Volume 33, Issue 5

A unique feature of molecular iodine by far, is its ability to bind to polymeric materials. A plethora of natural and synthetic polymers develop complexes when treated with molecular iodine, or with a mixture of molecular iodine and potassium iodide. Many unexpected findings have been encountered upon complexation of iodine and the polymer skeleton, including the color formation, the polymer morphology changes, the complexation sites or regions, the biological activity, and the electrical conductivity enhancement of the complexes, with polyiodides (I n ¯), mainly I 3 ¯ and I 5 ¯, as the actual binding species. Natural polymers that afford such complexes with iodine species are starch (amylose and amylopectin), chitosan, glycogen, silk, wool, albumin, cellulose, xylan, and natural rubber; iodine-starch being the oldest iodine-natural polymer complex. By contrast, numerous synthetic polymers are prone to make complexes, including poly(vinyl alcohol) (PVA), poly(vinyl pyrrolidone) (PVP), nylons, poly(Schiff base)s, polyaniline, unsaturated polyhydrocarbons (carbon nanotubes, fullerenes C 60 /C 70 , polyacetylene; iodine-PVA being the oldest iodine-synthetic polymer complex.

Hyperbranched polymers (HBPs) are highly branched, three-dimensional and polydisperse macromolecules and have been employed for modification of poly(ethylene terephthalate) (PET) fabrics. The PET fabrics treatment process parameters, like HBP concentration, temperature and time, play a major role in treatment yield and dyeability of treated PET fabrics by acid dyes. Two different quantitative models, comprising response surface methodology (RSM) and artificial neural networks (ANN), were developed for predicting color strength (K/S value) of treated fabrics. The experiments were conducted based on central composite design (CCD) and a mathematical model was developed. A comparison of the predicted color strength using RSM and ANN was studied. The results obtained indicated that both RSM and ANN models show a very good relationship between the experimental and predicted response values. However, the ANN model shows more accurate results than the RSM model.

The effects of processing parameters, including solution concentration, viscosity, nozzle diameter, voltage bias and the nozzle to collector distance, on the morphology and diameters of poly(methyl methacrylate) (PMMA) fibers have been systematically investigated, using a unique pump-free electrospinning method. For PMMA solution concentrations less than the critical entanglement concentration, c e , prolate spheroid-shaped droplets or beads with fibers were formed, whereas at concentrations above c e , good quality bead-free fibers were formed. Quantitative analysis revealed a linear dependence between the solution viscosity and fiber diameter. Larger fiber diameters were achieved by increasing the nozzle diameter and voltage bias. Increasing the bias voltage has the additional effect of broadening the diameter distribution, as a result of splaying and splitting. By contrast, when the strength of the electrical field was reduced by increasing the distance between the nozzle and collector, the overall fiber diameter was reduced.

In this research, a new direction for functionalizing of single-walled carbon nanotubes (SWCNTs) via the atom transfer radical polymerization (ATRP) method was utilized. SWCNTs were grafted with polystyrene (PSt) by the in situ ATRP method, in the presence of α-phenyl chloro acetylated SWCNT. This functional SWCNT was synthesized by the reaction between α-phenyl chloro acetyl chloride and a hydroxylated SWCNT that was obtained by reduction of a carboxylated SWCNT by lithium aluminum hydride (LiAlH 4 ). Oxidation, reduction and coupling reactions of SWCNTs were confirmed by Fourier transform infrared (FTIR) spectroscopy and polymerization of styrene from SWCNTs surfaces was illustrated by transfer electron microscopy (TEM). Thermal properties of attached polymers onto SWCNTs surfaces were investigated by thermogravimetry analysis (TGA), and differential scanning calorimetry (DSC) analysis.

Restoration of waste polymer based on low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polypropylene (PP) is studied using the dissolution/reprecipitation method. In this technique, pure turpentine, turpentine/petroleum ether (PetE) and turpentine/benzene as solvents with different fractions and PetE and n-hexane as non-solvents were examined. Commercial polymer products (packaging food, bags, laboratory plastic materials, detergent containers) used as raw materials were optimized with model polymers. Polymer recoveries in every case were <94%. Fourier transform infrared (FTIR) spectra and tensile mechanical properties of the samples before and after recycling were measured. Potential recycling-based degradation of the polymer was further investigated by measuring the thermal properties (melting point and crystallinity), before and after recycling, using differential scanning calorimetry (DSC). The blend solvents were seen as good solvents for all polyolefins used and the dissolution temperature was less than the pure solvent at the same time. High reconditioning was observed in most recycled samples, with no significant difference from the virgin materials. The studied technique seems to be viable for waste polyolefin polymer recycling.