Iranian Polymer Journal
Year:2010 | Volume:19 | Issue:5 (119)|Papers Count:6

The effect of butyl glycol acetate (BGA)/ethyl acetate (EA) mixed solvents com-position on nitrocellulose (NC) solution miscibility and rheological properties with or without non-ionic surfactants was investigated. In addition the emulsification of the solution containing two non-ionic surfactants with weight average hydrophilic/lipophilic balance of 14.75 (oil phase), its colloidal stability and microfilterability were studied. The results showed that oil phase viscosity and surface tension increase by high boiling point solvent (BGA) between 50 and 87.5 wt%, which reduced the colloid particle size from 35 mm down to 10mm. While surfactant free solution viscosity of NC in the BGA/EA mixed solvents increased to a maximum at 75 wt% of BGA, the addition of the non-ionic surfactants changed the situation to a minimum at the same BGA content. The complex behavior was assigned to the competitive interactions of solution components via hydrogen bond formation. The colloid particle size decreases depended also on Dgmixc, the Gibbs free energy density of mixing two phases, due to higher solution BGA content. Power law dependence of 0.09 and -1.31 was found for the colloid particle size or sedimentation rate dependence on Dgmixc and the oil phase viscosity, respectively. Finally, the prepared colloidal systems did not permeate through the membrane with 400 nm cross-through channels under 10 atm of nitrogen pressure, which was attributed to the oil phase non-ionic surfactants adsorption on the membrane surfaces.

The solution properties of the poly(carboxybetaine)s possessing structural units of [1-vinyl-3-(1-carboxymethyl) imidazolium betaine] (PNVIB-1); [1-vinyl-3-(2- carboxyethyl) imidazolium betaine] (PNVIB-2) and [1-vinyl-3-(2-carboxyisopropyl) imidazolium betaine] (PNVIB-3) were investigated by viscometric measurements and potentiometric titration. Deionized water as well as CaCl2 and NaCl aqueous solutions with different concentrations and two alcohols, i.e., methanol and ethanol were used as solvents. The solubility and viscometric behaviours of three poly (carboxybetaine)s were strongly dependent on the chemical nature of the spacer between N+ and COO- groups and the nature of the solvent. From the studies achieved the polyelectrolyte behaviour of PNVIB-2 in methanol and PNVIB-3 in all the solvents as well as an anti-polyelectrolyte behaviour of PNVIB-2 in water were all observed. Fuoss and Rao equations were used to assess intrinsic viscosity, [ h], values in the case of polymers with polyelectrolyte behaviours as well as Einstein-Simha and Rao equations in the case of the polymer with anti-polyelectrolyte behaviour. Using Henderson-Hasselbach equation and potentiometric titrations of aqueous solutions of poly (carboxybetaine)s with 0.5 M HCl the apparent pKa values were determined. These values are strongly dependent on the solvent nature. Also, when the water is used as solvent for polymers, it is observed that the PNVIB-2 and PNVIB-3 present the lowest pKa values, because of the lowest binding ability of the H+ by COO- groups.

Apressure sensitive adhesive (PSA) based on acrylic monomers was synthesized. For this purpose a solution copolymerization process was conducted for preparation of an acrylic copolymer containing 2-ethylhexylacrylate (2-EHA), 2- hydroxyethyl acrylate (2-HEA), glycidyl methacrylate (GMA) and vinyl acetate (VAc), using 2, 2'-azobisisobutyronitrile (AIBN) as an initiator. The initial amounts of feed monomers were constant in all formulations (2-EHA/VAc/ HEA/GMA; 67%, 28%, 4.9%, 0.1% by weights). With variation of different parametric conditions such as reaction times (3.5, 6.5 and 9.5 h), temperatures (70, 80 and 90oC) and initiator concentrations (0.25, 0.5 and 1 wt%) the copolymerization reactions were optimized. The adhesive properties have been evaluated in terms of intrinsic viscosity, glass transition temperature (Tg), peel strength and tack value for all samples. It was observed that the trends in peel strength and intrinsic viscosity variations are approximately correlated with the above changing parameters. The synthesized PSAs show good adhesive properties and could be easily peeled off from the surface without leaving any residue on the surface. These samples with satisfactory adhesion properties were characterized by Fourier transform infrared, proton nuclear magnetic resonance spectroscopy, differential scanning calorimetry and gel permeation chromatography. Based on the optimum time (3.5 h), temperature (70oC) and initiator concentration (0.5 wt%), a formulation with the best adhesion properties and high conversion (86%) was selected as the optimized PSA and it was compared with a commercialized PSA namely Duro-Tak 2287.

The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)- b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.

Heavy end waste is produced as a by-product in purification unit of vinyl chloride monomer in petrochemical complexes. This waste should be recycled or reused with ensured safety. Preparation of polysulphide polymer from this waste is one of the solutions to reuse this waste. This paper deals with the effects of polysulphide polymer (PSP) and waste residue from distillation of heavy ends waste (WR) on the morphology, engineering and rheological properties of bitumen. To achieve this goal, polysulphide polymer was prepared from the distillated heavy ends waste which consists of a mixture of various chlorinated organic hydrocarbons and alkali polysulphide. Subsequently, bituminous blends were produced by mixing 60/70 penetration grade bitumen and 1, 3 and 5 wt% of PSP or WR. An optical microscopy was employed to study the morphology of samples. The observed morphology was attributed to physical interactions acting between the phases. The engineering properties of modified bitumen containing PSP and WR were also determined and compared with those of blank bitumen. The experimental results showed that softening point of the bitumen increased whereas its penetration decreased upon incorporation of PSP. In the case of WR, a reverse effect was observed. The experimental master curves of G' and G" obtained from the oscillatory rheological measurements using time-temperature superposition principle were reported. The shift factors used in constructing master curves indicated an Arrhenius type temperature dependency. The calculated flow activation energy of the bituminous blends showed higher resistance against their flow. It confirmed less rutting at high temperatures in comparison with that of the base bitumen.

During the past decades, hydrogels have been introduced suitable as novel materials for a variety of applications such as biomedical engineering, sanitary products, agriculture, bioseparation, enhanced oil recovery, etc. They have been successfully used as superabsorbent materials and in drug delivery, cell encapsulation and tissue repair due to their high water content and consequent biocompatibility. Considering the fact that water retention in the hydrogels provides a suitable drug diffusion pathway; many hydrogel-based networks have been designed and fabricated as intelligent carriers of drugs. The rate and degree of hydrogel swelling are the most important parameters which control the release patterns of solvents and drugs from these polymeric networks. Therefore, the precise account of hydrogel behaviour as well as mathematical description of equilibrium swelling, dimensional changes due to solvent uptake, desorption and drug release profiles were the main objectives in many investigations. The objective of this manuscript is to give a brief review on existing mathematical models and theories in the field of hydrogel swelling as well as the description of the drug release mechanism from swelling-controlled networks. The most important properties of hydrogels relevant to their swelling behaviour as well as kinetics and thermodynamic of swelling are also presented.