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.
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.
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.
In this study, novel electrically conductive polymeric nanocomposites based on polybutylene terephthalate ( PBT ) filled with commercial carbon black ( CB ) and carbon nanotubes ( CNT s) at different relative ratios have been investigated. Field emission scanning electron microscope ( FESEM ) analysis revealed how a good nanofiller dispersion was obtained both by introducing CB and CNT . Melt flow index measurements highlighted that the processability of the nanocomposites was heavily compromised at elevated filler amounts, and the viscosity percolation threshold was established at 3 wt% for CNT s and between 6 and 10 wt% for CB nanocomposites. Differential scanning calorimetry ( DSC ) measurements evidenced how the presence of CNT slightly increased the glass transition temperature of the materials, and an increase of 12°C of the crystallization temperature was obtained with a CNT amount of 6 wt%. Also the crystalline fraction was increased upon CNT addition. Electrical resistivity measurements evidenced that the most interesting results were obtained for nanocomposites with a total filler content of 6 wt% and a CNT / CB relative amount equal to 2:1. The synergistic effect obtained with the combination of both nanofillers allowed the achievement of a rapid surface heating through Joule effect even at applied voltages of 2 V.
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.
Proton‐conductive electrospun nanofibers are promising potential materials for several advanced technological applications such batteries, sensors, and fuel cells. In this work, we prepared poly(vinyl butyral)/polyaniline ( PVB / PANI ) nanofibers via electrospinning and determined their proton conductivities. Structural characterization of the nanofibers was performed by FTIR analysis. Surface morphology of the nanofibers was determined by SEM and AFM . The addition of PANI significantly affected the fiber morphology, and over 90% reduction (with respect to neat PVB nanofibers) in the average nanofiber diameters was observed. Nanofiber mats were doped with polyphosphoric acid. The proton conductivity of the 2 wt.% PANI containing blend nanofibers was found as 18 × 10 −6 S/cm at room temperature and at 100% humidity.
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.
Aim of the present work was to develop alginate–pectin rafts by using box behnken design to provide symptomatic relief from gastroesophageal reflux disorders by forming floating gel or raft on the top of gastric contents. Sodium alginate and pectin were used as raft‐forming polymers, sodium bicarbonate as gas‐generating substance, and calcium carbonate for generation of calcium ions. Physical test of all compressed formulations were within pharmacopoeial limits. Effect of pH of medium on raft formation was observed by placing the formulation in different pH mediums. Raft was characterized by their strength, weight, volume, resilience, reflux resistance, thickness, buffering capacity, neutralizing capacity, floating lag time ( FLT ) and total floating time ( TFT ). Fourier transform infrared ( FTIR ) spectroscopy was performed to check the interaction between the polymers and other excipients. Raft was effectively formed at pH 1.2. Raft strength, reflux resistance, and thickness of optimized formulation APR 15 were 9.71 ± 0.013 g, 2670 ± 0.987 g, and 5.1 ± 0.045 cm, respectively. Raft resilience for the APR 15 was found to be greater than 480 min. TFT of APR 15 was greater than 8 hr with 50 s FLT . Buffering and neutralizing capacity were 12.70 ± 1.21 meq and 7.0 ± 0.34 meq, respectively. FTIR spectra showed no interactions between sodium alginate, pectin, and other excipients. This study demonstrated that alginate–pectin rafts are suitable for the treatment of gastro‐esophageal reflux disorders.
The aim of present work is to study the behavior of completely biodegradable starch‐based composites containing okra cellulosic fibers in the range from 5 to 25 wt%. The cornstarch matrix and composites were prepared by using urea–formaldehyde as a cross‐linking agent. The cross‐linked cornstarch matrix and its composites were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, and thermogravimetric analysis. Furthermore, thermal and different mechanical properties, i.e., tensile, compressive, and flexural strength of composites, were also studied. The thermal stability of fiber‐reinforced composite was increased as compared to starch matrix. The mechanical properties of composite such as tensile, compressive, and flexural have been found to increase with the increase in fiber content up to 15% loading. The composite specimens tested for tensile, compressive, and flexural strength at 15% fiber loading exhibited values of 17.78 ± 0.89, 33.55 ± 1.67 and 60.1 ± 3.01 MPa, respectively. Furthermore, the matrix and composites were subjected to biodegradation studies through the soil burial method.
