In this work, a series of BaTi 1− x Mn x O 3 –polyimide films were prepared by simple solution casting method. For the preparation of composite films firstly, manganese doped barium titanate, BaTi 1− x Mn x O 3 (where x = 0.00, 0.01, 0.03, 0.05) was synthesized by sol‐gel process. The effect of Mn doping on its structural and dielectric properties was nicely explained. The highest dielectric constant value of 7,104 was obtained for BaTi 0.99 Mn 0.01 O 3 ( BTM n) nanoparticles with low dielectric loss value 2.44. It was observed that Mn‐doping concentration on barium titanate influences its crystal structure. Improved dielectric properties were reported for nanocomposite thin films containing BaTi 0.99 Mn 0.01 O 3 and polyimide ( PI ). A series of five homogeneous nanocomposite films were successfully prepared and were characterized thoroughly. The dielectric properties were studied as a function of frequency and loading percentage of BTM n in PI . The dielectric constant of the BTM n/ PI nanocomposite films increased from 3.23 to 8.63 with the increase in loading percentage of ceramic from 0 to 5 wt%, respectively. The nanocomposite films were flexible with good mechanical properties and the flexibility decreased with increase in loading percentage of BTM n. The films showed high thermal stability in nitrogen atmosphere up to 571°C with 10% weight loss and also exhibited high glass transition temperature up to 337°C.
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.
An oral route of administration is a most acceptable route for a patient, so we designed chemically cross‐linked polyethylene glycol‐co‐poly(methacrylic acid) oral hydrogels ( PEGMA 4000) by free radical polymerization method for pH ‐responsive colon target delivery of oxaliplatin ( OXP ). Polyethylene glycol ( PEG 4000) was cross‐linked chemically with methacrylic acid ( MAA ) in distilled water. Ammonium peroxodisulfate ( APS ) and N, N‐methylene bisacrylamide ( MBA ) were used as initiator and cross‐linker respectively. OXP was loaded in prepared hydrogels. FTIR , DSC, TGA, SEM, and XRD were conducted for characterization of developed hydrogels which endorsed the formation of new polymeric network. The pH ‐sensitive behavior of hydrogels was observed by swelling dynamics and equilibrium swelling ratio at low (1.2) and higher pH (7.4). Toxicity study was also conducted on rabbits to evaluate toxicity and biocompatibility of developed carrier system to biological system. Hydrogels with higher PEG 4000 concentration showed maximum swelling and higher drug loading at 7.4 pH . Toxicity study confirmed the developed hydrogels as non‐toxic and biocompatible for biological system. Resultantly, these hydrogels can become an excellent candidates for colon targeting of OXP to treat colorectal cancer with no toxicity.
Currently, microporous polymer materials are being studied extensively due to their attractive properties which allow for a wide potential of applications, such as prolonged‐release systems ( PRS ). The objective of the present work was to prepare and characterize porous microparticles of wheat gluten ( WG ) using the electrospray technique. The effect of the physicochemical parameters of the solution and electrospray technique parameters on the morphology and size of the materials obtained was studied. For all of the concentrations of WG , porous microparticles with sphere geometry were obtained. At higher concentrations of WG (8% w/v), higher values of viscosity (0.32405 ± 0.002 Pa·s), density (0.997 ± 0.0005 g/cm 3 ), and particle size (1.42 ± 0.71 μm) were obtained, while at lower concentration, high stability rheological is presented, which exhibited Newtonian fluid behavior. Characterization by scanning electron microscopy ( SEM ), Fourier transform‐infrared spectroscopy ( FT ‐ IR ), and X‐ray diffraction indicated that the material obtained has a potential application in the PRS industry.
