In this study, two poly(acrylic acid)/alumina (PAA/alumina) nanocomposites with varied polymer loadings were prepared via in situ polymerization of preadsorbed acrylic acid. One composite would have a ~1/4‐monolayer polymer coverage, while the other had a ~2‐monolayer coverage. The produced composite materials were characterized in the adsorptive behavior of Pb2+ from aqueous solution. When there was less PAA produced in a nanocomposite sample, there was higher Pb2+ sorption capacity due to potentially less blocked alumina pores by in situ formed PAA. Isothermal and kinetic models for Pb2+ sorption were applied by considering the effects of the initial Pb2+ concentration and the contact time. The adsorption kinetics was best expressed using the pseudo‐second‐order equation. Through the isothermal studies, the maximum Pb2+ monolayer adsorption capacity of 167.79 mg/g was recorded for the composite with higher PAA loading.
Mesoporous alumina, as a porous, high specific surface area, high activity, and heat stable material, has been widely used as an industrial adsorbent, catalyst, and catalyst support. The modification of alumina with organic polymers has been widely investigated in recent years. In this study, we compared the dependence of the adsorption of a polyelectrolyte, poly(acrylic acid) (PAA) on γ‐alumina particles on polymer size via Fourier transform infrared spectroscopy, thermogravimetry, nitrogen adsorption–desorption isotherm analysis, and atomic absorption spectrophotometry. We found that PAA with a hydrodynamic diameter greater than the alumina pore size would only adsorb on the outer surface of the oxides. For polymers with hydrodynamic diameters smaller than the alumina pore size, PAA infiltration resulted in a monolayer coverage of both the outer and inner surfaces of the oxide. Among the three PAA that could infiltrate the alumina pores, the one with the smallest molecular weight showed the highest adsorbed amount on alumina. The temperature, pH, concentration, and ionic strength of the PAA solutions were varied to illustrate the physicochemical differences of the prepared polymer/oxide composite materials. The high PAA‐loaded composites were treated with a nickel ion solution, converted to Ni/alumina catalysts, and used in the methanation of carbon dioxide. The Ni/alumina catalysts were analyzed with X‐ray diffraction and temperature‐programmed reduction to illustrate the structural characteristics. The catalytic CO2 methanation of the catalyst samples revealed that a solution pH value higher than pKa of PAA favored the formation of catalysts with high catalytic activity.
ABSTRACT A novel allyl compound containing liquid crystalline structure, i.e., 4,4’‐bis(4‐allyloxy benzoic acid) phenyl ester (BAOBE), was synthesized. The chemical structure of BAOBE was characterized by Fourier transform infrared (FTIR) spectroscopy and 1H NMR spectra, and the liquid crystalline properties were confirmed by polarized optical microscopy (POM). Besides, a series of modified bismaleimide (BMI) resins were prepared based on N,N′‐4,4′‐bismaleimidodiphenylmethylene (BDM), BAOBE, and O,O’‐diallyl bisphenol A (DABPA). The results of thermogravimetric analysis (TGA) indicate that the modified resins have excellent thermal stability with the highest temperatures for 5% weight loss above 438°C. The results of dynamic mechanical analysis (DMA) suggest that the glass transition temperature (Tg) of the modified resins are above 280°C. Besides, the introduction of BAOBE leads to a significant improvement in the flexural and impact properties of the modified BMI resins. Compared with the resin with only DABPA as a modifier, the highest flexural and impact strength can reach 156.2 MPa and 15.6 kJ/m2, increased by 19.2% and 90.2%, respectively.