Poly(aminoamide) ( PAMAM ) dendrimer with 3.5 generation was synthesized with ethylenediamine as the primary core and methyl acrylate. Also, Fe 3 O 4 nanoparticles as magnetic ones were modified by (3‐aminopropyl)triethoxysilane ( APTES ) to fabricate amine‐functionalized magnetic nanoparticles (Fe 3 O 4 @ APTES ). Then, 3.5 GD dendrimer was conjugated with Fe 3 O 4 @ APTES to obtain dendrimer‐grafted magnetic nanoparticles (Fe 3 O 4 @3.5 GD ). The core‐shell structure of Fe 3 O 4 @3.5 GD nanoparticles was revealed via TEM . Also, progression of each step was studied by FT ‐ IR , 1 H NMR , CHN elemental analysis, and thermal gravimetric analysis (TGA) . Vibrating sample magnetometer ( VSM ) was used to show that the synthesized nanoparticles keep their superparamagetic properties after synthesis process. Finally, in vitro cellular cytotoxicity was applied to evaluate the biocompatibility of synthesized structures and investigate the cytotoxic effect of grafted dendrimer using HeLa cells. As a resultS, about 20 wt. % of dendrimer grafting was obtained and good correlation was observed with VSM results. Also, 3.5 GD dendrimer showed low cytotoxicity to HeLa cells while after dendrimer grafting, toxicity of Fe 3 O 4 @3.5 GD slightly increased.
Wettability properties of polyetheretherketone (PEEK) activated and non‐activated by nitrogen plasma have been investigated. Moreover, the PEEK plates were covered with antibacterial chitosan and its wettability properties were also investigated. Surface topography was determined using SEM and optical profilometry and surface composition by FT ‐ IR and XPS . For determination of apparent surface free energy, the hysteresis approach ( CAH ), acid base ( LWAB ), and Owens–Wendt (O–W) theory were used. The equilibrium contact angles were calculated from the Tadmor theory and further used for apparent surface energy calculation applying the above‐mentioned approaches. Due to the surface plasma activation both the roughness of the surface and the polar component of apparent surface free energy increased. It is shown that nitrogen plasma activation of PEEK surface increases the adhesion of chitosan to the surface due to the combination effect of: (i) the increase in surface roughness, (ii) introducing the polar groups onto the surface.
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 (Et OH ). 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 Et OH : 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.
The 4‐(2‐bromoisobutyroyl methyl)styrene [ BBMS ] monomer was synthesized. The homopolymer of BBMS was prepared by free radical polymerization method. The decomposition behavior of P( BBMS ) was thermally investigated by thermogravimetric analysis ( TGA ). For thermal decomposition kinetics of poly( BBMS ), Flynn–Wall–Ozawa method was applied to thermogravimetry curves. The first step, which is one of the two decomposition stages, is comprehensively related to elimination of hydrogen bromide and the other step is related to a multi‐step process. The activation energy ( E a ) of thermal decomposition of the first step and 50% weight loss is 148.5 and 190.7 kJ/mol, respectively. The results showed that the side group elimination without chain breaking comprehensively proceeded at lower temperature, and at progressive temperatures subsequently the specific chain scission did so. Degradation of poly( BBMS ) did not lead to depolymerization. 1 H, 13 C‐ NMR , and FT ‐ IR analyses showed that the decomposition products during degradation of poly( BBMS ) to 260°C were comprehensively HB r and methacrylic acid. Electrically conducting graphene‐based poly( BBMS ) composites were prepared. The DC and AC electrical measurements of graphene‐based poly( BBMS ) composites were carried out. The AC dielectric measurements of poly( BBMS ) were investigated up to 70°C between 100 Hz and 20 kH z depending on the alternating current conductivities. The dipolar functional groups (C–O, C=O, and Br) of the BBMS segment possesses significantly affect the dielectric constant. Also, the activation energy profile of different graphene/poly( BBMS ) composites were revealed by measuring DC conductivity of individual composite material.
The deflection behavior of carbon nanotube‐reinforced composite plate is investigated numerically using the finite‐element method and the result accuracy is established via three‐point experimental bending test data. The physical composite panel model is realized with the help of new mathematical model based on the higher order kinematic theory and the responses are computed using the in‐house computer code in the MATLAB environment. Further, the efficacy of the current higher order finite‐element model has been established by comparing the deflection responses with those of the references, simulation values ( ANSYS ), and the in‐house experimentation including the experimental elastic properties. Finally, the effect of different design parameters, such as aspect ratio, thickness ratio, edge constraints including the types of load on the deflection and stress responses of the composite plate has been studied in detail.