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.     

Synthesis of an elastic β‐cyclodextrin hydrogel cage by hydroxyethyl cellulose

Current cyclodextrin (CD) hydrogels have disadvantages, including a limited CD content, long reaction time, and complicated chemical reactions. To overcome these, a one‐pot reaction was adopted, and a concept of a β‐CD hydrogel cage was proposed. Hydroxyethyl cellulose (HEC) was used as the raw material with the adjustment of the stoichiometric relationship among the crosslinking agent of epichlorohydrin, alkali environment, and β‐CD amount, and an elastic β‐CD hydrogel cage system was established. After the β‐CD was caged, the contents of active β‐CD in hydrogel products reached 74.45 and 69.14 wt % by weight measurement and photometric titration, respectively. Furthermore, compared to the pure HEC hydrogel, the hydrogel mechanical strength improved obviously after the β‐CD was caged, and we obtained a faster water swelling rate at the same time. Finally, a hydrophobic molecule of phenolphthalein (PP) was used to evaluated the activity of caged β‐CD in the hydrogel. In addition, the absorption and release of PP by an elastic β‐CD hydrogel cage at certain time intervals were also studied. The results demonstrate that the β‐CD hydrogel cage was used as a functional molecule carrier to quickly absorb and sustain the release of PP. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44388.     

Alkyne cellulose for Huisgen [3 + 2] cycloaddition with azido‐terminated targets

Azido‐grafted cellulose has been reported widely applied for further functionalization by click chemistry. As an alternative method, we proposed alkyne‐grafted cellulose as a prototype molecule for Huisgen [3 + 2] cycloaddition with azido‐terminated target compounds. Alkyne cellulose was synthesized by acylation with prop‐2‐ynyl 5‐chloro‐5‐oxopentanoate and, subsequently cycloaddition with 4‐aminophenylazide, ethyl 2‐azidoacetate, and (S)‐2‐(Azidomethyl)‐1‐(tert‐butoxycarbonyl)pyrrolidine (Boc‐pyrrolidine azide) to form triazole cellulose in a click manner. The reactions were confirmed qualitatively by Fourier transform infrared and NMR spectroscopy and analyzed quantitatively with elemental analysis data. The results show that a degree of substitution of up to 1.91 was obtained for esterification and, in most cases, was preferred completely in a selective way for the primary hydroxyl groups at the O‐6 position and partially at the O‐2 and O‐3 positions. Cycloaddition conversions were found as high as 0.95, 0.99, and 0.99 for aniline–triazole cellulose, acetate–triazole cellulose, and Boc‐pyrrolidine‐triazole cellulose, respectively. Both esterification and cycloaddition were undertaken under mild conditions without additional heating. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44410.     

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

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

Chemical and structural characterization of alkaline‐extractable hemicelluloses from various eucalyptus species

Eucalyptus species are currently one of the main feedstock for pulping and papermaking industry in China. In the present study, alkali‐extractable hemicelluloses were isolated from different eucalyptus species (Eucalyptus camaldulensis, E. urophylla × grandis, and E. urophylla × E. tereticornis) at mild conditions prior to pulping. Structural characterization of these hemicellulosic polymers based on monosaccharide, molecular weight, Fourier transform infrared, ¹H, ¹³C, and two‐dimensional heteronuclear single quantum coherence nuclear magnetic resonance analysis revealed that these alkali‐extractable polysaccharides shared the common structure composed of the (1→4)‐linked‐β‐D‐xylopyranosyl backbone with 4‐O‐methyl‐α‐D‐glucuronic acid attached to O‐2 of the xylose residues. The potential structures of the alkali‐extractable hemicelluloses were proposed based on the comprehensive analysis. The well‐characterized structures of these hemicelluloses could enlarge the industrial application of these hemicelluloses from the Eucalyptus species in a biorefinery process. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2390–2398, 2013     