When considering energy consumption and environmental issues, solvent‐resistant nanofiltration (SRNF) based on polymeric materials emerges as a process for substituting conventional separation processes of organic solutions, such as distillation, which consume high amounts of energy. Because SRNF does not involve phase transition, this process can potentially decrease the energy consumption and solvent waste and increase the yield of active components. Such improvements could significantly benefit a number of fields, such as pharmaceutical manufacturing and catalysis recovery, among others. Therefore, SRNF has gained a lot of attention since the recent introduction of solvent‐stable polymeric materials in the manufacture of nanofiltration membranes. The membrane materials and the membrane structures depending on the fabrication methods determine the separation performance of polymeric SRNF membranes. Therefore, this article gives a comprehensive overview of the current state‐of‐art technologies of generating membrane materials and corresponding fabrication methods for SRNF membranes made from polymeric materials expected to provide the most benefit. The transport mechanisms and the corresponding models of SRNF membranes in organic media are also reviewed to better understand the mass transfer process. Various SRNF applications, such as in pharmaceutical and catalyst, among others, are also discussed. Finally, the difficulties and future research directions to overcome the challenges faced by SRNF processes are proposed.
ABSTRACT Polymer/clay nanocomposite particles with 2‐aminophenol (2AP) and polyaniline and modified montmorillonite by copper minerals were synthesized using an in situ intercalative oxidative polymerization method. The nanocomposites were characterized by elementary analysis, X‐ray diffraction, FTIR, thermogravimetric analysis, transmission electron microscopy, and conductivity measurements. The insertion of the polymer into the layer of the clay was confirmed by X‐ray diffraction analysis, which shows a significantly larger d spacing expansion from 13.35 to 13.45 Å, thus indicating that the conducting polymer chain was aligned with layers of the clay. The conductivity of the nanocomposites salt is between 8.87×10−5 and 9.78×10−4 S/cm, probably due to the confined environment in the nanometer size layers of the nanocomposite. The electrochemical behavior of the polymers extracted from the nanocomposites has been studied by cyclic voltammetry. Good electrochemical response has been observed for polymers grown into M‐Cu; the redox processes indicate that the polymerization into M‐Cu is electroactive.
ABSTRACT The present article deals with the preparation and characterization of pure and lead oxide (PbO) nanoparticles embedded polyvinyl alcohol (PVA) films by using a colloidal processing technique. PbO nanoparticles were successfully synthesized using the simple precipitation method. Polymer/ceramic‐based flexible and self‐standing films were obtained and further characterized using various analytical techniques. The mechanical and dielectric properties were also investigated. The Fourier Transform Infrared Spectroscopy (FTIR) results indicate that the structural characterization of PVA is strongly affected by the incorporation of PbO. Thermal analysis results indicate that the thermal stability of the PbO‐doped PVA film has improved as compared with the neat PVA film. The mechanical property of nanocomposites has improved significantly due to an increase in filler loadings, indicating that a good interaction exists between PbO nanoparticles and PVA matrix. The dielectric constant of PVA/PbO nanocomposites has significantly improved with comparatively low dielectric loss values, indicating that the nanocomposites can be considered as an attractive material for embedded capacitor applications.
Cellulose acetate/carbon nanotube composite nanofibers were prepared using electrospinning technique. The morphology, crystalline, and mechanical properties were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), Fourier transform infrared spectroscopy (FT‐IR), and tensile test. The result indicated that the CA with 0.5 wt% CNT shows better mechanical properties among the other sample which contains lower or higher percent of CNT. In addition, the diameter of the average fibers was 415 ± 45 nm and shows good dispersions of CNT into the nanofibers. Moreover, tensile strength and Young's modulus were enhanced with an average of 67% and 78%, respectively.
ABSTRACT The aim of this work is to use lignocellulosic wastes as low price additives in biodegradable polymers. The rice straw (RS) was treated by means of different methods, and then it was introduced to the poly(lactic acid)/starch composites. The effects of different treatments on RS properties were investigated using the Fourier transform infrared, tensile, charpy, hardness, differential scanning calorimetry, rheology, contact angle, and scanning electron microscopy. It was found that 5–10% of all the differently treated RS increases the overall properties. Moreover, silica and lignin were mainly affected by such treatments; however, a balance between silica and lignin shows the best results. The modified alkali‐treated rice straw (ARS treatment) prevented cellulose from degradation by creating a balance between silica and lignin, which controls the opposing effects of lignin including paste‐like and plasticating effects. Finally, the ARS‐filled samples show improved overall properties among the other samples. The obtained composites with optimum filler content may be used in the biomembranes and food packaging applications.
