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"Cellulose esters"
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Model cellulosic surfaces
\"Molecular interactions of cellulose surfaces govern the three-dimensional assembly of plant cell walls and play important roles in the pulp and paper, textile, and food industries. Interactions of cellulose surfaces with other polysaccharides, proteins, polynucleotides, and mammalian cells are of interest for biomedical cellulose applications and, more recently, interactions of cellulolytic enzymes with cellulosic substrates is of interest in the production of bioethanol from lignocellulosic feedstocks. The study of interactions and sorption phenomena involving cellulose and cellulosic materials requires well-defined model surfaces. Several methods to prepare such model surfaces have been developed over the past fifteen years and an increasing number of cellulose interaction studies involving such model surfaces can be found in the literature.
Book
Effects of Molecular Structure on the Physical Properties of Fully Substituted Cellulose Esters of Aliphatic Acids
According to the literature, mainly in relation to mixed cellulose esters (MCEs) with two types of acyl group, the solubility parameter (SP) is a measure of certain physical properties of MCE that is helpful for property prediction; contrary to expectations, it has been implied by different studies that simple cellulose esters (SCEs) with only one type of acyl group do not altogether follow the empirical relationship. In this study, MCE and SCE were systematically prepared to verify the SP—property relationship. It was revealed that the correlation between SP and physical properties exists only for MCE. Thermal analysis revealed that MCEs possess remarkable unidentified endothermic transition depending on the ratio of two acyl groups, suggesting that the formation of such a stable structure could contribute to the difference between MCE and SCE. It was also revealed that, even for MCE, the empirical relationship involving SP varies from acyl group to acyl group; there is no universal relationship. In spite of aforementioned limitation, the empirical relationship with SP was verified to be useful for the property prediction of MCE. We demonstrated that the Fox equation and Voigt model are also useful for this prediction.
Journal Article
Tensile and Surface Wettability Properties of the Solvent Cast Cellulose Fatty Acid Ester Films
Thermoplastic cellulose esters are promising materials for bioplastic packaging. For that usage, it is important to understand their mechanical and surface wettability properties. In this study, a series of cellulose esters are prepared, such as laurate, myristate, palmitate, and stearate. The aim of the study is to investigate the tensile and surface wettability properties of the synthesized cellulose fatty acid esters to understand their suitability as a bioplastic packaging material. Cellulose fatty acid esters are first synthesized from microcrystalline cellulose (MCC), then dissolved in pyridine solution, and after the solvent cast into thin films. The cellulose fatty acid ester acylation process is characterized by the FTIR method. Cellulose esters hydrophobicity is evaluated with contact angle measurements. The mechanical properties of the films are tested with the tensile test. For all the synthesized films, FTIR provides clear evidence of acylation by showing the presence of characteristic peaks. Films’ mechanical properties are comparable to those of generally used plastics such as LDPE and HDPE. Furthermore, it appears that with an increase in the side-chain length, the water barrier properties showed improvement. These results show that they could potentially be suitable materials for films and packaging materials.
Journal Article
The effect of side-chain length of cellulose fatty acid esters on their thermal, barrier and mechanical properties
Currently, long-chain cellulose esters are not produced commercially because of high price, and since their preparation typically requires a large quantity of chemicals. To reduce the chemical consumption, cellulose reactivity needs to be increased without losing its quality. One way to increase the reactivity of cellulose is to decrease its molar mass in a controlled manner. In this study, we have synthesized cellulose esters with different side-chain length (C6–C18) in a homogeneous system using ozone molar mass-controlled cellulose. The target was to keep the degree of substitution as low as possible while still ensuring the suitability of cellulose esters for solvent casting. Thermal, barrier and mechanical properties were studied depending on cellulose fatty acid ester side-chain length. All our molar mass-controlled cellulose esters form optically transparent, flexible and heat-sealable films with good water barrier properties and are processable without the addition of an external plasticizer. Furthermore, the films have mechanical properties comparable to some generally used plastics. These good properties suggest that our molar mass-controlled cellulose esters could be potential candidates for various applications such as films and composites.
