP–PBT films, the amorphous CAP was present as dispersed particles in the PBT matrix; but it became rods in the spun fibers. In addition, the presence of the amorphous CAP resulted in a decrease in the tensile strength and an increase in the elongation at break for the CAP–PBT fibers. The CAP–PBT films and fibers could be applied in a wide range of applications requiring renewable properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45013.     

Influence of humidity,temperature, and the addition of activated carbon on the preparation of cellulose acetate membranes and their ability to remove arsenic from water

Several composite membranes have been prepared from cellulose triacetate (CTA) and activated carbon (AC) by solvent casting, varying temperature from 35 to 55°C and relative humidity (RH): 10–70%. Some conditions promoted AC particle agglomeration which is evidenced by SEM and IFME^® program. In those membranes, where homogeneity is attained, a deep characterization has been carried out by DMA, MDSC, thermoporometry, solute transport, and AFM. When AC is added in films, T_g is lowered and the fraction of pores with bigger size is augmented. Molecular weight cut off calculated by solute transport, increases from 801.15 to 1194.29 kDa using 1% AC at RH 70% and T 35°C. Water flux is of 5.23 Lm^?2 h^?1 bar^?1. Arsenic removal has been performed, achieving a 45% tested from a 500 ppb arsenic solution, where several factors such as electrical rejection, adsorption and exclusion, could contribute to the total membrane nanofiltration process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40134.     

Influence of Lignin units on the properties of Lignin/PAN-derived carbon fibers

Lignin was proposed to an attractive precursor for making carbon fibers (CFs) owing to its high carbon yield, low-cost, and renewable sourcing. In this work, Lignin/polyacrylonitrile (PAN)-derived CFs were prepared and characterized to investigate the effects of Lignin units on their porous texture and surface chemistry. The results showed that the LP20-CF prepared from PAN with 20% Lignin had higher surface areas than that of the pristine LP0-CF, and it possessed interconnected multidimensional network with fiber bonding. Moreover, Lignin/PAN-derived CFs contained more oxygen functional groups of CO, COOR, and nitrogen functional groups of N-6, N Q than the pristine CFs. These results indicated that the Lignin could be beneficial to achieve CFs with special structure, developed porosity and rich surface chemistry without activation. Therefore, the utilization of Lignin to produce pores and improve surface chemistry of CFs was a simple and effective strategy for preparing the low-cost and high-performance functional carbon materials.     

The challenge of predicting spinnability: Investigating benefits of adding lignin to cellulose solutions in air-gap spinning

In this study, the underlying mechanism for improved spinnability when mixing lignin and cellulose in solution was investigated. Co-processing of lignin and cellulose has previously been identified as a potential route for production of inexpensive and bio-based carbon fibers. The molecular order of cellulose contributes to the strength of the fibers and the high carbon content of lignin improves the yield during conversion to carbon fibers. The current work presents an additional benefit of combining lignin and cellulose; solutions that contain both lignin and cellulose could be air-gap spun at substantially higher draw ratios than pure cellulose solutions, that is, lignin improved the spinnability. Fibers were spun from solutions containing different ratios of lignin, from 0 to 70 wt%, and the critical draw ratio was determined at various temperatures of solution. The observations were followed by characterization of the solutions with shear and elongational viscosity and surface tension, but none of these methods could explain the beneficial effect of lignin on the spinnability. However, by measuring the take-up force it was found that lignin seems to stabilize against diameter fluctuations during spinning, and plausible explanations are discussed.     

The electrospun polyhydroxybutyrate fibers reinforced with cellulose nanocrystals: Morphology and properties

Polyhydroxybutyrate (PHB) has been used in the biomedical field. However, the poor mechanical properties of PHB have limited its application. Here, electrospun fibrous nanocomposite mats reinforced with cellulose nanocrystals (CNCs) were fabricated by using PHB as polymeric matrix. The morphological, thermal, mechanical properties, as well as cytotoxicity were characterized. Increasing the concentration of CNCs caused a decrease in diameter of the electrospun fibers. Moreover, thermal analysis indicated that melting temperature of PHB/CNCs electrospun fibers were improved with the increased CNCs content. The addition of CNCs gradually enhanced the tensile strength till 8 wt % content followed by a gradual decrease at higher CNCs content (12–22 wt %) in tensile strength. The PHB/CNCs electrospun fibers were nontoxic to L‐929 and capable of supporting cell proliferation in all conditions. This study demonstrates that fibrous PHB/CNCs electrospun fibers are cytocompatible and potentially useful mechanical properties for biomedical application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43273.     

