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.
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 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.
Waterproof textiles have wide applications in many fields such as sportswear, protective clothing, and orthopedic dressing. Breathability is an important factor of clothing comfort. Nanofibrous layers have application in these fields due to their interconnected porous area and high surface area. In this work, two different nanofiber layers were fabricated and examined as waterproof and breathable layers. Polyurethane (PU) and PU/nylon 66 (hybrid) nanofiber layers were produced via electrospinning set up with different electrospinning durations. Some of the samples’ characteristics such as tensile strength, microindentation, air permeability, water vapor permeability (WVP), and contact angle of water were investigated. Moreover, a novel approach was applied for determining the performance of layers against acidic water to simulate acidic rain. The results show that the tensile strength, indentation force, and acidic waterproof ability of the layers increased with increasing the process duration, that is, while air permeability was decreased simultaneously. This work shows that the required force for indentation and strength of the hybrid layer was less than that of PU nanofiber layer. Also, the electrospun hybrid layers show better air permeability than the PU membrane but still have lower WVP, which affects the breathability of the layer.
Tricyclododecane dimethanol diacrylate (SR833s) was used to replace triethylene glycol dimethacrylate (TEGDMA) as a diluent monomer and mixed with 1,6‐bis(methacryloxy‐2‐ethoxy‐carbonylamino)‐2,4,4‐trimethylhexane (UDMA) to prepare 2,2‐bis[4‐(2‐hydroxy‐3‐methacryloyloxypropyl)‐phenyl]propane (Bis‐GMA) free dental resin system, and commonly used BaAlSiO 2 dental microfillers were added into UDMA/SR833s resin to prepare Bis‐GMA free dental composites. Physicochemical properties such as double bond conversion, polymerization shrinkage, water sorption and solubility, flexural strength, and modulus of UDMA/SR833s resin and relevant composites were investigated. The results showed that UDMA/SR833s resin had better physicochemical properties than UDMA/TEGDMA and Bis‐GMA/TEGDMA resins. Although UDMA/SR833s‐based composites had lower flexural strength and modulus than commercial dental composite Z250, they still met the International Organization for Standardization (ISO) standard requirement (in flexural strength and modulus for resin‐based dental materials). Except for the flexural strength and modulus, all the other properties of UDMA/SR833s‐based composites were comparable or better than those of Z250. Therefore, UDMA/SR833s resin and its relevant composites had potential to be used in dentistry as Bis‐GMA free dental materials.
Hexamethyldisilazane‐modified silica aerogel nanoparticles were used for in situ copolymerization of styrene and methyl methacrylate via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) to synthesize well‐defined random poly(styrene‐ co ‐methyl methacrylate) nanocomposites. Unique characteristics of the synthesized hydrophobic silica aerogel nanoparticles were evaluated by FTIR, thermogravimetric analysis (TGA), nitrogen adsorption/desorption isotherm, SEM, and TEM. Conversion and molecular weight determinations were carried out using gas and size exclusion chromatography, respectively. Adding of hydrophobic silica aerogel nanoparticles by 3 wt% results in a decrease of conversion from 92 to 76%. In addition, molecular weight of the copolymer chains decreases from 39,147 to 33,092 g⋅mol −1 ; however, the polydispersity index increases from 1.51 to 2.03. Copolymers composition was evaluated using 1 H NMR spectroscopy. Increasing thermal stability of the nanocomposites is demonstrated by TGA. Differential scanning calorimetry shows a decrease in glass transition temperature from 69.1 to 59.3°C by addition of 3 wt% hydrophobic silica aerogel nanoparticles.
From past few decades, emphasis of scientists is on the development of micro‐ and nanosized dosage forms to achieve the targeted and desired response from drugs. In this manner, they have developed microspheres, nanoparticles, niosomes, liposomes, etc. Now in recent past, work is going on the development of novel hydrogel microparticles that have more desirable response than conventional hydrogels. These newly developed hydrogel microparticles have a number of advantages over the conventional hydrogels as well as over other micro‐ or nanotechnologies. These are used to achieve either sustained or prolonged action as well as rapid release of drugs by complexation with hydrophilic polymers to enhance their solubility and ultimately bioavailability of poorly water‐soluble drugs. Various techniques are used to prepare hydrogel microparticles such as the ionic gelation method, spray drying, dispersion, photopolymerization ionotropic gelation method, free radical precipitation polymerization, inverse emulsion polymerization, free radical polymerization, etc. Certain polymers along with various types of initiators, cross‐linkers, and monomers are used in different concentrations depending upon the purpose of hydrogel microparticles. In recent review, we have focused upon the loading and drug release patterns from hydrogel microparticles, various technologies, and components applied in their preparations and applications in the pharmaceutical field. Hydrogel microparticles can be aimed for various purposes such as solubility enhancement of hydrophobic drugs, and targeted drug delivery, magnetic carriers; therefore, these are useful assets of pharmaceutical market.
