Melt processing of nanocomposites of cellulose nanocrystals with biobased thermoplastic polyurethane

Nanocomposites of thermoplastic polyurethane (TPU) with cellulose nanocrystals (CNC) without and with surface treatment are obtained by melt processing. Nanocomposites are obtained with nanofiller weight content near of the theoretical percolation threshold (3.9 wt%). Visual observation of CNC agglomerates is sufficient to prove the inefficiency of the mixing in systems with untreated CNC. The crystallization kinetics of the TPU changes with the addition of CNC and this is confirmed by differential scanning calorimetry analysis. Thermogravimetric analysis prove that the addition of CNC increases the thermal stability of the TPU. From the rheological analysis it is possible to verify the absence of percolation and an intermediate state of sol–gel transition in the nanocomposites. CNC/TPU nanocomposites with 5 wt% of treated CNC present better mechanical performance than de neat TPU and the other processed nanocomposites and display around 130% increase in Young's modulus while retaining significant values of toughness, tensile strength and elongation at break.     

Effect of dimethyl sulfoxide on synthesis of thermoplastic cellulose‐Graft‐poly(l‐lactide) copolymer using ionic liquid as reaction media

In this study, ring‐opening graft polymerization of l ‐lactide onto cellulose was carried out homogeneously in ionic liquid (IL)/dimethyl sulfoxide (DMSO) co‐solvent as a reaction media. Through the effective control of high viscosity and steric hindrance caused by the interaction between the IL and the hydroxyl group of cellulose by adding DMSO as a co‐solvent, cellulose‐graft‐poly(l ‐lactide) (Cell‐g‐PLLA) copolymer with higher substitution efficiency was successfully prepared, at relatively low concentration of l ‐lactide. The maximum values of molar substitution, degree of lactyl substitution, and degree of polymerization of poly(l ‐lactide) in the copolymer were 3.76, 1.74, and 2.16, respectively, determined by ¹H‐NMR. The prepared cell‐g‐PLLA copolymers showed thermal plasticization with a glass transition temperature of 155°C. In addition, the thermal processibility could be improved as the amount of grafted PLLA in the copolymer increased. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41331.     

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.     

Cellulose monoacetate/polycaprolactone and cellulose monoacetate/polycaprolactam blended nanofibers for protease immobilization

Enzymes can be used multiple times when they are immobilized on a support. More enzymes can be immobilized on a surface when nanofibers are used as a supporting surface because the specific surface area increases tremendously. In this regard, polycaprolactam/cellulose monoacetate (PA6/CMA) and polycaprolactone/cellulose monoacetate (PCL/CMA) blended nanofibers (NFs) were prepared via an electrospinning process. Protease enzymes were immobilized on neat PA6, PCL, PA6/CMA, and PCL/CMA nanofibers and glutaraldehyde (GA) activated analogs through the physical adsorption method. The immobilized enzyme activity was measured by using a casein substrate, and the results were compared with free enzyme activity. Among all of the samples, the highest immobilization yield of about 82% was obtained with GA‐activated neat PCL NF samples. The best remaining activity of the immobilized enzymes on pure CMA NFs was found to be 59% after seven reuses. Even after nine reuses, enzyme activities are still observed on the CMA NF samples. It was expected that the addition of CMA in PCL and PA6 NFs would increase the reusability number to reach the reusability of CMA NFs, but it was not significantly enhanced. If CMA chains could be mostly collected on the sheath or close to the sheath of the NFs during the electrospinnig process, this target could be achieved. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45479.     

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.     

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.     

Preparation of treelike and rodlike carboxymethylated nanocellulose and their effect on carboxymethyl cellulose films

In this work, carboxymethyl cellulose (CMC) with low substitution degree, followed by different posttreatments, was applied to prepare treelike CMC nanofibrils (CMCNFs) and rodlike CMC nanocrystals (CMCNCs), and their performance in CMC composite film was evaluated simultaneously. From transmission electron microscopy results, it was found that the treelike CMCNCFs exhibited a lager aspect ratio compared to the rodlike CMCNCs. As for reinforcing CMC film, 4 wt% was the best adding amount, at this time, the tensile strength of CMC/CMCNFs and CMC/CMCNCs composite films was increased by 72.1% and 47.3%, respectively. Moreover, adding these nanofillers to CMC also could enhance the thermal stability of composite films slightly, while the transmittance of composite films was reduced at the same time. In addition, CMC/CMCNFs film was designed as a packaging box to determine its performance. Therefore, this study could reveal the differences of properties for composites with different types of nanocellulose and provide a foundation for further application of nanocellulose.     

