Adsorption of dyestuffs onto chitin. External mass transfer processes

The effect of several variables on the adsorption rate of four dyestuffs onto chitin was studied. A model is proposed enabling the film mass transfer coefficients to be determined. The coefficients were independent of initial dye concentration, chitin mass, chitin particle size, and temperature; a slight dependence with agitation was obtained. The film mass transfer coefficients at 400 rpm were 2.8×10^?3, 2.9×10^?3, 3.9×10^?3, and 0.9×10^?3 cm/s for Acid Blue 25, Acid Blue 158, Mordant Yellow 5, and Direct Red 85, respectively.     

Copolymerization of methyl methacrylate with N-(methoxyphenyl) itaconimides

This article describes the synthesis and characterization of N-(3-methoxyphenyl) itaconimide (MAI) and N-(4-methoxyphenyl) itaconimide (PAI) obtained by the reaction of itaconic anhydride with m-anisidine and p-anisidine, respectively. Structural and thermal characterization of MAI and PAI monomers was performed with Fourier transform infrared (FTIR), ¹H-NMR, differential scanning calorimetry (DSC), and thermogravimetric analysis. Copolymerization of methyl methacrylate (MMA) with various amounts of MAI or PAI ranging from 0.1 to 0.5 was performed in solution with azobisisobutyronitrile as an initiator. Structural and molecular characterization of copolymers was performed with FTIR, ¹H-NMR, elemental analysis, and gel permeation chromatography. The nitrogen percentage was used to calculate the copolymer composition. The monomer reactivity ratios for MMA–MAI copolymers were found to be 1.00 ± 0.01 for MMA and 0.99 ± 0.07 for MAI; those for MMA–PAI copolymers were 0.93 ± 0.02 for MMA and 1.11 ± 0.10 for PAI. The molecular weights of the copolymers were in the range of 0.94–9.7 × 10³ (number-average molecular weight) and 3.3–101.8 × 10³ (weight-average molecular weight), with polydispersity indices in the range of 1.5–4.1. The molecular weight decreased with the increasing molar fraction of imide in the polymer backbone. The glass-transition temperature, as determined from DSC scans, increased with increasing amounts of itaconimides in the copolymers. A significant improvement in the char yield, as determined by thermogravimetry, was observed upon copolymerization. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Sweet potato amylose and amylopectin with narrower distribution of molar mass and chain length obtained by a repeated retrogradation–hydrolysis procedure

The wide molar mass distribution of native starch creates obstacles in investigating the physicochemical characteristics of starch, such as retrogradation, because samples thought to be the same are actually compounds containing many chains with different molar masses. In this paper, the sweet potato amylose and amylopectin isolated from retrograded starch were treated with the retrogradation–hydrolysis method three times, and their physicochemical changes in this process were determined by absorbance of the starch–iodine complex, light microscopy, and molar mass and chain length distributions. The results showed that repeated retrogradation and hydrolysis caused the molar mass distribution of sweet potato amylose and amylopectin to reduce from 4.2 × 10⁷–205 and 7971–223 to 6.0 × 10⁴–730 and 4533–211 g mol⁻¹, respectively. This retrogradation–hydrolysis cut the chain length distribution of sweet potato amylose from DP 9–35 to DP 3–13, but that of amylopectin remained unchanged. The double helix in sweet potato amylopectin will not form if the percentage of chain length with DP ≥ 4 is less than 25%. Repeated retrogradation and hydrolysis was an appropriate method to obtain amylose or amylopectin with a narrower molar mass distribution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43849.     

Optimum parameters for production of chitin and chitosan from squilla (S. empusa)

Chitin and chitosan of high quality were produced from squilla, a by‐catch of Indian Ocean fisheries, by demineralization, deproteination, and deacetylation. Optimum conditions for the production of chitin and chitosan were determined. The quality of chitin was assessed from its ash and protein content. Ash content was below 1% after treatment with 4% HCl for 12 h at 50°C. A protein content of less than 1% could be achieved by treatment with 4% NaOH in 12 h but only at a temperature of 70°C or higher. Production of chitin was also tested by a three‐stage treatment with altering sequence of sodium hydroxide and hydrochloric acid (HCl–NaOH–HCl or NaOH–HCl–NaOH). This three‐step treatment appeared to be successful to achieve a mineral content and protein content below 1% within 30 h and at a temperature not exceeding 50°C. The chitin obtained under optimum conditions was tested for deacetylation using NaOH concentrations of 40 and 50% for 12–44 h at 30, 50 and 70°C. The chitosan obtained had a degree of deacetylation of 77–86%, a viscosity of 8.2–16.2 × 10² cps, solubility of 98%, and molecular weight of ? 1 × 10⁶ dalton. The data show that processing of squilla waste can lead to a high quality chitosan, useful for a broad range of applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3694–3700, 2007     