The polyvinylidene fluoride ( PVDF )/multiwall carbon nanotube ( MWCNT ) composites, prepared by solution casting technique, can be used as electromagnetic interference ( EMI ) shielding material. The PVDF matrix shows MWCNT ‐dependent EMI shielding effectiveness, skin depth, morphology, mechanical, and dynamic mechanical properties. The transmission electron microscopy and field emission scanning electron microscopy images depict dispersion and distribution of MWCNT in PVDF matrix. The differential scanning calorimetry reveals MWCNT dependent crystalline melting temperature. The MWCNT is acting as reinforcing filler for PVDF matrix. The crystalline melting of PVDF and PVDF / MWCNT composites shows the occurrence of two endothermic peaks. Dynamic mechanical analysis of composites reveals MWCNT ‐dependent damping characteristics and storage modulus.
Poly (lactic‐co‐glycolic acid) (PLGA) is used to prepare biocompatible and biodegradable nanoparticles ( NP s). Unfortunately, PLGA NP s suffer from certain limitations such as short residence time when applied on mucosal tissues. Coating PLGA NP s surfaces with chitosan can improve their mucoadhesiveness and enhance the residence time. In this study, two molecular weights of chitosan (60 and 15 kDa) and three degrees of deacetylations ( DDA ) (92%, 75% and 55%) were used to study the effect of the molecular weight, concentration, and DDA of chitosan on the properties (size, PDI , charge, and mucoadhesion) of PLGA NP s. The results showed that the size of the NP s increases with increase in the concentration or molecular weight of chitosan but decreases with increase in the DDA . Also, coating PLGA NP s with chitosan give them a positive charge that increases as the chitosan concentration, DDA , or molecular weight increase. In general, all formulations with chitosan‐coated PLGA NP s had enhanced mucoadhesion, and this mucoadhesion improved as the chitosan concentration, DDA , or molecular weight increased.
This study was conducted to provide a quantitative understanding of the influence of the different solution and electrospinning variables on the morphology and the mean diameter of electrospun polystyrene nanofibers. In this regard, the effect of different solvents and ionic additives on the electrical conductivity, viscosity, and surface tension of the electrospinning solutions and thereby the morphology of nanofibers were examined. The results indicated that the morphology of the fibers is extremely dependent on the solvent's properties, especially volatility and electrical conductivity, and the ionic characteristics of additives. Finally, to estimate the optimal electrospinning conditions for production of nanofibers with minimum possible diameter, modeling of the process was undertaken using the response surface methodology. Experimentally, nanofibers with the finest diameter of 169 ± 21 nm were obtained under the optimized conditions, and these could be considered promising candidates for a wide practical range of applications ranging from biosensors to filtration.
This study was aimed to develop chemically cross‐linked matrix system of polycaprolactone‐co ‐ poly (methacrylic acid) through free radical polymerization method for controlled delivery of highly water‐soluble drug venlafaxine HC l. A hydrophobic polymer, polycaprolactone has been cross‐linked chemically with methacrylic acid by ethylene glycol dimethacrylate ( EGDMA ) as cross‐linking agent, and benzoyl peroxide was added as reaction initiator. Fourier transform infrared spectroscopy ( FTIR ), scanning electron microscopy, thermo gravimetric analysis ( TGA ), differential scanning calorimetry ( DSC ), and sol‐gel fraction were performed for characterization and structural analysis of polymeric system. Different feed ratios of polycaprolactone, methacrylic acid, and EGDMA were incorporated to investigate the effect of polymer, monomer, and degree of cross‐linking on swelling behavior and release pattern of model drug. pH ‐responsive nature of hydrogel was evaluated at low and high pH . FTIR , TGA , and DSC confirmed the formation of new cross‐linked network. pH sensitivity of hydrogel is revealed by increased swelling at pH 7.4. Toxicity study was also performed on rabbits to evaluate cytotoxicity and biocompatibility of developed formulation. Polycaprolactone hydrogels showed low swelling with increased polymer and cross‐linker concentration while swelling increased with high concentration of monomer. Swelling controlled in vitro drug release was found in hydrogels. Gel contents were increased with increase in ratio of polymer, monomer, and cross‐linking agent. Toxicity study endorsed that developed hydrogels were nontoxic and biocompatible.
