Iranian Polymer Journal
Year:2010 | Volume:19 | Issue:7 (121)|Papers Count:8

Production and consumption of plastic materials have increased in recent decades. The increase in plastic production and consumption has been largely responsible for the increase in plastics waste production. The problem of plastics waste is quite important in terms of environmental sustainability and solid waste management. Plastics recycling require the separation of materials insofar as being almost pure. To achieve this goal in an economical way, technologies developed in mineral processing are of great help. Each method has certain capabilities and limitations. Instance separation of PET and PVC by gravity techniques is practically not applicable, due to slight differences in density. In this research, separation of PET and PVC by selective floatation was studied. The use of floatation for plastic separation is particularly challenging because of inherent hydrophobic nature of plastics surfaces. To separate PET and PVC, from the mixture of the two, by floatation should make one of them hydrophilic and wettable by water. This can be achieved by several methods among which the addition of a wetting agent that interacts with the surface layer is one of many techniques designed. In this study, tannic acid was employed as the depressant of PET. The results showed that, virgin materials can be separated with 99.62% efficiency. In the case of post-consumer PET and PVC, 88.40% separation efficiency was achieved at optimum conditions. Also, in virgin and postconsumer materials, difference in the contact angles of PET and PVC increased as tannic acid dosage increased. Besides, the results indicated that the pH of the conditioning step is vital with respect to separation efficiency. 

Two new polymerizable fluorescent dyes based on naphthalimide derivatives were prepared. For this purpose, acenaphthene as a primary material was brominated and further reacted by various unit processes such as oxidation, imidation and amination in order to obtain polymerizable fluorescent dyes. The UV-vis spectrophotometry of the synthesized dyes in chloroform represents dyes that have wavelength of maximum absorption between 441-443 nm with extinction coefficients from 56.83 to 60.46 l.g-1.cm-1. The synthesized dyes have been characterized using differential scanning calorimetry (DSC), FTIR, 1H NMR, UV-vis spectroscopy and fluorometry. These dyes were copolymerized with methyl methacrylate and two intrinsically coloured copolymers were obtained. It is assumed that 97-99% of the dyes are chemically bonded to polymer chains. The fluorescent characteristics of copolymers in the solid state were determined by fluorometer and it was found that they have relatively high quantum yields (70-89%). Two synthesized copolymers containing propyl and butyl have also stock's shifts (lF -lA) about 75 nm and 61 nm, respectively. Thermal properties of the copolymers were evaluated by dynamic mechanical thermal analysis. The results showed that the glass transition temperatures of the synthesized copolymers containing propyl and butyl groups are similar to each other. It means that the nature of alkyl group (propyl or butyl) does not play significant role in the context of Tg change.

Effects of polyethylene-g-maleic anhydride (PE-g-MA) as a compatibilizer on tensile properties and morphology of low density polyethylene/thermoplastic sago starch (TPSS)-kenaf fibre composites were studied. TPSS was prepared by mixing the starch (65 wt%) and glycerol (35 wt%) and storing it overnight at room temperature. The mixture was then melt-compounded using a heated 2 roll-mills at 150°C for 20 min. LDPE/TPSS blend ratio was fixed at 80 wt% of LDPE and 20 wt% of TPSS. LDPE/TPSS-kenaf fibre composites with different fibre loadings, with and without the addition of PE-g-MA were prepared by using an internal mixer at 150°C. All mixings were carried out for 20 min at a rotor speed of 50 rpm. Tensile test specimens were cut out from the compression moulded sheets. Results indicated that the tensile strength and Young's modulus of LDPE/TPSS-kenaf fibre composites with the addition of PE-g-MA were greater than the composites without the addition of PE-g-MA particularly at higher fibre loading. The interfacial properties between LDPE, TPSS and fibre were improved after the addition of PE-g-MA as it is evident from the tensile surface fracture morphology using a scanning electron microscopy. Equilibrium water uptakes for LDPE/TPSS-kenaf fibre composites were higher than those of LDPE/TPSS-kenaf fibre composites with the addition of PE-g-MA due to lower abundance of hydrogen group.

A method for inclusion of lignosulphonate into superabsorbent hydrogels by graft copolymerization of partially neutralized acrylic acid and acrylamide onto lignosulphonate was developed. The Taguchi method, a robust experimental design, was employed for the optimization of synthetic conditions for the hydrogels based on water absorbency. The Taguchi L16 (45) orthogonal array was selected for experimental design. Concentrations of cross-linker N,N'-methylene-bisacrylamide (CNMBA), initiator potassium persulphate (CKPS) and magnesium lignosulphonate (CMgLS), neutralization degree of acrylic acid (NAA) and molar ratio of acrylamide to acrylic acid (RAM/AA) were chosen as five factors. From the analysis of variance of the test results, the optimal conditions were obtained as follows: CNMBA 7.5×10-4 mol/L, CKPS 4.0×10-3 mol/L, CMgLS 2.5 g/L, NAA 60 and RAM/AA 1:1. The confirmed maximum water absorbency of the optimized final hydrogel is found to be 1156 g/g. The hydrogel also shows high physiological saline absorbency (122 g/g) and high Pb2+ adsorption capacity (332 mg/g). FTIR analysis confirmed the graft copolymerization of lignosulphonate with acrylic acid and acrylamide. SEM Photograph showed a hydrogel of porous sponge structure with increased surface area. The thermogravimetric analysis indicated the hydrogel has good thermal stability with initial decomposition temperature of about 320°C and maximum decomposition temperature of about 360°C.  

