This is an editorial article. It has no abstract.
Natural rubber (NR) and butyl rubber (IIR) blends were compatibilized by isobutylene-isoprene block copolymer (IIBC) which was specifically synthesized with a relatively high content of isoprene (14.5% mole fraction). Aiming at high damping elastomers, the IIR acts as the high damping phase dispersed in the natural rubber (NR) matrix in this blend. The morphology and microstructure was characterized by atomic force microscope (AFM) and transmission electron microscope (TEM). The results indicated that the IIBC as a compatibilizer could greatly increase the interfacial thickness. Damping property was studied by dynamic mechanical thermal analyzer (DMTA) and rubber processing analyzer (RPA). The results showed that the loss factor greatly increased with adding IIBC, and this may be due to the improved stress transfer promoting the IIR phase to deform and then dissipate energy. The tensile test demonstrated that the tensile strength and modulus increased when 4 parts per hundred rubber [phr] of IIBC was added. Finally, the NR and new NR/IIR isolation bearing samples were prepared and tested on a pressure shear testing machine that could simulate the actual situation during an earthquake.The results showed that hysteretic loss (for one cycle) of the new NR/IIR sample is 83% higher than that of the NR sample, rendering the compatibilized blends potential in isolation rubber bearings application.
The inherently poor flame retardancy and comparatively low tensile strength of poly(lactic acid) (PLA) have limited its wide adoption as alternative ‘green’ engineering plastic in many fields. This manuscript reports the synthesis of a new phosphorus flame retardant – phenylphosphonic 3(2-aminobenzothiazole) (P-TAB) and its combination with recycled short wool fibers (WF) for improving the flame retardancy and the mechanical properties of PLA. Fourier transform infrared (FTIR), 1H, and 13C nuclear magnetic resonance (NMR) spectra proved that P-TAB was effectively synthesized. Considerable reductions in heat release rate, total heat released, CO and CO2 produced were attained with 3 wt% P-TAB and various WF loadings. The fire performance index (FPI), and fire growth index (FGI) improved by 38.2 and 48.1% respectively. The composite achieved a V-0 rating at 20 wt% WF loading and an LOI value of 28.5%. TG-IR results showed substantial reductions in evolved gaseous products. The tensile strength and Young’s modulus improved significantly with the increasing content of WF in the composite.
The electrical conductive behaviours of polymer-based three-phase composites prepared by spatial confining forced network assembly
S. Kormakov, D. Wu, J. Sun, X. Gao, X. He, X. Zheng, I. Skopincev, N. Memetov, A. Tkachev, Z. Zhi
Vol. 13., No.8., Pages 713-723, 2019
Vol. 13., No.8., Pages 713-723, 2019
Spatial Confining Forced Network Assembly (SCFNA) method is an effective method for the enhancement of electrical conductivity. In the current paper, a composite material consisting of polydimexilsiloxane (PDMS) and short carbon fiber (SCF) was modified by adding graphene nanoplateletes (Gr) at a concentration of 1~4 wt% into the composite system. The electrical properties of the obtained samples were compared with those prepared by compression molding to evaluate the effectiveness of SCFNA. The results showed that the addition of graphene increased the electrical conductivity of the composites by more than 4 orders of magnitude. Meanwhile, a polymer-based three-phase composite with the highest electrical conductivity of 287 S/m was obtained utilizing the SCFNA method in the present work.