Regioselective substitution of 2‐isocyanatoethylmethacrylate onto cellulose

Cellulose is a well‐known versatile polymer that presents a wide range of material properties via the substitution and grafting reactions of its hydroxyl groups. Because of their commercial potential, combinations of cellulose and vinyl polymers have been examined with various grafting methods. In this study, the condensation reactions of regioselective and nonregioselective substitution with 2‐isocyanatoethylmethacrylate were performed in a homogeneous solvent system of dimethyl acetamide/lithium chloride. The successful substitution was confirmed by Fourier transform infrared spectroscopy, ¹H‐NMR, cross‐polarization/magic angle spinning ¹³C‐NMR, thermogravimetric analysis, and X‐ray diffraction. The substituted celluloses showed excellent thermal stability and a different polymorph with a depressed cellulose–intrinsic polymorphic phase. The 2‐isocyanatoethylmethacrylate side chain seemed to expand the intermolecular distance with enhanced chain mobility and trigger the formation of a novel crystalline polymorph with a dramatically improved thermal stability. This investigation provided us with a useful understanding of the modification of cellulose with spatial distribution control for advanced future applications requiring a combination of cellulose with vinyl polymers. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Microwave‐assisted synthesis of silver nanoparticles on cotton fabric modified with 3‐aminopropyltrimethoxysilane

In this study, silver nanoparticles were synthesized on cotton fabric modified with 3‐aminopropyltrimethoxysilane (APTMS) using sodium citrate as a reducing/stabilizing agent by microwave‐assisted process. The presence of a highly oriented amino‐terminated self‐assembled monolayer and formation of APTMS was demonstrated by an X‐ray photoelectron spectroscopy (XPS) analysis. The silver‐coated cotton fabrics were examined by scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX). UV protection, antistatic, and hydrophobic properties were also evaluated. The results show that silver‐coated fabric modified with APTMS possesses excellent antistatic, UV protection with ultraviolet protection factor (UPF) of 396.5 and superhydrophobic properties with contact angle of 153.2°. APTMS pretreatment improves the adhesive strength between silver coatings and cotton fabric. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3862–3868, 2013     

Rapeseed oil‐based polyurethane foams modified with glycerol and cellulose micro/nanocrystals

A rapeseed oil‐based polyol (ROPO) was synthesized using chemical modification of the rapeseed oil (RO) by epoxidation reaction followed by oxirane ring‐opening with diethylene glycol. The ROPO was used in the formulation of low‐density green polyurethane (PU) foams. The use of glycerol as hydroxyl component, water as a reactive blowing agent and micro/nanocellulose (MNC) as a reinforcement increases the content of natural components in the formulations with important effects on the final foam properties. The ROPO and their intermediate products are characterized by analytical techniques and FTIR spectroscopy, while the final PU foams are characterized by morphological and mechanical analysis. The results show that the addition of glycerol increases the modulus and yield stress. The incorporation of MNC in small amounts is enough to increase the modulus at low temperatures. Both modifiers cause an increase in water absorption and the fragility of the cell walls, reflected in the micrographs of the foams. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41602.     

High‐strength regenerated cellulose fibers spun from 1‐butyl‐3‐methylimidazolium chloride solutions

High‐performance regenerated cellulose fibers were prepared from cellulose/1‐butyl‐3‐methylimidazolium chloride (BMIMCl) solutions via dry‐jet wet spinning. The spinnability of the solution was initially evaluated using the maximum winding speed of the solution spinning line under various ambient temperatures and relative humidities in the air gap. The subsequent spinning trials were conducted under various air gap conditions in a water coagulation bath. It was found that low temperature and low relative humidity in the air gap were important to obtain fibers with high tensile strength at a high draw ratio. From a 10 wt % cellulose/BMIMCl solution, regenerated fibers with tensile strength up to 886 MPa were prepared below 22 °C and relative humidity of 50%. High strengthening was also strongly linked with the fixation effect on fibers during washing and drying processes. Furthermore, an effective attempt to prepare higher performance fibers was conducted from a higher polymer concentration solution using a high molecular weight dissolving pulp. Eventually, fibers with a tensile strength of ～1 GPa and Young's modulus over 35 GPa were prepared. These tensile properties were ranked at the highest level for regenerated cellulose fibers prepared by an ionic liquid–based process. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45551.     