Anovel modification method is used for the synthesis of reactive organoclays. A commercial organoclay (Cloisite® 30B) was therefore remodified with two kinds of acid chloride based monomers. Chlorinated diacid monomers of different chemical structures, terephthaloyl chloride (TPC) and adipoyl chloride (APC), were used as remodifying agents. The remodification process was confirmed by Fourier transform infrared (FTIR) spectroscopy. A series of poly(ethylene terephthalate) (PET)-based nanocomposites were formed by compounding the remodified clays and also the commercial organoclay with the polymer using a twin-screw extruder. The morphology of the nanocomposites was examined by transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques and their thermal stability by thermogravimetry analysis (TGA). The XRD and TEM investigations confirmed that the reactive remodified clays were much more efficiently dispersed in PET matrix compared to conventional commercial clay. The PET/virgin commercial clay nanocomposites showed a partially intercalated structure, however the PET/remodified clays showed exfoliated structure. Both remodification processes through aromatic and aliphatic moieties proved to be useful in aiding the exfoliation process, but the nanocomposites made from the remodified clays with APC monomer showed more improvement in thermal stability as compared to the samples made from TPC. This was attributed to the slightly better dispersion of APC-based clays in PET matrix. This study demonstrated the success of the reactive remodification process in more efficient dispersion of the clays in PET matrix changing the morphology from a partially intercalated to a more complete exfoliated structure and leading to an improved thermal stability.

A new kind of drug loaded superabsorbent polymer was prepared and the properties of drug delivery performance are reported in the current study. The superabsorbent polymer was prepared via a process in which polyacrylic acid (PAA) was cross-linked via complex formation with polyaluminium chloride (PAC) through AlCl3 hydrolysis under alkaline conditions followed by freeze drying. The drugs were loaded into the network structure of the superabsorbent during the complex formation of cross-linking process. The new drug loaded superabsorbents were prepared aiming to overcome the drawbacks of those prepared via conventional method. The loading as well as the sustained release of the model drug acetaminophen (AMP) using the prepared superabsorbent has been studied by UV-absorption spectroscopy, and compared with superabsorbent prepared via conventional free radical polymeri-zation method. It was found that the AMP loaded before complex formation of cross-linking process and showed a much better loading performance and drugs sustained release properties compared to the product with which AMP was added during the process of complex formation of cross-linking process. The drug release mechanism has been analyzed for the polymers with different cross-linking densities via numerical simulation based on different kinetic models as well as the Ritger-Peppas equation. At the same time, it is found that the AMP release rate at pH 4 is initially greater than that at pH 10 and release rate increases as temperature is increased.

Polypyrrole (PPy) and polyaniline (PAni) conducting polymers were synthesized chemically on the surface of wood sawdust (SD) to remove Eosin Y (EY), an anionic dye, from aqueous solution. The important parameters such as pH, initial concentration, sorbent dosage and contact time on uptake of EY solution were also investigated. The experiments were carried out using both batch and column systems at room temperature. It was found that both polymers can be used to remove anionic dyes such as EY from aqueous solutions very efficiently. The sorption process of EY dye using both polypyrrole and polyaniline coated onto sawdust (respectively termed as PPy/SD and PAni/SD) was less dependent on the pH of the solutions at least at pH values from 2-10. Considerable decrease in sorption performance occurred only at high pH values (pH ³ 12). According to our "breakthrough analysis", it was found that PAni/SD adsorbent is more efficient for EY removal in flow or column system. Adsorption of EY on the PPy/SD and PAni/SD under different conditions was examined by pseudo-first-order and pseudo-second-order models, and their respective rate constants of first-order adsorption (k1) and second-order adsorption (k2) were estimated. The experimental data fitted very well into pseudo-second-order kinetic model. The experimental data were also analyzed by the Langmuir and Freundlich models of adsorption. Based on the correlation coefficient values obtained (R2), it was found that equilibrium data fitted well with both models. In order to find out the possibility of desorption for frequent use, the chemical regeneration of the employed adsorbents was also investigated. It was found that more than 96% of the EY dye can be recovered from PPy/SD column using a dilute NaOH solution (0.05 M).

Polyvinylidene fluoride (PVDF)/multi-nanoparticles composite hollow fibre ultrafiltration (UF) membranes were prepared with different compositions of SiO2/TiO2/Al2O3 nanoparticles in PVDF/DMAc/NMP solution by wet-spinning method. Behaviour of nanoparticles on membrane dopes were evaluated by the viscosity and surface tension. By adding nanoparticles, obviously the membrane dope viscosity increased; however, the surface tension of each membrane dope changed inconsistently. The hollow fibre membranes were characterized by SEM, mechanical testing, TGA, permeability and rejection test, porosity measurement and pore size distribution. The test results indicate that different nanoparticles and their related compositions induce different characteristics on membrane morphology, mechanical property, thermal stability, permeation property, as well as porosity and pore size distribution, due to the different particle characteristic, the combination effect and the size effect. For membranes with PVDFM2 (18 wt% PVDF, 1 wt% TiO2 (P25), 1 wt% SiO2 and 1 wt% Al2O3) dope and PVDFM5 (18 wt% PVDF, 2 wt% TiO2 (P25) and 1 wt% Al2O3), the pure water permeation flux and bovine serum albumin rejection reach 179 L.m-2.h-1.bar-1 and 98.9%, 352 L.m-2.h-1.bar-1 and 89.1%, respectively; while their mean efficient pore sizes are 10.1 nm and 11.0 nm, and both membranes present narrow pore size distribution and other good performances.