Thermoplastic composites of polyamide‐12 reinforced by cellulose nanofibers with cationic surface modification

Cellulose nanofibers (CNFs) have many useful properties, including high strength and low thermal expansion, and are also environmentally friendly, readily renewable, safe, and biodegradable. The focus of this study was the development of lightweight thermoplastic polymer composites with good mechanical properties based on the incorporation of CNFs that have undergone surface pretreatment with a cationic reagent. The polyamide (PA12) was mixed with surface‐treated CNFs using a twin screw extruder and the resulting pellets were injection molded. The Izod impact strength without notch of CNF‐based composites exceeded that of composites incorporating organophilic montmorillonite (OMMT), a representative nanocomposite material. When the Izod impact test without notch, the impact hammer was stopped by the specimen with incorporation of surface treated CNF. Furthermore, the bending modulus and strength were equal to or greater than that of OMMT composites. The heat distortion temperature was improved as 33°C from neat PA12, and moreover improved as 29°C from OMMT composites. Cationic pretreatment of the CNF surfaces was found to increase the dispersion of the fibers and also to greatly improve the mechanical and thermal properties of the composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40920.     

Morphological investigation of cellulose acetate/cellulose nanocrystal composites obtained by melt extrusion

Composites were prepared from cellulose acetate (CA) and cellulose nanocrystals (CNC) by melt extrusion using two methods for the introduction of CNC: direct mixing and predispersion in CA solution. CNC were isolated using hydrochloric acid to increase thermal stability allowing the composites to be processed above 150 °C. The effect of CNC dispersion on the composites morphology, thermal, and mechanical properties was investigated. Field emission scanning electron microscopy and transmission electron microscopy results indicated that the predispersion method allows better CNC dispersion and distribution when compared to the direct mixture method. In addition, predispersion promotes preferential CNC orientation in relation to the injection flow. The predispersion method also showed a 14% Young's modulus increase in composites containing 15 wt % CNC while no significant change was observed when using the direct mixing. The results obtained in this work show that, to achieve the percolation threshold, nanoparticle distribution is as important as their content. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44201.     

Melt spinnability of long chain cellulose esters

Technical and hygienic nonwovens, originating typically from fossil-based synthetic polymers, are the fastest growing applications in the textile industry. Recently developed thermoplastic cellulose fatty acid esters have polyolefin like rheology properties and therefore the suitability of these cellulose esters for fiber production was evaluated. In this study, the melt spinning of textile fibers has been demonstrated using thermoplastic cellulose octanoate. The mechanical properties of melt spun fibers were analyzed by using tensile testing and both the surface and cross-section morphology of melt spun fibers were studied using the scanning electron microscopy. The surfaces of the fibers were very smooth and also the cross-section was very uniform and no porosity was observed. While mechanical properties of the produced fibers are not yet as good as those reported for commercial polypropylene (PP) monofilament fibers, they are somewhat more comparable to other cellulose ester-based fibers. The melt spinning results indicate that the novel cellulose-based fibers can provide a renewable and recyclable alternative, for example, spun-laid PP in several hygienic textile and fully oriented in technical applications in future.     

Cauliflower-like poly(3,4-ethylenedioxythipohene)/nanocrystalline cellulose/manganese oxide ternary nanocomposite for supercapacitor

A cauliflower-like ternary nanocomposite of poly(3,4-ethylenedioxythipohene)/nanocrystalline cellulose/manganese oxide (PEDOT/NCC/MnO₂) was synthesized using one-step electropolymerization technique. The effect of manganese (Mn) concentration on the supercapacitive performance was investigated. The structural and morphology studies were conducted using field emission scanning electron microscope, Fourier transform infrared spectroscopy, Raman spectroscopy, and X-ray diffraction. The morphology of ternary nanocomposite at an optimized concentration of Mn resembles the cauliflower-like structure. The two-electrode electrochemical analysis of a ternary nanocomposite PEDOT/NCC/MnO₂ exhibited a higher specific capacitance of 144.69 F/g at 25 mV/s in 1.0 M potassium chloride compared to PEDOT/NCC(63.57 F/g). PEDOT/NCC/MnO₂ ternary nanocomposite was able to deliver a specific power of 494.9 W/kg and 10.3 Wh/kg of specific energy at 1 A g⁻¹ and retained 83% of initial capacitance after 2,000 cycles. These promising results from the incorporation of Mn displayed great prospective in developing PEDOT/NCC/MnO₂ as an electrode material for supercapacitor.     

Controlled‐release drug carriers based hierarchical silica microtubes templated from cellulose acetate nanofibers

We report a facile method to synthesize hollow silica microtubes (SMTs) from electrospun cellulose acetate fiber precursors. Specific surface areas of up to 765 m²/g (Brunauer–Emmett–Teller) were measured for the SMTs, which had a typical wall thickness of ～100 nm and submicron inner diameters. An average pore size of 4.6 nm and pore volume of 0.41 cm³/g were derived from Barrett–Joyner–Halenda fitting, whereas Horvath–Kawazoe pore size distribution analysis revealed microporous median pore size and maximum pore volume of 0.7 nm and 0.18 cm³/g, respectively. The as‐prepared SMTs featuring micro‐ and mesoporous structures in the walls where amino‐functionalized to facilitate a very high drug loading (15% by weight). Drug release profile revealed sustained release rates (79% of acetylsalicylic acid was released after 6 h). It is concluded that the high drug loading and sustained release resulted from the advantageous integration of SMTs' hollow structure and wall mesoporosity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42562.     

