Showing papers in "Polymer Bulletin in 2020"

Poly(N-vinylpyrrolidone)-stabilized colloidal graphene-reinforced poly(ethylene-co-methyl acrylate) to mitigate electromagnetic radiation pollution

Abstract: Electrically conducting flexible polymeric nanocomposite has been fabricated through wet mixing method where conducting inclusion was acoustically exfoliated pristine graphene nanosheets. Colloidal graphene is the key component here which has been prepared by acoustic cavitation in the presence of macromolecular dispersion. The significance of the method is their green preparation strategy without using any chemical reducing agents and long self-life without drastic sedimentation rate. Thermoplastic poly(ethylene-co-methyl acrylate) was chosen as flexible phase where graphene sheets were distributed to make spatial conducting network architecture. The prepared nanocomposites showed 0.259 S/cm DC electrical conductivity and frequency-independent electroconducting character in higher concentration. The electromagnetic interference shielding effectiveness of the nanocomposites was around 30 dB in ~ 1.0 mm thickness in X-band (8.2–12.4 GHz) frequency range without affecting its mechanical toughness and flexibility. Thus, such pristine graphene-based thermoplastic matrix could be a desirable replacement of metallic shielding materials on the ground of flexible, conducting, lightweight characteristics.

Anticorrosive property of hexafunctional epoxy polymer HGTMDAE for E24 carbon steel corrosion in 1.0 M HCl: gravimetric, electrochemical, surface morphology and molecular dynamic simulations

Abstract: The novel hexafunctional epoxy polymer synthesized in our laboratory, namely hexaglycidyl trimethylene dianiline of ethylene (HGTMDAE), has been evaluated as corrosion inhibitor of E24 carbon steel (CS) in the aggressive environment (1.0 M HCl) by using a gravimetric measurements, electrochemical impedance spectroscopy (EIS) and molecular dynamic simulations (MD). However, to better understand information on the surface adsorption mechanism of the CS/HGTMDAE/1.0 M HCl medium, the corrosion protection was investigated by using the scanning electron microscopy. Furthermore, the gravimetric test results showed that the inhibition performance will increase with increasing in the concentration of HGTMDAE to reach a maximum of 90% at concentration 10−3 M. In addition, the EIS has a better inhibitory efficiency of 95% for the optimal concentration (10−3 M) of the epoxy polymer HGTMDAE. Moreover, the polarization results indicate that this macromolecular binder acts as a mixed inhibitor. The epoxy polymer formed protective layer on surface of the E24 CS by adsorption according to Langmuir model. The inhibitor adsorption phenomena have been tested through the estimation of kinetics thermodynamic parameters. MD simulations were used to describe the electronic and adsorption properties of epoxy polymer HGTMDAE.

5-Fluorouracil and curcumin co-encapsulated chitosan/reduced graphene oxide nanocomposites against human colon cancer cell lines

Abstract: Recent attention on chemotherapy against cancer is to explore the effective therapy through targeted delivery of anticancer agents to the tumor site by manipulating pharmacokinetic properties of nanocarriers. 5-Fluorouracil (5-FU) and curcumin (CUR) loaded chitosan/reduced graphene oxide (CS/rGO) nanocomposite has been prepared via simple chemical method. The polymer matrix-type chitosan/rGO nanocomposite, before and after encapsulation, has been analyzed by various characterizations. Entrapment and loading efficiencies were estimated. The results that demonstrated higher entrapment efficiency (> 90%) were achieved by CS/rGO nanocarrier. Various kinetic models were used to analyze the release model and to elucidate the release mechanism of the drug from CS/rGO nanocomposite. The synergistic cytotoxicity was observed on addition of 5-FU + CUR-loaded CS/rGO nanocomposite which shows the effectiveness of the system toward the inhibition of growth of HT-29 colon cancer cells. The better cytotoxicity with an IC50 of 23.8 μg/mL was observed for dual-drug-loaded nanocomposite.

A detailed comparative study on electrical and photovoltaic characteristics of Al/p-Si photodiodes with coumarin-doped PVA interfacial layer: the effect of doping concentration

Abstract: In this study, three different poly(vinyl alcohol) (PVA) films doped with weight percentages of 0.05, 0.10 and 0.20 coumarin were coated on p-Si wafer via spin-coating method for the purpose of investigating the interaction of coumarin dopant with polymer host at molecular level. Therefore, metal–polymer–semiconductor (MPS) structures were formed and their current–voltage (I–V) and admittance measurements were taken to compare the main electrical parameters of the MPS structures with different film thicknesses. The values of ideality factor (n), barrier height (Φb), rectification ratio (RR = IF/IR), series resistance (Rs) and energy-dependent profiles of surface states (Nss) were calculated using the forward bias I–V data. There exists increasing trend for Nss values from mid-gap energy of Si toward the bottom of conductance band. The highest values of RR and photosensitivity (Iphoto/Idark) were found as 4.62 × 104 at ± 4 V for the MPS structure with 0.10 wt% coumarin doping level, respectively. The photoresponse of the structures was also analyzed using $$I_{\text{ph}} = AP^{m}$$ relation, and the value of m was obtained from the slope of ln(Iph)–Ln(P) plot for each diode as 1.48, 1.27 and 1.57, respectively. Experimental results suggest that 0.10% coumarin-doped PVA caused MPS structure to reveal better performance considering higher RR and lowest Nss, and so it can be considered as an alternative interfacial layer material for replacing traditional insulators.