In this study, the authors present a promising structure of shape‐stabilized phase change materials (PCMs) with remarkable thermal energy storage capacity as core/shell phase change nanofibers. In this regard, solutions of polyethylene glycol (PEG) (as an important category of PCMs) and cellulose acetate (CA) were used as core and shell solutions, respectively. Electrospinning with a coaxial spinneret was performed, and nanofibers with the mean diameter of 545 nm under the controlled condition were produced. The formation of the core/shell structure was verified by scanning electron microscopy, attenuated total reflection Fourier transform infrared spectroscopy, and transmission electron microscopy analyses. Moreover, thermogravimetric analysis results not only revealed the thermal stability improvement of PCM but also confirmed the presence of the core/shell structure too. Differential scanning calorimetry analysis was also performed to measure the thermal energy storage capacity of the core/shell phase change nanofibers before and after a thermal cyclic test. A major finding in the present study is that the thermal energy storage capacity of core/shell nanofibers after the thermal cyclic test is significantly higher (41.23 J/g) than initial one (14.77 J/g). Ultimately, it can be summarized that the special core/shell configuration provides desirable thermal stability and durability concurrently along with high thermal energy storage capacity.
This article is an overview of a novel polymerization technique known as admicellar polymerization (ADPM). ADPM is known as a “surface analogue” of emulsion polymerization, and it consists of three main steps that include (1) admicelle formation, (2) adsolubilization, and (3) polymerization. This review encompasses all the applications of ADPM in the field of textiles. ADPM has been used mainly for finishing of textiles, e.g., for achieving flame retardancy, UV protection, water repellency, etc. It has also been used for improving the adhesion of natural fibers used for the reinforcement of polymer matrices. It was observed that though an extensive and constructive research work has been conducted at laboratory level to understand ADPM process and explore its applications, its industrial acceptance in textiles has not been reported yet. Scope for further research has also been discussed in this review article.
The present study was done to develop and evaluate a matrix transdermal patch for bisoprolol fumarate. Different combinations of Eudragit RS 100 and HPMC E5 were used with polyethylene glycol 400 as a plasticizer on a polyvinyl alcohol backing layer by the solvent evaporation technique. The patches were evaluated for organoleptic characteristics and physicochemical parameters. Initial in vitro dissolution experiments were conducted to optimize formulation parameters prior to ex vivo skin permeation studies. Eudragit RS 100 and HPMC E5 (9:1) combination was studied for skin permeation because of the sustain release effect. The effect of control patch and permeation enhancer including Tween 80, propylene glycol, and DMSO were evaluated at 10%–40% concentration in the Franz diffusion cell using excised abdominal skin of rabbit. Different kinetic models were used to interpret the release kinetics and drug release mechanism. The patch M04‐PE containing 40% Tween 80 had better sustained release effect and had closer flux to the desired flux. M04‐PE followed the zero‐order kinetics with super case II release drug mechanism.
Experiments were carried out to study the extrusion characteristics of a vane extruder based on extensional flow. The effects of rotor speed and die pressure on output were studied and compared with a single screw extruder. The responses of melt pressure to rotor speed and die pressure were also studied in real timescale. Experimental results show that the die pressure has little effect on output, which is significantly different from that of single screw extruders. Oscillation pressure was introduced into the extrusion process by the dynamic convergent–divergent flow channel of the vane extruder. The oscillation frequency of melt pressure is four times of that of the rotor angular frequency. The die pressure has a little influence on the oscillation amplitude of melt pressure. The oscillation amplitude of melt pressure increases with the increase of rotor speed. The oscillation amplitude of melt pressure decreases along the extrusion direction.
In this study, sago starch was physically blended with low‐density polyethylene (LDPE) via the melt blending process followed by injection molding to produce LDPE/sago starch (LPS) composites. The sago starch content was varied from 5 to 30 wt% of LDPE. The addition of starch to LDPE reduced the melt flow rate (MFR), the tensile strength, and impact strength, whereas the tensile modulus, flexural strength, and flexural modulus increased. To improve poor mechanical properties of the LPS, LDPE/glycerol thermoplastic starch (LPGTS) or LDPE/2:1 mixture of glycerol and urea thermoplastic starch (LPMTS) was used in this study. The effect of compatibilizer (maleic anhydride) on properties of the LPMTS specimens was also investigated. The LPS, LPGTS, LPMTS, and maleic anhydride treated LPMTS (LPMTSM) samples were analyzed for the MFR, mechanical properties (tensile, flexural, and impact tests), thermal (TGA and DSC), and morphological properties. As a result, the incorporation of plasticizers or compatibilizer into LPS caused the considerable improvement in MFR and mechanical properties. Moreover, the presence of compatibilizer produced better properties for the LPMTSM sample than for the other samples, indicating better dispersion and homogeneity of starch to the matrix. In addition, thermal stability, DSC, and phase morphology were carried out for different LPS samples.
