Synthesis and characterization of fluorine functionalized graphene oxide dispersed quinoline-based polyimide composites having low-k and UV shielding properties

Polyimide nanocomposites having low-k and UV shielding properties have been developed using fluorine functionalized graphene oxide and bis(quinoline amine) based polyimide. The polyimide was synthesized using bis(quinoline amine) and pyromellitic dianhydride at appropriate experimental conditions, and its molecular structure was confirmed through various spectral analysis such as FTIR and NMR. The polyimide (PI) composites were prepared using bis(quinoline amine), pyromellitic dianhydride, and separately filled with 1, 5, 10 wt% of fluorinated graphene oxide (FGO) through in situ polymerization. The polymer composites were characterized using thermo gravimetric analysis (TGA), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). In addition, the water contact angle, dielectric behavior, and UV–Vis shielding behavior of FGO/PI composites were evaluated. The value of the water contact angle of the polyimide was increased with increment of FGO in the polyimide matrix. The highest water contact angle of polyimide composites observed 108° was obtained for 15 wt% FGO reinforced polyimide composite. The value of the dielectric constant for neat, 1, 5, and 15 wt% FGO reinforced polyimide composites was obtained as 4.5, 3.7, 2.6, and 2.0, respectively. It is also observed from by UV–Vis spectroscopy analysis that the FGO reinforced polyimide composites have good UV shielding behavior.     

Selective solid-phase microextraction of polycyclic aromatic hydrocarbons in water based on oriented phosphorus-containing titanium oxide nanofibers grown on titanium support prior to high-performance liquid chromatography with ultraviolet detection

A novel solid-phase microextraction coating of phosphorous-containing titanium oxide composite was developed using titanium fiber as a support and a titanium source by hydrothermal oxidation in a phosphoric acid solution containing hydrogen peroxide. The morphology of the fiber coatings was controlled by the conditions of the hydrothermal oxidation reaction. The oriented nanofiber coating was employed to extract several types of representative aromatic analytes. The experimental results demonstrated that the as-prepared fiber exhibited excellent extraction efficiency toward polycyclic aromatic hydrocarbons. Combined with high-performance liquid chromatography with ultraviolet detection, main extraction conditions were optimized, including pH, ionic strength, extraction temperature, stirring rate, extraction time and desorption time. The established method presented good linearity from 0.05 to 200 μg/L with limit of detection ranging from 0.012 to 0.126 μg/L. This convenient and green procedure was suitable for the selective extraction and determination of typical polycyclic aromatic hydrocarbons in environmental water samples. The relative recoveries of 85.8–112% were obtained for the determination of target polycyclic aromatic hydrocarbons in water samples spiked with 5.0 and 15.0 μg/L. Moreover, the as-prepared fiber showed at least 210 extraction/desorption cycles due to its high mechanical and chemical stability.     

Low percolation conductive graphite flakes-filled poly(urethane-imide) composites with high thermal stability via imidization self-foaming structure

In the study, the conductive graphite flakes filled poly(urethane-imide) composites (PUI/GFs) with high performance were constructed by the thermal imidization self-foaming reaction. It was found that the foaming action could promote the redistribution of GFs during curing process and the formation of stable linear conductive pathways. The percolation threshold of PUI/GFs composites was lowered from 1.26 wt% (2000 mesh GFs) or 0.86 wt% (1000 mesh GFs) to 0.79 wt% (500 mesh GFs), which were relatively low percolation thresholds for polymer/GFs composites so far. When the content of 500 mesh GFs was 4.0 wt%, the electrical conductivity of the composite was as high as 3.96 × 10^?1 S/m. Also, a poly(urethane-imide) (PUI) matrix with excellent thermal stability (T_d10%: 334.97 °C) and mechanical properties (elongation at break: 324.52%, tensile strength: 15.88 MPa) was obtained by introducing the rigid aromatic heterocycle into the polyurethane (PU) hard segments. Moreover, the zero temperature coefficient of resistivity for the composites was observed at the temperature range from 30 °C to 200 °C. Consequently, PUI/GFs composites may provide the novel strategy for considerable conductive materials with high thermal stability in electrical conductivity.     

