Preparation and characterization of transparent cellulose films using an improved cellulose dissolution process

Effective dissolution of cellulosic macromolecules is the first predominant step to prepare functional bio‐based materials with desirable properties. In this study, we developed an improved dissolution process using a freeze‐drying pretreatment to promote the dissolution of cellulose. Rheological measurements of cellulose solutions and physicochemical characterization of regenerated cellulose films (scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, and thermogravimetric analysis) were performed. Cellulose solution prepared from 5% microcrystalline cellulose (w:v) in the solvent exhibits a Newtonian fluid character while cellulose solutions at higher concentrations show a pseudo‐plastic fluid behavior. Results from physicochemical characterization indicate that a freeze‐drying pretreatment step of cellulose leads to a complete dissolution at 5% concentration while only part of cellulose is dissolved at 10% and 15% concentrations. The results obtained indicated that the use of a freeze‐drying pretreatment step under mild conditions lead to a complete dissolution of cellulose at 5% concentration. The cellulose films prepared from 5% concentration exhibited desirable properties such as good optical transparency, crystallinity, and thermal stability. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44871.     

Fire retardant cellulose aerogel with improved strength and hydrophobic surface by one-pot method

Bio-based materials with multifunctional performance are getting immense attention nowadays for their environment friendly and renewable character. Inspired by toughening effect of graphene nanosheets and borate chemistry, a simple in-situ borate crosslinking in water and freeze-drying method was employed to fabricate a fire retarded bio-based aerogel. The structure of the material was evaluated and analysis by SEM, XRD, FTIR, Raman and XPS. Importantly, the bio-based aerogel has improved strength and adsorption properties due to unique structure. The compressive strength of rGO(reduced graphene oxide) + CMC (carboxymethyl cellulose) aerogel could reach 128 ± 2.1 kPa which is five times that of neat CMC aerogel. The bio-based aerogel can load more than 2500 times of self-weight. The adsorption capacity for organic solvents and oil of rGO+CMC aerogel is also greatly improved by a little rGO (1%) introducing due to its unique porous structure and hydrophobic nature of rGO. Additionally, rGO+CMC aerogel is also found fire resistant with relatively low thermal conductivity due to the borate and GO introduction.     

Nanocomposites of ethylene vinyl alcohol copolymer with thermally resistant cellulose nanowhiskers by melt compounding (II): Water barrier and mechanical properties

In the present work, the crystallinity and crystalline morphology, thermal stability, water barrier, and mechanical properties of ethylene vinyl alcohol copolymer (EVOH) nanocomposites prepared by melt compounding and incorporating both plant (CNW) and bacterial cellulose nanowhiskers (BCNW) are reported. An improvement in the water barrier performance was observed, that is, 67% permeability drop, only for the microcomposite sample incorporating 2 wt % of bacterial cellulose fibrils. No significant differences in the water‐barrier properties of the nanocomposites generated through the two studied preincorporation methods were observed despite the fact that an excellent dispersion was observed in the previous study. On the other hand, direct melt‐mixing of the freeze‐dried nanofiller with EVOH resulted in increased water permeation. The aggregation of the filler in the latter nanocomposite was also ascribed to the detrimental effect on the mechanical properties. Interestingly, by using the precipitation method, an increase in the elastic modulus and tensile strength of ～36 and 22%, respectively, was observed for a 3 wt % BCNW loading, which was thought to coincide with the percolation threshold. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nanocomposites of ethylene vinyl alcohol copolymer with thermally resistant cellulose nanowhiskers by melt compounding (I): Morphology and thermal properties

In this study, ethylene‐vinyl alcohol copolymer (EVOH) nanocomposites were prepared by melt compounding both plant cellulose nanowhiskers (CNW) and bacterial cellulose nanowhiskers (BCNW) as nanofillers. Electrospinning and a “dissolution precipitation” method were used as strategies for the incorporation of CNW in EVOH before melt compounding with the aim of enhancing the degree of dispersion of the nanocrystals when compared with direct melt‐mixing of the freeze‐dried product with the polymer. As revealed by morphological characterization, the proposed preincorporation methods led to a significant improvement in the dispersion of the nanofiller in the final nanocomposite films. Furthermore, it was possible to incorporate concentrations as high as 4 wt % BCNW without causing significant agglomeration of the nanofiller, whereas increasing the CNW concentration up to 3 wt % induced agglomeration. Finally, DSC studies indicated that the crystalline content was significantly reduced when the incorporation method led to a poor dispersion of the nanocrystals, whereas high‐nanofiller dispersion resulted in thermal properties similar to those of the neat EVOH. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Feasibility of recycled newspaper as cellulose source for regenerated cellulose membrane fabrication

