Morphological and separation performance study of polysulfone/titanium dioxide (PSF/TiO2) ultrafiltration membranes for humic acid removal

In this study, polysulfone (PSF) hollow fiber membranes with enhanced performance for humic acid removal were prepared from a dope solution containing PSF/DMAc/PVP/TiO₂. The main reason for adding titanium oxide during dope solution preparation was to enhance the antifouling properties of membranes prepared. In the spinning process, air gap distance was varied in order to produce different properties of the hollow fiber membranes. Characterizations were conducted to determine membrane properties such as pure water flux, molecular weight cut off (MWCO), humic acid (HA) rejection and resistance to fouling tendency. The results indicated that the pure water flux and MWCO of membranes increased with an increase in air gap distance while HA retention decreased significantly with increasing air gap. Due to this, it is found that the PSF/TiO₂ membrane spun at zero air gap was the best amongst the membranes produced and demonstrated > 90% HA rejection. Analytical results from FESEM and AFM also provided supporting evidence to the experimental results obtained. Based on the anti-fouling performance investigation, it was found that membranes with the addition of TiO₂ were excellent in mitigating fouling particularly in reducing the fouling resistances due to concentration polarization, cake layer formation and absorption.     

Effect of chemical modification of oil fly ash and compatibilization on the rheological and morphological properties of low‐density polyethylene composites

In this study, the effect of oil fly ash (OFA), a by‐product of oil fuel power plants, on the rheological and morphological behavior of low‐density polyethylene (LDPE) is investigated. As received and acid‐functionalized OFA (COOH‐OFA) are used to examine the effect of surface modification of OFA on polymer–filler composites. LDPE/OFA composites were prepared by melt mixing with filler loading in the range 1–10 wt %. The results are compared with pure LDPE. The effect of polyethylene‐grafted‐maleic anhydride (PE‐g‐MA) as a compatibilizer was also studied. Both viscous and elastic properties of composites increased with OFA loading especially at low frequency. The surface modification of OFA has influenced the properties of OFA. As‐received OFA showed some agglomeration at high loading that resulted in two‐phase system as described by scanning electron microscopy (SEM) and Cole–Cole plot. Field emission‐SEM (FE‐SEM) images showed improvement in the dispersion of COOH‐LDPE/OFA composites. In addition, the surface modification reduced the size of agglomeration. In general, the COOH modification of OFA improved both the dispersion and rheological properties of OFA. With chemical modification, the concentration of the filler can be increased to 10% without compromising the properties of the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Calorimetric and rheokinetic analyses merged to capture crystallization kinetics in polyamide/clay nanocomposites: Revisiting predictability of models

Crystallization kinetics of polymer/clay systems was the subject of numerous investigations, but still there are some ambiguities in understanding thermal behavior of such systems under isothermal and nonisothermal circumstances. In this work, isothermal rheokinetic and nonisothermal calorimetric analyses are combined to demonstrate crystallization kinetics of polyamide6/nanoclay (PA6/NC) nanocomposites. As the main outcome of this work, we detected different regimes of crystallization and compared them by both isothermal dynamic rheometry and nonisothermal differential scanning calorimetry (DSC), which has not been simultaneously addressed yet. A novel analysis, somehow different from the common ones, is used to convert the storage modulus data to crystallinity values leading to more reasonable Avrami parameters in isothermal crystallization. It was found based on isothermal rheokinetic studies that increase of NC content and shear rate are responsible for erratic behavior of Avrami exponent and crystallization rates. Optimistically, however, isothermal crystallization by rheometer was confirmed by DSC. Nonisothermal calorimetric evaluations suggested an accelerated crystallization of PA6 upon increasing NC content and cooling rate. The crystallization behavior was quantified applying Ozawa (r² between 0.070 and 0.975), and combinatorial Avrami–Ozawa (r² between 0.984 and 0.998) models, where the latter appeared more appropriate for demonstration of nonisothermal crystallization of PA6/NC nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46364.     