Electrospun polyimide ultrafine non-woven fabrics with high whiteness and good thermal stability from organo-soluble semi-alicyclic polyimides: Preparation and properties
C. Y. Guo, Q. W. Wang, J. G. Liu, L. Qi, M. G. Huangfu, X. Wu, Y. Zhang, X. M. Zhang
Vol. 13., No.8., Pages 724-738, 2019
Vol. 13., No.8., Pages 724-738, 2019
A series of organo-soluble polyimide (PI) resins were synthesized by a two-step chemical imidization reaction from two semi-alicyclic dianhydrides, 1,4-dihydroxyphenyl-dicyclohexanecarboxylate-3,3′,4,4′-tetracarboxylic acid dianhydride (HTA-HQ, I) and 4,4′-dihydroxybiphenyl dicyclohexanecarboxylate-3,3′,4,4′-tetracarboxylic acid dianhydride (HTABP, II) and two rigid-rod aromatic diamines, 2,2′-dimethylbenzidine (DMBZ, a) and 2,2′-bis(trifluoromethyl)benzidine (TFMB, b), respectively. Then, PI ultrafine non-woven fabrics were successfully fabricated via a one-step electrospinning procedure with the synthesized semi-alicyclic PI resins dissolved in N,N-dimethylacetamide (DMAc), followed by heat treatment at 200 °C. Comparatively, the standard wholly aromatic PI fabric, poly(pyromellitic dianhydride-oxydianiline) (PI-ref, PMDA/ODA) was prepared by a two-step electrospinning procedure with poly(amic acid) (PAA), followed by the high-temperature imidization procedure up to 350 °C. The derived electrospun semi-alicyclic PI non-woven fabrics exhibited much higher optical reflectance and whiteness than that of the PI-ref. For example, PI-IIb (HTA-BP/TFMB) fabric showed an optical reflectance (R457) value of 90.6% at the wavelength of 457 nm and whiteness index (WI) of 92.7, which were quite higher than those of PI-ref (R457: 37.3%; WI: 59.0). In addition, the semi-alicyclic PI fabrics exhibited good thermal stability with the glass transition temperatures (Tg) higher than 217°C.
In the present experimental work new polymer-reduced graphene oxide (rGO) nanocomposites with bimetallic platinum-palladium nanoparticles as functional electrodes for chemical power sources were prepared. The size and shape of nanoparticles in the composites have been studied by use of atomic force and high-resolution transmission electron microscopy techniques, X-ray phase analysis and small-angle X-ray scattering. Model tests on the basis of chemically-obtained composite electrodes under operating conditions of fuel elements with formic acid oxidation were carried out.
Barium titanate/epoxy resin composite nanodielectrics were manufactured and their capability to store and harvest energy, upon request under DC conditions, was studied in this work. Morphological characterization in all nanocomposites was performed via scanning electron microscopy images and X-ray diffraction spectra, indicating the successful nanofiller’s integration and dispersion within the polymer matrix. Applied DC voltage level varied from 10 to 240 V and the measurements were performed in the temperature range from 30 to 160 °C. Filler content enhances the energy efficiency of the manufactured systems, reaching the highest value of 58.2% for the 7 phr BaTiO3 nanocomposite. Increase of temperature results in an exponential decay of the coefficient of energy efficiency (neff), indicating leakage currents’ augment. DC and AC conductivity have been determined as a function of temperature for all nanodielectric systems. The temperature dependence of conductivity under DC and AC condition follows an Arrhenius form, which allowed the determination of activation energy in both cases.
Inspired by the lubrication mechanism of human articular cartilage tissue, the porous self-lubricating polyurethane (PU) materials with micron-meter pore were fabricated by non-solvent induced phase separation (NIPS) method with 60 wt% N,N-dimethylformamide (DMF) as a coagulation agent. The scanning electron microscopic (SEM) images demonstrated that the cross-section morphology of the materials is similar to that of the sponge and adjacent macropores were connected by interpenetrating pores to exhibit an ‘ink-bottle’ type pore structure. Meanwhile, the porosity of the porous self-lubricating PU materials could be controlled by adjusting the PU solution concentrations and the oil content increased as the increasing of porosity. The results of centrifugation/heating test indicated that the porous self-lubricating PU materials have an excellent oil retention performance owing to the pore structure. The tribological properties of porous self-lubricating materials with different porosity under various loads and sliding velocities were investigated by a block-on-ring wear tester which revealed that excellent friction reduction and wear resistance properties of the porous self-lubricating materials were achieved by the lubricating oil squeezed from pores which the friction coefficient of the materials significantly reduced, from 0.174 to 0.078 with the increases of oil content. Furthermore, the lubrication mechanism of porous self-lubricating PU material was discussed as well.