Sava J. Velickovic

Characterization of chitosan/montmorillonite membranes as adsorbents for Bezactiv Orange V-3R dye

The synthesis, characterization and environmental application of chitosan/montmorillonite membrane for adsorption Bezactiv Orange V-3R were investigated. Chitosan/montmorillonite membranes were synthesized in different ratios, containing 10-50% of montmorillonite (MMT) in membrane. These membranes were characterized by using Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and scanning electron microscopy (SEM). The adsorption kinetics were investigated using three different concentrations of Bezactiv Orange dye (30, 50 and 80 mg/L). The adsorption capacity increases with increasing amount of MMT in membranes. These membranes show the highest adsorption capacity when the initial dye concentration was 80 mg/L. The results show that the optimum condition for adsorption of Bezactiv Orange is pH 6. A comparison of kinetic models was evaluated for the pseudo-first and pseudo-second order and intra-particle diffusion. The experimental data were fitted to the pseudo-second order kinetic model, and also followed by intra-particle diffusion. Intra-particle diffusion is not the only rate-controlling step. The Langmuir and Freundlich adsorption isotherms were applied to experimental equilibrium data at different concentration of dye solution. The results indicated the competency of chitosan/MMT membranes adsorbent for Bezactiv Orange adsorption.

The thermal degradation of some alkali metal salts of poly(itaconic acid)

The Li-, Na- and K salts of poly(itaconic acid) (PIA) were prepared by treating the polyacid with the corresponding aqueous hydroxide.The resulting polysalts were analyzed by elemental analysis, FTIR spectroscopy and thermogravimetry. The results indicate that the polysalts are thermally more stable than the parent PIA, they all degrade in a similar manner and somewhat more complexly than the poly(methacrylic acid) salts.

Novel composite films based on amidated pectin for cationic dye adsorption.

Pectin, with its tendency to gel in the presence of metal ions has become a widely used material for capturing the metal ions from wastewaters. Its dye-capturing properties have been much less investigated, and this paper is the first to show how films based on amidated pectin can be used for cationic dye adsorption. In the present study amidated pectin/montmorillonite composite films were synthesized by membrane casting, and they are stable in aqueous solution both below and above pectin pKa. FTIR, thermogravimetry and SEM-EDAX have confirmed the presence of montmorillonite in the cast films and the interactions between the two constituents. In order to evaluate the cationic dye adsorption of these films Basic Yellow 28 was used, showing that the films have higher adsorption capacity compared to the others reported in the literature. The results were fitted into Langmuir, Freundlich and Temkin isotherms indicating an exothermic process and setting the optimum amount of montmorillonite in the films to 30% of pectin mass. According to the Langmuir isotherm the maximum adsorption capacity is 571.4 mg/g.

Cross-linking of highly methoxylated pectin with copper: the specific anion influence

The aim of this work was to investigate the influence of specific anions on the cross-linking process of highly methoxylated pectin using the following copper salts CuSO4; Cu(C2H3O2)2; CuCl2; and Cu(NO3)2 wherein the initial salt concentrations were varied from 0.5 up to 10 g l−1. It was found that the anions affected the sorption capacity wherein the Cu2+ sorption capacity from the sulphate solution was the highest, while it decreased in the presence of CH3COO−, Cl− and NO3− ions, respectively. This difference was mostly pronounced at the higher initial salt concentrations (c0(Cu2+) > 2 g l−1). The obtained beads were characterized by FTIR, AAS, SEM/EDS microanalysis and mechanical compression tests up to 80% of deformation. The sorption data were applied to the Langmuir and Freundlich isotherm models and various calculated parameters confirmed the sulphate anion supportive nature in metal ion binding. The value of the Kf parameter for the cross-linking process of pectin in the presence of acetate, chloride and nitrate was approximately the same (Kf ≈ 0.027 g g−1), while it was higher in the presence of sulphate anions by more than 20% (Kf = 0.0352 g g−1). The predicted 1/n values (1/n 1, 1/n = 1 for the sulphate, nitrate and acetate, and chloride anions, respectively) were the quantitative confirmation of the specific interactions involved in the cross-linking mechanism caused by different anions. The established anion influence was in accordance with the typical ion-specific influence on macromolecules in aqueous systems proposed by Hofmeister.