A new computer model has been developed to simulate a starve‐fed single‐screw extrusion process of polymer blends. This is a composite model, which is based on combining melt conveying models with new fusion models for polymer blends. The model is able to predict pressure and temperature profiles, filling of the screw and rate of polyblend fusion. Computer calculations were executed for extrusion of high‐density polyethylene and polystyrene blend at various technological conditions, and fill factor, pressure, temperature, and fusion profiles were calculated. The results of simulation studies were verified by experiment.
Novel green composites were successfully prepared from bacterial poly(3‐hydroxybutyrate) (PHB) and pita fibers derived from the agave plant (Agave americana). Various weight contents (10, 20, 30, and 40 wt.‐%) of pita fibers at different lengths (5, 15, and 20 mm) were successfully incorporated into PHB by compression molding. The newly prepared PHB/pita fibers composite sheets were characterized in terms of their mechanical and thermomechanical properties and then related to their morphology after fracture. Attained results indicated that the mechanical stiffness of PHB significantly improved with both the content and length of pita fibers, although ductile properties were reduced. In particular, the elastic modulus of the 40 wt.‐% PHB composite sheets containing 20‐mm‐long pita fibers was approximately 55% higher than the unfilled PHB sheet. Shore D hardness also improved, achieving the shortest pita fibers the highest improvement. Pita fibers with lengths of 15 and 20 mm also increased the Vicat softening point and heat deflection temperature (HDT) by 38 and 21°C, respectively. Due to their optimal shape, it is concluded that pita fibers with lengths above 15 mm can potentially reinforce and improve the performance of PHB biopolymer. In addition, the compression‐molding methodology described in this research work represents a cost‐effective pathway to feasibly prepare long‐fiber‐reinforced thermoplastics (LFRTs) fully based on renewable raw materials. Resultant green composite sheets can be of interest for the development of sustainable parts in the automotive industry and other advanced applications in polymer technology.
Protein adsorption is the first phenomenon that occurs when foreign materials are inserted into the body. Materials used in biomedical applications can have different surface topologies. Knowledge of the effect of the surface on protein adsorption is important due to its influence on cell behavior. The main objective of this study was to analyze polycaprolactone (PCL) films with different surface topologies. Protein adsorption was studied using bovine serum albumin (BSA) as the biomolecule. Different surface topologies of PCL were induced by phase separation using solvents with various solubility parameters. The investigated solvents were chloroform, acetone, tetrahydrofuran (THF), and ethanol (EtOH). The PCL films with different surface topologies and protein‐adsorbed PCL films were studied with respect to their hydrophobicity, the concentration and nature of functional groups on their surface, their surface roughness, and their cytotoxicity. Atomic force microscopy revealed that the films with the roughest surface were cast from 40:60 EtOH:THF and contained significantly larger amounts of adsorbed protein. Proteins preferentially adsorbed onto rough surfaces. The cell culture also indicated that mouse‐calvaria‐derived pre‐osteoblastic cells proliferated best and exhibited the greatest amount of calcium deposition on the surface with the largest amount of adsorbed protein.
Filling process of micro prism array by isothermal hot embossing in solid‐like state (IHESS) with different mold temperature, pressure, and holding time were simulated by DEFORM. Polymethyl methacrylate (PMMA) samples processing by IHESS were tested to validate the numerical simulation results and select the best processing condition. The reliability of simulation was tested quantitatively and qualitatively by comparing the cross‐profile and its developing trend separately. It was found that the cross‐profiles from the simulations and experiments were in high agreement. The simulated and experimental developing trends of cross‐profiles were also the same. These results proved the reliability of simulation and its guidance to the experiments. In order to show the advantages of IHESS, a brief introduction and comparison of IHESS and traditional hot embossing were made.