Fe(II) Spin Crossover/Polymer Hybrid Materials: Investigation of the SCO Behavior via Temperature-Dependent Raman Spectroscopy,Physicochemical Characterization and Migration Release Study

Polymeric composites constitute an appealing class of materials with applications in various fields. Spin crossover (SCO) coordination complexes are switchable materials with potential use in data storage and sensors. Their incorporation into polymers can be considered an effective method for their wider practical application. In this study, Fe(II) SCO/polylactic acid hybrid polymeric composites have been prepared by film casting. The mononuclear coordination complex [Fe{N(CN)₂}₂(abpt)₂] was incorporated into polylactic acid. The morphological, structural and thermoanalytical characterization of the composite films were performed via scanning electron microscopy (SEM), attenuated total reflectance (ATR/FTIR), Raman spectroscopy and differential scanning calorimetry (DSC). In addition, the migration release study (MRS) of the SCO compound from the polymeric matrix into the food simulant 50% v/v water/ethanol solution was also examined via UV/Vis absorption. Of particular interest was the investigation of the SCO behavior of the coordination complex after its incorporation into the polymer matrix; it was accomplished by temperature-dependent micro-Raman spectroscopy. The described attempt could be considered a preparatory step toward the development of SCO-based temperature sensors integrated into food packaging materials.     

Reactive TiO2 Nanoparticles Compatibilized PLLA/PBSU Blends:Fully Biodegradable Polymer Composites with Improved Physical,Antibacterial and Degradable Properties

The fully biodegradable polymer blends remain challenges for the application due to their undesirable comprehensive performance.Herein,remarkable combination of superior mechanical performance,bacterial resistance,and controllable degradability is realized in the biodegradable poly(L-lactide)/poly(butylene succinate) (PLLA/PBSU) blends by stabilizing the epoxide group modified titanium dioxide nanoparticles (m-TiO2) at the PLLA-PBSU interface through reactive blending.The m-TiO2 can not only act as interfacial compatibilizer but also play the role of photodegradation catalyst:on the one hand,binary grafted nanoparticles were in situ formed and stabilized at the interface to enhance the compatibility between polymer phases.As a consequence,the mechanical properties of the blend,such as the elongation at break,notched impact strength and tensile yield strength,were simultaneously improved.On the other hand,antibacterial and photocatalytic degradation performance of the composite films was synergistically improved,it was found that the m-TiO2 incorporated PLLA/PBSU films exhibit more effective antibacterial activity than the neat PLLA/PBSU films.Moreover,the analysis of photodegradable properties revealed that that m-TiO2 nanoparticles could act as a photocatalyst to accelerate the photodegradation rate of polymers.This study paves a new strategy to fabricate advanced PLLA/PBSU blend materials with excellent mechanical performance,antibacterial and photocatalytic degradation performance,which enables the potential utilization of fully degradable polymers.     

Synergic Enhancement of High-density Polyethylene through Ultrahigh Molecular Weight Polyethylene and Multi-flow Vibration Injection Molding: A Facile Fabrication with Potential Industrial Prospects

General-purpose plastics with high strength and toughness have been in great demand for structural engineering applications. To achieve the reinforcement and broaden the application scope of high-density polyethylene(HDPE), multi-flow vibration injection molding(MFVIM) and ultrahigh molecular weight polyethylene(UHMWPE) are synergistically employed in this work. Herein, the MFVIM has better shear layer control ability and higher fabrication advantage for complex parts than other analogous novel injection molding technologies reported.The reinforcing effect of various filling times and UHMWPE contents as well as the corresponding microstructure evolution are investigated.When 5 wt% UHMWPE is added, MFVIM process with six flow times thickens the shear layer to the whole thickness. The tensile strength and modulus increase to 2.14 and 1.39 times, respectively, compared to neat HDPE on the premise of remaining 70% impact strength. Structural characterizations indicate that the enhancement is attributed to the improvement of shish-kebab content and lamellae compactness, as well as related to the corresponding size distributions of undissolved UHMWPE particles. This novel injection molding technology with great industrial prospects provides a facile and effective strategy to broaden the engineering applications of HDPE materials. Besides, excessive UHMWPE may impair the synergistic enhancement effect, which is also reasonably explained.     