An environmental friendly regenerated cellulose membrane (RCM) was successfully prepared via NaOH/urea aqueous solution system by utilizing recycled newspaper (RNP) as the cellulose source. The morphological and chemical structure of resulting membrane were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD) spectroscopy, and thermogravimetric analysis (TGA). Results from FTIR and XRD verified that the transparent RCM possesses cellulose II structure. SEM observation revealed that the transparent RCM consist of homogeneous dense symmetric membrane structure and composed of a skin layer with mean roughness parameter R_a, obtained from AFM analysis of 29.53 nm. Pure water flux, water content, water contact angle, porosity, and pore size of the resulting membrane were also measured. This study promotes the potential of the cellulose‐based membrane obtained from low cost cellulose source for application in filtration and separation system. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42684.     

Construction of porous cellulose tubes and the evaluations of mechanical properties and cytocompatibility

In this work, regenerated cellulose (RC) tubes with the porous structure were successfully fabricated for constructing the non-invasive detection platform of vascular microenvironment. Polyethylene oxide (PEO) as a porogen was applied to induce porous structure of cellulose tubes. Tensile and burst pressure tests were carried out to evaluate the effects of PEO molecular weight and amount on the mechanical properties of cellulose tubes. The results showed that tensile strength of RC tubes was increased with increasing PEO molecular weight. The compliance of cellulose tubes decreased with increasing the PEO content. When 120 kDa PEO was applied, the average tensile strength of RC tubes could reach 1.27 MPa. The maximum burst pressure and compliance of RC tubes could reach 488.25 ± 35 mmHg and 7.50 ± 3.7%/100 mmHg, respectively. Human umbilical vein endothelia cells (HUVECs) exhibited obvious proliferation on cellulose tubes, and the collagen coating further improve the biocompatibility. The incorporated collagen further improved adhesion of the cells and growth on cellulose tubes. This work provided a kind of cellulose-based tube material with potential application for the construction of the vitro vascular microenvironment.     

High oxygen barrier materials from paper to regenerated cellulose films

A transparent, bendable, high oxygen barrier cellulose-based film was prepared, which has far better oxygen barrier properties than conventional polyethylene, polypropylene and cellophane materials. A series of regenerated cellulose films (RCs) were prepared from filter paper lacking oxygen barrier properties under different cellulose concentrations and gelation times. It was shown that the cellulose concentration and gel time had a greater effect on the oxygen barrier properties of RCs. When the cellulose concentration was 4 wt% and the gel time was 3 h, the RCs obtained the lowest oxygen permeability coefficient (OPC) down to 2.21 × 10⁻¹⁷ cm³ cm cm⁻² s⁻¹ Pa⁻¹. The films have a tensile strength of 109.5 MPa, an elongation at break of 27.3% and a light transmission rate of 89%. In further, molecular dynamics simulations showed that when the filter paper was converted to RCs, the increase in hydrogen bonding and the decrease in free volume between cellulose chains caused a decrease in the diffusion coefficient of oxygen. As a novel biobased high oxygen barrier material, the film has broad application prospect in packaging and chemical industry.     

Modification of the wood-plastic composite for enhancement of formaldehyde clearance and the 3D printing application

As the formaldehyde is one of the main indoor pollutants, the purpose of this study is to effectively remove indoor formaldehyde pollution by using environmentally friendly 3D printing ornaments. The wood 3D printing filaments cellulose/polylactic acid composite (Cellu/P) was selected as the starting material, and 3-aminopropyltriethoxysilane (APTES) was used for chemical modification to obtain a series of cellulose composite materials with amino groups. The modified composite materials (APTES@Cellu/P) were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy, thermogravimetric analysis, and mechanical tests, and a formaldehyde removal experiment was performed. The feasibility of 3D printing was evaluated, and the process of 3D printing-functionalized customized ornaments was proposed, and then a school emblem was used for modeling, printing, and surface modification. Compared with the commercially traditional activated carbon, 3D printing-customized ornaments of APTES@Cellu/P material has a better formaldehyde removal effect, and can even avoid the secondary pollution that is common to the activated carbon.     

