Iranian polymer journal
Volume:19 Issue: 5, 2010

The effect of butyl glycol acetate (BGA)/ethyl acetate (EA) mixed solventscom-position on nitrocellulose (NC) solution miscibility and rheological propertieswith or without non-ionic surfactants was investigated. In addition the emulsificationof the solution containing two non-ionic surfactants with weight averagehydrophilic/lipophilic balance of 14.75 (oil phase), its colloidal stability and microfilterabilitywere studied. The results showed that oil phase viscosity and surfacetension increase by high boiling point solvent (BGA) between 50 and 87.5 wt%, whichreduced the colloid particle size from 35 μm down to 10 μm. While surfactant freesolution viscosity of NC in the BGA/EA mixed solvents increased to a maximum at75 wt% of BGA, the addition of the non-ionic surfactants changed the situation to aminimum at the same BGA content. The complex behaviour was assigned to thecompetitive interactions of solution components via hydrogen bond formation. Thecolloid particle size decreases depended also on Δgmixc, the Gibbs free energydensity 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 ratedependence on Δgmixc and the oil phase viscosity, respectively. Finally, the preparedcolloidal systems did not permeate through the membrane with 400 nm cross-throughchannels under 10 atm of nitrogen pressure, which was attributed to the oil phasenon-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 measurementsand potentiometric titration. Deionized water as well as CaCl2 and NaClaqueous solutions with different concentrations and two alcohols, i.e., methanol andethanol were used as solvents. The solubility and viscometric behaviours of threepoly(carboxybetaine)s were strongly dependent on the chemical nature of the spacerbetween N+ and COO- groups and the nature of the solvent. From the studies achievedthe polyelectrolyte behaviour of PNVIB-2 in methanol and PNVIB-3 in all the solventsas well as an anti-polyelectrolyte behaviour of PNVIB-2 in water were all observed.Fuoss and Rao equations were used to assess intrinsic viscosity, [η], values in the caseof polymers with polyelectrolyte behaviours as well as Einstein-Simha and Raoequations in the case of the polymer with anti-polyelectrolyte behaviour. UsingHenderson-Hasselbach equation and potentiometric titrations of aqueous solutions ofpoly(carboxybetaine)s with 0.5 M HCl the apparent pKa values were determined. Thesevalues are strongly dependent on the solvent nature. Also, when the water is used assolvent for polymers, it is observed that the PNVIB-2 and PNVIB-3 present the lowestpKa 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 forpreparation 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 feedmonomers 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 reactiontimes (3.5, 6.5 and 9.5 h), temperatures (70, 80 and 90°C) and initiator concentrations(0.25, 0.5 and 1 wt%) the copolymerization reactions were optimized. The adhesiveproperties have been evaluated in terms of intrinsic viscosity, glass transitiontemperature (Tg), peel strength and tack value for all samples. It was observed that thetrends in peel strength and intrinsic viscosity variations are approximately correlatedwith the above changing parameters. The synthesized PSAs show good adhesiveproperties and could be easily peeled off from the surface without leaving any residueon the surface. These samples with satisfactory adhesion properties werecharacterized by Fourier transform infrared, proton nuclear magnetic resonancespectroscopy, differential scanning calorimetry and gel permeation chromatography.Based on the optimum time (3.5 h), temperature (70°C) 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 PSAnamely 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 crosslinkedpolyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA)blends were investigated. The XLPE/SEBS samples were characterized by means ofdifferential scanning calorimetry, scanning electron microscopy, dielectric spectralanalysis and the accelerated water treeing experiment. The results clearly showed thatalthough SEBS was partially compatible with LDPE and it was dispersedevenly in XLPE matrix, the blends demonstrated excellent dielectric performances,such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBSblends was decreased with increase in SEBS content and it was further decreased withthe addition of EVA. SEBS could effectively improve the water-tree resistance of XLPEand both SEBS and EVA were found to improve the water tree resistance of XLPEsynergistically as expected. The differences in sample preparation processes couldchange the phase morphology and dielectric performance of the blends, and could alsoinfluence the dispersion of SEBS in XLPE matrix as well as the crystallinity of theblends. Different preparation processes led to different water tree resistancebehaviours of the samples. The improvement of SEBS dispersion in XLPE matrixhelped to improve the water tree resistance of XLPE.

Heavy end waste is produced as a by-product in purification unit of vinyl chloridemonomer in petrochemical complexes. This waste should be recycled or reusedwith ensured safety. Preparation of polysulphide polymer from this waste is oneof the solutions to reuse this waste. This paper deals with the effects ofpolysulphide polymer (PSP) and waste residue from distillation of heavy ends waste(WR) on the morphology, engineering and rheological properties of bitumen. To achievethis goal, polysulphide polymer was prepared from the distillated heavy ends wastewhich consists of a mixture of various chlorinated organic hydrocarbons and alkalipolysulphide. Subsequently, bituminous blends were produced by mixing 60/70penetration grade bitumen and 1, 3 and 5 wt% of PSP or WR. An optical microscopywas employed to study the morphology of samples. The observed morphology wasattributed to physical interactions acting between the phases. The engineeringproperties of modified bitumen containing PSP and WR were also determined andcompared with those of blank bitumen. The experimental results showed that softeningpoint of the bitumen increased whereas its penetration decreased upon incorporationof PSP. In the case of WR, a reverse effect was observed. The experimental mastercurves of G'' and G" obtained from the oscillatory rheological measurements usingtime-temperature superposition principle were reported. The shift factors used inconstructing master curves indicated an Arrhenius type temperature dependency. Thecalculated flow activation energy of the bituminous blends showed higher resistanceagainst their flow. It confirmed less rutting at high temperatures in comparison with thatof the base bitumen

During the past decades, hydrogels have been introduced suitable as novelmaterials for a variety of applications such as biomedical engineering, sanitaryproducts, agriculture, bioseparation, enhanced oil recovery, etc. They havebeen successfully used as superabsorbent materials and in drug delivery, cellencapsulation and tissue repair due to their high water content and consequentbiocompatibility. Considering the fact that water retention in the hydrogels provides asuitable drug diffusion pathway; many hydrogel-based networks have been designedand fabricated as intelligent carriers of drugs. The rate and degree of hydrogel swellingare the most important parameters which control the release patterns of solvents anddrugs from these polymeric networks. Therefore, the precise account of hydrogelbehaviour as well as mathematical description of equilibrium swelling, dimensionalchanges due to solvent uptake, desorption and drug release profiles were the mainobjectives in many investigations. The objective of this manuscript is to give a briefreview on existing mathematical models and theories in the field of hydrogel swellingas well as the description of the drug release mechanism from swelling-controllednetworks. The most important properties of hydrogels relevant to their swellingbehaviour as well as kinetics and thermodynamic of swelling are also presented.