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     

Regenerated cellulose aerogel: Morphology control and the application as the template for functional cellulose nanoparticles

This article focuses on controlling the morphology of regenerated cellulose aerogel (RCA) and its application as a template for the preparation of functional cellulose nanoparticles (FCNPs). RCA is prepared by lyophilizing cellulose hydrogel which is fabricated through a sol–gel method in sodium hydroxide (NaOH)/urea aqueous solution. The morphology of RCA is adjusted by varying the gelation temperature and time. With the gelation temperature and time increasing, lamellar RCA transforms into strings of cellulose nanoparticles. Subsequently, RCA with the morphology of "strings of nanoparticles" is modified through the bulk condensation of l -lactic acid and RCA. Eventually, the prepared functionalized RCA (FRCA) is dispersed in an organic solvent to obtain purified FCNPs. The results demonstrate that single FCNP can be obtained by dispersing FRCA in dimethyl sulfoxide. Moreover, the prepared FCNPs have uniform size, good thermal-stability, and increasing hydrophobicity, which are ideal candidates for polymer composites in terms of fillers.     

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.     

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     

Alkaline extraction of xylan from wood using microwave and conventional heating

This study aims to investigate the effect of microwave heating versus conventional heating for the alkaline hydrolysis of xylan from birch wood to understand the effect of the heating process on the dissolution of wood, the yield of xylan, and the degree of polymerization of the isolated xylan. The results indicate that the rate of wood dissolution is significantly higher (0.020/s) during microwave extraction than the conventional extraction (0.001/s). Wood solubilization, after an initial rapid removal of damaged fibers, is linear with time for both conventional and microwave extraction, with microwave showing a rate 20 times faster. The yield of xylan reaches a limit of about 60% for both processes but then declines slowly as thermal degradation become significant. Microwave heating provides 60% yield in 1/10th the time of the conventional process. This is found to be associated with the rapid temperature rise, and also with local “hot spots” generated during microwave treatment. The results indicated that xylan degradation was significant above 95°C. The nature of the isolated xylan was different for the two heating methods: the xylan isolated using microwave extraction for 20 min exhibits higher molecular weight (i.e., a greater degree of polymerization, about 150) than the xylan isolated using conventional extraction for the same duration (degree of polymerization, about 124) demonstrating the effectiveness of microwave heating for extraction of xylan from wood. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41330.     

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.     

Cassava starch‐based nanocomposites reinforced with cellulose nanofibers extracted from sisal

Cellulose nanofibers were extracted from sisal and incorporated at different concentrations (0–5%) into cassava starch to produce nanocomposites. Films' morphology, thickness, transparency, swelling degree in water, water vapor permeability (WVP) as well as thermal and mechanical properties were studied. Cellulose nanofiber addition affected neither thickness (56.637 ± 2.939 µm) nor transparency (2.97 ± 1.07 mm^?1). WVP was reduced until a cellulose nanofiber content of 3.44%. Tensile force was increased up to a nanocellulose concentration of 3.25%. Elongation was decreased linearly upon cellulose nanofiber addition. Among all films, the greatest Young's modulus was 2.2 GPa. Cellulose nanofibers were found to reduce the onset temperature of thermal degradation, although melting temperature and enthalpy were higher for the nanocomposites. Because cellulose nanofibers were able to improve key properties of the films, the results obtained here can pave the route for the development and large‐scale production of novel biodegradable packaging materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44637.     

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.     

Study on the preparation and mechanical properties of injection‐moulded wood‐based plastics

The objectives of this study were to prepare injection‐moulded wood‐based plastics and to characterize their mechanical properties. Injection‐moulded wood‐based plastics with satisfactory flexural (65.7 MPa) and tensile strengths (30.1 MPa) were successfully obtained through a simple reaction of mulberry branch meal with phthalic anhydride (PA) in 1‐methylimidazole under mild condition. The X‐ ray diffraction results indicated complete disruption of the crystallinity of cellulose because the pattern obtained for esterified fiber was almost a straight line without any peaks. The peaks in the Fourier transform infrared spectroscopy spectra (1738 and 748 cm^?1) and NMR spectra (173.3 and 133.5 ppm) indicated the attachment of 0‐carboxybenzoyl groups onto the wood fibers via ester bonds. The differential scanning calorimetry curves showed that the glass transition temperature decreased with increasing weight percentage gain (WPG). The derivative thermogravimetric analysis curves indicated that esterified wood fiber was less thermally stable than the untreated fiber and that the component tends to be homogeneous with increasing WPG. Scanning electron microscope revealed that the fractured surfaces of most samples were smooth and uniform but that high temperature and less PA dosage could lead to the appearance of holes and cracks. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41376.     