New biocomposite obtained using poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH) and microfibrillated cellulose

This research evaluates the effects of filler content and silanization on thermal, morphological and mechanical properties of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH)-based composites. Microfibrillated cellulose (MFC) was obtained by a mechanical treatment of high-pressure homogenization, starting from oat hull fiber, a byproduct of the agri-food sector. MFC reinforced PHBH composites were prepared by melt compounding. SEM and FT-IR analysis showed a good dispersion of the filler in the polymeric matrix, denoting the effectiveness of the surface silanization process. The thermal stability of PHBH composites remains substantially unchanged, and the glass transition temperature marginally increases with the increase of the filler content. Furthermore, silanized MFC shows slightly reinforcing mechanical effects on PHBH composites, such as the increase of 10% of the Young modulus with an increase of the maximum tensile stress as well. This finding has an economical interest since the results showed that MFC, deriving from a byproduct, can be successfully used as filler, decreasing the cost of the bio-based compound leaving substantially unaltered its mechanical and thermal properties. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48953.     

Sustainable bionanocomposite from d,l‐lactide/δ‐valerolactone triblock and bionanowhiskers: Preparation,characterization, and properties

Bionanocomposites were prepared using d ,l ‐lactide–δ‐valerolactone–d ,l ‐lactide triblock and unmodified and modified cellulose nanowhiskers (CNs) at different loadings (0, 2, 4, 8 wt %). Poly(δ‐valerolactone) chains were grafted on CNs for modification. These were characterized by various techniques. The broadening of OH (hydroxyl) stretching region and the presence of low‐intensity peaks at 1064 cm^?1 for C? O/C? C stretching vibration and 1426 cm^?1 for bending vibration of CH₂ group_, were evident in Fourier transform infrared spectra of the nanocomposites. The increase in crystallinity was noticed as the amount of nanowhiskers was increased. The nanowhiskers having the width in the range of 80–300 nm were uniformly dispersed in the triblock matrix. The tensile strength and modulus increased by 130% and 50% respectively at 8 wt % of filler loading. The storage modulus, loss modulus, complex viscosity, and tan δ values increased with increased filler loading. Further improvement in mechanical properties was observed with the modified CNs. The modulus mapping from atomic force microscopy confirmed the effective reinforcement behavior of the nanowhiskers. Scaffold fabrication using the bionanocomposite exhibited porous nature, having a homogeneous dispersion of CNs on the surface of the scaffold. The 3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay confirmed the suitability of the composite material for scaffold application. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 135, 46035.     

Asolectin from soybeans as a natural compatibilizer for cellulose‐reinforced biocomposites from tung oil

The free radical copolymerization of tung oil, divinylbenzene, and n‐butyl methacrylate results in bio‐based thermosetting polymers with tunable properties. Biocomposites have been obtained by the reinforcement of such bio‐based resins with α‐cellulose. Asolectin from soybeans consists of a mixture of natural, polyunsaturated phospholipids. Because of its long, unsaturated fatty acid chains, and the presence of phosphate and ammonium groups, asolectin from soybeans is a good candidate for acting as a natural compatibilizer between the hydrophobic matrix and the hydrophilic reinforcement. In the current work, we investigate the changes in properties resulting from the addition of asolectin to a tung oil‐based polymer reinforced with α‐cellulose. An evaluation of the cure‐kinetics of the tung oil‐based resin has been conducted by dielectric analysis (DEA), and the final biocomposites have been thoroughly characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical analysis (DMA), Soxhlet extraction, and scanning electron microscopy (SEM). © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41833.     

Behavior of cellulose liquefaction after pretreatment using ionic liquids with water mixtures

Ionic liquid (IL)‐water mixtures were applied in cellulose pretreatment experiment and the pretreated cellulose was used in subsequent phenol liquefaction process as a new application method. Cellulose recovery rate and the average molecular weight (M_w) of pretreated cellulose were investigated to understand the influence of these mixtures on cellulose structure. X‐ray diffraction, Fourier transform infrared, gel permeation chromatograph, and scanning electron microscope were used to clarify the changes of pretreated cellulose. The liquefied residues from untreated cellulose and pretreated cellulose were considered as significant index to determine the effect of IL‐water mixtures on cellulose. Moreover, liquefied residues were initially characterized by the variation of the average M_w. It was suggested that the lower M_w of cellulose obtained in IL‐water mixtures, and the crystalline structure was disrupted. So, some cracks were found on the cellulose surface obviously. The liquefied residues result suggested that the pretreated cellulose obtained the lower residues at the same time or the same amount of residues by using the less time. The behavior of cellulose liquefaction efficiency using IL‐water mixture pretreatment was discussed. The lower M_w of cellulose was the major factor, which accelerates the cellulose phenol liquefaction process efficiency. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40255.     

