Poly(acrylic acid–sodium styrene sulfonate) organogels: Preparation,characterization, and alcohol superabsorbency

Polymeric organogels based on acrylic acid and sodium styrene sulfonate (SSS) were synthesized and characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, dynamic mechanical thermal analysis (DMTA), and rheometrical analyses. The organogels exhibited medium alcohol absorbency because of counterion binding that formed in solvents with low dielectric constants. After acid treatment, the possibility of counterion binding was decreased, and the organogels achieved superabsorbency in alcohols, for example, about 80 and 50 g/g in methanol and ethanol, respectively. The superabsorbency was also measured in higher alcohols (i.e., n‐propanol and isopropyl alcohol) and polyols (i.e., ethylene glycol, propylene glycol, 1,3‐propanediol, and glycerol). The dielectric constant, viscosity, and structural features of the alcohols were investigated as important parameters determining the alcohol superabsorbency. DMTA of dried samples showed two glass‐transition temperatures (T_g's), that is, the matrix T_g and the complex T_g, which increased with increasing SSS content. The tan δ peak intensity increased after the acid treatment. With increasing SSS, the storage modulus of the dried gel increased; whereas that of the rheometrically measured hydrated gel decreased. Tan δ decreased with increasing SSS because of enhanced counterion binding. These alcohol‐specific superabsorbing organogels are suggested as excellent candidates for the manufacture of products with high alcohol contents, such as hand sanitizers and fuel gels. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Biosurfactant-producing bacterium, Pseudomonas aeruginosa MA01 isolated from spoiled apples: physicochemical and structural characteristics of isolated biosurfactant

An extensive investigation was conducted to isolate indigenous bacterial strains with outstanding performance for biosurfactant production from different types of spoiled fruits, food-related products and food processing industries. An isolate was selected from 800 by the highest biosurfactant yield in soybean oil medium and it was identified by 16S rRNA and the two most relevant hypervariable regions of this gene; V3 and V6 as Pseudomonas aeruginosa MA01. The isolate was able to produce 12 g/l of a glycolipid-type biosurfactant and generally less efficient to emulsify vegetable oils compared to hydrocarbons and could emulsify corn and coconut oils more than 50%. However, emulsification index (E(24)) of different hydrocarbons including hexane, toluene, xylene, brake oil, kerosene and hexadecane was between 55.8% and 100%. The surface tension of pure water decreased gradually with increasing biosurfactant concentration to 32.5 mNm(-1) with critical micelle concentration (CMC) value of 10.1mg/l. Among all carbon substrates examined, vegetable oils were the most effective on biosurfactant production. Two glycolipid fractions were purified from the biosurfactant crude extracts, and FTIR and ES-MS were used to determine the structure of these compounds. The analysis indicated the presence of three major monorhamnolipid species: R(1)C(10)C(10), R(1)C(10)C(12:1), and R(1)C(10)C(12); as well as another three major dirhamnolipid species: R(2)C(10)C(10), R(2)C(10)C(12:1), and R(2)C(10)C(12). The strain sweep experiment for measuring the linear viscoelastic of biosurfactant showed that typical behavior characteristics of a weak viscoelastic gel, with storage modulus greater than loss modulus at all frequencies examined, both showing some frequency dependence.     

The effect of resin formulation on the cellular morphology and mechanical properties of phenolic foams

In the present study, the effects of blowing agent concentration, surfactant, and resin viscosity on the cellular structure, density, and compressive strength of phenolic foams were investigated. The mechanism of foaming was studied by thermal analyses, as well. The scanning electron microscopy was performed to investigate the morphology of foams. The presence of surfactant was essential to obtain a foam structure. By increasing the amount of blowing agent in the formulation, the bubbles became larger. The variation of the resin viscosity had the sharp effect on the cell size and its distribution so that the cell size dropped from 108 to 77 μm in the sample with the highest viscosity. The mechanical properties were significantly affected by foam structure as well as the cell uniformity. By decreasing the average cell sizes, the compression strength and modulus were improved up to more than 60%. Finally, the optimum values for viscosity of resin and, blowing agent, and surfactant concentrations were obtained. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48331.     

An investigation into novel multifunctional cross-linkers effect on microgel prepared by precipitation polymerization

Novel microgels composed of acrylaic acid and multifunctional cross-linkers, acrylate/methacrylate cross-linkers, were synthesized via thermal initiated free radical precipitation polymerization in organic solvents. The effect of cross-linker functionality on the properties of microgels was investigated. Results showed both the solvent absorbency and apparent viscosity depend on the network structure, the cross-linker functionality and number of hydrophobic groups. Gel content indicated more reactivity of acrylate than methacrylate cross-linkers. A linear relation exists between elastic modulus (G′) and functionality (f). Also the results suggested an equation that confirmed a direct relationship between glass transition temperature (T_g) and (f). The rotational and apparent viscosity results supported the thickening properties of the microgels. Based on the observations, it is concluded that trifunctional AC cross-linker (TMPTA) choose as an improvement of thickening properties over another cross-linkers.     

