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.
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.
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.
A more sustainable dialysis and water filtration membrane has been developed, by using the new, safer, bio-based solvent Cyrene (R) in place of N-methyl pyrrolidinone (NMP). The effects of solvent choice, solvent evaporation time, the temperature of casting gel, and coagulation bath together with the additive concentration on porosity and pore size distribution were studied. The results, combined with infrared spectra, SEM images, porosity results, water contact angle (WCA), and water permeation, confirm that Cyrene (R) is better media to produce polyethersulfone (PES) membranes. New methods, Mercury Intrusion Porosimetry (MIP) and NMR-based pore structure model, were applied to estimate the porosity and pore size distribution of the new membranes produced for the first time with Cyrene (R) and PVP as additive. Hansen Solubility Parameters in Practice (HSPiP) was used to predict polymer-solvent interactions. The use of Cyrene (R) resulted in reduced polyvinylpyrrolidone (PVP) loading than required when using NMP and gave materials with larger pores and overall porosity. Two different conditions of casting gel were applied in this study: a hot (70 degrees C) and cold gel (17 degrees C) were cast to obtain membranes with different morphologies and water filtration behaviours.
Topological insulator two-dimensional (2D) Bi2Se3 hexagonal nanoplates, which are highly insulating in the bulk and have a conductive topological surface state, have been prepared via an EG- (ethylene glycol-) sol method and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Bi2Se3/PVDF (polyvinylidene fluoride) nanocomposites with various Bi2Se3 contents have been fabricated by a tape-casting method. The microstructure and dielectric performance of the Bi2Se3/PVDF nanocomposites are studied. The dielectric constant of the dense nanocomposite films keeps a relatively low value of about 16 when the Bi2Se3 content is lower than 12 vol.% then suddenly increases to 36 with a critical Bi2Se3 content of 13 vol.% due to the percolation effect of the large aspect ratio of the 2D Bi2Se3 nanoplates. The study of the Bi2Se3/PVDF nanocomposite system is conducive to the exploration of high-performance dielectrics.
Some fiber types have a high aspect ratio and it is very difficult to predict their composites using traditional finite element (FE) modeling. In this study, an FE model was developed to predict the anisotropy of composites reinforced by short aramid fibers. Three fiber distribution types were studied as follows: perfectly aligned, normally distributed, and randomly distributed fibers. The elastic constants were obtained, and, for different alignment angles and parameters in the fiber orientation distribution function, their numerical results were compared to those of the Mori-Tanaka model. Good agreement was obtained; thus, the employed FE model is an excellent and simple method to predict the isotropy and anisotropy of a composite with high-aspect-ratio fibers. Therefore, the FE model was employed to predict the orientation distribution of a composite fiber with a nonlinear matrix. The predicted and experimental results agree well.
In this article, photoinduced electron transfer–reversible addition–fragmentation chain transfer ( PET ‐ RAFT ) polymerization of methyl methacrylate ( MMA ) was investigated at moderate temperature in N,N‐dimethylformamide with ZnO as photocatalyst. The polymerization has a living characteristic: a linear increase in molecular weight ( M n, GPC ), good agreement between experimental ( M n, GPC ) and theoretical molecular weights ( M n,th ), a decrease in molecular weight distribution ( M w / M n ) with increasing monomer conversion, and chain extension. The PET ‐ RAFT polymerization of MMA can be regulated by switching “ ON ” and “ OFF ” the light.
Temperature stability is critical to the consistency of product quality in the injection molding process, and it is very necessary to improve the temperature control accuracy under dynamic conditions. However, due to the large time delay, strong coupling, and the dynamic characteristics existing in the system, it is not an easy task to achieve precise temperature control in the injection molding process. In this paper, a new intelligent temperature compensation control strategy for the injection molding process under dynamic conditions is proposed in order to solve two key problems in the compensation control strategy: the compensation time and compensation quantity. A data-based feedforward iterative learning control (ILC) algorithm is designed to learn the optimal compensation time. Once the optimal compensation time is learned, a deep Q-learning algorithm which combined Q-learning with an artificial neural network (ANN) is proposed to learn the optimal compensation quantity. An experimental platform is designed to validate the superiority of the proposed method. Experimental results show that the proposed method can effectively improve temperature control accuracy under dynamic conditions. Meanwhile, the product consistency has also been improved.
