Regenerated Cellulose Matrix Research Articles

Ionic liquid, ultrasound-assisted synthesis of lignin nanoparticles for barrier-enhanced all-cellulose nanocomposite films

The primary purpose of this work was to develop novel all-cellulose nanocomposite (ACNC) films by following a green approach that uses an ionic liquid as solvent and requires no additional reducing agents or stabilizers. In this way, biodegradable, UV-blocking ACNC films were obtained by partially dissolving cellulose to entrap lignin nanoparticles (LNP) within. Lignin particles in proportions of 3–7 wt% were modified by sonication in an ionic liquid (IL) to obtain lignin-IL dispersions. The influence of the LNP-IL medium on the chemical, physical, and morphological properties of the resulting nanocomposites was examined, and the properties compared with those of an all-cellulose composite (ACC) film and untreated paper. The TEM technique revealed the formation of unevenly spherical LNPs as small as 5.133 ± 0.003 nm, and XRD spectroscopy a transition from cellulose I to II and an increase in the proportion of non-crystalline cellulose as a result of partial dissolution and regeneration. In addition, SEM images confirmed the deposition of LNPs onto the surface of the regenerated cellulose matrix. The incorporation of LNPs considerably enhanced the UV-blocking, oxygen and water-barrier, biodegradation, antioxidant and antibacterial properties of the films. Moreover, LNPs in proportions of 3 and 5 wt% increased tensile strength, and a proportion of 7 wt% allowed the films to block 97% of light at 280 nm and increased antioxidant activity by 68% relative to the control sample. Interestingly, a 7 wt% LNP content in the films decreased antibacterial activity against Staphylococcus aureus and Escherichia coli by about 42.85% and 63.88%, respectively. The new, multifunctional biocomposite films are suitable for various uses in cellulose-based food packaging.

Promising nanocomposites for food packaging based on cellulose – PCL films reinforced by using ZnO nanoparticles in an ionic liquid

The fact that most composites consist of polluting synthetic materials has prompted a search for biodegradable replacements based on cellulose fibers and polycaprolactone as potential packaging materials. In this work, we developed a green, efficient approach to rendering hydrophobic polycaprolactone (PCL) compatible with hydrophilic cellulose fibers by using an ionic liquid as a nanowelding agent in the presence of zinc oxide nanoparticles (ZnONPs). Transparent biobased nanocomposite films were thus directly obtained by in situ ring-opening polymerization (ROP) of ε-caprolactone (CL) monomers onto the dissolved cellulose matrix by using the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM]Ac). [EMIM]Ac and ZnONPs were efficiently catalyzed ε-caprolactone ROP under mild conditions. Cellulose-grafted PCL nanocomposite films were obtained by adding variable amounts of CL and ZnONPs to the cellulose matrix. The maximum grafting of 40% was achieved by using 5▒wt% ZnONPs and 70% CL. FTIR spectra confirmed the presence of PCL in the nanocomposites. Also, FE-SEM revealed uniform dispersion of ZnONPs and PCL in the regenerated cellulose matrix, and trapping of nanoparticles in nanofibrils after the cellulose matrix was regenerated. X-ray diffraction (XRD) spectra showed a decreased apparent crystallinity and crystallite size. The XRD results also confirmed that the crystal properties of the nanocomposite films and an all-cellulose composite (ACC) were almost identical. The mechanical, barrier and optical properties of the nanocomposite films were significantly better than those of the ACC film by effect of the incorporation of ZnONPs and PCL especially with 5▒wt% ZnONPs and 70% CL). The nanocomposite films exhibited acceptable antioxidant activity and UV-light barrier properties, so they hold promise for used in food packaging. Nanocomposite films are in fact multifunctional materials with the potential for use in cellulose-based food packaging by virtue of their being transparent and bio-based, and possessing very good water vapor and oxygen barrier properties.