Investigation of the gas permeability properties from polysulfone/polyethylene glycol composite membrane

Abstract: In this research, the effect of polyethylene glycol (PEG) molecular weight on permeability and selectivity of polysulfone/polyethylene glycol (PSF/PEG) composite membrane is investigated. Polyethylene glycol with molecular weights of 4000, 6000, and 10,000 is applied. It is shown from the results that PEG applied in composite membranes with molecular weight of 1000 had the best diffusivity in comparison with the other composite membranes containing PEG with lower molecular weights. In addition, it is perceived that the permeability of CO2 from PSF/PEG10000 composite membranes has increased with enhancing weight percent. CO2 permeability into PSF/PEG composite membranes containing 20 wt% PEG10000 is calculated 7.64 barrer (1 barrer = 10−10 cm3 (STP) cm/cm2 s cmHg). The ideal selectivity for CO2/N2 gas pair in PSF pure membrane and composite membranes containing 10 wt% and 20 wt% PEG10000 are calculated 26.57, 30.61, and 32.12, respectively. Finally, the morphology and membrane structure of the membrane were evaluated with infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and tensile strength test.

Tailoring the optical and dielectric properties of PVC/CuO nanocomposites

Abstract: The solvent casting method has been applied to prepare PVC/CuO nanocomposite films with CuO ratios (0, 2.5, 5.0, 10.0 and 15.0 wt%). X-ray diffraction (XRD), Fourier transform infrared spectroscopy, optical absorption and dielectric experimental analysis are applied to these nanocomposite films. The CuO nanoparticles have been prepared by using sol–gel method. XRD pattern analysis revealed the formation of CuO (30 nm) single-phase with monoclinic structure and space group C2/c and the amorphous structure of polyvinyl chloride (PVC) matrix. Energy-dispersive X-ray data revealed the increase in CuO content, and scanning electron microscopy morphology analysis approved the dispersion of CuO nanoparticles on the PVC film surface. The optical absorption increased with CuO content, while the transmission decreased. Both direct and indirect energy gaps decrease, while the Urbach energy increases as CuO content increases. The real dielectric permittivity enhanced as the concentration of CuO increased and the imaginary permittivity showed single relaxation at high frequency. The estimated values of both static and high-frequency dielectric constant increased as CuO percentage increases. The presence of CuO causes increase in the loss tangent values for the PVC/CuO polymer films.

DFT study of the application of polymers cellulose and cellulose acetate for adsorption of metal ions (Cd 2+ , Cu 2+ and Cr 3+ ) potentially toxic

Abstract: In this work, the functional density theory calculations were performed to investigate the interaction mechanism (adsorption) of Cu2+, Cr3+ and Cd2+ metal ions in cellulose (CE) and cellulose acetate (AC). After the optimization of the structures at their energy minima, the following analyses were performed: molecular electrostatic potential (MEPs), reactivity indexes, frontier molecular orbitals (FMOs), structural parameters, interaction energy and QTAIM analysis. The study of MEPs, FMOs and reactivity indexes showed that it is possible to predict the site of interaction. Structural analyses have proven that the interactions occur. The calculated electron interaction energies showed that all ions interact with the matrix of CE and AC, and among them, the Cr3+ ion was the one that interacted most effectively. Finally, the QTAIM analysis allowed to characterize the nature of the interaction, in which the interactions of cellulose acetate-Cr3+ and cellulose-Cu2+ presented electrostatic character, and the other interactions were partially covalent.

Modern biopolyamide-based materials: synthesis and modification

Abstract: The wider use of renewable feedstock in structural applications, where high mechanical performance is required, can be achieved by the application of recently developed engineering biopolymers and their further modification by micro- and nanoparticles. In this review, we present the current state of the art of biopolyamide materials for structural and functional applications. The overview includes all stages of the manufacturing—from the synthesis of building blocks, through the synthesis of polymers and its physical modification, with special emphasis on the properties of the obtained engineering biocomposites as a final product of modern polymer technology. In the first part, the synthetic routes of bio-derived counterparts of common polyamides as well as specialty polymers with functional properties arising from the complex structure of biochemicals were exemplified. The development of environmentally friendly composites and nanocomposites based on biopolyamides and natural fillers, such as plant fibers or cellulosic nanofibers, was of particular interest due to preserved sustainable character of such materials.