Complexation of amidated pectin with poly(itaconic acid) as a polycarboxylic polymer model compound

Complexes based on amidated pectin (AP) and poly(itaconic acid) (PIA) were prepared by casting films from solutions of AP and PIA in different ratios with the pectin amount ranging from 10% to 90% by mass. The complexes were investigated by elemental analysis, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetry (TG). In all investigated ratios of AP/PIA glassy transparent films with a uniform structure were obtained. The results of elemental analysis confirmed the composition of the complexes, and FTIR spectroscopy has shown carboxylic and amide peak shifting, indicating complex formation between AP and PIA. Comparison of thermograms of AP/PIA films with different ratios of AP indicated that the increase of the amount of AP increases the thermal stability of the films by retarding the onset of the main degradation processes.

The Mechanical Properties of a Poly(methyl methacrylate) Denture Base Material Modified with Dimethyl Itaconate and Di-n-butyl Itaconate

This study investigates a wide range of clinically relevant mechanical properties of poly(methyl methacrylate) (PMMA) denture base materials modified with di-methyl itaconate (DMI) and di-n-butyl itaconate (DBI) in order to compare them to a commercial PMMA denture base material. The commercial denture base formulation was modified with DMI and DBI by replacing up to 10 wt% of methyl methacrylate (MMA) monomer. The specimens were prepared by standard bath curing process. The influence of the itaconate content on hardness, impact strength, tensile, and thermal and dynamic mechanical properties was investigated. It is found that the addition of di-n-alkyl itaconates gives homogenous blends that show decreased glass transition temperature, as well as decrease in storage modulus, ultimate tensile strength, and impact fracture resistance with increase in the itaconate content. The mean values of surface hardness show no significant change with the addition of itaconates. The magnitude of the measured values indicates that the poly(methyl methacrylate) (PMMA) denture base material modified with itaconates could be developed into a less toxic, more environmentally and patient friendly product than commercial pure PMMA denture base material.

Poly(methyl methacrylate) denture base materials modified with ditetrahydrofurfuryl itaconate: Significant applicative properties

The aim of this work was to examine the possibility of modification of commercial denture base materials with itaconic acid esters, in order to obtain materials with lower toxicity and higher biocompatibility. Despite their relatively higher price compared to methacrylates, itaconic acid and itaconates are materials of choice for environmentally friendly applications, because they are not produced from petrochemical sources, but from plant products. A commercial system based on poly(methyl methacrylate) was modified using ditetrahydrofurfuryl itaconate (DTHFI), whereby the ratio of DTHFI was varied from 2.5 to 10 % by weight. Copolymerization was confirmed using FTIR spectroscopy, while SEM analysis showed the absence of micro defects and pores in the structure. The effects of the itaconate content on the absorption of fluids, the residual monomer content, thermal, dynamic-mechanical and mechanical properties (hardness, toughness, stress and elongation at break) were investigated. It was found that the addition of DTHFI significantly reduced the amount of residual methyl methacrylate, which made these materials less toxic. It was shown that increasing the DTHFI content resulted in materials with decreased glass transition temperatures, as well as with decreased storage mod ulus, ultimate tensile strength and impact fracture resistance; however the mech anical properties were in the rang prescribed by ADA standards, and the materials could be used in practice. The deterioration in mechanical properties was therefore worthwhile in order to gain lower toxicity of the leached monomer.

