Iranian polymer journal
Volume:19 Issue: 7, 2010

Production and consumption of plastic materials have increased in recentdecades. The increase in plastic production and consumption has been largelyresponsible for the increase in plastics waste production. The problem ofplastics waste is quite important in terms of environmental sustainability and solidwaste management. Plastics recycling requires the separation of materials insofar asbeing almost pure. To achieve this goal in an economical way, technologies developedin mineral processing are of great help. Each method has certain capabilities andlimitations. Instance separation of PET and PVC by gravity techniques is practically notapplicable, due to slight differences in density. In this research, separation of PET andPVC by selective floatation was studied. The use of floatation for plastic separation isparticularly challenging because of inherent hydrophobic nature of plastics surfaces. Toseparate PET and PVC, from the mixture of the two, by floatation should make one ofthem hydrophilic and wettable by water. This can be achieved by several methodsamong which the addition of a wetting agent that interacts with the surface layer is oneof many techniques designed. In this study, tannic acid was employed as thedepressant of PET. The results showed that, virgin materials can be separated with99.62% efficiency. In the case of post-consumer PET and PVC, 88.40% separationefficiency was achieved at optimum conditions. Also, in virgin and postconsumermaterials, difference in the contact angles of PET and PVC increased as tannic aciddosage increased. Besides, the results indicated that the pH of the conditioning step isvital 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 pectrophotometry 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 (λF -λA) about 75 nm and 61 nm, respectively.Thermal properties of the copolymers were evaluated by dynamic mechanicalthermal analysis. The results showed that the glass transition temperatures of thesynthesized copolymers containing propyl and butyl groups are similar to each other. Itmeans that the nature of alkyl group (propyl or butyl) does not play significant role inthe 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.

Amethod for inclusion of lignosulphonate into superabsorbent hydrogels by graftcopolymerization of partially neutralized acrylic acid and acrylamide ontolignosulphonate was developed. The Taguchi method, a robust experimentaldesign, was employed for the optimization of synthetic conditions for the hydrogelsbased on water absorbency. The Taguchi L16 (45) orthogonal array was selected forexperimental 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 toacrylic acid (RAM/AA) were chosen as five factors. From the analysis of variance of thetest 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 maximumwater absorbency of the optimized final hydrogel is found to be 1156 g/g. The hydrogelalso shows high physiological saline absorbency (122 g/g) and high Pb2+ adsorptioncapacity (332 mg/g). FTIR analysis confirmed the graft copolymerization oflignosulphonate with acrylic acid and acrylamide. SEM Photograph showed a hydrogelof porous sponge structure with increased surface area. The thermogravimetricanalysis indicated the hydrogel has good thermal stability with initial decompositiontemperature 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 improvedthermal stability.

Polypyrrole (PPy) and polyaniline (PAni) conducting polymers were synthesizedchemically on the surface of wood sawdust (SD) to remove Eosin Y (EY), ananionic dye, from aqueous solution. The important parameters such as pH,initial concentration, sorbent dosage and contact time on uptake of EY solution werealso investigated. The experiments were carried out using both batch and columnsystems at room temperature. It was found that both polymers can be used to removeanionic dyes such as EY from aqueous solutions very efficiently. The sorption processof EY dye using both polypyrrole and polyaniline coated onto sawdust (respectivelytermed as PPy/SD and PAni/SD) was less dependent on the pH of the solutions at leastat pH values from 2-10. Considerable decrease in sorption performance occurred onlyat high pH values (pH ≥ 12). According to our "breakthrough analysis", it was found thatPAni/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 examinedby pseudo-first-order and pseudo-second-order models, and their respective rateconstants of first-order adsorption (k1) and second-order adsorption (k2) wereestimated. The experimental data fitted very well into pseudo-second-order kineticmodel. The experimental data were also analyzed by the Langmuir and Freundlichmodels of adsorption. Based on the correlation coefficient values obtained (R2), it wasfound that equilibrium data fitted well with both models. In order to find out thepossibility of desorption for frequent use, the chemical regeneration of the employedadsorbents was also investigated. It was found that more than 96% of the EY dye canbe 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 anoparticles on membrane dopes were evaluated by the viscosity and surface tension. By dding 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.