Surface modification of lignin for applications in polypropylene blends

The surface modification of wet‐milled softwood lignin produced with the LignoForce System was successfully carried out in a one‐step aqueous process. Different hydrophobic molecules, including cetyl trimethyl ammonium bromide, poly(ethylene oxide), polyethylene‐block‐poly(ethylene glycol), dodecenyl succinic anhydride, and alkyl ketene dimer (AKD), were investigated to design the hydrophobicity of lignin with the objective of improving the adhesion and compatibility in polymer blends composed of polar lignin particles and, for example, nonpolar polypropylene (PP). AKD, among all of the investigated approaches, proved to be the simplest and most effective for significantly increasing the contact angle of lignin while preserving the original micrometer size of wet‐milled, spray‐dried lignin particles. This treatment led to a noticeable improvement in the stiffness of lignin–PP composite blends, with an increase of approximately 15% in Young's modulus. The compatibility of the AKD‐treated lignin with PP was assessed through tensile strength measurements and blend morphology observation, whereas the mechanism of AKD interaction with lignin was investigated with contact angle measurement, differential scanning calorimetry, Fourier transform infrared spectroscopy, and ¹H‐NMR spectroscopy measurements. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45103.     

Phosphorylated cellulose/electrospun chitosan nanofibers media for removal of heavy metals from aqueous solutions

Contamination of water resources by toxic heavy metals has significant impacts on environmental and human health. Their removal from aqueous media is essential to ensure water sustainability and to provide safe freshwater availability to population. Electrospun chitosan (CS) nonwoven mats are efficient at removing heavy metals from aqueous media. However, they suffer from low permeability and low-mechanical strength. They are also unable to remove contaminants in a nonselective way. A bilayer sorbent media made of a porous phosphorylated cellulose substrate covered by electrospun CS nanofibers was developed to overcome those weaknesses. The hydrophilic composite shows good water permeability and mechanical strength with appropriate thermal and chemical characteristics. Adsorption tests with Cd(II) indicate that pseudo-second order and Langmuir models best fitted experimental data, with a maximum adsorption capacity of 591 mg/g at 25°C. Adsorption with multielement samples containing Cr(VI), Cu(II), Cd(II), and Pb(II) also reveal their capability to remove them in a selective way. This mechanically resistant, hydrophilic, and permeable adsorbent media was able to capture both cationic and anionic metallic contaminants.     

Nanomechanical properties and thermal stability of recycled cellulose reinforced starch–gelatin polymer composite

Samples of starch?gelatin polymer reinforced with 5% of recycled cellulose were prepared using an extrusion‐compression molding process. Nanoindentation and atomic force acoustic microscopy (AFAM) techniques were used to study the effect of reinforcement at nanoscale level. Nanoindentation tests show a 163% increase in hardness and 123% of elastic modulus enhancement after recycled cellulose inclusion. AFAM shows that distribution of recycled cellulose into the polymer matrix is rather homogeneous at nanoscale which improves load transfer. Thermogravimetric analysis indicates an increase in thermal stability of the cellulose reinforced polymer matrix samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41787.     

Utilization of tall oil to enhance natural fibers for composite applications and production of a bioplastic

Tall oil is one of the side products from the kraft pulping process of lignocellulosic material. The most abundant acid found in this crude viscous material is abietic acid. Strangely, in the past, the utilization of tall oil has been limited to incineration for cogeneration of power. In this study, tall oil rosin acids (TORAs) were used in two different applications. First, it was used to enhance the hydrophobicity and thermal properties of hemp fibers. Second, TORAs were used to supplement epoxy for the production of a polymeric material. The reaction conditions from a model study were mimicked using a crude tall oil rosin acid mixture to enhance hemp fibers. Treated hemp fibers were characterized with increased surface hydrophobicity and improved thermal properties. Also, IR and X‐ray photoelectron spectroscopy confirmed successful chemical modification and grafting of carbon rich moieties onto the surface of the fibers, respectively. Furthermore, TORAs were used to supplement epoxy resin and produced plastics with comparable properties to pure epoxy based plastics. Specifically, 25% (w/w) replacement exhibited little difference in thermal stability and curing when compared to virgin epoxy plastics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44327.     