Shear‐induced morphology changes in N,N′‐dimethylacetamide/lithium chloride pretreated cellulose

A new mechanochemical treatment was performed on cellulose with the objective of modifying its morphology, reducing its crystallinity, and enabling better dissolution. Cellulose treated with N,N′‐dimethylacetamide (DMAc)/lithium chloride (LiCl) was subjected to shear with natural rubber as the carrier and shear‐transfer medium. When cellulose was subjected to such a mechanochemical treatment, significant changes in its surface morphology and a decrease in crystalline index were observed. The dissolution of the mechanochemically treated cellulose samples in DMAc/LiCl was found to be better compared with the dissolution of samples subjected to either mechanical shear or the chemical action of DMAc/LiCl independently. Chemical interactions between DMAc/LiCl and cellulose were enhanced synergistically under shear‐induced deformation. When shear alone was used in the absence of a DMAc/LiCl treatment, changes in the morphology, crystalline index, and dissolution were found to be negligible. The shear‐induced cellulose samples were characterized with Fourier transform infrared spectroscopy, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and thermogravimetric analysis. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44809.     

The effect of borax‐modified starch on wheat straw‐based paper properties

This study was focused on the improvement of mechanical strength properties of wheat straw‐based paper through modification of wet‐end cationic starch with borax. Borax has been used extensively in many industrial applications for its unique physical and chemical properties. We investigated the strengthening effect of borax‐modified starch (BMS) as wet‐end paper strength additive on the mechanical strength properties especially the tensile strength of wheat straw‐based paper. Hand‐sheets made of typical wheat straw‐based papermaking furnish were investigated. Experimental results showed that BMS substantially increased the strength properties. Tensile index, elongation, tensile energy absorption, and wet tensile index were increased by 17%, 23%, 20%, and 21%, respectively. A short mill trial was also conducted on papermaking machine in which the impact of BMS on wheat straw‐based low grammage paper (<90 gsm) was investigated. The objective of mill trial was to reduce costly virgin softwood pulp content in wheat straw‐based paper recipe. Mill trial results showed similar trends in strength properties as in case of laboratory studies. Virgin softwood pulp was reduced from 30% to 25% in papermaking furnish. Furthermore, no sheet breaks were reported during trial which often happened due to poor strength of paper web. This study strongly suggests that modification of wet‐end cationic starch with borax holds a tremendous potential as wet‐end strength additive. It can provide significantly improved strength properties, reduction in softwood pulp costs, and better papermaking machine performance. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Solvent‐free acetylation of lignocellulosic fibers at room temperature: Effect on fiber structure and surface properties

Acetylation is one of the most interesting chemical treatments to improve the affinity of lignocellulosic fibers with polymeric matrices for the elaboration of several types of composites. In this paper, the acetylation of flax and wood pulp (bleached softwood Kraft pulp and thermomechanical pulp) fibers was carried out at room temperature in a solvent‐free system with acetic anhydride in the presence of sulfuric acid as catalyst. The effect of acetylation on the fine structure of fibers was investigated by spectroscopic methods, while the extent of acetylation was quantified by weight percent gain. The effect of reaction time on fiber morphology was studied at macro‐ and microscale using scanning electron microscopy, optical microscopy, and fiber quality analysis. The evolution of the hydrophobic/hydrophilic character of fibers was determined by contact angle measurements. The wettability of fibers by liquid epoxy resin was also evaluated to confirm the improvement of the affinity of acetylated fibers with the epoxy matrix. It was found that the hydrophilic character of fibers decrease with increasing reaction time, whereas the trend was less pronounced beyond specific reaction times. Acetylated fibers can therefore be potential candidates for replacing nonbiodegradable reinforcing materials in composite applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42247.     

Oxidation of γ‐irradiated microbial cellulose results in bioresorbable,highly conformable biomaterial

Conformability to tissues and adequate mechanical strength are clinically useful properties of resorbable biomaterials used in soft tissue repair. Microbially derived cellulose is attractive as a high strength, highly conformable, and biocompatible material for tissue repair, but is not naturally resorbable. Here we show that controlled oxidation of microbial cellulose sheets that have been pre‐irradiated with γ‐radiation results in a resorbable and fully conformable membrane that can be rapidly rehydrated in aqueous fluids. In vitro studies showed that degradation of the resorbable membranes occurs in two major phases: (1) initial rapid degradation of about 70–80% of the entire sample followed by (2) slower degradation of an additional 5–10% which eventually levels off leaving a small amount of nonresorbable material. In vivo, prototype materials showed marked degradation at all time points, with the most rapid degradation occurring in the first 2–4 weeks. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39995.     

