This is an editorial article. It has no abstract.
Synthesis of sulfonated poly (arylene ether sulfone) copolymer by direct copolymerization of 4,4'-bis(4-hydroxyphenyl) valeric acid, benzene 1,4-diol and synthesized sulfonated 4,4'-difluorodiphenylsulfone and its characterization by using FTIR (Fourier Transform Infrared) and NMR (Nuclear Magnetic Resonance) spectroscopic techniques have been performed. The copolymer was subsequently cross-linked with 4, 4!(hexafluoroisopropylidene)diphenol epoxy resin by thermal curing reaction to synthesize crosslinked membranes. The evaluation of properties showed reduction in water and methanol uptake, ion exchange capacity, proton conductivity with simultaneous enhancement in oxidative stability of the crosslinked membranes as compared to pristine membrane. The performance of the membranes has also been evaluated in terms of thermal stability, morphology, mechanical strength and methanol permeability by using Thermo gravimetric analyzer, Differential scanning calorimetery, Atomic force microscopy, XPERT-PRO diffractometer, universal testing machine and diffusion cell, respectively. The results demonstrated that the crosslinked membranes exhibited high thermal stability with phase separation, restrained crystallinity, acceptable mechanical properties and methanol permeability. Therefore, these can serve as promising proton exchange membranes for fuel cell applications.
The nanocarrier is linked to the core and shell by hydrogen bond. This drug delivery system represents a smart, biodegradable, and pH-sensitive nanocarrier for breast cancer therapy. These drug nanocarriers were linked by hydrogen bond from –NH2 on chitosan and –OH on mesoporous silica nanoparticle (MSN). And MSN was prepared by the cetyltrimethyl ammonium bromide (CTAB)-templated method via sol-gel and the loading of ibuprofen (IBU) into the pores of MSN was visualized by coprecipitation which was assessed by Fourier Transform Infrared Spectroscopy (FTIR) and nitrogen adsorption-desorption techniques. The wrapping of chitosan (CS) onto the surface of MSN was demonstrated by FTIR too. When the nanocarriers entered an acidic environment where large quantity cancer cells existed, the chitosan shell swell into loose random coil, exposing the drug and making them easy to be released. The results showed that the IBU could be successfully and effectively loaded into MSN and CS/MSN. The system was pH responsive. Drug release was much higher at pH 6.8 than at 7.4. This drug delivery system will represent a smart and biodegradable pH-responsive nanocarrier for breast cancer.
In this study, styrene butadiene rubber (SBR) was devulcanized using microwave irradiation. In particular, effect of ionic liquid (IL), pyrrolidinium hydrogen sulfate [Pyrr][HSO4], on the devulcanization performance was studied. It was observed that the evolution of the temperature reached by rubber powder exposed to microwave irradiation for different energy values was favored by the presence of ionic liquid [Pyrr][HSO4] significantly over the whole range of the microwave energy values. Beyond the threshold point of 220 Wh/kg, the soluble fraction after devulcanization sharply increased with increasing devulcanization microwave energy. For the powder mixed with [Pyrr][HSO4], the increase was more significant. Furthermore, the crosslink density was observed to decrease slowly with the microwave energy up to 220 Wh/kg, beyond which the crosslink density decreased significantly for the rubber impregnated with IL. For the rubber with IL, significant and continuous increase in Tg with microwave energy values was observed in comparison with the SBR where no change in transition temperature was observed. Mechanical shearing of rubber gums in the two-roll mill favored the devulcanization process, which indicated that the combination of mechanical loading with microwave energy and IL is an efficient procedure allowing an optimal devulcanization of rubbers.