Preparation and analysis of poly(l-lactic acid) composites with oligo(d-lactic acid)-grafted cellulose

α-Cellulose extracted from jute fiber was grafted with oligo( d -lactic acid) (ODLA) via a graft polycondensation reaction in the presence of para-toluene sulfonic acid and potassium persulfate in toluene at 130 °C for 9 h under 380 mmHg. ODLA was synthesized by the ring-opening polymerization of d -lactides in the presence of stannous octoate (0.03 wt % lactide) and d -lactic acid at 140 °C for 10 h. Composites of poly( l -lactic acid) (PLLA) with the ODLA-grafted α-cellulose were prepared by the solution-mixing and film-casting methods. The grafting of ODLA onto α-cellulose was confirmed by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The analysis of the composites was performed with FTIR spectroscopy, SEM, wide-angle X-ray diffraction, and thermogravimetric analysis. The distribution of the grafted α-cellulose in the composites was uniform and showed better compatibility with PLLA through intermolecular hydrogen bonding. Only homocrystalline structures of PLLA were present in the composites, and the thermal stability increased with increasing percentage of grafted α-cellulose. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47424.     

Improvement in impact strength of modified cardanol‐bonded cellulose thermoplastic resin by adding modified silicones

The impact strength of cellulose diacetate (CDA) bonded with a modified cardanol (3‐pentadecylphenoxy acetic acid: PAA) was greatly improved up to 9 kJ/m² by adding a relatively small amount of modified silicones while suppressing a decrease in bending strength. In our recent research, this thermoplastic resin (PAA‐bonded CDA) exhibited high rigidity, glass transition temperature, and water resistance. However, its impact strength was insufficient for use in durable products. Therefore, silicones modified with polyether, amino, and epoxy groups were investigated as possible ways to improve the impact strength. The results show that adding polyether‐modified silicone (polyether silicone) with moderate polarity relative to PAA‐bonded CDA resulted in shearing deformation greatly enhances its impact strength while maintaining other properties, including glass transition temperature (T_g), water resistance, and thermoplasticity. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40366.     

Forcespinning technique for the production of poly(d,l-lactic acid) submicrometer fibers: Process–morphology–properties relationship

This work addresses a systematic study for the process development and optimization of poly(d ,l -lactic acid) (PDLLA) submicrometer fibers utilizing the centrifugal spinning technique known as Forcespinning. This study analyzes the effect of polymer concentration (8, 10, and 12 wt %) and angular speed on the fiber morphology, diameter distribution, and fiber yield. The increase in polymer concentration and angular speed favored the formation of continuous and homogeneous submicrometer fibers with an absence of bead formation and higher output. The optimal conditions were established considering the morphological characteristics that exhibit a greater surface area (homogeneous and submicrometer fibers); and they were achieved at a polymer concentration of 10 wt % at an angular speed ranging from 8000 to 10 000 rpm. Optimization of PDLLA submicrometer fiber fabrication lays the groundwork for scaling up the process and serves as a platform to further develop promising applications of PDLLA nonwoven mats, particularly in the biomedical area such as in scaffolds for tissue engineering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47643.     

Waterborne polyurethane nanocomposites based on vegetable oil and microfibrillated cellulose

This work analyzes the differences in the final properties of two waterborne polyurethanes (WBPU) prepared with two macrodiols of different chemical structure, but similar molecular weight, as well as the variations caused by incorporating low percentages of microfibrillated cellulose nanocrystals. One of the polyurethanes was based on a synthetic but biodegradable precursor (polycaprolactone diol, PCL) and a second one based on a bio‐based macrodiol derived from castor oil (CO1). The bio‐based material presented higher mechanical properties at room temperature than the synthetic one, with the Young's modulus (MPa) ranging from 2.23 ± 0.09 to 84.88 ± 0.96 for the PCL and bio‐based WBPUs, respectively. Additionally, the PCL‐based WBPU showed to be more sensitive to the incorporation of cellulose than the bio‐based WBPU, and it also suffered changes during time due to delayed crystallization. The behavior of the two systems were compared and related to the different structure of the macrodiols that led to different interfacial interactions. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44207.