Facile synthesis of extremely biocompatible double‐network hydrogels based on chitosan and poly(vinyl alcohol) with enhanced mechanical properties

An easy and ecofriendly method for designing double‐network (DN) hydrogels based on chitosan and poly(vinyl alcohol) (PVA) with high mechanical performance is described. When covalent bonds in the networks are used as crosslinking agents in the achievement of a higher mechanical strength, the irreversible deformation of these hydrogels after a large force is applied is still one of the most important obstacles. To overcome this problem, we used physical crosslinking for both networks. The mechanical strength, surface morphology, and cytotoxicity of the films were studied by tensile testing, scanning electron microscopy analysis, and an MTT assay. The synthesized chitosan–PVA DN hydrogels showed a large improvement in the tensile strength to 11.52 MPa with an elongation of 265.6%. The surface morphologies of the films demonstrated the effective interactions between the two networks and a suitable porosity. Also, because of the use of a natural polymer and honey as a plasticizer, the cell culture indicated that the synthesized DN hydrogels had good biocompatibility (with 327.49 ± 11.22% viability) and could be used as capable biomaterials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45752.     

Synthesis and characterization of new polysiloxane bearing vinylic function and its application for the preparation of poly (silicone-co-acrylate)/montmorillonite nanocomposite emulsion

A new silicone containing acrylic monomer, methacryloxyethyl polymethylhydrosiloxane ether (MEPMHSE), based on polymethylhydrosiloxane (PMHS) and 2-hydroxyethyl methacrylate (HEMA) has been synthesized for formulation of nanocomposite emulsion. Then Poly (silicone-co-acrylate)/montmorillonite (PSAM)/nanocomposite emulsion were prepared by in situ intercalative emulsion polymerization of methyl methacrylate (MMA), butyl acrylate (BA), methacrylic acid (MAA) and MEPMHSE, in the presence of organic modified montmorillonite (OMMT) with different OMMT contents (0, 0.5, 1.0, 1.5 and 2 wt%) and auxiliary agents in the presence of potassium persulphate (KPS) as initiator. Alkylphenol ethersulphate and Arkupal N-300 were used as anionic and non-ionic emulsifiers, respectively. The resulting monomer was characterized by Fourier transformer infrared spectroscopy (FTIR), proton (¹H NMR), and carbon (¹³C NMR) nuclear magnetic resonance spectroscopes. The OMMT was characterized by FTIR and X-ray diffraction (XRD). The nanocomposite emulsions were characterized by using Fourier transform infrared spectroscopy (FTIR), laser light scattering and surface tension. Thermal properties of the copolymers were studied by using thermogravimetric analysis (TGA) and dynamic mechanical thermal analysis (DMTA) and then the effects of OMMT percent on the water absorption ratio and drying speed were examined. Results showed that OMMT could improve the properties of emulsion, in other words, the properties of nanocomposite emulsion were better when compared with those of the silicone–acrylate emulsion. The property of nanocomposite emulsion containing 1 wt% OMMT was the best one, and the following advantages were obtained: smaller particle size, faster drying speed, smaller surface tension, and improved resistant water by the incorporation of OMMT.     

Water assisted exfoliation of PA6/clay nanocomposites using a twin screw extruder: Effect of water contact time

Polyamide 6/Na⁺ montmorillonite (Na⁺ MMT) nanocomposites (NCs) were produced in a corotating twin screw extruder. Water was injected into the extruder as an intercalating/exfoliating agent. The wide angle X‐ray diffraction and linear dynamic measurements were used to investigate the structure of the prepared samples. The results showed that the contact time between water and melt PA6/Na⁺MMT in the extruder is an important factor to achieve a high level of exfoliation. The ratio of water‐injection rate to clay feeding rate did not reveal a major effect on the exfoliation of pristine MMT. The results also demonstrated that the order of injection of water during the mixing process did not have a distinguishable effect on the level of exfoliation. This processing method was found to be controlled by a diffusion mechanism caused by the presence of water molecules during the process. Improvement of tensile properties is in a great agreement with the rheological and morphological findings. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Preparation of nanocomposite dispersions based on cellulose whiskers and acrylic copolymer by miniemulsion polymerization: Effect of the silane content