Journal Article
A sustainable approach for providing water repellency in textiles by using long-chain cellulose esters
Long-chain cellulose esters (LCCEs) are recently developed cellulose derivatives showing properties that are relevant to diverse applications, such as coatings, films and plastics. The nonpolar aliphatic tails of the fatty ester groups impart strong hydrophobic properties to LCCEs, the physicochemical basis for most of the proposed uses. In previous work, we developed LCCE-based formulations as hydrophobicity-promoting agents for pure cotton textiles. Herein, we aimed to expand the use of LCCEs as eco-friendly hydrophobic additives in textiles with different compositions, namely synthetic fibers and mixtures thereof. The LCCE-based formulations were applied by a conventional textile dry-cleaning industrial process, using three types of solvents (one conventional and two green alternative ones). We observed that even for synthetic fibers or blends, there was no need to use crosslinkers to anchor LCCEs to textiles, nor need for pre-treatments to promote an increase in hydrophobic capacity. Water-repellent textiles were thus obtained through sustainable flourine-free compounds, with easy and self-cleaning properties.
Journal Article
Cellulose-based Composites Prepared by Two-step Extrusion from Miscanthus Grass and Cellulose Esters
Natural fibres from regional plants like miscanthus grass have gained a lot attention as a replacement of synthetic fibres due to their eco-friendly nature, abundant local availability, low cost, reducing food versus fuel competition and their applications in bio-based composites. Nevertheless, the polar nature of natural fibres usually leads to a weak interfacial compatibility with hydrophobic thermoplastic matrices, resulting in poor strengths of the composites. In our study a way to prepare cellulose-based composites in a two-step extrusion process is investigated. The cellulosic fibres are first fibrillated from refined miscanthus fibres through (chemo-)thermomechanical pulping by extrusion. The fibre morphology including the aspect ratio is measured by field flow fractionation with optical measurement system. Infrared spectroscopy is applied to analyse the degree of substitution (DS) values quantitatively. In a second extrusion step, the modified cellulosic fibres are compounded with cellulose acetate (CA) and cellulose acetate butyrate (CAB) to cellulose-based injection-mouldable composites. The thermal, rheological, mechanical and morphological properties are characterised to analyse the composites. The properties of the composites prepared by this method are compared with their unmodified grades and with composites using drop-in biopolymers bio-based polypropylene (bio-PP) and bio-based polyethylene (bio-PE) as matrices. It shows, that the mechanical properties of mechanically fibrillated cellulose fibres reinforced CA are comparable to glass fibre reinforced polypropylene with similar fibre weight content. We have also seen, that the influence of mechanical fibrillation exceeds the influence of the chemical modification.
Journal Article
Synthesis, characterization and properties of novel cellulose derivatives containing phosphorus: cellulose diphenyl phosphate and its mixed esters
Using ionic liquid 1-allyl-3-methylimidazolium chloride as reaction medium, a series of novel cellulose esters containing phosphorus including cellulose diphenyl phosphate (C-Dp) and cellulose acetate (CA)–diphenyl phosphate mixed esters was synthesized homogeneously. The degree of substitution was well controlled by altering reaction conditions, such as the molar ratio of the acylating reagents/anhydroglucose unit and reaction time. The structure and thermal properties of cellulose esters were characterized by FTIR, NMR, wide-angle X-ray powder diffraction and differential scanning calorimetry. All the products possessed excellent solubility in some common organic solvents, and transparent films of cellulose esters were obtained by solution casting. In contrast to C-Dp, CA–diphenyl phosphate mixed esters showed clear glass transitions. More interestingly, these cellulose mixed esters exhibited thermoplastic behavior and could be processed by traditional melt processing methods.