Blood meal‐based thermoplastic protein (Novatein) was plasticized with up to 40 parts ethylene glycol, glycerol, propylene glycol, or tri(ethylene glycol) per hundred parts blood meal. The effect of plasticizers was investigated by relating the effect of equilibrium moisture content, phase separation, and protein secondary structure to the glass transition temperature and the mechanical properties. Plasticizers can diffuse through the polymer network and either be part of a protein‐rich phase where primary plasticization dominates or a plasticizer‐rich phase where secondary plasticization dominates. Equilibrium moisture content and added theoretical hydrogen bonding sites had the strongest correlation with the results. The point at which the equilibrium moisture content reached an equivalent moisture content ( POE ) to that of compositions without a plasticizer was found to be a critical point at which plasticization changes from primary to secondary, with a corresponding change in mechanical properties from brittle to ductile.
Polymer/graphene nanocomposites have shown promising potentials in energy storage applications due to their high permittivity, enhanced energy storage density, flexibility, and improved thermal and mechanical properties. The addition of graphene nanosheets to polymer matrix improves existing and incorporate new properties on such nanocomposites for various engineering applications. For instance, graphene nanosheets in polymer matrix are believed to form microcapacitors. Each microcapacitor contributes to the effective capacitance and dielectric constant of the composite. Although research has proved polymer/graphene composites as high dielectric constant materials, the major challenges facing their practical applications are high energy dissipation, high dielectric loss, and low electric field strength. In view of this, many researchers have shown efforts to minimize energy losses associated with polymer/graphene composites by insulating graphene nanosheets with different organic and inorganic substances. This is believed to prevent direct contact of graphene nanosheets and reduce the high mobility of π‐orbital or free electrons in the polymer matrix. However, maintaining high dielectric constant at low dielectric loss in polymer/graphene composites has not been achieved. If this challenge can be addressed in the future, polymer/graphene composites can yield energy storage capacity comparable with those of electrochemical capacitors. Therefore, this review considered energy storage and loss capacity of poly(vinylidene fluoride)/graphene nanocomposites from the perspective of electrical and dielectric properties. This article to the best of our ability reviewed various research results on dielectric constants/losses, breakdown strengths, energy densities, and electrical and thermal conductivities of poly(vinylidene fluoride)/graphene nanocomposites. Results extracted from the different published literature were tabulated and discussed at length to outline the reasons for the high dielectric loss in the neighborhood of percolation thresholds and the way forward.
The article presents the results of study related to upscaling chitin esterification reaction to the industrial scale. The obtained results allowed for creation of a product which can later be used in manufacturing biologically active dressing materials. The implementation of the laboratory scale showed that there is a possibility of upscaling the procedure to make it suitable for the needs of industry. Problems and risks associated with the transition to an industrial scale, such as process temperature control, time of the reaction and the method of isolation of product (emptying the industrial reactor from the reaction mixture), have been presented and discussed. The results of the tests showed the interdependence between the stages of production process, both in laboratory and in industrial scale. The realization of the presented project enabled solving the problems arising both from the preparation to the synthesis, carrying out the process itself, and obtaining the final product. An important factor in this case was to obtain the same physicochemical properties of the final product on both laboratory and industrial scale. The tests of biodegradation of butyric–acetic chitin copolyester in fresh human plasma and blood serum confirmed that two enzymatic degradation processes occur due to the presence of the enzymes in these body fluids. At the same time, enzymatic hydrolysis of ester bonds and enzymatic hydrolysis of the glycoside bonds of the main polysaccharide chain take place.