The purpose of present study was to develop chemically cross‐linked chitosan‐ co ‐poly(AMPS) hydrogel for pH‐responsive and controlled delivery of valsartan. Hydrogels were synthesized using the free radical polymerization technique. A polymer (high molecular weight chitosan) was chemically cross‐linked with monomer (2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS)) in aqueous medium. N ʹ N ʹ‐Methylenebisacrylamide was used as a cross‐linker. Sodium hydrogen sulfite and ammonium peroxodisulfate were used as initiators. Drug loading was performed with valsartan as a model drug. Characterization of hydrogels was performed by SEM, FTIR, and DSC. Hydrogels were evaluated for pH‐responsive behavior by the equilibrium swelling ratio and swelling dynamics at low and high pH. The developed cross‐linked network showed pH‐dependent drug release characteristics. Maximum swelling, drug loading, and release have been observed at pH 7.4. It is concluded that highly stable chitosan and AMPS‐based polymeric matrices are developed. These polymeric matrices have potential to be used as a carrier for controlled delivery of valsartan.
The aim of this study was to develop a simple and cost‐effective Febuxostat film coated tablet formulation by the direct compression method. To obtain the best optimized product, nine different formulations were developed using a central composite rotatable design. Avicel PH‐102, Magnesium stearate, and croscarmellose sodium were taken as independent variables. Micromeritic properties of powder blend showed excellent flow properties and were within USP limits. Tablets were compressed and before coating the core was tested for weight variations, hardness, thickness, friability disintegration, and dissolution. Tablets were film coated using hydroxypropyl methylcellulose 5cps, titanium dioxide, polyethylene glycol, and Instacoat blue, and again tested for the weight variations, assay, and single point dissolution. Three different dissolution media, i.e., 0.1 N HCl (pH 1.2) and phosphate buffer pH 4.5 and 6.8, were used for calculating the percentage release of Febuxostat and their release pattern was compared with an innovator brand by using the model‐independent methods such as similarity ( f 2 ), dissimilarity ( f 1 ), and model‐dependent methods such as first‐order, Hixson Crowell, and Weibull methods. The results revealed that Trial‐06 showed the maximum similarity, i.e., 81.18, 75.15, and 67.19 in three different pH dissolution media. Dissimilarity factor was also comparable in Trial 06, i.e., 5.21, 11.27, and 6.01 at pH 1.2, 4.5, and 6.8, respectively. Model‐dependent approaches showed the maximum r 2 values for Trial 06, i.e., greater than 0.900 for all models in the above‐mentioned pH, whereas the overall release kinetics followed the Weibull model. Selected formulation was kept at 40 ± 5°C and 75 ± 2% relative humidity for accelerated stability studies, and no specific change was observed.
In this work, we studied the parameters affecting the localization of multiwalled carbon nanotubes (MWCNTs) and its impact on morphology development of poly(methyl methacrylate)/polystyrene/polypropylene (PMMA/PS/PP) ternary blends, which originally have a thermodynamically preferred core–shell type morphology. We compared the results with the morphological prediction based on the thermodynamic approach. The MWCNTs localization and morphological features of nanocomposite samples were studied by means of melt linear viscoelastic experiments together with electron microscopy results. It was found that at 0.5 wt% of MWCNTs the original core–shell type morphology of the ternary blend samples almost remained intact. and this observation was independent of the sequence of feeding. At 1 wt% of MWCNTs, the core–shell morphology was retained only for those nanocomposite samples prepared using the sequential feeding mode. In addition, it was demonstrated that the thermodynamic predictions could be utilized for the nanocomposites containing low MWCNTs contents. However, this was not true for the nanocomposites with higher MWCNTs contents due to the predominating role of viscoelastic properties of the PS shell.