A one‐step method was used to prepare stable aqueous nanocomposite dispersions based on cellulose whiskers extracted from the rachis of the date palm tree and a poly(styrene‐co‐2‐ethyl hexylacrylate) copolymer via miniemulsion polymerization. A reactive silane, i.e., methacryloxypropyl triethoxysilane was added to stabilize the dispersion and favor the anchoring of the whiskers on polymer particles. Dynamic light scattering was used to study the effect of the silane and whiskers contents on the average particle size of the polymer. Nanocomposites materials were prepared from these dispersions using a casting/evaporation method. The effect of the silane and whiskers contents on the thermal and mechanical properties were studied using differential scanning calorimetry and dynamic mechanical analysis. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers     

Soft-templating pathway to create nanostructured Mg–Al spinel as high-temperature absorbent for SO2

Interest in reducing SO₂ emission from the fluid catalytic cracking (FCC) crude oil has been encouraging the development of new materials to achieve such goal. The nanostructured Mg–Al spinel (MgAl₂O₄) was prepared by co-precipitation and post hydrothermal treatment in the presence of glucose and followed by elimination of the organic components by calcination at 700 °C for 3 h. Physical and chemical properties were characterized by XRD, N₂ sorption, TG, FTIR, SEM, and TEM methods. Mesoporous nanostructured MgAl₂O₄ with a high surface area of 324 m² g^?1 were obtained. The organic components contributed to the development of mesoporosity, functioning as a soft template. SO₂ adsorption tests showed that the nanostructured MgAl₂O₄ had a 51.58 % increase of SO₂ sorption capacity than MgAl₂O₄ prepared without glucose. These results showed that the nanostructured MgAl₂O₄ is a promising candidate as catalyst for flue gas desulfurization in FCC process. Three kinetic models were also applied to analyze the SO₂ adsorption kinetics; the pseudo-second order kinetic model fit well with a correlation coefficient (R²) of 0.991 for nanostructured MgAl₂O₄.     

Unique microstructure analysis of ethylene-propylene copolymer synthesized using catalytic system based on α-diimine nickel complexes: a comparative study by 13C NMR technique

The microstructure of rubber-like ethylene-propylene copolymer (MN4) produced by a mixed nickel-based system (MN) containing catalysts of dibromo[N,N′-bis(2,6-diisopropylphenyl)-2,3-butanediimine]nickel(II) n1 and dibromo[N,N′-(phenanthrene-9,10-diylidene)bis(2,6-diisopropylaniline)]nickel(II) n2 was determined by ¹³C NMR technique. Sequences distribution of ethylene (E), propylene (P), EP, inverted propylene and uninterrupted methylene and also methylene number-average sequence lengths for the copolymer (MN4) were estimated. The results obtained from the MN4 EP copolymer were compared with reported copolymers which had been synthesized using constrained geometry catalyst (CGC) and vanadium-based Ziegler-Natta catalyst. The results demonstrated that the MN4 EP copolymer had fewer alternating comonomer sequences than ethylene-propylene elastomers obtained by CGC and vanadium-based (V) catalysts. A large number of the inversion structures (66 %) and high mole percent of sequences containing a long branch (3.2 mol%) were also observed in unique microstructure of the copolymer (MN4).     

Mortality response of folate receptor-activated,PEG–functionalized TiO2 nanoparticles for doxorubicin loading with and without ultraviolet irradiation

TiO₂ nanoparticles (NPs) were synthesized by hydrothermal assisted sol–gel technique. In the next step, as-synthesized NPs were modified by poly ethylene glycol (PEG). Then, folic acid (FA) was conjugated to TiO₂–PEG. Finally, Doxorubicin (Dox) as an anticancer drug was loaded on as-prepared TiO₂–PEG–FA nanocarrier. The optimization of TiO₂ and FA concentration and the influence of ultraviolet (UV) irradiation on photocatalytic activity of nanocarrier and Dox loaded carrier were assessed by utilizing the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT)-assay method.