Microcrystalline cellulose as reactive reinforcing fillers for epoxidized soybean oil polymer composites

Microcrystalline cellulose (MCC) and its oxidized product dialdehyde cellulose (DAC) were introduced as the reinforcing filler in epoxidized soybean oil (ESO) thermosetting polymer. The composites comprising up to 25 wt % cellulose fillers were obtained via a solution casting. The reinforcing effects of the cellulose were evaluated by microstructure analysis, dynamic mechanical analysis, and tensile and thermal stability tests. The results showed that at the same filler concentration, DAC led to higher stretching strength, modulus, and break elongation than MCC. The 5 wt % DAC loading in ESO polymer exhibits the highest toughness and thermal stability due to the good dispersion and interfacial interaction between DAC and ESO polymer matrix. The increased storage modulus and glass transition temperature also indicate the cellulose fillers impart stiffness to the composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42488.     

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.     

Polyethylenimine-modified sugarcane bagasse cellulose as an effective adsorbent for removing Cu(II) from aqueous solution

Polyethylenimine-modified sugarcane bagasse cellulose (SBCMP), as a new adsorbent, was synthesized by the reaction of polyethylenimine (PEI) with sugarcane bagasse cellulose and glutaraldehyde. The adsorption of Cu(II) by SBCMP was pH-dependent, and the higher removal efficiency of Cu(II) appeared in the range of pH 3.0–6.0. The adsorption isothermal data fitted well with the Langmuir model, and the maximum adsorption capacity of SBCMP was up to 107.5 mg/g. The adsorption kinetics was best described by the pseudo-second-order kinetic. The adsorption of Cu(II) by SBCMP was unfavorable at high temperatures, and thermodynamic analyses implied that the adsorption of Cu(II) by SBCMP was an exothermic reaction. Fourier transform infrared spectroscopy (FT-IR) combined with X-ray photoelectron spectroscopy (XPS) revealed that Cu(II) adsorption on SBCMP mainly controlled by the nitrogen atoms of  NH group in PEI. The results of regeneration cycles showed that SBCMP was suitable for reuse in the adsorption of Cu(II) from aqueous solution. These experimental results suggested that SBCMP is expected to be a new biomass adsorbent with high efficiency in removing Cu(II) from wastewater.     

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.     

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.     

Homogeneous synthesis and characterization of polyacrylamide‐grafted cationic cellulose flocculants

In this work, cationic cellulose (CC) with different degrees of substitution (DS) was successfully synthesized by the reaction between cellulose and 3‐chloro‐2‐hydroxypropyl‐trimethylammonium chloride (CHPTAC) in a 7 wt % NaOH and 12 wt % urea aqueous solution. The structure of the CC was characterized by using elemental analysis, ¹H‐NMR, and FTIR. The DS values of CC ranged between 0.18 and 0.50, which could be obtained by adjusting the reaction temperature, reaction time, and molar ratio of CHPTAC to anhydroglucose unit of cellulose. The cationic cellulose–graft–polyacrylamide flocculant (CC‐g‐PAM) based on CC and polyacrylamide (PAM) was also synthesized in a homogeneous aqueous solution. The flocculation characteristics of CC and CC‐g‐PAM were evaluated in a kaolin suspension. The results showed that CC‐g‐PAM was an effective flocculant for the kaolin suspension under acidic or neutral conditions, and the flocculation efficiency was over 90%, while the CC showed better flocculation performance under alkaline conditions. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43106.     

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.     

Lightweight investigation of long chain branching polypropylene/cellulose nanofiber composite foams

Long chain branching polypropylene (LCBPP)/cellulose nanofiber (CNF) composite foams were prepared by short shot foam injection molding method and their morphological, mechanical, and thermal properties were also investigated. The cellular structure of LCBPP/CNF composite foams was improved with weight reduction (WR) ratios increasing. The cell densities of LCBPP/CNF composite foams were dramatically increasing with WR ratios rising. More, the fine and uniform cellular structures were obtained due to the incorporation of CNF. The highest cell density, specific flexural strength, and modulus could achieved 20 × 10³ cell/cm², 65 MPa/(g/cm³) and 2.7 GPa/(g/cm³), respectively. Furthermore, the specific Charpy impact strengths were also higher than the ones of solid samples. At last, the thermal insulation properties were discussed accordingly.     

Preparation and characterization of antimicrobial films based on nanocrystalline cellulose

Nanocrystalline cellulose (NCC) has great potential in applications in medical and food packaging due to its abundance, high specific surface area, biodegradability, biocompatibility, and reproducibility. N-Halamine is one of the most effective antibacterial agents, with broad-spectrum efficacy against microorganisms, good stability, and reproducibility. Due to the nanosize effect and high specific surface area of NCC, N-halamine-modified NCC is potentially an excellent biocidal compound. In this paper, an N-halamine precursor 1-hydroxymethyl-5,5-dimethylhydantoin (HDH) was used to modify NCC with cyanuric chloride (cych) as the bonding agent. After chlorination, the produced NCC-cych-HDH-Cl became antibacterial. The synthesized NCC-cych-HDH-Cl was added to a chitosan (CS) and polyvinyl alcohol (PVA) solution to prepare antibacterial films. The optimum mixing ratio of PVA and CS in the PVA/CS films and concentration of NCC-cych-HDH-Cl were investigated. The surface morphologies and mechanical properties of the antibacterial films were characterized with scanning electron microscopy, transmission electron microscopy, and mechanical strength tests. The results indicated that the film with 90/10 PVA/CS and 7.0% loading of NCC-cych-HDH-Cl exhibited excellent tensile strength. The antibacterial film with 5.91 × 10¹⁷ atoms/cm² of active chlorine displayed an excellent antibacterial property against Staphylococcus aureus (ATCC 6538) and Escherichia coli O157:H7 (ATCC 43895). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47101.     