Ionic Liquid/ZnO Assisted Preparation of High Barrier Cellulose Nanocomposite Films by In Situ Ring-Opening Polymerization of Lactide Monomers

Cellulose-based composites have aroused increasing interest as potential replacements for fossil fuel-based plastics. In this work, transparent cellulose-grafted-PLA nanocomposite films were prepared by grafting polylactide (PLA) onto cellulose. PLA was synthesized by in situ ring opening polymerization from a regenerated cellulose matrix, using zinc oxide nanoparticles (ZnONPs) in 1-ethyl-3-methylimidazolium acetate (EmimAc) as solvent. A facile route was devised to modify the starting material (cellulose paper) by partial dissolution and regeneration that used an ionic liquid (IL) as a smart nanowelding agent to assemble nanometric cellulose structures. The influence of the proportion of ZnONPs (1–5 wt%) and textit{L}-lactide (LA) monomers (10–70 wt%) used on the properties of the resulting nanocomposite films was examined by comparison with an all-cellulose composite (ACC) and pure cellulose paper. Incorporating ZnONPs and PLA was found to enhance the mechanical, barrier and optical properties of the films. The maximum tensile strength and best barrier properties were those of a film obtained from 5%ZnONPs and 70%LA. FTIR spectra confirmed a new form of interaction between PLA and the regenerated cellulose matrix. Also, XRD spectra revealed a transition from cellulose I to II and an increase in the proportion of noncrystalline cellulose through partial dissolution and regeneration. Although the surface morphology of the nanocomposite films was influenced by the presence of ZnONPs and PLA chains, their color and chemical structure were not. The transparent cellulose-grafted-PLA nanocomposite films obtained are highly promising as packaging materials.

Adsorption isotherms and kinetics for the removal of cationic dye by Cellulose-based adsorbent biocomposite films

Various fillers (commercial, nipa palm, sisal activated carbon, zeolite) were incorporated with regenerated cellulose matrix that dissolved using lithium chloride/N, N-dimethylacetamide solution. The biosorbent films were successfully prepared via solution casting and then characterized by Fourier transform infrared spectrometer (FTIR), X-ray Diffractometer (XRD), thermogravimetric analyzer (TGA), and scanning electron microscope (SEM). The biocomposite films with embedded commercial activated carbon exhibited the largest adsorption capacity of methylene blue (146.81 mg g−1). Although the adsorption ability of the nipa palm and sisal activated carbon biocomposite was lower than the commercial activated carbon biosorbent film, both nipa palm and sisal activated carbon still could potentially be used as an alternative filler for cationic dye removal. On the contrary, zeolite had low adsorption efficiency owing to its morphology. The equilibrium adsorption experiment revealed that the Langmuir isotherm model best fitted the biocomposite films with commercial and sisal activated carbon, whereas the Freundlich adsorption model suited the biosorbent films with nipa palm activated carbon and zeolite than other models. The kinetics results of adsorption for all biocomposite films were well described using a pseudo-second-order kinetic model. The cellulose/activated carbon films would be promisingly utilized as a biosorbent for treatment of dye-contaminated wastewater.

Study on the rheological properties of regenerated cellulose/thermoplastic polyurethane blend spinning solutions

The rheological behavior of regenerated cellulose/thermoplastic polyurethane (TPU) blend spinning solutions was investigated by an advanced rotary rheometer. The viscosity decreases with increasing shear rates, exhibiting shear thinning behavior. The storage modulus of G′ and the loss modulus G″ both increase with increasing frequencies, while the complex viscosity decreases gradually. The non-Newtonian index increases while the flow activation energy decreases with increasing TPU content. The composite fibers were characterized by FTIR and XRD, indicating that the addition of TPU into regenerated cellulose matrix destroyed the crystallinity to some extent. The mechanical property tests illustrate that the toughness of the fiber was greatly improved with the incorporation of TPU.

