This is an editorial article. It has no abstract.
In this paper, we have designed a solution processable macroscopically oriented conductive polymer of fluorene dangled 3-pentadecylphenol (Polyfluorene pentadecyl benzene, PFLPDB) through side chain engineering and self-assembly approach. Initially fluorene was coupled with 3-pentadecylphenol (3-PDP) and further subjected to oxidative polymerisation in the presence of anhydrous ferric chloride (FeCl3). Effects of polarity of the solvent and time on self-assembly process was studied using various microscopic techniques which suggested the formation of macroscopically oriented fibers having 20–30 nanometer diameter in chloroform with an electrical conductivity of (2.1・10–2 S・cm–1). Optical and electrochemical band gaps were calculated from the studies made by UV-Vis spectroscopy and cyclic voltammetry. Its field effect transfer characteristics were further studied by fabricating an Organic field effect transistor (OFET) device having configuration (Si/SiO2/PFLPDB/Ag) and measured its field effect mobility (1.076 cm2・v–1・s–1) at 1 V and ON/OFF ratio of the device calculated as 1.82・103 suggests its application as an excellent active material for organic microelectronics.
In this paper, a kind of polypropylene (PP) foam plastic parts with special weld lines were obtained by core-back foam injection molding with chemical blowing agent. A new kind of weld line was found and its formation process was proposed. The unique principle of the weld lines formation in core-back foam injection molding process was revealed. The surface and internal morphologies, fracture morphologies, cell structure, and mechanical properties of the weld line area of the specimens respectively obtained by core-back foam injection molding and conventional foam injection molding were compared and analyzed. The mechanism of core-back foam injection molding in improving the mechanical properties of the weld line was clarified. The results show that the specimens with special weld lines not only have relatively uniform inner cell structure in size and distribution, but also have a special reticular structure in the weld line area. This reticular structure can not only play a role similar to fiber reinforcement itself, but also increases the bonding degree of polymer at weld lines. Under the action of this special weld line structure, the tensile strength and elongation at break of the specimen are significantly improved, and the weight reduction effect is much better under the premise of ensuring certain mechanical properties.
Effect of ultrasonic treatment on the properties of multiwalled carbon nanotubes – polymethylmethacrylate composites: Effect of applied voltage and pressure on conductivity of the composites
S. I. Moseenkov, V. L. Kuznetsov, G. V. Golubtsov, A. V. Zavorin, A. N. Serkova
Vol. 13., No.12., Pages 1057-1070, 2019
Vol. 13., No.12., Pages 1057-1070, 2019
The effect of sonication time during the synthesis of multiwalled carbon nanotubes – polymethylmethacrylate (MWCNT/PMMA) composites by coagulation technique on the MWCNT distribution in the bulk of the composites close to the percolation threshold was systematically studied by SEM and by measurements on specific resistivity in a wide range of voltages and external pressure. It was found that the resistivity of composites is irreversibly reduced up to 105 times during the first 1–3 measurements, while further measurements are characterized by high repeatability. Change of the composite resistivity during the measurements is discussed assuming that several types of contacts between the nanotubes changing during the measurement are present. It was found that an increase of the sonication time changed the ratio between ohmic and non-ohmic contacts. It affected the type of changes in the sample resistivity during the voltage variation in the range of 0–103 V/mm and resulted in a nonuniform dependence of the composite specific resistivity on the sonication time. An increase of the composite volume during the resistivity measurements was observed at the current densities above 4・10–8 A/cm2. New ohmic contacts were found to form when external pressure was applied due to squeezing of the polymer matrix from the space between adjacent nanotubes.