Weak mechanical possession is one of the limiting factors in application of hydrogels. To modify this inherent disadvantage, different approaches have been studied including synthesizing interpenetrating polymer network (IPN) and nanocomposite hydrogels. So, this study has focused on preparation of a novel full‐IPN structure based on anionic monomers of 2‐acrylamido‐2‐methylpropane sulfonic acid/acrylic acid–sodium acrylate via facile solution polymerization technique in an aqueous media with incorporation of graphene oxide (GO) nanosheets. Mechanical performance of materials in the “as‐prepared condition” and “swollen state” was characterized via tensile, compression, and rheology tests, respectively. Significant improvement of both elastic and storage modulus (ca. four times higher than pure hydrogel) is observed in this approach. Also dynamic mechanical thermal analysis results revealed that incorporation of high GO content (0.5 wt%) can suppress formation of full‐IPN structure, whereas low GO content has not such an effect, interestingly. Moreover, these novel hydrogels could easily be stretched or compressed followed by full recovery after unloading.
Local delivery of bioactive molecules to the inner ear via diffusion through the round window membrane is becoming an attractive approach to treat sensorineural hearing loss compared to systemic drug administration. Pluronics® (Lutrol F127) are a class of thermosensitive hydrogels that remain liquid prior to injection and rapidly gel under physiological conditions. They are, however, limited to short‐term drug release due to rapid hydrolysis in aqueous solution. Therefore, the aim of this study was to investigate an approach, using an ink‐jet printing system, to sustain the drug release by incorporating hydrogel microspheres within Lutrol F127. Various concentrations of Lutrol F127 and calcium chloride (CaCl 2 ) were examined by rheology to determine the optimum combinations to use for injection and then blended with inkjet‐printed alginate microspheres. Drug release (FITC‐Dextran) from Lutrol F127 alone reached completion in less than 24 h. Release from alginate spheres alone showed a burst release and reached 100% in 6 h. Interestingly, the incorporation of microspheres within Lutrol F127 allowed a more sustained release profile and a slower burst release. By varying the quantity of microspheres, concentration of alginate, or ionic cross‐linking ratio, the release profile can be adjusted to suit the desired application.
To the best of our knowledge, for the first time in this study, nano pore molecularly imprinted polymers were prepared using thymol as a template. A molecularly imprinting polymer with high performance for recognizing thymol was prepared by a novel surface molecular imprinting technique. First, silica nanoparticles were modified with γ ‐methacyloxypropyl trimethoxysilane (KH‐570) as a support material. Afterward, surface molecularly imprinted polymers (SMIP) were obtained through polymerization with methacrylic acid as the functional monomer and trimethylolpropane trimethacrylate as the cross‐linking agent. The produced polymers were characterized by transmission electron microscopy, scanning electron microscopy, Brunauer–Emmett–Teller analysis as well as Fourier transform infrared spectroscopy. The SMIP were obtained with the average core shell thickness of 17 nm, an average pore diameter of 3.9 nm, and the high specific surface area of 282.3 m 2 g −1 . The adsorption properties were revealed by batch binding experiments. The results indicated that the SMIP had higher binding capacity for thymol than its nonimprinted polymers. The selectivity of the SMIP obtained was clarified by using thymol and structurally related compounds. The selectivity coefficient of SMIP for thymol with respect to competition species obtained was 2.44, which revealed SMIP had good selectivity and site accessibility for thymol. A kinetic binding study showed that adsorption capacity of SMIP increased continuously with time and reached saturation adsorption at 90 min.
Four novel antimicrobial maleimido phenyl thiourea derivatives were synthesized from N ‐[4‐(chlorocarbonyl) phenyl] maleimide with phenyl thiourea and its derivatives ( p ‐methyl, o ‐chloro, and p ‐carboxy). Their structures were characterized by FTIR, 1 H NMR, mass spectra, and elemental analyses. Their antimicrobial activities against three types of bacteria ( Bacillus subtilis, Streptococcus pneumoniae , and Escherichia coli ) and against three crop‐threatening pathogenic fungi ( Aspergillus fumigatus , Geotricum candidum , and Syncephalastrum racemosum ) were investigated. The results revealed that these derivatives are effective in inhibiting the growth of the tested bacteria and fungi as indicated from the inhibition zone diameter and minimum inhibitory concentration. The antibacterial activities of these derivatives were more effective against Gram‐positive bacteria than Gram‐negative bacteria. These derivatives were investigated as thermal stabilizers for rigid poly(vinyl chloride) at 180°C in air by measuring the rate of dehydrochlorination and the extent of discoloration. The results reveal the greater stabilizing efficiency of the investigated derivatives as shown by their longer thermal stability periods ( Ts ) and lower dehydrochlorination rates in relation to dibasic lead carbonate, cadmium–barium–zinc stearate, and n ‐octyltin mercaptide industrial stabilizers. The stabilizing efficiency increases with the introduction of electron‐donating substituent groups in the aromatic ring of the stabilizer molecules. Moreover, the investigated stabilizers impart better color stability for the degraded samples as compared with the reference stabilizers.