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 Pb 2+ from aqueous solution. When there was less PAA produced in a nanocomposite sample, there was higher Pb 2+ sorption capacity due to potentially less blocked alumina pores by in situ formed PAA . Isothermal and kinetic models for Pb 2+ sorption were applied by considering the effects of the initial Pb 2+ concentration and the contact time. The adsorption kinetics was best expressed using the pseudo‐second‐order equation. Through the isothermal studies, the maximum Pb 2+ 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 CO 2 methanation of the catalyst samples revealed that a solution pH value higher than p K a of PAA favored the formation of catalysts with high catalytic activity.
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 1 H 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 ( T g ) 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/m 2 , increased by 19.2% and 90.2%, respectively.
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.
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.
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.
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.
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.
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 d 33 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 d 33 coefficient is presented and discussed.
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.
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 ( LFRT s) 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.
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 objective of this article was to review the use of carbon black (CB) as a conductive filler in polymers and polymer blends. Important properties of CB related to its use in conducting polymers are discussed. The effects of polymer structure, molecular weight, surface tension, and processing conditions on electrical resistivity and physical properties of composites are discussed. Several percolation. models applicable to CB/polymer blends are reviewed. Emphasis is placed on recent trends using polymer blends as the matrix to obtain conducting composites at a lower CB loading. A criterion for the distribution of CB in polymer blends is discussed. (C) 2002 Wiley Periodicals, Inc.
In materials processing, quality and productivity are notably important and must be controlled for each product type produced. In the injection molding process, quality is measured as the extent of warpage of molded parts and productivity is measured in terms of the molding cycle time. This paper presents a new design of milled grooved square shape (MGSS) conformal cooling channels, which provide more uniformity in cooling with a larger effective cooling surface area compared to circular and other types of cooling channels with a similar cross‐section. This study examined the warpage of molded parts, and the cooling time, which affected the molding cycle time. A case study involving a front panel housing was performed, and the performance design of the MGSS conformal cooling channels was compared to that of conventional straight‐drilled cooling channels by simulation using Autodesk Moldflow Insight 2013 and validated experimentally. The result of MGSS conformal cooling channels is in a good agreement with the result of simulation. The MGSS conformal cooling channels reduced the warpage in both x and y directions by 14% to 54% and improved the cooling time by 65% compared to straight‐drilled cooling channels.
In this study, the tensile strength and M‐Rockwell hardness of polycarbonate (PC)‐nanoalumina composites are investigated under various processing parameters. For this purpose, PC using a twin‐screw extruder is melt compounded with nanoparticle of Al 2 O 3 in the presence of styrene‐co‐maleic anhydride (SMA) as the compatibilizer. Influences of weight percentage of nanoalumina and injection processing parameters including injection pressure and holding pressure (all in four levels) are investigated on tensile and hardness properties of nanocomposite samples using Taguchi's L 16 orthogonal array. The scanning electron microscopy (SEM) results reveal that an appropriate distribution of nanoparticles in polymeric matrix is achieved. According to the results, nanoalumina content is the most effective parameter on tensile strength and hardness with about 51% and 85% contribution, respectively. Results indicate that by addition 1.5 wt% of nanoalumina, the tensile strength and hardness of samples increase as much as 4.5% and 11%, respectively. Also, the results reveal that injection pressure and holding pressure are also effective parameters to change hardness and tensile strength.