Acetylation reaction of polytetramethylene glycol with acetic anhydride in pyridine

The acetylation reaction of polytetramethylene glycol (PTMG) with acetic anhydride in pyridine was studied. The extent of acetylation was measured by ¹H‐NMR, and the acetylation product was characterized with FTIR, ¹H‐NMR, and ¹³C‐NMR. The effects of the experimental conditions, i.e., reaction time and temperature, acetylation reagent concentration (anhydride and hydroxyl molar ratio), were investigated. The increase in reaction temperature and reaction time favored the acetylation yields. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1138–1142, 2007     

Influence of molar mass on the thermal properties,conductivity and intermolecular interaction of poly(ethylene oxide) solid polymer electrolytes

The sample preparation pathway of solid polymer electrolytes (SPEs ) influences their thermal properties, which in turn governs the ionic conductivity of the materials especially for systems consisting of a crystallizable constituent. Majority of poly(ethylene oxide) (PEO)‐based SPEs with molar masses of PEO well above 10⁴ g mol^?1 (where PEO is crystallizable and should reach an asymptote in thermal behaviour) display molar mass dependence of the thermal properties and ionic conductivities in non‐equilibrium conditions, as reported in the literature. In this study, PEO of different viscosity‐molar masses (M _η = 3 × 10⁵, 6 × 10⁵, 1 × 10⁶, 4 × 10⁶ g mol^?1) and LiClO₄ salt (0 to 16.7 wt%) were used. The SPEs were thermally treated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization for sufficient experimental time to develop morphology close to equilibrium conditions. The thermal properties (e.g. glass transition temperature, melting temperature, crystallinity) according to differential scanning calorimetry and the ionic conductivity obtained from impedance spectroscopy at room temperature (σ _DC ～ 10^?6 S cm^?1) demonstrate insignificant variation with respect to the molar mass of PEO at constant salt concentration. These findings are in agreement with the PEO crystalline structures using X‐ray diffraction and ion ? dipole interaction by Fourier transform infrared results. © 2017 Society of Chemical Industry     

Two-resistance mass transfer model for the adsorption of various dyestuffs onto chitin

The kinetics of the adsorption of various dyestuffs onto chitin have been studied. The dyestuffs used are Neoland Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL and a number of process variables were considered, such as adsorbent mass and dye concentration. The mass transfer model is based on the assumption of a pseudoirreversible isotherm and two resistances to mass transfer. These are external mass transfer and internal pore diffusion mass transfer. The rate of adsorption of dyestuffs onto chitin can thus be described by an external mass transfer coefficient and a pore diffusion coefficient. The external mass transfer coefficients are 5.0 × 10^?5, 5.0 × 10^?5, and 1.0 × 10^?5 m·s^?1 and the pore diffusivities are 3.0 × 10^?10 and 4.0 × 10^?11 m²·s^?1 for Neolan Blue 2G, Eriochrome Flavine A, and Solophenyl Brown 3RL, respectively.     

The kinetics of poly(butylene succinate) synthesis and the influence of molar mass on its thermal properties

The synthesis of poly(butylene succinate) (PBS) of M_w ranging from 4000 to 180,000 g mol^?1 is realized with molar ratios [COOH]₀/[OH]₀ of 1 and 0.98, and varying amounts of titanium (IV) tetrabutoxide (TBT) catalyst. Polycondensation kinetics are followed by chemical titration of carboxylic groups, and the kinetic rate constants of self‐catalyzed and external‐catalyzed reactions are calculated. The synthesis of PBS with high molar mass follows the classical Flory theory. The effect of molar mass on PBS thermal properties is also studied. A faster crystallization rate and a higher temperature of crystallization are observed, for very high molar masses. This behavior could be due to a memory effect of the polymer. Complex melting behavior of PBS is induced by a continuous reorganization of the crystalline phase, as observed by MTDSC. DSC measurements also reveal that the crystallinity—and so the amorphous phase—is limited to about 35% when the molar mass M_n is higher than 40,000 g mol^?1. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40639.     