Improvement of storage stability and physicochemical properties by addition of benzoguanamine in melamine‐formaldehyde resin synthesis

The improvement of melamine‐formaldehyde resin storage stability was achieved using benzoguanamine as partial replacement of melamine during synthesis (up to 15% substitution of melamine). The results showed that when benzoguanamine is added in the later stages of reaction, the resulting resins have improved storage stability (4 days or more, compared to 1 day in unmodified melamine‐formaldehyde resin). High‐pressure laminates produced with décor paper impregnated with the new developed resins showed surface properties equivalent to those obtained using commercial melamine‐formaldehyde resins. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45185.     

Synthesis and application of cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) side chains

Cotton‐based chelate fibers grafted with poly(1‐vinyl‐1,2,4‐triazole) (PVTAZ) side chains were synthesized facilely by ozone‐induced graft polymerization of 1‐vinyl‐1,2,4‐triazole (VTAZ) monomer onto cotton fibers. The synthesis conditions were optimized to improve the yield and mechanical strength of the products. The obtained cotton‐g‐PVTAZ fibers were characterized and evaluated for batch adsorption of heavy metal ions from aqueous solutions. The maximum adsorption capacity of Ag(I), Pb(II), and Cu(II) on the fibers at pH 6.8 was 522, 330, and 184 mg/g, respectively. At 30% graft yield, the Young's modulus of cotton fiber increased about 26.5%, and its adsorption capacities of Ag(I), Pb(II), and Cu(II) increased about 2.6, 1.9, and 1.4 times, respectively. After washed with 0.1 mol/L HNO₃ solutions, the adsorbed metal ions were eluted, and the regenerated cotton‐g‐PVTAZ fibers could be used repeatedly for water treatment. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41617.     

Study on the poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate)‐based nanocomposites reinforced by surface modified nanocrystalline cellulose

As a kind of reinforcing agent, the application of nanocrystalline cellulose (NCC) is widely limited in hydrophobic polymers owing to its rich hydroxyl surface. In this study, NCC was modified with lauric acid/p‐toluensulfonyl chloride mixture, then the modified nanocrystalline cellulose (mNCC) was incorporated into biopolyester poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P(3,4)HB) by solution casting to prepare P(3,4)HB/mNCC nanocomposites. The prepared mNCC and P(3,4)HB/mNCC nanocomposites were characterized by Fourier transform‐infrared, X‐ray diffraction, contact angle test, transmission electron microscopy, scanning electron microscopy, differential scanning calorimetric, polarized optical microscope, dynamic mechanical analysis, and thermogravimetric analysis. The results show that the crystallinity and mechanical properties of P(3,4)HB are greatly improved due to the fact that NCC can be modified successfully and the mNCC can distribute uniformly in nanoscale in the matrix with good compatibility along the interface. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2015–2022, 2013     

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

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

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.     

Morphological,thermal, and mechanical properties of poly(ε‐caprolactone)/poly(ε‐caprolactone)‐grafted‐cellulose nanocrystals mats produced by electrospinning

Electrospun nanocomposites of poly(ε‐caprolactone) (PCL) incorporated with PCL‐grafted cellulose nanocrystals (PCL‐g‐CNC) were produced. PCL chains were grafted from cellulose nanocrystals (CNC) surface by ring‐opening polymerization. Grafting was confirmed by infrared spectroscopy (FTIR) and thermogravimetric analyses (TGA). The resulting PCL‐g‐CNC were then incorporated into a PCL matrix at various loadings. Homogeneous nanofibers with average diameter decreasing with the addition of PCL‐g‐CNC were observed by scanning electron microscopy (SEM). PCL‐g‐CNC domains incorporated into the PCL matrix were visualized by transmission electron microscopy (TEM). Thermal and mechanical properties of the mats were analyzed by differential scanning calorimetry (DSC), TGA and dynamic mechanical analysis (DMA). The addition of PCL‐g‐CNC into the PCL matrix caused changes in the thermal behavior and crystallinity of the electrospun fibers. Significant improvements in Young's modulus and in strain at break with increasing PCL‐g‐CNC loadings were found. These results highlighted the great potential of cellulose nanocrystals as a reinforcement phase in electrospun PCL mats, which can be used as biomedical materials. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43445.     

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.