Carbon Nanotube Reinforced Titanium Metal Matrix Composites Prepared by Powder Metallurgy—A Review

Titanium-based metal composites (TMCs) are showing great potential to replace existing traditional materials in aerospace, automotive, and other high temperature engineering applications. This is due to their excellent mechanical, thermal, and physical properties and improved strength to weight ratio. Weight savings in the aerospace industry results in higher efficiency. Carbon nanotubes (CNTs), because of their low density and high Young's modulus, are considered to be an excellent reinforcement for metal matrix composites (MMCs). In the last 20 years extensive research has been carried out to investigate the combination of carbon nanotubes with aluminum, nickel, copper, magnesium, and other metal matrices. The production techniques such as mechanical alloying through powder metallurgy routes and their effects on the mechanical properties of CNT reinforced TMCs are reviewed in this article. The role of the volume fraction of carbon nanotubes and their dispersion into the metal matrix are highlighted. Governing equations to predict the mechanical and tribological properties of CNT reinforced titanium matrix composites are deduced. With the help of this initial prediction of properties, the optimal processing parameters can be optimized. Successful development of CNT reinforced TMCs would result in better wear and mechanical behavior and enhance their ability to withstand high temperature and structural loading environments.     

Facile Preparation of α‐Zirconium Phosphate/Polyaniline Hybrid Film for Detecting Potassium Ion in a Wide Linear Range

A novel α‐zirconium phosphate/polyaniline (α‐ZrP/PANI) hybrid film used as K⁺ ion sensor was fabricated on carbon paper by electrochemical method. Mechanisms of film formation and detection of K⁺ ions were also proposed. The exfoliated α‐ZrP was mixed with PANI and deposited on carbon paper. The resultant α‐ZrP/PANI film exhibited a good current response to K⁺ ion with different concentrations. It also showed a wide logarithmic linear response in detecting K⁺ ions in the ranges of 10^?8–10^?4 M and 10^?4–10^?2 M, respectively. The results can be attributed to the synergetic effect of α‐ZrP and PANI.     

Gold Decorated Graphene by Laser Ablation for Efficient Electrocatalytic Oxidation of Methanol and Ethanol

A well‐known limitation in the fabrication of metal‐graphene composite has been the use of surfactants that strongly adsorb on the surface and reduce the performance of the catalyst. We demonstrate here a novel one‐pot synthesis of gold nanoparticles by laser ablation of gold strip and in‐situ decoration on graphene substrate. Not only the impregnation of nanoparticles was linker free, but also the synthesis by itself was surfactant‐free. The composite materials were well characterized morphologically and functionally using electron microscopy, X‐ray and electron diffraction, Raman spectroscopy, Zeta potential, electrochemical measurements and UV‐Visible spectroscopic techniques. This linker‐free gold‐graphene based composite has been employed for catalytic applications pertaining to electrooxidation. We have explored the use of this composite as a binder‐free electrode in electrocatalytic oxidation of methanol and ethanol in alkaline medium. Additionally, the onset potential for ethanol oxidation was found to be more negative, ?100 mV, an indication of its promising application in direct ethanol fuel cells.     

Recycling ground tire rubber (GTR) scraps as high‐impact filler of in situ produced polyketone matrix

A sustainable procedure for recycling powdered rubber coming from scrap tires (ground tire rubber [GTR]) is proposed as based on the dispersion in polyketone (PK) matrix, obtained in situ by CO/ethylene copolymerization. Three types of catalysts are used operative in solvents of different polarities. The catalyst productivity and the hybrids morphology are evaluated and optimized to final composites features. The obtained products are characterized by scanning electron microscopy, atomic force microscopy, and solvent extractions in order to investigate the occurrence and the extent of interactions between PK macromolecular chains and the GTR components; and their effects on the final properties were tested by differential scanning calorimetry, thermogravimetric analysis, and rheological measurements. For comparison purpose, a composite with GTR included into the matrix through blending is prepared. The results evidenced the key role exerted by the catalyst that, when operative in apolar solvent (able to swell the rubber phase), provides composites with good interfacial adhesion and breaking up of the particles with beneficial effects on final properties particularly thermal features and processability. Copyright © 2014 John Wiley & Sons, Ltd.