With the increasing demands of environmental protection, the properties of water-borne coatings film must meet or exceed current solvent-based coatings. It is an important part of coating science for characterizing the film properties of polymers which was used in the water-borne and the solvent-based coating. In this study, UV-visible spectroscopy, gravimetric analysis, scanning electron microscopy, and electrochemical impedance spectroscopy were used to characterize the properties of the water-borne and the solvent-based poly(butyl acrylate/styrene) (P(BA/St)) copolymer films. The water-borne and the solvent-based P(BA/St) copolymer was synthesized by two methods. The copolymer had a Tg of approximately 14.4 degrees C, which was close to room temperature. The water-borne copolymers were prepared via a three-step film formation process, while the solvent-based copolymer films were prepared in two steps. Comparing the properties of the water-borne and the solvent-based films, the water absorption capacities decreased with increasing film formation times, and the film barrier properties and electrochemical properties of both films improved as the film formation time increased.
The ozonization modification of polystyrene (PS) was conducted in acidic condition to enhance the interfacial interaction between PS and polyvinyl alcohol (PVA). Infrared spectra results revealed that the carbonyl and hydroxyl groups were successfully introduced to the PS film by ozonization. The hydrophobic PS was turned to be hydrophilic to some extent by contact angle experiment, which led to the enhancement of interfacial adhesion between PS and PVA. In addition, the adsorption of PS to PVA was also improved. Nano indenter measurement indicated the interfacial interaction between PS film and PVA film was obviously enhanced by 40% after ozonization at room temperature for 2h in acidic condition, which will benefit for fabricating laser inertial confinement fusion container.
Antibacterial and biodegradable whey protein isolate (WPI-) gelatin nanocomposites were prepared using natural orange peel extract (OPE) in percentage of 7, 14, and 21% (v/v solution) and Cloisite 30B (5% w/w dry whey protein) made by a casting method. Mechanical, physical, and antibacterial properties of prepared films were measured as a function of OPE concentration. Higher concentrations of OPE led to higher antibacterial activity, tensile strength, and water solubility, but lower moisture content and transparency. The films microstructures were studied by field emission scanning electron microscopy (FESEM) and ATR-FTIR. Overall, the film containing 21%(v/v) OPE resulted in the best antibacterial, mechanical, and physical performance. Addition of tripolyphosphate (TPP) as a crosslinker to this sample led to the significant increase in transparency. Cloisite 30B, OPE, and TPP can therefore be used to improve the properties of WPI films as a promising natural food packaging.
Polymer modification can improve the stability and corrosion resistance of wood, but it could create defects inside wood during the modification processing. Detection of defects inside polymer-modified wood can reduce wood losses and prevent the occurring of defects. Data simulation and tomographic imaging of polymer-modified wood internal defects were carried out using electromagnetic waves with nondestructive testing. This study constructed the polymer-modified wood models, simulated the electromagnetic scattering wave, and used the total focusing method to perform tomography of the defects in the polymer-modified wood. By analyzing the imaging characteristics of different types of defects, the effectiveness of electromagnetic waves in the detection of internal defects of polymer-modified wood was proved. This method can be extended to test internal defects of other high molecular polymers.
Fiber print-through effect is a limitation to the use of carbon fiber-reinforced composites in space applications, namely, mirror telescopes. Replica method is used for the production of lightweight telescope mirrors. However, this method requires a polished mandrel, increasing considerably the final cost. In this work, we report a cheaper and simpler alternative production method, which consists in the addition of a carbon nanotube filled epoxy resin layer on the surface of carbon reinforced composites, in order to reduce fiber print-through of the materials. The influence of different carbon nanotube functionalizations, concentrations, and dispersion levels are also assessed. The surface properties are evaluated by interferometry (roughness and waviness) and scanning electron microscopy (morphology). The results show that the waviness, roughness, and consequently fiber print-though are considerably reduced with the addition of a thin layer of nonfunctionalized carbon nanotubes.
Multiwalled carbon nanotubes (MWCNTs) were synthesized by the reduction of ethyl alcohol with sodium borohydride (NaBH4) under a strong basic solvent with the high concentration of sodium hydroxide (NaOH). Nanocomposites of different concentration of MWCNT dispersed in poly(3,4-ethylene dioxythiophene) polymerized with poly(4-styrene sulfonate) (PEDOT:PSS) were prepared and deposited on a flexible polyethylene terephthalate (PET) polymer substrates by the spin coating method. The thin films were characterized for their nanostructure and subsequently evaluated for their piezoresistive response. The films were subjected to an incremental strain from 0 to 6% at speed of 0.2mm/min. The nanocomposite thin film with 0.1wt% of MWCNT exhibits the highest gauge factor of 22.8 at 6% strain as well as the highest conductivity of 13.5 S/m. Hence, the fabricated thin film was found to be suitable for piezoresistive flexible strain sensing applications.