Thermal characterization by DSC and TGA analyses of PVA hydrogels with organic and sodium MMT

Abstract: Polyvinyl alcohol (PVA) hydrogels were prepared by a cyclic freezing–thawing technique without any cross-linker agent, using PVA and Maghnite water dispersion with different ratios. The obtained results have shown a higher thermal stability of samples with sodium than with alkylammonium Maghnite. Furthermore, thermal stability was maximum at the lowest investigated Maghnite/PVA ratio, but higher than for the pure PVA at all the investigated compositions. DSC analysis has shown both a low crystal degree and a low heat capacity jump at the glass transition temperature for samples with high Maghnite content. This phase does not seem to depend on the kind of cations, sodium or alkylammonium into the gallery of the clay.

Chitosan–polyaniline–copper(II) oxide hybrid composite for the removal of methyl orange dye

Abstract: Chitosan–polyaniline–copper(II) oxide (Ch–PANI–CuO) nanocomposite has been synthesized using batch adsorption method. It was characterized using UV–Vis, scanning electron microscopy (SEM), X-ray diffraction and Fourier transform infrared (FTIR) and transmission electron microscopy (TEM). The SEM and TEM showed that the surface of the nanocomposite was rough and porous with pleats, which is probably responsible for better dye adsorption. The maximum percentage of dye degradation was found to be 94.6% for methyl orange dye. The desorption study and FTIR results confirmed the presence of hydroxyl and amino functional groups. The results clearly indicate that the polymer matrix could be used as an adsorbent for the removal of methyl orange from aqueous solution.

Study of hybrid alginate/gelatin hydrogel-incorporated niosomal Aloe vera capable of sustained release of Aloe vera as potential skin wound dressing

Abstract: Nowadays, wound dressings serve as advanced skin products, which mainly aim to accelerate the wound healing process. The wound dressings with a potential of localized and prolonged release of therapeutic agents have attracted tremendous attention. In this study, synthesis of a sustained release of niosomal Aloe vera (AV) loaded in alginate/gelatin (AG) hybrid hydrogel is aimed at improving skin regeneration as wound dressing. For this purpose, AV-loaded niosomes are synthesized and incorporated in the hybrid AG hydrogel. The size and polydispersity index (PdI) of niosomes, AV entrapment efficacy and AV in vitro release are characterized. In addition, the hydrogel characteristic, such as swelling ratio, degradation behavior and mechanical property, are studied. MTT assay is utilized to evaluate the effect of AV incorporation and release on the proliferation of fibroblast cells. Results demonstrate that size, PdI and EE% of AV-loaded niosomes are 270.080 nm, 0.108 and 42.039 ± 4.090%, respectively, and in vitro release of AV is about 20% after 7 days. AG hybrid hydrogel loaded by niosomal AV shows an extended sustained release manner, where its swelling ratio and percentage of degradation are 60 wt% after 72 h and 70 wt% after 6 days, respectively. The average Young’s modulus of the hybrid hydrogel is measured around 12.64 ± 1.3 kPa, which seems suitable as a wound dressing. Finally, MTT assay confesses an increased fibroblast proliferation in the presence of AV, particularly in the niosomal AV-loaded hydrogel. Concludingly, alginate/gelation hybrid hydrogel incorporated with niosomal AV, with sustained release potential can be suggested as a promising candidate for wound dressing applications.

A review on polyimide reinforced nanocomposites for mechanical, thermal, and electrical insulation application: challenges and recommendations for future improvement

Abstract: Polyimide nanocomposites have drawn much attention as mechanical, thermal, and electrical insulation materials due to its superior dielectric, thermal stability, and corona resistance properties. The polyimide nanocomposites are defined as substance of polyimide matrix reinforced with certain weight percent of nanofillers. Researchers have demonstrated the usage of polyimide nanocomposites in mechanical, thermal, and electrical insulation application. However, the nanocomposites are noted to face interfacial bonding issues, which have affected their mechanical performance for thermal and electrical insulation properties. The dielectric behaviour and corona resistance lifetime of the polyimide nanocomposites are reportedly degraded over a long-term exposure to high-temperature environment. Although, there have been an advancement on improving the mechanical, thermal, and electrical properties of polyimide nanocomposites for multifunctional insulations. This review summarises the effects of nanofillers, such as silica (SiO2), titania (TiO2), alumina (Al2O3), graphene’s, nanotubes, boron nitride and some other fillers on the mechanical, thermal, and electrical properties of polyimide nanocomposites for insulation application. The authors concluded the review with advancement, challenges and recommendations for future improvement of polyimide nanocomposites as an insulation material. Thus, the review study offers discernment into the improvement and selection of polyimide nanocomposites material for mechanical, thermal, and electrical insulation. More so, the review will also give a way for further research.