Two-Stage Hot-Water Extraction of Galactoglucomannans from Spruce Wood

In order to preserve the polymeric structure and the acetylation degree of extracted galactoglucomannans and, at the same time, achieve high yield, ground spruce wood was subjected to a series of sequential two-stage extractions with an Accelerated Solvent Extraction (ASE) apparatus using plain water at 170°C. The total combined extraction time was one hour in all the extractions. The total yield of the dissolved material after 1 h extraction was almost the same, about 25% of the wood, irrespective of the time ratios between the first and the second extractions. The yield of hemicellulose high polymers with the weight average molar mass of 8–10 kDa during the first extraction had a maximum at 20 min extraction time, amounting to about 7% on dry wood basis, and comprising about half of the total extract. Along with the progress of the extraction, the molar mass of the hemicelluloses decreased and hemicellulose-derived low polymers with the weight average molar mass of 6–2 kDa became dominating. The extracted substances were fractionated, mainly according to their molar mass, by sequential precipitation with ethanol, acetone, and methyl tert-butyl ether (MTBE). The hemicelluloses with some amount of pectins comprised 83–90% of the precipitated polymeric material and the content of galactoglucomannans was about 80%.     

Effect of deacetylation on sorption of dyes and chromium on chitin

Deacetylated chitins (10.7–67.2%) were prepared by alkaline hydrolysis to determine an optimal degree of deacetylation (DD) which can effectively remove four dyes and chromium ions from textile effluent. Sorption isotherms were carried by varying the treatment time, pH, and initial concentration of dyes or chromium ions. Experimental results were analyzed in three ways: (1) equilibrium sorption capacity and sorption rate constant, (2) Langmuir isotherms, and (3) separation factor. Results indicated that except for the chitin with a 67.2% DD, rate and capacity of the dye sorption on the chitin increased with the increase of the DD in chitin for each pH but decreased with the increase of pH for each deacetylated chitin. This was mainly due to the increase of—NH⁺₃ groups in chitin with a high DD and the low pH of the system. On the contrary, dye desorption from the deacetylated chitin was highly effective at 80° and pH ≥ 10, which could facilitate the reduction of—NH⁺₃ ions and the increase of electrostatic repulsion. The number of chromium ions sorbed on the chitin also increased with the increase of the DD at a specific time. Therefore, by controlling the DD of the deacetylated chitin maximum efficiency can be achieved in the removal of dyes and metal ions from textile effluent.     

Surface‐pegylated chitin whiskers as an effective additive to enhance the mechanical properties of recycled ABS

The recyclability of materials is a key issue related to the use of polymers in the automotive and electronic industries, among others. The multiple thermal and mechanical operations used in recycling can cause severe damage to the molecular architecture and microstructure of polymers that frequently leads to a reduction in their mechanical properties, which restricts their recyclability. In this work, nanocomponents (whiskers) derived from chitin were surface‐modified by grafting different molar masses of methoxylated poly(ethylene glycol) (mPEG). The modified chitin whiskers were then incorporated into reprocessed ABS (acrylonitrile–butadiene–styrene) to yield nanocomposites with 0.5% (mass/mass) whiskers. The obtained whiskers and nanocomposites were investigated using techniques such as transmission electron microscopy, atomic force microscopy, scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. The properties of the nanocomposites were also investigated using tensile tests and dynamic mechanical tests. The results show that the surface‐modified chitin whiskers with high molar mass mPEG grafts increased the strength, elongation at break, and stiffness of the reprocessed ABS over virgin and reprocessed ABS and reprocessed ABS nanocomposites with unmodified whiskers. This indicates that the use of surface‐modified chitin whiskers can be valuable in improving the mechanical properties of recycled polymers and, consequently, enhancing their recyclability. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42463.     

Characterization of Anadenanthera macrocarpa exudate polysaccharide

Exudate gum from Anadenanthera macrocarpa Benth. trees was purified and fractionated using 0·1M aq. NaCl/ethanol as a solvent/non-solvent system. The composition of the polysaccharide was determined as 67% arabinose, 24% galactose, 2% rhamnose and 7% glucuronic acid, by a combination of high performance liquid chromatography of fully hydrolysed gum and colorimetric analysis of uronic acid. Molecular characteristics of the polysaccharide and its fractions were investigated by light scattering intensity, dilute solution visco-metry and gel permeation chromatography (GPC). The whole gum was shown to possess a broad molar mass distribution with Mw = 3·7×10⁶ g mol^-1 and [η] = 11cm³ g^-1. Hydrodynamic properties indicated a highly branched structure. Fractions were obtained covering a range of molar masses. The intrinsic viscosity in 1·0 M aq. NaCl at 25°C was found to depend on molar mass according to: [η]/cm³ g^-1 =0 ·0145 M^0·44. The hydrodynamic volume parameter [η]M gave a common GPC calibration for branched polysaccharide fractions and linear poly(oxyethylene) standards. ©1997 SCI     