Facile preparation of cellulose-SiO2 composite aerogels with high SiO2 contents using a LiBr aqueous solution

Cellulose-SiO2 composite aerogels (CSGs) with high SiO2 content up to 90% were successfully developed via the mixing of SiO2 particles and a cellulose solution dissolved in a LiBr aqueous solution. The characteristic properties resulting from the direct gelation of a dissolved cellulose solution could facilitate the preparation of a variety of forms of SiO2-embedded gels. The introduction of SiO2 particles reduced the pore sizes while maintaining the three-dimensional porous structure of the regenerated cellulose matrix, resulting in increased density and decreased porosity. CSGs exhibited excellent mechanical properties, large surface areas, and thermal stability up to 250 °C in an air atmosphere. Furthermore, CSGs showed low thermal conductivity ranging from 0.038 to 0.048 W/m K despite the influence of higher density and lower porosity with increased SiO2 contents. These results suggested that CSGs could provide a new option with regard to advanced porous organic-inorganic composite materials.

Self-reinforcing composites from commercial chemical pulps via partial dissolution with NaOH/urea

Self-reinforcing composites (SRCs) were produced from various commercially available chemical pulp fibers by the partial dissolution method using aqueous sodium hydroxide/urea (NaOH/urea) solvent. Surfaces of fibers dissolve during solvent treatment and in regeneration stage form a matrix between fibers improving mechanical properties. The ability of solvent to dissolve cellulose from fiber surfaces have large influence on properties of produced SRCs. The potential for use of bleached spruce, eucalyptus, bleached and unbleached pine, and abaca pulp as raw materials for SCR was investigated by producing SRCs and comparing the field-emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), tensile strength to the untreated counterparts. Also, a short crush index test is measured for cellulose based SRCs for first time in this study, which is widely used test illustrating compression resistance. The tensile test results showed that bleached pulps and eucalyptus had the largest increase in mechanical strength by a factor of more than 2 up to a value of 52kNm/kg. In unbleached pine, the lignin seems to hinder the dissolution process, leading to smaller improvements of mechanical properties, while the solvent was not able to dissolve abaca fibers at all. Further, it was found that good solubility and a high amount of regenerated cellulose matrix does not inevitably mean better mechanical properties in SRCs.

Flexible regenerated cellulose/polypyrrole composite films with enhanced dielectric properties

Flexible regenerated cellulose/polypyrrole (RC-PPy) conductive composite films were prepared by insitu polymerization of pyrrole on regenerated cellulose (RC) matrix using ammonium persulphate as oxidant. FTIR, XPS and XRD analysis of RC-PPy composite films revealed strong interaction between polypyrrole (PPy) and RC matrix. XRD results indicated that crystalline structure of RC matrix remains intact even after composite formation. SEM micrographs revealed the formation of a continuous conductive network of PPy particles in the RC matrix, leading to significant improvement in electrical and dielectric properties. The electrical conductivity of RC-PPy composites with 12wt% of PPy was 3.2×10−5S/cm, which is approximately seven fold higher than that of RC. Composites showed high dielectric constant and low dielectric loss values, which is essential in capacitor application.

One-pot synthesis of cellulose-templated copper nanoparticles with antibacterial properties

We report a facile in situ synthesis of spherical copper nanoparticles (NPs) templated by a gelled cellulose II matrix under alkaline aqueous reaction conditions. In under 20min, the hybrid material could be obtained in a one-pot reaction. Field-emission scanning electron microscopy (FE-SEM) revealed that the polycrystalline NPs of 200–500nm were well distributed in the regenerated cellulose matrix. The average Cu crystallite size was of the order of 20nm, as estimated from both X-ray diffraction (XRD) and FE-SEM. XRD data also indicated that the composite contained up to approximately 20% Cu2O. In suspensions containing the hybrid material, growth of Escerichia coli and Staphylococcus aureus strains was inhibited by 80% and 95%, respectively, after 72h. The synthesis procedure offers a general approach to designing various low-cost hybrid materials of almost any shape, and the concept could be extended to utilization areas such as catalysis, functional textiles, and food packaging as well as to electronic applications.