Performance of nylon 6 composites reinforced with modified agave fiber: Structural,morphological, and mechanical features

Nylon 6 (Ny6) composites reinforced with treated agave fiber (AF) at different concentrations (5–20 wt%) were achieved by melt mixing process at 250°C, without the addition of any compatibilizing or coupling agents, and characterized in terms of their structural, morphological, and mechanical properties. The alkaline-ultrasound (NaOH-U) treatment in AF resulted in the removal of the low thermal stability components (pectin and hemicellulose), concentrating the cellulose fraction, and favoring the crystallinity percentages (X_c) of the Ny/AF composites. Moreover, the interfacial interactions between functional groups of agave fiber and Ny6 resulted in the increase Young's modulus (18.8%), flexural strength (11.3%), and density (3.7%). These findings could be useful when looking for potential applications in the mobility industry.     

The utilization of thermomechanical pulp fibers in WPC: A review

Thermomechanical pulp (TMP), among other natural fibers, features characteristics that make it a promising candidate for the utilization in polymer composites. This review is providing an overview on the current state of research on TMP reinforced polymer composites. More than 50 references were reviewed. The cited literature is catalogued according to pretreatments, batch or continuous procedures, processing at laboratory or industrial scale, fiber contents, polymer types, coupling agents as well as wood species. The reinforcing potential of TMP utilized in composites is demonstrated. Tensile strength was found to be peaking at a fiber content of around 40 wt %. Fiber morphology is presumed to be an important determinator for composite properties. Specific mechanical energy [kWh/kg] is presented as an indicator suitable to compare the influence of various processes on fiber morphology. Furthermore, the feed‐in and dosing issue that generally accompanies the utilization of cellulosic fibers is described and possible solutions are discussed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45161.     

Preparation and characteristic of a sodium alginate/carboxymethylated bacterial cellulose composite with a crosslinking semi‐interpenetrating network

A novel ionic crosslinking sodium alginate (SA)/carboxymethylated bacterial cellulose (CM‐BC) composite with a semi‐interpenetrating polymer network (semi‐IPN) structure was developed in this study. The composite was prepared through the blending of an SA gel with CM‐BC then crosslinking by Ca²⁺ followed by a freeze‐drying process. Scanning electron microscopy showed the composite matrix organized in a three‐dimensional network of CM‐BC interpenetrated against SA molecular chains with a quantity of calcium alginate microspheres upon the surface. The swelling ratios of the composite were enhanced by 183, 198, and 212% with the supplementation of CM‐BC weight fractions of 25, 50, and 75%, respectively; the swelling ratios changed with changing pH. The tensile modulus, tensile strength, and elongation at break of SA were enhanced by 165, 152, and 188%, respectively, with the addition of 50 wt % CM‐BC. This study demonstrated that the semi‐IPN structure dramatically changed the swelling and mechanical properties of the composite, and the semi‐IPN will be a promising candidate for biomedical applications such as wound dressings and skin tissue engineering. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39848.     

Influence of the solvent and nonsolvent composition on the electrospinning of a cellulose acetate ternary system

A series of cellulose acetate (CA) ternary system solutions consisting of the CA, N,N‐dimethylacetamide, and various nonsolvents, such as 1‐propanol, 1‐hexanol, 1‐octanol, 1‐decanol, 1,3‐propane diol, and glycerol, were prepared, and the effects of the component composition on the solutions characteristics and electrospinning were examined. In particular, the effects of the nonsolvent concentration, structure, and degree of miscibility with other components were studied. In some cases, increasing the nonsolvent content increased the solution viscosity and facilitated the electrospinning process. However, we found that electrospinning was also governed by the structure of the nonsolvents and by the solution viscosity. An increase in the number of hydroxyl groups or an increase in the hydrocarbon chain length of the monohydroxyl alcohol nonsolvent improved the fiber formation. The calculated Hansen sphere [D_(S‐p)] values of the CA ternary system solution were then used to explain their electrospinnability. The increases in the hydrophilicity and hydrophobicity of system caused by changes in the nonsolvent structure increased the D_(S‐p) values and improved fiber formation in electrospinning process. The calculated D_(S‐p) values were also shown to be in good agreement with the obtained microscopy images of the electrospun fiber. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42819.