Synthesis and characterization of iota-carrageenan biopolymer electrolyte with lithium perchlorate and succinonitrile (plasticizer)

Abstract: A non-toxic and bio-active natural polymer electrolyte iota-carrageenan (i-carrageenan) with LiClO4 has been prepared by conventional solution casting technique. Succinonitrile (SN) plastic crystal has been used as an additive to optimize the conductivity of i-carrageenan biopolymer electrolytes. The obtained biopolymer electrolytes are characterized by X-ray diffraction, Fourier-transform infrared, differential scanning calorimetry and AC impedance studies. The highest ionic conductivity at room temperature is 3.57 × 10−4 S cm−1 for the film composition of 1.0 g i-carrageenan/0.5 wt% LiClO4. The inclusion of 0.3 wt% of SN into this polymeric system has improved the value of ionic conductivity to 3.33 × 10−3 S cm−1 at ambient temperature, and the activation energy is found to be very low for this concentration. Transference number analysis also reveals that the cause of conductivity is primarily due to ions with the highest ionic transference number of 0.92 (Wagner’s method) and cationic transference number of 0.58 (Bruce and Vincent method) for the highest conducting plasticized sample. Transport parameters of diffusion coefficients and mobility of cations and anions are also in tune with the conductivity results. Linear sweep voltammetry shows that the highest conducting sample is electrochemically stable up to 2.36 V without SN, and it is 3.1 V with SN addition. These results recommend the suitability of the fabricated polymer electrolyte for lithium ion battery system.

Preparation of chitosan/gelatin composite foam with ternary solvents of dioxane/acetic acid/water and its water absorption capacity

Abstract: Green superabsorbent polymer has attracted more attention in recent years. In this study, the natural-derived polymers of chitosan and gelatin composite foam with excellent water absorption capacity (WAC) were successfully prepared with ternary solvents. The optimal process parameters are: chitosan/gelatin mass ratio of 90:10 (w/w), ternary solvents of dioxane/acetic acid/water = 2:0.8:77.2 (v/v/v), chitosan/gelatin total concentration of 1% (w/v), and freezing temperature of − 196 °C. Under the optimal conditions, the prepared chitosan/gelatin composite foam reached water absorption equilibrium less than 60 min and the WAC was 651 g/g. The composite foam also had excellent WAC in a wide range of pH, temperature, and salt concentration. It demonstrates that water absorption capacity can be improved by combining chitosan with gelatin without chemical modification and optimizing the physical microstructure by the ternary solvents system and freezing temperature. The non-toxic chitosan/gelatin composite foam with super water absorbency can find potential applications especially in the fields of hygiene and biomedicine.

Swelling and drug delivery kinetics of click-synthesized hydrogels based on various combinations of PEG and star-shaped PCL: influence of network parameters on swelling and release behavior

Abstract: Polyethylene glycol (PEG)- and polyethylene glycol–polycaprolactone (PEG–PCL)-based hydrogels were synthesized with various compositions of prepolymers by using ROP and click chemistry methods. Relevant prepolymers were characterized by 1H NMR and FTIR spectroscopy. In order to study the influence of network parameters on swelling and release kinetics, experimental data were approximated by several mathematical models including zero order, first order, Higuchi and Korsmeyer–Peppas to determine the kinetics of swelling and diclofenac sodium release from hydrogels. The obtained results showed that the swelling and release data were best fitted to Korsmeyer–Peppas model. The results of the swelling study showed that the swelling properties of the hydrogels varied with the changes in the PEG molecular weights, as well as concentration of PCL. All of the hydrogels showed non-Fickian diffusion, but when PCL concentration increased and PEG molecular weights decreased, the n values were decreased and reached n = 0.5 (Fickian diffusion). The kinetics of diclofenac sodium release from hydrogels showed similar behavior so that in F hydrogels with the highest PCL concentration, the release mechanism fully changed from non-Fickian to Fickian diffusion. In other words, with increasing cross-link density and PCL concentration, the swelling degree and flexibility of networks decreased. Therefore, the swelling and release mechanism changed from non-Fickian to Fickian diffusion.