The drug‐loaded polyvinyl alcohol (PVA)/chitosan (CS) composite nanofibers intended to be used as matrix for transdermal drug delivery were fabricated by electrospinning, and then crosslinked through glulataraldehyde (GA). The morphology, chemical structure, thermal behavior, mechanical properties, hydrophilicity and drug release properties of drug‐loaded PVA/CS composite nanofibers before and after crosslinking were characterized. The results showed that the morphology of PVA/CS composite nanofibers was not been destroyed in both crosslinking and in vitro drug release process. The Young's modulus, tensile strength, thermal properties and hydrophobicity of crosslinked PVA/CS composite nanofibers significantly increased in comparison with those of PVA/CS (without crosslinking) due to the formation of crosslinking network structure. In vitro release studies showed that crosslinked PVA/CS composite nanofibers had lower drug release rate and smaller amount of drug burst release than that of PVA/CS. According to release exponent “n”, the release of ampicillin sodium from crosslinked PVA/CS composite nanofibers fit to the Fickian diffusion mechanism. Those results demonstrate the potential utilization of crosslinked PVA/CS composite nanofibers as a transdermal drug delivery system.
Chitosan graft poly(acrylic acid‐co‐2‐acrylamide‐2‐methyl propane sulfonic acid) (CTS‐g‐P(AA‐co‐AMPS)) hydrogel is prepared and used to remove methylene blue (MB) and rhodamine B (RB) mixed dyes from aqueous solutions. The effect of adsorption conditions, including the initial concentrations of dye solutions, contact time, initial pH values, ionic strength, and the adsorbent dosage, on the adsorption capacities is investigated. The maximal adsorption capacity for MB and RB is 936.0 and 556.9 mg/g, respectively. The adsorption isotherms of the mixed dyes are discussed using the extended Langmuir (EL) and the extended Freundlich (EF) isotherm equations. It indicates that the adsorption of both dyes is in good agreement with the extended Freundlich isotherm. Meanwhile, the adsorption processes of both dyes are spontaneous. Adsorption kinetics is in accordance with the pseudo‐second‐order kinetic equation. It is concluded that the available adsorption sites are shared by both kinds of the dye molecules. The difference of the maximal adsorption capacities of the two dyes is due to their different affinity to the adsorbent.
ABSTRACT Because of their ability to show ferroelectret behavior when exposed to an external electric field, cellular polymers have been recently considered for ferroelectret applications. These cellular polymer films can be produced by stretching or foaming, but depending on the application and conditions, different polymers, such as polypropylene (PP), poly(ethylene terephthalate), poly(ethylene naphthalate), poly(tetrafluoro ethylene), cross‐linked PP, and some cyclo‐olefines, have been considered. Nevertheless, cellular PP was the most investigated material because of its outstanding properties such as high piezoelectric d33 coefficient, flexibility, good fatigue resistance, good charge trapping properties, and low cost. In this review, recent advances related to the materials used for ferroelectret applications and their processing are discussed. The effect of different parameters such as pressure, electrical breakdown strength of the gas phase, presence of fillers, and service temperature on the d33 coefficient is presented and discussed.
Hybrid composite materials, which combine two or more types of fiber in a single matrix, have currently drawn the interest of researchers. This research investigates the tensile and impact properties of hybrid kenaf/glass reinforced metal laminates (FMLs) with different fiber orientations and stacking configurations. FMLs were formed by sandwiching the annealed aluminum 5052 sheets to the composite laminates using hot press molding compression technique. The tensile test was performed at a quasi‐static rate of 2 mm/min with reference to ASTM E8 whereas Charpy impact test was conducted using impact pendulum tester according to ASTM E23. Results showed that improvement in tensile and impact strength was observed in hybrid FMLs compared to kenaf fiber reinforced FMLs. Fiber orientation of ±45° reduced the tensile strength but increased the impact strength of FMLs in comparison with fiber orientation of 0°/90°. Overall, hybrid FMLs incorporated with a fiber stacking sequence of glass/kenaf/glass showed superior characteristic in tensile and impact performance.