The present work focuses on the development of polypropylene (PP) filaments containing paraffin microcapsules (MC), aimed at being incorporated in hybrid yarns to produce multifunctional thermoplastic laminates for thermal energy storage (TES). Benchmark experiments carried out on a small-scale melt compounder and piston-type melt spinning device resulted in the successful production of single filaments containing up to 30 wt% of MC, with diameters of 70–140 µm depending on the collection speed and a surface roughness that increases with the MC content. An increase in the MC fraction also determines a rise in the complex viscosity, but this effect is less evident at higher shear rates and likely almost negligible at the deformation rates typical of the spinning process. Although the MC have a considerable thermal stability, the compounded mixtures reported a sensible mass loss in isothermal thermogravimetric analysis (TGA) tests, which is linked to a not negligible MC damage during the compounding. Nevertheless, differential scanning calorimetry (DSC) on the spun filaments evidenced an increase in the phase change enthalpy with the MC content up to approx. 48 J/g, which is remarkably higher than that of similar systems reported in the literature. The elastic modulus and the properties at break decrease with an increase in the MC content, but the fiber strength is acceptable to produce a hybrid yarn and a thermoplastic laminate up to a MC fraction of 20 wt%.
The composites consisting of ethylene-vinyl acetate rubber (EVM) and acrylonitrile butadiene rubber (NBR) were prepared by two-step blending method, and were reinforced with carbon black (CB) using 1,4-bis(tert-butylperoxyisopropyl) benzene (BIPB) as crosslinking agent. In addition, wear and oil resistance, morphology, vulcanization and dynamic mechanical properties of the composites were systematically investigated. 3D graph was used to analyze the trend of wear and oil resistance of the composites. SEM images showed that the wear mechanism of the composites was mainly abrasive wear, accompanied by fatigue wear. With the increase of NBR content, the wear resistance was effectively improved, which was revealed by the DIN abrasion volume, worn surfaces morphology and roughness. Meanwhile, the oil resistance was also improved according to the rate of volume change and surface contact angle. The EVM/NBR composites prepared by the two-step blending method showed higher ΔH (maximum torque MH – minimum torque ML) than pristine EVM or NBR did. The composites containing 30 phr of CB exhibited excellent wear and oil resistance, which broadened the applications field of the EVM/NBR composites.
Bio-based star-shaped poly(ε-caprolactone)s (S-PCL) derived from sugar-based D-sorbitol as an initiator were obtained via solvent-free enzymatic ring-opening polymerization (eROP). The star S-PCL were converted into UV-curable maleates by employing maleic anhydride for subsequent crosslinking with tri(ethylene glycol) divinyl ether (DVE-3) in the presence of Darocur 1173 as a radical photoinitiator. The kinetics of the UV-induced radical copolymerization was monitored by real-time Fourier-Transform InfraRed (FTIR) spectroscopy, which revealed that the star S-PCL maleate/divinyl ether system was not scavenged by molecular oxygen (donor/acceptor polymerization). The UV-crosslinking reaction was fast (~10 s) to reach near quantitative conversions. The S-PCL maleate / divinyl ether liquid formulation cast on glass substrates successfully gave films upon UV-crosslinking. The thermal properties of the polymer films and their precursor polymers were characterized by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Finally, the crosslinked polymer film demonstrated promising adhesive properties on steel, aluminum and glass substrates.
The fatigue of rubber products is usually accompanied by undesirable transformation in their properties. The present work was dedicated to the investigation of consequences of fatigue loading on volume electric conductivity of natural rubber (NR) reinforced with 30 phr of fillers composed from various weight combinations of carbon nanotubes (CNTs) and carbon black (CB). Special attention was paid to study the influence of CNTs content on residual electric conductivity and a possible mechanism of fatigue driven rearrangement of hybrid filler network inside of rubber matrix was propounded forward. An increase in the CNTs content over the complete range of concentrations, enhanced the conductivity of fabricated samples up to two orders of magnitude in comparison to rubber compounds without CNTs. All the samples were subjected to harmonic sinusoidal loading at a frequency of 5 Hz up to 105 loading cycles at three different strains of 0.1, 0.25 and 0.5. Despite very little transformation in the polymer matrix, fatigue caused a progressive degradation of conductivity with an increase in applied strain. It was also found that with the addition and a subsequent increase in the concentration of CNTs, the undesirable reduction of conductivity was significantly arrested. This novel finding added another number to the list of the outstanding properties of CNTs.