Three kinds of thermoplastic poly(urethane‐urea) PCM s were synthesized by two‐step condensation polymerization for thermal energy storage. Polyethylene glycol ( PEG ) was employed as the phase‐change functional chain, and three kinds of diamine compounds were individually adopted as chain extender. The chemical structure, crystalline properties, phase‐change behaviors, thermal stabilities, and reliabilities were studied by Fourier transform infrared spectroscopy, X‐ray diffraction, polarizing optical microscopy, and thermogravimetric, respectively. The crystalline structure of synthesized thermoplastic PCM s is identical to pure PEG , but the spherulite size decreases to some extent due to the confined crystalline region. The synthesized thermoplastic PCM s have proper phase‐change temperature with high phase‐change enthalpy of about 88 J/g. The synthesized thermoplastic PCM s are stable at their processing and working temperature with the onset degradation temperature higher than 250°C, and tensile strength reaches 20.59 MP a. Thus, the synthesized thermoplastic PCM s can be processed into desirable shape for the special applications in energy storage.
In this work, microcellular ABS foams were studied. A series of injection molding samples defined by a design of experiments was carried out to analyze the effect of shot volume, mold temperature, and injection velocity on the morphology, mechanical properties, and surface roughness of microcellular samples. A predominant influence of shot volume on the cell structure and tensile properties was evidenced. Higher cell densities and narrower cell size distributions were obtained at lower injection volume. However, elastic modulus and tensile strength were improved by increasing the shot size. The effect of mold temperature and injection velocity was secondary. Higher levels of mold temperature and injection rate provided finer cell morphologies, but their effects on the elastic modulus and tensile strength were negligible. The decrease in shot volume and increase in gas content led to poor surface quality, whereas it was greatly improved by raising both mold temperature and injection velocity.
The article presents unreported yet in the subject literature results of the research that aim was the examinations of the effect of wheat, rye, and triticale straws obtained from three different fragmentation methods, on the properties of natural rubber composites. Sieve analysis was performed to produce composites with variable filler size fractions. Characterization of mechanical and damping properties, tear strength, hardness, thermo‐oxidative aging performance, and cross‐linking density of obtained biocomposites were reported and studied. It was found that straw fillers with different particle size and shape significantly affected properties of natural rubber composites. The addition of filler (in an appropriate amount and degree of fragmentation) modified natural rubber biocomposites, improving mechanical and physical properties of composites or the ability to damp under the influence of compression stress.
In the injection molding process, mold temperature control is one of the most efficient methods for improving product quality. In this research, an external gas-assisted mold temperature control (Ex-GMTC) with gas temperature variation from 200 degrees C to 400 degrees C was applied to thin wall injection molding at melt thicknesses from 0.2 to 0.6 mm. The melt flow length was evaluated through the application of this system to the mold of a thin rib product. The results show that the heating process achieves high efficiency in the initial 20 s, with a maximum heating rate of 6.4 degrees C/s. In this case, the mold surface reached 158.4 degrees C. By applying Ex-GMTC to a 0.2 mm flow thickness, the flow length increased from 37.85 to 41.32 mm with polypropylene (PP) material and from 14.54 to 15.8 mm with acrylonitrile butadiene styrene (ABS) material. With the thin rib mold and use of Ex-GMTC, the mold temperature varied from 112.0 degrees C to 140.8 degrees C and the thin rib height reached 7.0 mm.
The article presents the results of the investigations of isotactic polypropylene composites with the following fillers: flame retardants, glass fiber, glass beads, and talc. The process of preparing composites and test samples is described. The investigations were performed using the DMTA method. The evaluation of thermal effects for the investigated molded parts using special device was also presented. The scope of the research included ten polypropylene composites with different content and type of fillers. These measurements allowed us to determine the influence of the filler type and content on the dynamic mechanical properties of iPP composites. The results will be useful for determining the scope of application of the mentioned materials in various fields of industry in the future.
The aim of this study was to investigate the effect of a new intensive plasticizing and mixing screw zone design on the effectiveness of the corotating twin-screw extrusion process for talc-filled polypropylene. The study determined the effect of the angle between the trilobe kneading elements forming the intensive plasticizing and mixing zone of the screws, the screw rotational speed, and the polypropylene/talc filling ratio on the characteristics of the extrusion process in a corotating twin-screw extruder EHP-2x20. The paper describes the experimental design and obtained results as well as the developed empirical models for selected variables of the extrusion process.