Journal Article
Continuous production of cellulose mixed esters via homogeneous reactive twin-screw extrusion catalyzed by ionic liquid
Cellulose mixed esters (CMEs) substituted with two different types of acyl groups are promising polymeric materials with various tunable properties but are arduous to produce. This is because of the insolubility of cellulose in common solvents, and thus, the industrial production of CMEs with desired degrees of substitution (DSs) requires a costly multistep process. To accomplish their facile production, homogeneous reactions have been performed using ionic liquids (ILs) as solvents for cellulose. However, the high viscosity of the cellulose-IL solutions causes insufficient mixing in batch reactors; thereby, favoring low cellulose concentrations with long reaction times (typically hours). Herein, we demonstrate a rapid and scalable production of CMEs by exploiting the excellent shear mixing of a twin-screw extruder as a flow reactor. A co-solvent system comprising an IL, 1-ethyl-3-methylimidazolium acetate, and dimethyl sulfoxide was applied to dissolve cellulose at a high concentration (15 wt.%) via twin-screw extrusion. During continuous extrusion at 80 °C, cellulose reacted with two acyl reagents, isopropenyl acetate (IPAc) and vinyl propionate (VPr) (2.5:0.5, mol/mol), to yield cellulose acetate propionate (CAP) within minutes. The CAP was stably produced during the operation time of 50 min with an average isolated yield of 71%. The DSs of the acetyl and propionyl groups of CAP were 1.77 and 0.50, respectively, corresponding to sufficiently high conversion rates of 70% for IPAc and 100% for VPr.
Journal Article
Material design of retardation films with extraordinary wavelength dispersion of orientation birefringence: A review
Orientation birefringence and its wavelength dispersion for various types of cellulose esters are reviewed. Cellulose esters such as cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB) show positive orientation birefringence with extraordinary wavelength dispersion, which is determined mainly by the ester groups rather than the main chains. The acetyl group provides negative orientation birefringence with strong ordinary wavelength dispersion, whereas the propionyl and butyryl groups give positive orientation birefringence with weak wavelength dispersion. Although all groups show ordinary wavelength dispersion, the summation of their orientation birefringences gives extraordinary dispersion. Moreover, the wavelength dispersion is dependent on the stretching ratio due to the difference in the orientation relaxation of each group. On the contrary, cellulose triacetate (CTA) shows negative birefringence with ordinary wavelength dispersion because it has no positive contribution. However, doping a plasticizer having positive orientation birefringence changes the orientation birefringence of CTA from negative to positive, and the wavelength dispersion from ordinary to extraordinary. This is attributed to the cooperative orientation of plasticizer molecules to the stretching direction with CTA chains, known as nematic interaction upon a hot drawing process.
Journal Article
Controlling Temporally and Spatially Homogeneous Temperature Distribution of Paper Substrates by Biogenic Phase Change Hybrid Material Coatings
Here the performance of phase change material (PCM)‐coated paper made from unbleached kraft pulp is introduced. The applied PCM consists of a mixture of ethylene glycol distearate (EGDS), a well‐known PCM wax material, and a fully substituted cellulose stearoyl ester (CSE). Transfer of the PCM material onto/into paper is achieved by spray as well as blade coating of EGDS + CSE mixture. It is shown that the kind of coating method used does not interfere with observed PCM properties. The significantly higher melt viscosity of the EGDS + CSE blends ensures that the EGDS wax is not bleeding out of the paper, which avoids the use of further encapsulation processes. The PCM behavior, as observed by thermal load measurements, and the thermal buffering of the coated paper is a function of the applied mass of the PCM material applied. The thermal retention exhibited a quasi‐isothermal behavior at ≈65 °C with EGDS + CSE coatings. These effects can offset fluctuations in temperature, and the PCM papers can be employed to achieve a more uniform temperature setting. PCM‐modified papers are therefore interesting candidates for paper‐based packaging or for use in paper‐based sensors, where overheating can strongly affect reliability of results. Phase change materials (PCMs) can absorb energy during their melting process, whereby heat, for example, is attenuated as it passes through. In this study, a mixture of ethylene glycol distearate (EGDS) and cellulose stearoyl ester (CSE) was used as a PCM in paper without the need for encapsulation.
Journal Article