Nanoparticle opsonization: forces involved and protection by long chain polymers

Abstract: The interactions between nanoparticles and opsonins have been studied thoroughly through various models in order to elucidate the basic underlying forces of such interactions. The results of these studies give an insight about the nature of interactions and help devising methods for inhibiting opsonization. Opsonization poses major hindrance in functioning of nanoparticles. A number of forces like electrostatic, hydrophobic, van der Waal forces, etc., are involved. Among the techniques used for nanoparticle protection, PEGylation has been extensively studied and used to increase circulation times of nanoparticles. Polyethylene glycol (PEG) and PEG-like and other hydrophilic polymers with long chains have flexible nature that helps reduce opsonin adsorption on nanoparticles and hence make them stealth and unrecognized by elimination mechanisms of our body. It is suggested that polymer chain length is significant in reducing interactions between nanoparticles and opsonins. This review gives an outlook of driving forces of particulate adsorption and various mechanisms of how polymer chain length affects protein–particulate interactions.

Coating of modified poly(ethylene terephthalate) fibers with sericin-capped silver nanoparticles for antimicrobial application

Abstract: In this work, a kind of amine-type PET fibers was synthesized by reacting hexamethylenediamine (HMDA) with methacrylic acid-g-poly(ethylene terephthalate) (PET-g-MAA) fibers for the adsorption of silk sericin-capped silver nanoparticles (S-AgNPs) to produce antimicrobial fibers. Firstly, PET fibers were grafted MAA by using free radical polymerization technique and HMDA was covalently connected to the grafted PET fibers. Then, for S-AgNPs synthesis, 10 mL of AgNO3 solution (1 mM, 5 mM and 10 mM) was mixed with 10 mL of 1% sericin solution at pH 11. The obtained solution was stirred at room temperature for 24 h. The color change from transparent to yellow–brown indicated the formation of S-AgNPs. AgNPs formation was also determined by measuring the absorbance spectra of S-AgNPs between 300 and 600 nm using UV–Vis spectrophotometer. To determine the antimicrobial properties of S-AgNPs, agar-well diffusion tests were performed. 5 mM and 10 mM S-AgNPs groups showed antimicrobial activity on Escherichia coli and Staphylococcus aureus. After characterization of the synthesized S-AgNPs with UV–Vis spectrophotometer, Zetasizer, FTIR and TEM, the modified PET fibers were coated with S-AgNPs (5 mM and 10 mM). The S-AgNPs coated PET fibers were characterized by FTIR, SEM and X-ray fluorescence spectroscopy. The antimicrobial activities of the obtained PET fibers were investigated on S. aureus and E. coli bacteria by using disk diffusion test. It was found that the S-AgNPs coated modified PET fibers exhibited antimicrobial activities toward both gram-positive and gram-negative bacteria. The resulting polymeric PET fibers containing nano-silver can be used as an antimicrobial surface for many applications such as wound dressing.

A comparison study on the mechanical properties of composites based on kenaf and pineapple leaf fibres

Abstract: The arising trend of using natural fibres in the composite materials has stimulated the continuous exploration of their mechanical properties. The positive environmental behaviours of natural fibres are the driving factor that allows them to gain their wide acceptance in industries. However, the mechanical behaviour of natural fibre-based composites is still not fully explored. In this research study, the mechanical properties of composite materials with different types of natural fibre and various fibre compositions were investigated. The polypropylene-based composite materials were fabricated through hot press compression moulding method using a hydraulic hot press machine. The composites were then subjected to mechanical tests to study the tensile, flexural and impact properties of such materials. The results demonstrated that the tensile strength and flexural strength of pineapple leaf fibre (PALF)-based composites were 7.83% and 54.23% higher than kenaf-based composites at a fibre content of 30 wt%. Moreover, the impact strength of PALF-reinforced composites was 3.08% and 5.56% higher than kenaf fibre-reinforced composites in the flatwise and edgewise impact orientations. Overall, composites with 30 wt% evidenced the top most mechanical properties irrespective of types of plant fibre.

Preparation and characterization of silica nanoparticles from sugarcane bagasse ash for using as a filler in natural rubber composites

Abstract: Silica nanoparticles from sugarcane bagasse ash (SBA) were prepared from sol–gel process. Particle size, specific surface area, morphology, chemical composition and chemical structure of SBA and prepared silica nanoparticles were characterized. The effect of drying techniques such as freeze drying (FD) and heat drying (HD) on the properties of silica nanoparticles was investigated. High purity of silica nanoparticles in size range of 90 ± 10 nm were successfully prepared. FD provided silica nanoparticles with high specific surface area and high porosity compared to conventional HD. The effect of silica nanoparticle contents on cure characteristics, mechanical properties, and morphology of natural rubber (NR) composites was studied. Scorch time of NR composites was increased with an increase in silica nanoparticle content due to the disturbance of vulcanization process by silica surface. FD-silica/NR composites provided longer scorch time and cure time compared to HD-silica/NR composites due to higher active surface area of FD-silica. Modulus and hardness of NR composites were increased while elongation at break was decreased with an increase in silica nanoparticle content. Tensile strength of the composites increased with silica nanoparticle content and tended to reduce at high silica nanoparticle content. FD-silica/NR composites exhibited better mechanical properties than HD-silica/NR composites due to better filler-rubber interaction.