Building and origin of bio‐based bismaleimide resins with good processability,high thermal,and mechanical properties

Bio‐based high performance thermosetting resins have been urgently required by cutting‐edge fields for meeting sustainable development. A new kind of high performance thermosetting resins (BA‐n) with good processability, high thermal resistance, and mechanical properties was developed based on 4,4′‐bismaleimidodiphenylmethane (BDM) and renewable bis(5‐allyloxy)‐4‐methoxy‐2‐methylphenyl)methane (ABE) from bio‐based lignin derivative. The effect of the molar ratio of allyl to imide (n) on structures and properties of BA resins were systematically researched. BA‐n resins have much better processability, thermal, and mechanical properties than their petroleum‐based counterparts, 2,2′‐diallylbisphenol A‐modified BDM (BD‐n) resins. Compared with BD‐0.86, the best available bismaleimide (BMI) resin, BA‐0.86 not only has 6 h longer process window and 13.7 °C higher glass transition temperature, but also owns the highest flexural strength and modulus among all bio‐based allyl compound‐modified BMI resins reported. The origin behind these attractive performances of BA resins is revealed by discussing the unique crosslinked structure. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45947.     

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.     

Influence of microfibrillated cellulose and soft biocomponent on the morphology and thermal properties of thermoplastic polyurethanes

Composite materials from thermoplastic polyurethanes (TPUs) with biodegradable segments and microfibrillated cellulose (MFC) were developed as alternatives to traditional materials used in packaging or biomedical applications. Two TPUs were synthesized by the prepolymer method starting from different soft segments, poly(ε-caprolactone)/poly(butylene adipate) (PUBA) or poly(ε-caprolactone)/poly(ethylene oxide) (PUEO), and isophorone diisocyanate/aliphatic chain extender. Proton nuclear magnetic resonance (¹H NMR) confirmed the structure and Fourier transform infrared spectroscopy (FTIR) along with scanning electron microscopy showed that the soft segments with different hydrophobicity led to a higher phase mixing in PUBA and improved microphase separation in PUEO. MFC was added in the TPUs with different soft segments to increase biocompatibility, strength, and degradation rate. A better thermal stability, a gradual increase of crystallinity and a better dispersion of MFC were noticed in PUEO composites compared to PUBA ones. The crystallinity increased with 78% and 50% in PUBA and PUEO composites with 5 wt% MFC compared to the neat polyurethanes showing the nucleating ability of MFC. In addition, the enhanced storage modulus, with 75% and 25% in PUEO and PUBA composites, highlighted the reinforcing efficiency of MFC. Therefore, the addition of MFC to the already synthesized TPUs allows tailoring the morphology and thermal properties of TPUs for industrial application.     

Processing and thermal properties of composites based on recycled PET,sisal fibers,and renewable plasticizers

This investigation focuses on the preparation of bio‐based composites from recycled poly (ethylene terephthalate) (PET) and sisal fibers (3 cm, 15 wt %), via thermopressing process. Plasticizers derived from renewable raw materials are used, namely, glycerol, tributyl citrate (TBC) and castor oil (CO), to decrease the melting point of the recycled PET (T_m ∼ 265°C), which is sufficiently high to initiate the thermal decomposition of the lignocellulosic fiber. All used materials are characterized by thermogravimetric analysis and differential scanning calorimetry, and the composites are also characterized via dynamic mechanical thermal analysis. The storage modulus (30°C) and the tan δ peak values of CT [PET/sisal/TBC] indicate that TBC also acts as a compatibilizing agent at the interface fiber/PET, as well as a plasticizer. To compare different processing methods, rheometry/thermopressing and compression molding are used to prepare the recycled PET/sisal/glycerol/CO composites. These two different methods of processing show no significant influence on the thermal properties of these composites. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40386.     

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.     

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.     

Preparation and properties of cotton stalk bark fibers using combined steam explosion and laccase treatment

Cotton stalk bark fibers (CSBF) were prepared using combined steam explosion and laccase treatment (explosion–laccase). CSBF have been applied to reinforce thermoplastic composites, but were difficult to be spun into yarns due to their inferior fineness and high stiffness. In order to improve the fineness and flexibility with a green method, explosion–laccase treatment was used to separate bark of cotton stalks. The results indicated that steam explosion at 1.7 MPa for 3 min effectively facilitated laccase penetration into the lignocellulose complex to enhance delignification without negative effects on activity of laccase. Compared with CSBF after explosion, CSBF after explosion–laccase had better fineness (31 dtex), higher aspect ratio (1110), higher tensile strength (2.81 cN/dtex), higher flexibility (321 twist/(m·dtex)), and better thermal stability, which meets the requirement of textile fibers. CSBF had higher water retention (127%) and moisture regain (10.3%) than cotton. Explosion–laccase is an effective and eco‐friendly method of preparing CSBF for textiles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45058.     

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.     

Preparation and thermomechanical properties of nanocrystalline cellulose reinforced poly(lactic acid) nanocomposites

A two‐step process was developed to prepare nanocrystalline cellulose (NCC) reinforced poly(lactic acid) (PLA) nanocomposites using polyethylene glycol (PEG) as a compatibilizer. It was composed of solvent mixing and melt blending. The NCC was well dispersed in the PLA matrix. A network was formed at high NCC‐to‐PEG ratio at which the amount of the PEG was not enough to cover all the surfaces of the NCC. The formation of the network was confirmed by the occurrence of a plateau for the storage modulus at low frequency. The incorporation of the PEG and NCC could improve the crystallinity of the PLA. The elongation at break increased from 11.0% for the neat PLA to 106.0% for the composites including 6 wt % NCC, impact strength was improved from 0.864 to 2.64 kJ m^?2 and tensile strength did not change significantly for the same 6 wt % NCC composites. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44683.