Comparison of chitins produced by chemical and bioprocessing methods

Lactic acid fermentation was used to extract chitin from prawn shell (Nephrops norvegicus) at two different scales of operation. The fermentation products were characterized and compared with chitin extracted from the same source by a chemical method. Chitosans produced from the obtained chitins were evaluated in terms of their intrinsic viscosity, molecular weight and degree of acetylation (DA). The fermentation removed 690 g kg^?1 and 770 g kg^?1 of inorganic matter, 490 and 440 g kg^?1 of protein and 540 and 770 g kg^?1 of lipids from the shells at laboratory and pilot plant scales, respectively. However, the functional properties such as the DA of the chitin, the molecular weight and the DA of the chitosans were similar to those obtained for the chemically‐obtained chitin and its chitosan. Despite the incomplete extraction of chitin this biological process could be useful to produce chitin and chitosan in a more environment‐friendly approach. Copyright © 2004 Society of Chemical Industry     

Optical and conductivity studies of Pseudo‐doped chitin‐polyaniline blend

In this article, we report the preparation and characterization of self‐doped conducting chitin, polyaniline blends by solution blending method. The characterization of the blends was done by UV–vis absorption spectrum, FTIR, and conductivity studies. Conductivity of the self doped blends increases from less than ～10^?7 S/cm to 2.15 × 10^?5 S/cm, depending on the percentage of polyaniline in the blend. Spectroscopic analysis shows interaction between chitin and polyaniline and the electronic states are similar to those of the emeraldine and protonically doped forms of polyaniline. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Polymerization of t-butylacetylene initiated by tungsten carbene complex

Polymerization of t-butylacetylene initiated by a tungsten carbene complex (I) was investigated under various conditions. t-Butylacetylene was polymerized in high yield in chlorinated hydrocarbons such as CHCI₃ and CCI₄ and in the presence of AICI₃. The molar mass of the polymers formed was as high as 8.2 ×10⁴ ～ 3.2 × 10⁵. Moreover, when the solution of tungsten carbene complex in CCI₄ was irradiated with UV light, the molar mass was remarkably enhanced. This phenomenon may occur because tungsten dichlorocarbene immediately forms. Apparent rate constants were determined by gas chromatography. NMR spectra show a predominant characteristic of high cis content in the structure of poly(t-butylacetylene) in contrast to poly(phenylacetylene). The cis content increased ca. 11% when poly(t-butylacetylene) was heated in decalin at 110°C. X-Ray diffraction diagrams show that poly(t-butylacetylene) has an amorphous structure.     

Effect of surface acetylated‐chitin nanocrystals on structure and mechanical properties of poly(lactic acid)

In this work, the miscibility between chitin nanocrystals (ChNs) and poly(lactic acid) (PLA) was expected to be improved by surface acetylation of ChN. The reaction of acetic anhydride onto the ChN surface was confirmed by FTIR and ¹³C NMR, while XRD and TEM proved the crystalline structure and rod‐like morphology were maintained. The acetylated ChN (AChN) was incorporated into a PLA matrix by solution blending, and resulted in an increase of tensile strength and Young's modulus and they reached to the maximum value as 45 and 37% higher than neat PLA film, respectively, with the loading level of AChN reaching to 4 wt %. The enhancement could be attributed to that acetylation improved dispersion of AChN in the PLA matrix and interfacial adhesion between AChN and PLA. The performances of the nanocomposites based on PLA and chitin nanocrystals derived from renewable resources have good potential for industrial applications. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39809.     

In vivo aging of gutta‐percha dental cone

Gutta‐percha cone is the most widely used material for root canal filling. The in vivo aging of this cone focus on the degradation of its main organic component, trans‐1,4‐polyisoprene, was studied. Aged cones (25 samples) from 2 to 30 years of root canal filling were extracted from different patients in the occasion of retreatment by mechanical way. The information about the aging time was given by the patients. Gel‐permeation chromatography (GPC) and infrared spectroscopy (FTIR) were the analytical techniques used. Polyisoprene degrades with time of aging, but in a slow process. Decrease in polymer molar mass from 5.7 × 10⁵ to 1.7 × 10⁵ g/mol was observed in polyisoprene from cone after 30 years of root canal filling and inside a noninfected tooth. In tooth with caries and periodontal infection, the decrease in molar mass is higher (4.6 × 10⁴ g/mol in cone with 10 years of aging). The production of carbonyl and hydroxyl groups in the aged material indicates that the process is oxidative, even in closed teeth. In these cases, the oxygen could be provided from tissue fluid. The degradation mechanism is complex and depends on many factors, besides time of root canal filling. The dental problem caused by the aging could be the production and migration of cytotoxic substances to periodontal ligament and the reduction on the canal sealing property due to the polymer weight loss. Both of them could contribute to the root canal treatment failure. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100:4082–4088, 2006     