The use of industrial by-products of the vegetable oil industry as ductility increasing additives of polylactide (PLA) was investigated. Vegetable oil deodorization condensates were melt-blended by twin-screw extrusion up to a maximum inclusion quantity of 20 wt% without preliminary purification. Sample films were obtained by single screw cast extrusion. Compounded PLA films featured largely improved ductility in tensile testing with an elongation at break up to 180%. The glass transition temperature remained higher than room temperature. The native mixture of molecules, which composed the deodorization condensates, had superior performance compared to a synthetic mixture of main compounds. The investigation of the correlation between composition of the additives and the ductility of the PLA blends by Principal Component Analysis showed synergy in property improvement between fatty acids having a melting point below and beyond the room temperature. Furthermore, a compatibilizing effect of molecules present in the native mixture was evidenced. Oil deodorization condensates, which are a price competitive by-product of the vegetable oil industry, are therefore a very promising biobased and biodegradable additive for improving the ductility of PLA.
In the present study, the effect of nano magnetite (Fe3O4) content on structural, dielectric/electrical, magnetic and thermal properties of poly(vinylidene fluoride)/carbon nanotubes matrix, is investigated. Nanocomposite films of polyvinylidene fluoride, carbon nanotubes and Fe3O4 nanoparticles were prepared by the twin screw compounding method. Fe3O4, as magnetic inclusions was incorporated into the composites with carbon nanotubes loadings well above the percolation threshold, where conductive networks were formed. Magnetic characterization revealed the ferrimagnetic behavior of nanocomposites, with saturation magnetization values depending on magnetite content. Results obtained from the analysis of Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD) and Differential Scanning Calorimetry (DSC) techniques were very informative for the study of the polymorphism and crystallinity in PVDF. The incorporation of Fe3O4 inclusions in PVDF/CNT matrix, gradually increase both electrical conductivity and dielectric permittivity up to 10 wt% Fe3O4 content, while at the higher Fe3O4 content (15 wt%) reduced values were obtained. This behavior, at higher Fe3O4 content, should be possible related to the insulating and barrier role of Fe3O4 nanoparticles.
To better understand the role of the fiber curvature on the tensile properties of short-natural-fiber reinforced composites, a photoelastic model and a finite element analysis were performed in a well characterized henequen fiber-high density polyethylene composite material. It was hypothesized that the angle of orientation of the inclusion and the principal material orientation with respect to the applied load was very important in the reinforcement mechanics. From the photoelastic and finite element analysis it was found that the stress distribution around the fiber inclusion was different on the concave side from that observed on the convex side and an efficient length of stress transfer was estimated to be approximately equal to one third the average fiber length. This approach was used to predict the short-natural-fiber reinforced composite mechanical properties using probabilistic functions modifications of the rule of mixtures models developed by Fukuda-Chow and the Fukuda-Kawata. Recognizing the inherent flexibility that curves the natural fibers during processing, the consideration of a length of one third of the average length l should improve the accuracy of the calculations of the mechanical properties using theoretical models.
In this work, silane crosslinking of poly (lactic acid) (PLA) was studied. PLA was grafted with vinyl-trimethoxysilane (VTMO) via melt mixing in an internal mixer, followed by a crosslinking reaction in hot water for different times. The effect of simultaneous hydrolytic degradation in hot water (70°C) during crosslinking was monitored. Silane grafting of PLA was characterized using mixing torque and gel permeation chromatography (GPC) analysis. The results revealed that by increasing the silane (0–7 wt%) and peroxide (0–0.5 wt%) contents, the degree of grafting was increased. A peak corresponding to higher molecular weight in GPC chromatograms appeared in comparison to pure PLA due to the grafting reaction. Gel content, swelling test, GPC and thermal gravimetric analysis (TGA) were performed to monitor gel structure and concurrent hydrolytic degradation. Results confirmed that the occurrence of hydrolytic degradation during crosslinking and gel content of some samples tended to zero over 10 hr of immersion in hot water. The effect of hydrolytic degradation was not significant up to 10 hr and a tight gel structure was obtained. However, at longer crosslinking times, hydrolytic degradation was the dominant mechanism that leads to network defects.