The effect of the accelerated aging on the mechanical properties of the PMMA denture base materials modified with itaconates

This study evaluated the effect of accelerated ageing on the tensile strength, elongation at break, hardness and Charpy impact strength in commercial PMMA denture base material modified with di-methyl itaconate (DMI) and di-n-butyl itaconate (DBI). The samples were prepared by modifying commercial formulation by addition of itaconates in the amounts of 2.5, 5, 7.5 and 10% by weight. After polymerization samples were characterized by FT-IR and DSC analysis while residual monomer content was determined by HPLC-UV. Accelerated ageing was performed at 70°C in water for periods of 7, 15 and 30 days. Tensile measurements were performed using Instron testing machine while the hardness of the polymerized samples was measured by Shore D method. The addition of itaconate significantly reduces the residual MMA. Even at the small amounts of added itaconates (2.5%) the residual MMA content was reduced by 50%. The increase of itaconate content in the system leads to the decrease of residual MMA. It has been found that the addition of di-n-alkyl itaconates decreases the tensile strength, hardness and Charpy impact strength and increases elongation at break. Samples modified with DMI had higher values of tensile strength, hardness and Charpy impact strength compared to the ones modified with DBI. This is explained by the fact that DBI has longer side chain compared to DMI. After accelerated ageing during a 30 days period the tensile strength decreased for all the investigated samples. The addition of DMI had no effect on the material ageing and the values for the tensile strength of all of the investigated samples decreased around 20%, while for the samples modified with DBI, the increase of the amount of DBI in the polymerized material leads to the higher decrease of the tensile strength after the complete accelerated ageing period od 30 days, aulthough after the first seven days of the accelerated ageing the values of hardness have increased for all of the investigated samples. Such behavior is explained as the result of the polymer chain relaxation. The values of Charpy impact strength decreased after accelerated ageing. The amount of added DMI have no affect on the decrease of Charpy impact strength after accelerated ageing, the decrease was similar as for pure PMMA. The decrease of Charpy impact strength increased as the amount of added DBI increases.

The thermal degradation of poly(ditetrahydrofurfuryl itaconate)

Abstract The goal of this investigation was to study the thermal degradation of poly(ditetrahydrofurfuryl itaconate) (PDTHFI) by thermogravimetry (TG). The monomer was polymerized in bulk at 40°C using AIBN as initiator. Non-oxidative degradation was studied under nitrogen, while oxidative degradation was studied under air, applying four heating rates (2.5, 10, 20 and 40 K/min), up to 600°C. The apparent activation energy of thermal degradation, Ea, was calculated using the Flynn–Wall method. The obtained non-oxidative TG curves of PDTHFI are parallel and no heating rate effect was observed. A carbonaceous residue remained at 600°C, regardless of the heating rate applied. The Ea of PDTHFI is constant in the whole mass loss range and its mean value is 124 kJ/mol. The non-oxidative differential TG (DTG) curves of PDTHFI consist of two peaks, the second being dominant. If it is assumed that depolymerization is the main degradation mechanism, analogous to other polyitaconates, these two peaks could be ascribed to two depolymerization initiation modes: end-chain β-scission and random main chain scission. The oxidative TG curves are more complex than the non-oxidative ones and show a heating rate effect. The Ea steadily increases in the mass loss range of 5–50% from 120 to 200 kJ/mol. The oxidative DTG curves consist of a major peak with two shoulders and a second minor peak.

The thermal degradation of some isomers of poly(di-butyl itaconates)

Abstract The non-oxidative and oxidative thermal degradation of poly(di-iso-butyl itaconate) (PDiBI), poly(di- n -butyl itaconate) (PDnBI), and poly(di-sec-butyl itaconate) (PDsBI) were studied by following changes in the polymer residue such as mass loss, limiting viscosity number (LVN) and the formation of carboxylic groups. Depolymerization is the dominant degradation mechanism of PDiBI, while PDnBI and PDsBI predominantly degrade by deesterification. The thermolysis mechanism is determined by the number of β-hydrogen atoms in the ester substituent: five in PDsBI, two in PDnBI and one in PDiBi.