The role of poly (ethylene oxide)-water solution phase behaviour in the retention of fibre fines and clay

The retention of fibre fines and clay particles in chemi-thermo-mechanical pulp (CTMP) suspensions with poly (ethylene oxide) as a retention aid was investigated. The experiments were conducted at 303 and 343 K. These two temperatures correspond to points below and above the Lower Critical Solution Temperature (LCST) of a 0.005 mass% Poly (ethylene oxide) solution in the presence of 2 mol/L KCl. The KCl was added to lower the LCST to a temperature near papermaking conditions. Poly (ethylene oxide) with molar masses of 1 × 10⁶ and 5 × 10⁶ Da was used. All the LCST measurements of the poly (ethylene oxide)-KCl system agree with those in the literature. The retention study revealed that considerably more fibre fines as well as clay are retained at temperatures above the LCST. In particular, the average fibre fines retention was 5.9 percent at 303 K and 22.1 percent at 343 K when the poly (ethylene oxide) with the molar mass of 1 × 10⁶ Da was used. Clay retention was also measured and found to be 5.0 and 15.9% at 303 and 343 K, respectively. Higher retention values were obtained when the polymer with a molar mass of 5 × 10⁶ Da was used. At 303 K the fibre fines retention was 55.0%, whereas at 343 K it was 82.2%. The corresponding clay retentions were 31.7 and 71.9%.     

Synthesis of Ultra-high Weight Average Molecular Mass of Poly-L-lactide

High purity in high yield L-lactide was prepared using a new purification method, and poly-L-lactide (PLLA) with ultra-high weight average molecular mass and narrow polydispersity index was synthesized by ring-opening polymerization. The effects of the purification method on the purity and yield of L-lactide were investigated, and the influences of initiator concentration, polymerization temperature and polymerization time on the weight average molecular mass of PLLA were also studied. A synthetic purification method involving a water bath and two times recrystallization could improve the purity of L-lactide to 100%. The yield of L-lactide reached 40.6% and increased 12.1% compared with the recrystallization method. Poly-L-lactide with a weight average molecular mass of about 102.4 × 10⁴ and a polydispersity index of 1.16 was obtained when polymerization was conducted with molar ratio of monomer to initiator ([M]/[I]) of 12000 for 24 h at 140°C.     

Flockung und Entwässerung von Klärschlamm mit Hilfe von Polyelektrolyten

An investigation was performed with the aim of ascertaining how a digested sewage sludge could be converted into mechanically stable flocs through the addition of a flocculating agent, while achieving the best possible dewatering efficiency with the lowest possible dosage of flocculation agent. In order to obtain conclusive results which can be transferred to large-scale plants, the effectiveness of the flocculating agents and the various flocculation procedures were tested in a patented, mobile, computer-assisted flocculation and dewatering apparatus. The sewage sludge was conditioned with flocculating agents which had previously been thoroughly characterized in terms of their chemical structure, charge density and molar mass. The cationic flocculating agents had charge densities ranging from 25–55 mol-% and molar masses from 1.5 · 10⁶–12.9 · 10⁶ g mol^?, whereas the anionic flocculating agent had a charge density of 36 mol-% and a molar mass of 7.6 · lo6 g mol^?. In contrast to other suspensions already investigated, for sewage sludge it was found that no improvement can be achieved in the already very high dewatering level when cationic monoflocculation is used (laboratory trial: 95% filtrate yield by mass after 4 s). Nor was it possible to reduce the optimum dosage by using the dual procedure. In addition, it was possible to show that the chemical structure, i.e. the nature of the polyelectrolyte, and the molar mass of the cationic polyelectrolytes investigated exert a by far larger influence on the dewatering efficiency than the charge density in a range between 25 and 55 mol-%. Furthermore, it has also been observed that the conditioning efficiency of the polyelectrolytes increases as the molar mass rises and the chemical structure influences the dewatering result primarily through the position of the charge-bearing group.