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of polymeric matrices, polyolefins are the most used to realize natural fiber reinforced (NFR) composites. Unless virgin cellulose fibers are mainly used as reinforcement in composites, in the last years recycled cellulose has been also proposed, in
The chromatographic behavior of the dithiocarbamate fungicides mancozeb, NaDDC, propineb, ziram, and zineb has been studied on TLC plates coated with cellulose or with cellulose impregnated with heavy metal salts. The mobile phases used were prepared from distilled water, n -butyl acetate, isopropanol, and sodium lauryl sulfate. High R F values (0.97) were obtained when aqueous mobile phases were used whereas use of organic mobile phases led to low R F values. Important separations achieved included zineb from mancozeb, NaDDC from propineb, ziram from zineb, and ziram from zineb.
The retention behavior of amino acids on cellulose layers has been determined. With organic-aqueous mobile phases, linear second order relationships were established between volume fraction of organic solvent (tetrahydrofuran, acetonitrile, and 2-propanol) in water and retention, R M , for all the solutes investigated. The results obtained experimentally were compared with those calculated by use of polynomial and Soczewinski-Wachtmeister models of retention. Multiple development techniques (UMD and IMD) were also used. Predicted and experimentally obtained results were compared and assessed statistically. Chromatographic systems with the best separation selectivity were used for analysis of amino acids in reference solutions used for testing blood plasma.
Abstract
Thermal decomposition of cellulose has been widely studied for the past several years. It has been reported that the source of cellulose and its composition greatly affect its pyrolysis. One of the most widely used analytical tools for the study of cellulose pyrolysis is thermogravimetric (TG) analysis. Several model-fitting methods have been employed to study cellulose pyrolysis kinetics. An alternative to the model-fitting approach is the so-called model-free method developed by Vyazovkin. This isoconversional technique calculates the activation energy as a function of the degree of the conversion. In this article, the pyrolysis of cellulose in cotton fibers compared to microcrystalline cellulose (Avicel, PH 105) was investigated. TG curves were acquired as a function of the heating rates (4, 5, 8, 10, and 16 °C min−1) and the model-free method was used to analyze the data. Activation energies of cotton fibers and Avicel were obtained, and compared to the data reported in the literature. In addition, models for isothermal decomposition were calculated and compared with experimental data at the same temperature.
Abstract
Cellulose was chemically modified with SOCl2 to obtain chlorodeoxycellulose, followed by a reaction that gave bonded ethylene-1,2-diamine (en), producing 6-(2′-aminoethylamino)-6-deoxycellulose. The reactions were carried out without the presence of solvent, in water or in N,N′-dimethylformamide, in which the highest amount of amino compound was incorporated onto the biopolymer backbone. The X-ray diffraction patterns for the chlorodeoxycellulose indicate new crystallinities that result from hydrogen bonds established through bonded chorine atoms and the remaining hydroxyl groups, while all the aminodeoxycelluloses were amorphous compounds. Thermal stabilities, for all aminated celluloses gave lower final mass losses than for the chlorinated biopolymer, whose value is lower than unmodified cellulose.
Abstract
A cellulose xanthate supported palladium(0) complex was synthesized using a simple method and characterized by XPS, TG/DTA etc. The complex has good thermal stability from room temperature to 250 °C and it was found to be an efficient catalyst for the Heck reaction of acrylic acid or styrene with aryl iodide at low temperature under atmospheric pressure, and the substituted trans-cinnamic acid or 1, 2-stilbene was obtained with high yield at 90 °C. The reaction duration is about 8 h. The cellulose xanthate supported palladium(0) complex could be separated from the reaction mixture easily and reused for several cycles. The yield of the product was up to 55.3% when the catalyst was run for 10 times. The active center in the complex is Pd metal.
The chromatographic behavior of uroporphyrin I, uroporphyrin III, coproporphyrin I, coproporphyrin III, and protoporphyrin IX has been examined using silica gel 60F 254 , polyamide 11F 254 , and cellulose F TLC plates as stationary phases. Homologous series of n -alcohols, acetonitrile, and tetrahydrofuran were used as mobile phases. Chromatographic retention data and a possible retention mechanism are discussed. The electrostatic interactions operating in these chromatographic systems were analyzed by studying relationship between log (1/ R F ) values and the molecular polarizabilities of the solvents.
Introduction Cellulose is one of the most abundant organic substances on the planet, being the main constituent of vegetable fiber. Cellulose is a linear hydrophilic homopolysaccharide and this structure consists of units of β
fermentation. Bio-based reinforcers in composites range from wood pellets and wood fiber, to micro and nano cellulose fibers [ 4 ]. Owing to its abundance and remarkable reinforcing capacity, cellulose has been widely accepted as a reinforcer for polymer
Introduction Why cellulose? Early research for thermoplastic nanocomposites focused on inorganic nano-scale fillers such as nanoclay, montmorillonite, silica and mica, but interest in cellulose nanofibril