Stretchable strain sensors based on polyaniline/thermoplastic polyurethane blends

Abstract: Thermoplastic polyurethane/polyaniline-based stretchable strain sensors were prepared via in situ polymerization of aniline in the TPU solution in the form of thin films. The sensors where characterized for morphological and thermal properties, mechanical hysteresis and cyclic piezoelectric performance. Thermogravimetric analysis showed blends to be thermally stable up to 230 °C. Electrical conductivity increased up to 30 wt% of Ani.DBSA loading after which a decline was observed due to reduced conversion of aniline monomer to polyaniline. Piezo-resistive measurements also showed a decrease in electrical conductivity upon stretching due to disconnection mechanism between Ani.DBSA particles. The cyclic piezo-resistive properties were evaluated at a strain of 10%. The sensors showed a gauge factor of 2.59. The dispersion and distribution was uniform at all levels of Ani.DBSA loading as visualized by SEM analysis. Beside uniform dispersion, SEM analysis also revealed polyaniline chains connecting with the polyurethane matrix which increases its conductivity. Hence, the proposed sensors can be employed as flexible strain sensors.

Interpenetrating polymer network as a pioneer drug delivery system: a review

Abstract: Interpenetrating polymer network (IPN) is an enterprising drug delivery system, comprising of two polymers with several advantages like stability, biocompatibility, high swelling capacity and biodegradability which plays an important function in targeted and controlled drug delivery. IPN acquired appreciable focus in the pharmaceutical sector mostly for the last few decades because of their utility in biomedical applications like tissue engineering and drug delivery at the target site at desired rate. For the past few years, different types of polymers obtained from natural or artificial sources have been used to prepare the IPN, resulting in improved properties; thus, IPN is considered in the category of the novel technologies demonstrating the superior performances as compared to the conventional technique. IPN development leads to the formation of dosage form with reduced side effects and prolonged drug action. The current topic includes IPN, types of IPN, mode of preparation, applications, delivery systems and list of polymers employed in the synthesis of IPN.

Preparation of new PVC composite using green reduced graphene oxide and its effects in thermal and mechanical properties

Abstract: In the present study, it was focused on developing mechanically stronger and thermally more stable polyvinyl chloride (PVC) composites by using green reduced graphene oxide (GRGO) filler to strengthen the negative features of PVC. For this purpose, GRGO reduced by vitamin C (ascorbic acid) with antibacterial properties was selected as filler. The PVC/GRGO composites were produced via colloidal blending method at different amounts of GRGO in PVC matrix (0.1, 0.3, 0.5 and 1% by weight), while pure PVC was also produced for comparison. The XRD and FTIR results showed that GRGO incorporated in the polymer matrix; this finding was also evident in SEM analysis. TGA and DSC analyses showed that the composite with 1% loading content of GRGO provided an important improvement on the thermal stability. The tensile strength and hardness of the composite having 0.1% GRGO increased by 42% and 98%, respectively. SEM image of PVC/GRGO-0.1 composite showed the galleries of GRGO filled with PVC. As a consequence, thermal and mechanical properties of PVC can be altered by changing loading content of GRGO. Moreover, the GRGO may be a good candidate for substitution of harmful fillers for PVC-based products.

Polysiloxanes as polymer matrices in biomedical engineering: their interesting properties as the reason for the use in medical sciences

Abstract: Polysiloxanes have been found to be the most important and commercial family of synthetic inorganic polymers. The unique structure of the siloxane bond provides them with unusual features such as a high bond angle, nearly inexistent torsional barrier and a semi-ionic character due to the difference of electronegativities between the silicon and oxygen atoms. Also, silicon-based polymers have been used for the delivery of pharmaceutical and diagnostic compounds involving the use of nanoparticles with different shapes and sizes, as well as hydrogels, including those based on silicon compounds. Hydrogels based on silicon polyolates are rather promising. Some of them exhibit pronounced anti-inflammatory, regenerating, and protective activity, readily penetrate the organism and facilitate drug penetration into the tissues. Due to these properties, polysiloxanes have encountered a big opportunity as an important material in the area of biomedical engineering; the big influence they have in the area of prosthetic dentistry, tissue engineering, cell growth, wounded skin treatments is noteworthy. For the reasons briefly described above, we consider the fact of doing a review about how the polysiloxanes have been used over the years as polymeric matrices that are used in several applications in the field of biomedical engineering.