Evaluation of toughening mechanisms of polypropylene/ethylene–octene copolymer/maleic anhydride‐grafted poly(ethylene‐co‐octene)/clay nanocomposite

The toughness of a polypropylene (PP)/ethylene‐octene copolymer (EOC)/maleic anhydride‐grafted poly(ethylene‐co‐octene) (EOC‐g‐MA)/clay nanocomposite and blends of PP/EOC and PP/EOC/EOC‐g‐MA was investigated using Charpy impact and single‐edge‐notch tensile (SENT) tests. In order to understand the toughening mechanisms, impact fracture surfaces and damage zones of single‐edge‐notch samples were studied with scanning electron microscopy and transmission optical microscopy, respectively. It was observed that the addition of EOC‐g‐MA to PP/EOC blend led to improvements in both impact strength and fracture energy of SENT tests because of the enhanced compatibility of the blend, which resulted from reduced EOC particle size and improved interfacial adhesion, and the decreased crystallinity of PP. The incorporation of clay to PP/EOC/EOC‐g‐MA blend caused a further increase of the toughness, owing to the greater decrease in the size of elastomer particles, to the presence of clay tactoids inside the elastomer phase and presumably to debonding of clay layers during the low‐speed SENT tests. The results of microscopic observations showed that the main toughening mechanism in PP/EOC/EOC‐g‐MA blend and PP/EOC/EOC‐g‐MA/clay nanocomposite is crazing. Copyright © 2012 Society of Chemical Industry     

Preparation of stealth micellar nanoparticles of novel biodegradable and biocompatible brush copolymers with cholesteryl-modified PLA and PEG side chains

Novel amphiphilic brush copolymers, P(CPLAMA)-co-P(PEGMA), of cholesteryl poly(l-lactic acid) (CPLA) and poly(ethylene glycol) monomethyl ether (PEG) with determined hydrophobic/hydrophilic ratios were synthesized by the methacrylate (MA) macromonomer copolymerization method. Brush copolymers were prepared via both free radical polymerization (FRP) and atom transfer radical polymerization (ATRP). The copolymer compositions were determined by ¹H NMR spectroscopy. The synthesized copolymers were used to prepare the micellar nanoparticles with hydrophobic CPLA and hydrophilic PEG forming the core and shell, respectively. The critical micelle concentration (CMC) values of the samples produced by FRP (brush copolymer 1) and ATRP (brush copolymer 2) were estimated to be approximately 0.9 and 0.7 mg/L in aqueous solution by a fluorescence probe technique, respectively. The transmission electron microscopy (TEM) images of micelles of the brush copolymers 1 and 2 showed that micelles were spherical in shape with a mean diameter of 111 and 32 nm, respectively. The results showed that the size of micelles became larger with the increase of the molecular weight of polymer and the relative content of the hydrophilic PEG as well. The drug loading efficiency and drug-releasing properties of the micelles were investigated by using naproxen as a hydrophobic model drug. The in vitro release of naproxen-loaded micelles with about 85–89 % loading efficiency and 17–18 % loading capacity was studied by a using dialysis method in phosphate-buffered solution at 37 °C. The drug-releasing characteristics exhibited a phase of slow release. On the basis of the results obtained, the proposed brush copolymers may be useful in various targeted drug delivery applications, especially those involving hydrophobic drugs.     

Effects of mechanical and geometrical properties of adhesive and metal layers on low-velocity impact behavior of metal laminate structures

In this study, the effects of mechanical and geometrical properties of the adhesive layers and mechanical properties of the metal layers on low-velocity impact behavior of adhesively bonded metal laminates (ABML) were investigated. The contact force, the transverse displacement, the contact duration, and the dissipated energy were considered as the main structure responses under impact loading. To study the effects of mechanical and geometrical properties of adhesive layers on low-velocity impact behavior of ABML, two different adhesive materials and two different adhesive thicknesses were considered. The results showed that the contact force was more depended on the adhesive thickness and nearly unaffected by the adhesive material, whereas the dissipated energy was more depended on the adhesive material rather than the adhesive thickness in case the overall structure thickness was remained fixed. To determine the effects of material parameters of the metal layers including the yield stress, the elastic modulus, the density, and the tangent modulus on the impact behavior of ABML, finite element analyses were carried out. The results showed that increasing the number of metal layers in a constant total thickness caused decrease of the total contact force and increase of the contact duration and transverse displacement of the structure due to more widespread plastic deformation occurred in the layers. The material yield stress and Young’s modulus were the most influencing material parameters on the mechanical behavior of ABML under low-velocity impact loading. The finite element models were well validated against the experimental and numerical results.     

Preparation of high surface area activated carbon from corn by chemical activation using potassium hydroxide

Activated carbons were prepared through chemical activation of corn cob precursor, using potassium hydroxide as the chemical agent. The effect of different parameters, such as particle size, method of mixing, chemical/corn ratio, activation time and activation temperature, on weight loss and BET surface area of the produced activated carbons were discussed. The porosity of the activated carbons was evaluated through nitrogen adsorption. The storage capacity of the activated carbon was evaluated using natural gas. Under the experimental conditions investigated, the optimal conditions for production of high surface area carbons by chemical activation were identified. The results were compared with commercial activated carbons from coal.     

Characterization and modification of commercial acrylic fibers grafted with acrylic acid

The graft copolymerization of acrylic acid (AA) onto commercial acrylic fibers (PAN) has been studied using Azobis(isobutyro)nitrile (AIBN) as an initiator. AA grafting initiated by radicals formed from thermal decomposition of AIBN. In this study, the effects of monomer and initiator concentration, time and temperature reaction on the grafting yield have been investigated. The optimum conditions for this grafting reaction were obtained with an AA concentration of 1.67 M, an AIBN concentration of 0.0097 M, a reaction temperature of T=85 °C and with reaction time of 60 minutes. The fiber structure has been investigated by different experimental techniques of characterization such as Fourier transform infrared spectroscopy (FT‐IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), water absorption and also in this study has been investigated the mechanical property. The thermal analysis data showed that increasing in grafting yield, decreases the thermal stability of fiber. Grafting also affected slightly the fiber morphology. The experimental data of mechanical properties show clearly that by increasing of grafting yield, max extension will decrease. Grafting of poly AA improved water absorption.