Ultrathin and nanofibers via room temperature electrospinning from trifluoroacetic acid solutions of untreated lignocellulosic sisal fiber or sisal pulp

Lignocellulosic sisal fiber (LSF) and sisal pulp (SP) were electrospun at room temperature from solutions in trifluoroacetic acid (TFA) prepared at concentrations of 2 × 10⁻² g mL⁻¹ and 3 × 10⁻² g mL⁻¹, respectively. Scanning electron microscopy images of the electrospun LSF showed fibers with diameters ranging from 120 to 510 nm. The presence of defects decreased along with increasing the flow rate of the SP solution, which generated nanofibers and ultrathin fibers with diameters in the range of 40–60 (at 5.5 µL min⁻¹) up to 90–200 nm (at 65.5 µL min⁻¹). Despite the known ability of TFA to esterify the hydroxyl groups present in the starting materials, the Fourier transform infrared spectra indicated the absence of trifluoroacetyl groups in the electrospun samples. The thermal stability of the final materials proved suitable for many applications even though some differences were observed relative to the starting materials. This study demonstrated a feasible novel approach for producing nano/ultrathin fibers from lignocellulosic biomass or its main component, which allows for a wide range of applications for these materials. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41826.     

H3PW12O40·4H2O as an efficient catalyst for the conversion of cellulose into partially substituted cellulose acetate

The preparation of partial acetylation of cellulose derived from rice straw was catalyzed by phosphotungstic acid with various numbers of crystal water, and H₃PW₁₂O₄₀·4H₂O was found to be as effective catalyst. The yield of the cellulose acetate was significantly enhanced by converting cellulose directly isolated from rice straw into microcrystalline cellulose before acetylation. The optimization of the acetylation was investigated by varying the amount of catalyst and acetic anhydride as well as reaction conditions including reaction time and medium, and a degree of substitution (DS) value of 2.29 and yield of 62.9% were obtained under the optimized conditions. The structure and the formation of the acetylated product were confirmed by Fourier transform infrared spectroscopy (FTIR) and powder X‐ray diffraction (XRD) technique, the thermal properties were determined by thermal analysis including thermogravimetry analysis (TGA) and differential scanning calorimetry (DSC), and the morphology was observed by scanning electron microscope (SEM). © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41212.     

Polyamide-6/cellulose nanocomposites: Influence of fiber treatment and screw rotation on nanofibrillation of jute during extrusion process

The present work studied the preparation of nanocomposites of polyamide-6 (PA6) containing nanofibrillated cellulose by melt blending in a twin screw extruder at different screw rotations to verify the fibrillation of cellulose fibers. Initially, the jute fibers were purified, hydrolyzed, and modified with titanium isopropoxide and aminopropyl silane, as well as with the two chemical modifications. They were incorporated into the polymeric matrix aiming that the shear in processing further aids in fiber fibrillation. The scanning electron microscopy analysis images of the composites showed the presence of fibers with nanodiameters dispersed in the PA6 matrix. The doubly modified fibers resulted in more fibrillation during extrusion. Increasing the screw speed of the extruder improved the degree of crystallinity for the composites with the modified fibers. The thermogravimetric measurements showed that the composite containing the doubly modified fibers increased the maximum degradation temperature. The storage modulus increased for the composites with the insertion of the treated fibers, and the glass transition temperature decreased in some composites. The composites showed higher pseudoplastic behavior, especially at high shear rates.     

Rheological behavior of cellulose nanocrystal suspension: Influence of concentration and aspect ratio

The steady and dynamic rheological behaviors of two cellulose nanocrystal (CNC) suspensions were investigated over a wide range of concentrations. The viscosity, storage and loss modules increased with increasing CNC concentration, and both CNC suspensions showed three regions in a viscosity‐concentration graph. The two critical concentrations depended on the aspect ratio and corresponded to the overlap and gelation concentration. Because of the higher aspect ratio, switchgrass CNC suspension transitioned into a biphasic state and formed a hydrogel at lower concentrations than those of cotton CNC suspensions. Furthermore, the complex viscosities of both CNC suspensions were higher than their steady viscosities; therefore, neither CNC suspension followed the Cox–Merz rule, which may be attributed to the existence of a liquid crystal domain in each suspension. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40525.     

Pineapple agroindustrial residues for the production of high value bacterial cellulose with different morphologies

Bacterial cellulose (BC) with different morphologies was biosynthesized by Gluconacetobacter medellinensis strain under static and dynamic culture conditions using sugar cane juice and pineapple residues as sources of carbon and other nutrients. Hestrin and Schramm's standard culture medium was used as reference. The fermentation condition and resulting yield, physico‐chemical properties, and morphology relationships of obtained cellulose were analyzed. Pineapple agroindustrial residues can be envisaged as an inexpensive and sustainable alternative resource for the production of different BC morphologies. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41237.