Adsorption of Eosin Y, methyl orange and brilliant green from aqueous solution using ferroferric oxide/polypyrrole magnetic composite

Abstract: Ferroferric oxide/polypyrrole (Fe3O4/PPy) composites were prepared by an in situ polymerization method. Several analysis techniques including X-ray diffraction, Fourier transform infrared spectra, thermogravimetric analysis and scanning electron microscopy are applied to analyze the structure and morphology of Fe3O4/PPy. The magnetic Fe3O4/PPy was further used as an adsorbent for removing Eosin Y, methyl orange and brilliant green from aqueous phase. The adsorption kinetics were investigated by pseudo-first-order, pseudo-second-order and intraparticle diffusion models, and the experimental data were well fitted to the pseudo-second order. The equilibrium adsorption data can be described by both the Langmuir and Freundlich isotherm models. The calculated Langmuir maximum adsorption capacities of Eosin Y, methyl orange and brilliant green at 25 °C are 212.31, 149.48 and 263.85 mg/g, respectively. Thermodynamic studies indicated that the adsorption process occurred spontaneously, in an endothermic and physisorption nature, and with increased disorder. Furthermore, the convenient magnetic separability of Fe3O4/PPy makes it a good candidate for practical application in the removal of organic dyes from polluted water.

Mechanical, structural, thermal and morphological properties of epoxy composites filled with chicken eggshell and inorganic CaCO3 particles

Abstract: In this study, chicken eggshell particles (ESPs) were used as a biofiller to fabricate epoxy-based biocomposites. The purpose of using these waste-based particles was to find their suitability to be used as low-cost biofillers for epoxy-based composites. The samples were fabricated by a solution-casting method. A special steel-cast metal mold was used to fabricate the composites. The ESPs were loaded into the epoxy with amounts of 5, 10, 15 and 20 wt.%. An amine-based curing agent was used for the curing process. The samples were characterized for the mechanical (tensile, flexural and impact), thermal (TGA and DSC), structural (FTIR and XRD) and morphological (SEM) properties. Result analyses showed that 15 wt.% of ESPs was the optimum loading for the better properties of the composites. Therefore, the properties of the ESPs-based epoxy composite were compared with the inorganic CaCO3 -based composite at a similar amount of filler loading (15 wt.%). Results showed that the addition of fillers decreased the tensile strength of the composites than neat epoxy, whereas tensile modulus was increased. The flexural strength of the composite was increased at the loading of 15 wt.% of ESPs, but it was decreased for the composite prepared with CaCO3 at the same amount. Overall, the ESPs showed better properties than CaCO3, and they can be used as an ecological, environmentally friendly and low-cost alternative of some inorganic fillers.

Fabrication of pristine-multiwalled carbon nanotubes/cellulose acetate composites for removal of methylene blue

Abstract: Here, we report the effect of mixing different amounts of pristine-multiwalled carbon nanotubes (p-MWCNTs) with the cellulose acetate (CA) on dye removal. The p-MWCNTs loadings of the composites were varied from 0 to 1.0 wt%, and the non-solvent-induced phase separation methodology was used to fabricate the composite membranes, which were extensively characterized. The rheological tests confirmed that with 1.0 wt% of p-MWCNTs there was a classical filler effect in the viscoelastic behavior of the composite solution, but with no percolation of CNTs. The ATR-FTIR spectra identified specific interactions between CNTs and acetate groups of CA. SEM images showed a top dense layer sustained by a porous support layer consisting of a sponge-like structure in the middle layer. Aggregates of CNTs were seen at higher loadings of CNTs (> 0.1 wt%). The XRD diffractograms of composite membranes showed peak shifts compared to CA membranes due to the presence of CNTs into the CA structure, and their thermal stability was effective up to 320 °C. From the water permeability experiments, the calculated values of the membrane hydraulic resistance (Rm) of the composites were higher since a dense top layer and reduced pore size were achieved. Among all the composite membranes, M7 and M8 had the most desirable antifouling properties due to the high surface hydrophilicity imparted by the CNTs, and also showed an improvement in the removal of methylene blue (MB).

Silver nanoparticle-embedded pectin-based hydrogel for adsorptive removal of dyes and metal ions

Abstract: Silver nanoparticles made by green synthesis have been incorporated into pectin-based copolymer gel to make a nanocomposite gel to be used as an adsorbent material for the removal of divalent metal ions and dyes from aqueous solutions. Silver nanoparticles were obtained by mixing silver nitrate with aqueous solution of pectin followed by microwave irradiation. The nanocomposite hydrogel was obtained by the microwave-assisted polymerization of 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) and acrylamide (AAm) in the presence of N,N’-methylene-bis-acrylamide (MBA) in pectin solution containing silver particles. Characterization of the nanocomposite gel was done by FTIR, TGA, XRD, FESEM and EDS techniques. The system was evaluated for its capacity to adsorb cationic dye, crystal violet (CV) and metal ions [Cu(II) and Pb(II)] from aqueous solutions. The presence of Ag nanoparticles is observed to enhance the adsorption capacity of the gel for the above mentioned adsorbates. The kinetic studies revealed second-order adsorption processes which fit well into Langmuir model. The evaluation of thermodynamic parameters indicated the adsorption process to be exothermic and spontaneous. A maximum of 1950 mg/g CV, 111 mg/g Cu(II) and 130 mg/g Pb(II) could be removed from the aqueous solution which is quite high in comparison with other reported materials. The desorption studies indicated the possible reusability of the nanocomposite.