Treated Nypa fruticans Husk-filled Regenerated Cellulose Biocomposite Films

The effects of filler content and methacrylate acid (MAA) treated Nypa fruticans husk (NFH) on the mechanical properties, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and morphology of NFH regenerated cellulose (RC) biocomposite films were investigated. Ionic liquid containing 8 wt% of lithium chloride (LiCl)/N,N-dimethylacetamide (DMAc) was used to dissolve microcrystalline cellulose (MCC) and NFH to produce NFH RC biocomposite films. Methacrylate acid was used as a modifying agent on the NFH to promote better mechanical and thermal properties for the resulting NFH RC biocomposite films. The results showed that the tensile strength, Young’s modulus, crystallinity index (CrI), moisture content, and thermal stability of the untreated NFH RC biocomposite films increased with increasing NFH content up to 3 wt% and decreased with further increments. The MAA-treated NFH showed improved tensile strength and Young’s modulus compared with the untreated NFH RC biocomposite films. The presence of MAA enhanced the crystallinity index (CrI), moisture resistance, and thermal stability of the NFH RC biocomposite films. Good interfacial interaction between the NFH and RC matrix was proven by scanning electron microscopy (SEM).

Tensile Properties and Morphology of Oil Palm Empty Fruit Bunch Regenerated Cellulose Biocomposite Films

The regenerated cellulose (RC)biocomposite films were prepared using casting method where oil palm empty fruit bunch (OPEFB) and microcrystalline cellulose (MCC) were dissolved in N-dimethylacetamide/lithium chloride (DMAc/LiCl)solution. The increasing of OPEFB contents up to 2 wt% increased the tensile strength and modulus of elasticity of RC biocomposite films while the elongation at break decreased. However, at 3 and 4 wt% of OPEFB content, the tensile strength and modulus of elasticity decreased with increases OPEFB content, but elongation at break increased. The increment of tensile strength and modulus of elasticity at 2 wt% is due to the OPEFB fiber that partially dissolved and dispersed with the OPEFB matrix. The morphology studies illustrate that at 2 wt% of OPEFB content of biocomposite films surface consists less voids and agglomerations than at 4 wt%. This can be considered the RC filler was partially dispersed with the RC matrix in the biocomposite films.

Graphene reinforced regenerated cellulose nanocomposite fibers prepared by lyocell process

Nanocomposites of regenerated cellulose containing different amounts of graphene nanoplatelets (GNPs) (0.5, 1, and 2 wt%) have been prepared by wet spinning using Lyocell process. The thermal stability, mechanical, and electrical properties of the nanocomposite fibers were studied. The nanocomposite fibers were characterized by Fourier transform infrared (FTIR), Transmission electron microscopy, X‐ray diffraction, and Scanning electron microscopy (SEM). The tenacity and initial modulus of the nanocomposite fibers improved by 66% and 61%, respectively with the addition of 2 wt% GNPs. The T20 decomposition temperature of regenerated cellulose fibers improved with the addition of GNPs up to 2 wt%. The morphology by SEM revealed exfoliated dispersion of GNPs into the regenerated cellulose matrix which subsequently resulted in good interaction between the nanofillers and the matrix. The addition of exfoliated GNPs generated electrical conductivity. The nanocomposite fibers containing 2 wt% GNPs has a conductivity of 2.3 × 10−4 S/cm. The FTIR spectra showed that the addition of GNPs in regenerated cellulose did not result in any noticeable change in its chemical structure. The resulting nanocomposite may find potential applications in the areas of carbon fiber precursor, conductive fibers, electrical tools, and biodegradable composites. POLYM. COMPOS., 38:E81–E88, 2017. © 2015 Society of Plastics Engineers

Regenerated cellulose/multiwalled carbon nanotube composite films with efficient electric heating performance

We have manufactured regenerated cellulose-based composite films reinforced with pristine multiwalled carbon nanotube (MWCNT) by a facile casting of cellulose/DMAc/LiCl solutions containing 0.2–10.0wt% MWCNT and have investigated their application as electric heating materials by examining microstructure, thermal stability, and electrical properties. TEM images showed that the pristine MWCNT was dispersed well in the regenerated cellulose matrix. The composite films were found to be stable thermally up to ∼275°C. The electrical resistivity of the regenerated cellulose/MWCNT composite films decreased significantly from ∼109Ωcm to ∼101Ωcm with increasing the MWCNT loading, particularly at a certain MWCNT content between 2.0 and 3.0wt%. Accordingly, the composite films with 5.0–10.0wt% MWCNT contents, which possessed low electrical resistivity of ∼102–101Ωcm, exhibited excellent electric heating performance in aspects of temperature responsiveness, steady-state maximum temperature, and electrical energy efficiency at constant applied voltages. For instance, the composite film with 10.0wt% MWCNT had well-controlled steady-state maximum temperatures of 40–189°C at 20–80V, characteristic temperature growth constant of ∼1s, and electric power efficiency of ∼5.4mW/°C, which performance remained unchanged under repeated experiments for several hours.