The ethylene glycol diglycidyl ether (EGDE) as a viscosity reducer, plasticizing agent, and crosslinking agent was introduced into the adhesive system to improve the properties of the soy-based adhesive. The adhesive properties including viscosity, solid content, and shear adhesion of soy protein adhesive were measured. The morphology, infrared spectra, and crystallinity of the cured adhesives were evaluated with scanning electron microscopy (SEM), Fourier transform infrared (FTIR), and X-ray diffraction (XRD). The results showed that the viscosity of soybean flour (SF) adhesive was reduced by 48% and the solid content increased from 25.9% to 31.7% with the addition of 10 wt% EGDE. The wet shear strength of the plywood bonded by EGDE-modified SF adhesive was significantly improved owing to the formation of crosslinking structure in the adhesive system. The SEM, FTIR, and XRD results demonstrated that the crosslinking reaction among epoxy group of EGDE, the amino group of SF, and the hydroxyl groups of polyvinyl alcohol occurred successfully during the curing process.
A compatibilized blend membrane of polystyrene ( PS )/polyethylene‐vinyl acetate ( PEVA ) (50: 50) wt % was produced by compression molded at 180°C after irradiated by gamma ray at 50‐kGy dose. The influence of gamma radiation on the properties of the blend ( PS / PEVA ) membrane was investigated. The irradiated samples showed an increase in the degree of crystallinity due to the presence of additional chemical bonds as observed by X‐ray diffraction. As a result of irradiation, the miscibility of the two polymer matrix is enhanced by interfacial adhesion between the components in the blend polymer without any voids as observed by scanning electron microscopy. Furthermore, electrical conductivity in the blend ( PS / PEVA ) membrane was enhanced by introducing SO 3 H groups. Sulfonation process converts the blend from noncontact (5 × 10 −8 S cm −1 ) to semi‐contact (3.8 × 10 −3 S cm −1 ) by AC current at wet condition, and this can find applications in the fuel cells.
The repeatability precision of weight for injection molded products is important technical parameter to measure the quality and accuracy of injection molded products and evaluate the performance of injection molding machine. The influence of mold temperature, melt temperature, packing pressure, and packing time on the weight of microinjection molding products was studied by Taguchi orthogonal experiment. The influence of peak cavity pressure on the weight of products also was analysed. The experimental results show that the packing pressure is the most important process parameter affecting both the weight of the tensile and the impact specimens. With the increase of the packing pressure, the weight of the tensile and the impact specimens increases. When the peak cavity pressure reaches a certain value, the pressure value of the tensile specimen is 65MPa, and the pressure value of the impact specimen is 68MPa, the weight of the product increases quickly. The packing pressure increased from 85MPa to 100MPa, the weight of the tensile specimen increased from 0.544g to 0.559g, an increase of 2.7%, and the weight of the impact specimen increased from 0.418g to 0.425g, an increase of 1.7%.
In the present investigation, an attempt was made to formulate timolol maleate (TML) loaded polymeric nanoparticles of flax seed gum (FX) and chitosan (CH) for ocular delivery using ionic gelation method. The process of nanoparticle preparation was optimized using 2-factor, 3-level central composite experimental design. The optimal concentration of FX and CH that yielded nanoparticles with minimum particle size (267.06 +/- 8.65 nm) and maximum encapsulation efficiency (74.96 +/- 4.78%) was found to be 0.10% w/v and 0.08% w/v, respectively. The formulated nanoparticles revealed considerable bioadhesive strength and exhibited sustained release of drug in in vitro diffusion studies. The ex vivo transcorneal penetration study revealed higher corneal penetration of TML compared to marketed eye drops. The confocal scanning laser microscopy (CSLM) studies also confirmed the ability of nanoparticles to penetrate into deeper layers of cornea. The histopathological studies revealed corneal biocompatibility of nanoparticles. The nanoparticles were found to reduce the intra ocular pressure (IOP) in rabbits for prolonged period when compared to conventional eye drops. The results of the present study suggested a promising role of polymeric nanoparticles for ocular drug delivery in treatment of glaucoma.
In this work, gelatin was chemically cross‐linked using epichlorohydrin. Then, a series of gelatin‐based hydrogel nanocomposites containing CuO nanoparticles were prepared by immersion of gelatin hydrogel in CuCl 2 solution with different concentrations. Gelatin was chosen, due to its cheapness, nontoxicity, and biocompatibility. The structure and morphology of hydrogel nanocomposites were characterized by a number of techniques such as FT‐IR, XRD, energy dispersive X‐ray spectroscopy, and scanning electron microscopy. Then, swelling behavior of synthesized hydrogel nanocomposites in distilled water and different saline solutions was investigated. Their sensitivity to pH, biodegradability, and gel content was determined. Moreover, the water uptake and shrinking kinetics of hydrogel nanocomposites were evaluated. Finally, they were used as drug delivery agent, and the different concentrations effect of CuO nanoparticles present within the hydrogel nanocomposites compared with neat hydrogel on mentioned tests was studied.
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.