Conducting biopolymer electrolyte based on pectin with magnesium chloride salt for magnesium battery application

Abstract: Currently, biopolymer electrolytes are attracting a great deal of interest as substitute for synthetic polymer electrolytes in electrochemical devices, as they are carbon neutral, sustainable, reduce dependency on non-renewable fossil fuels and easily biodegradable. Some of the biopolymers under research are chitosan, pectin, agar–agar, cellulose acetate and carrageenan. The current work deals with the study of ion conducting polymer electrolyte, pectin with magnesium chloride salt for magnesium battery application. Biopolymer electrolytes of different compositions of pectin with different concentrations of magnesium chloride salt are prepared by solution casting technique and subjected to various studies like by X-ray diffraction (XRD), Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), AC impedance spectroscopy and linear sweep voltammetry (LSV). XRD analysis has been used to identify the amorphous/crystalline nature of the sample. The complex formation between the polymer pectin and the magnesium chloride salt has been analyzed by FTIR spectroscopy. DSC analysis is a thermo-analytical technique which is used to observe the glass transition temperature (Tg) of the samples. AC impedance technique has been used to find the ionic conductivities of the sample. The electrochemical stability of the polymer electrolyte has been analyzed by linear sweep voltammetry. Among the prepared polymer electrolytes, 30 M wt% pectin: 70 M wt% MgCl2 offers the highest ionic conductivity of 1.14 × 10−3 S cm−1. The electrochemical stability of the highest conducting sample is 2.05 V. The primary magnesium battery has been constructed using the highest conducting sample, 30 M wt% pectin: 70 M wt% MgCl2, and the battery performance has been studied.

Strong alginate/reduced graphene oxide composite hydrogels with enhanced dye adsorption performance

Abstract: The alginate/reduced graphene oxide composite hydrogels with hierarchical network structures were synthesized through the hydrothermal treatment of graphene oxide and alginate in an aqueous solution followed by ionically cross-linking of metal ions. The network of reduced graphene oxide was prepared via self-assembly of graphene nanosheets in the presence of alginate during the hydrothermal process; then, the polymer network of alginate was obtained by ionically cross-linking, forming the composite hydrogel. The effect of metal ions on the physical properties of the composite hydrogels was investigated. The prepared alginate/reduced graphene oxide composite hydrogel cross-linked by Fe3+ ions showed higher compression strength and lower swelling ratio. Moreover, due to the synergetic interaction between graphene and alginate, the composite hydrogels exhibited the improved dye adsorption performance, especially for cationic dyes. Even after ten adsorption/desorption cycles, the composite hydrogels can retain more than 90% dye adsorption capacity. The results indicated that the composite hydrogel with good stability, adsorption and regeneration ability could be a promising candidate for dye removal from waste aqueous solutions.

Comparative study of Fourier transform infrared spectroscopy (FTIR) analysis of natural fibres treated with chemical, physical and biological methods

Abstract: Kenaf and luffa fibres are hydrophilic due to the presence of water sensitive constituents, which tend to form a poor compatibility when binding with polymers. Thus, the surface of fibres was modified through fungal, alkaline and heat treatment to reduce the main hydroxyl functional groups (O–H) that caused the water absorption as well as to cleave the formed hydrogen bonds that hindered the compatibility. The samples were treated with Phanerochaete Chrysosporium (PC) and Fusarium Oxysporum fungi separately for 5, 10 and 15 days. Furthermore, the samples were alkaline treated with 5 wt% of sodium hydroxide at increased temperature of 25 °C, 50 °C, 70 °C and 90 °C, where it showed improvement in the hydrogen bond removal rate. Moreover, the samples that heat treated under higher temperatures of 120 °C, 140 °C, 160 °C and 180 °C were found to have the lower cellulose and hemicellulose contents due the evaporation of water molecules. Generally, through Fourier transform infrared spectroscopy analysis, both the fibres treated with PC fungi had the lowest O–H content due to the detection of the largest reduction of the O–H stretching band intensity compared to others. Furthermore, the highest weight loss and the lowest water absorption percentages were also detected from these fibres, which also indicated the good modification between the fibres and the PC fungi. Therefore, the fungal treatment using PC fungi is the most effective and environmentally friendly method to improve the fibres’ hydrophobic property.