Antimicrobial regenerated cellulose/nano-silver fiber without leaching

The formation of antimicrobial regenerated cellulose fibers using an ionic liquid solvent, 1-butyl-3-methylimidazolium chloride, and silver nanoparticles was studied. The cellulose preparation and dispersion efficiency of the silver nanoparticles in the solvent were evaluated via scanning electron microscope and transmission electron microscopy in terms of different processing conditions. The influence of silver nanoparticles on regenerated cellulose fiber crystallization and strength was examined using a wide angle X-ray diffractometry and tensiometry, respectively. The bioactive efficacy of the cellulose/nano-silver fiber was tested in accordance with the standard method of ASTM E 2149-10. The cellulose/nano-silver fibers were bioactive and killed Escherichia coli almost completely without any leaching problems. The addition of nano-silver significantly increased the cellulose fiber tensile strength and modulus with an insignificant reduction in fiber elongation, and a slower thermal decomposition rate, evidenced by increased fiber crystallinity. Higher processing temperatures improved the nano-silver dispersion efficiency. The final nano-silver suspension in the regenerated cellulose matrix was composed of scattered clusters with an average size of 700 nm and a distribution density of 14,098 mm−2.

Mechanically robust, flame-retardant and anti-bacterial nanocomposite films comprised of cellulose nanofibrils and magnesium hydroxide nanoplatelets in a regenerated cellulose matrix

Nanocomposite films consisting of cellulose nanofibrils (CNFs), magnesium hydroxide nanoplatelets (MHNPs) and regenerated cellulose were prepared via simple blending and casting processes. The CNFs were obtained from bamboo pulp by ultrasonic treatment coupled with high shear homogenization. The morphology, structure and properties of the nanocomposite films were comprehensively analyzed using various characterization techniques, including the scanning electron microscope, digital microscope, limiting oxygen index (LOI), micro-scale combustion calorimetry, antibacterial assays, tensile testing, etc. When the MHNP content was optimized to 30 wt%, the nanocomposite film exhibited the best overall properties. The LOI of the composite film increased from 20.0 (0 wt% MHNPs) to 32.7 (30 wt% MHNPs), making it a flame-retardant material in air. In addition, the film containing 30 wt% MHNPs showed excellent antibacterial activity. However, the increase in MHNP content would result in gradual deterioration of the films’ mechanical properties. However, the incorporation of CNFs could significantly suppress this trend. The present work provided a promising pathway for manufacturing multifunctional and high-performance cellulose-based composite films, which were potentially useful for a variety of packaging materials, especially in the biomedical and food packaging fields.

Fabrication, Characterization and Photocatalytic Activity of TiO<sub>2</sub>/Cellulose Composite Aerogel

nanoTiO2/cellulose composite gels have been uniformly blended during the dissolving process of cellulose in ionic liquids (ILs). After the regeneration process, the obtained hydrogel was finally dried through supercritical CO2 to obtain the TiO2/cellulose composite aerogel. The structure and properties of the composite aerogel were characterized by XRD, SEM, FT-IR, UV-vis, and photocatalytic degradation tests. The porous structure and hydroxyl groups in the regenerated cellulose matrix provided cavities and affinity for the immobilization of TiO2 in the cellulose gels through electrostatic and hydrogen bonding interactions. The TiO2/cellulose composite gels exhibited a good photocatalytic activity for photodegradation of Rhodamine B (RhB) under UV light irradiation. This research highlights another opportunity for the development of the portable and flexible photocatalyst.

Portable Visible-Light Photocatalysts Constructed from Cu2O Nanoparticles and Graphene Oxide in Cellulose Matrix

For the first time, portable visible-light photocatalysts were fabricated by in situ synthesizing Cu2O in the micropores of regenerated cellulose (RC)/graphene oxide (GO) composite films, in which the porous matrix was used as a microreactor for the formation of Cu2O nanoparticles. Cu2O nanoparticles were immobilized and evenly distributed in the RC matrix to excite and generate free photoelectrons and electron holes, leading to the high photodegradation efficiency against methyl orange dye under visible-light irradiation. Moreover, the introduction of GO has dramatically improved the photocatalytic activities of Cu2O nanoparticles in the Cu2O/GO/RC nanocomposite films, leading to a significant enhancement of the photodegradation rate from 2.0 to 6.5 mg h–1 gcat–1. In the Cu2O/GO/RC photocatalysts, Cu2O nanoparticles inside the matrix tended to generate on the GO sheets, which transferred the yielded photoelectrons to prevent local high potential zone generation and to induce the chain degradation reactio...

Bionanocomposites of regenerated cellulose/zeolite prepared using environmentally benign ionic liquid solvent

Bionanocomposite films based on regenerated cellulose (RC) and incorporated with zeolite at different concentrations were fabricated by dissolving cellulose in 1-ethyl-3-methylimidazolium chloride (EMIMCl) ionic liquid using a simple green method. The interactions between the zeolite and the cellulose matrix were confirmed by Fourier transform infrared spectra. Mechanical properties of the nanocomposite films significantly improved as compared with the pure regenerated cellulose film, without the loss of extensibility. Zeolite incorporation enhanced the thermal stability and char yield of the nanocomposites. The scanning electron microscopy and transmission electron microscopy showed that zeolite was uniformly dispersed in the regenerated cellulose matrix. In vitro cytotoxicity test demonstrated that both RC and RC/zeolite nanocomposite films are cytocompatible. These results indicate that the prepared nanocomposites have potential applications in biodegradable packaging, membranes and biomedical areas.

Reinforcement of all-cellulose nanocomposite films using native cellulose nanofibrils

All-cellulose nanocomposite films were prepared using native cellulose nanofibrils (CNFs) as fillers and lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) dissolved regenerated cellulose as the matrix. The CNFs, with diameters in the range of 15–40nm were obtained by combined physical methods of ultrasonic treatment and high shear homogenization. The morphology, structure, and properties of the nanocomposite films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), optical transmittance, thermal gravimetric analysis (TGA), and mechanical testing. The nanocomposite films exhibited good optical transparency, thermal stability, and remarkably enhanced mechanical properties compared to the regenerated cellulose matrix. By varying the CNFs content, the tensile strength of the nanocomposite films increased from 61.56MPa to 99.92MPa and the Young's modulus increased from 0.76GPa to 4.16GPa. This work provided a promising pathway for manufacturing high performance and environmental-friendly all-cellulose nanocomposites.

Development of regenerated cellulose/halloysite nanotube bionanocomposite films with ionic liquid

In this study, novel nanocomposite films based on regenerated cellulose/halloysite nanotube (RC/HNT) have been prepared using an environmentally friendly ionic liquid 1-butyl-3-methylimidazolium chloride (BMIMCl) through a simple green method. The structural, morphological, thermal and mechanical properties of the RC/HNT nanocomposites were investigated using X-ray diffraction (XRD), Fourier transform infrared (FTIR), field emission scanning electron microscopy (FESEM), thermal analysis and tensile strength measurements. The results obtained revealed interactions between the halloysite nanotubes and regenerated cellulose matrix. The thermal stability and mechanical properties of the nanocomposite films, compared with pure regenerated cellulose film, were significantly improved When the halloysite nanotube (HNT) loading was only 2wt.%, the 20% weight loss temperature (T20) increased 20°C. The Young's modulus increased from 1.8 to 4.1GPa, while tensile strength increased from 35.30 to 60.50MPa when 8wt.% halloysite nanotube (HNT) was incorporated, interestingly without loss of ductility. The nanocomposite films exhibited improved oxygen barrier properties and water absorption resistance compared to regenerated cellulose.