A novel phosphorus-nitrogen-containing flame retardant (DOPT) has been successfully synthesized via the substitution reaction of cyanuric chloride, pentaerythritol phosphate and 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The chemical structure of DOPT was confirmed by 1H, 31P and 13C nuclear magnetic resonance, Fourier transform infrared spectroscopy and elemental analysis. Then, flame retardants were added to epoxy resin to prepare epoxy resin composites by pouring method. Thermal properties, flame retardancy, and combustion behavior of epoxy resin composites were evaluated by thermogravimetric analysis, vertical burning, limiting oxygen index and cone calorimeter test. Thermogravimetric analysis test showed that the carbon residue rate of DOPT at 800°C reached 52.53%, which indicated that the introduction of high-efficiency char-forming agent triazine and pentaerythritol phosphate groups could significantly improve its char-forming performance and thermal stability. The epoxy resin composite achieved vertical burning V-0 grade and the limiting oxygen index value reached 35.5% when 7 wt% DOPT was incorporated. Furthermore, the cone calorimeter test results manifested that the addition of DOPT stimulated degradation of the epoxy resin matrix during the combustion process and accelerated the formation of an expanded and dense carbon layer. Additionally, the incombustible gas produced during the decomposition of DOPT had played a flame-retardant effect in the gas phase. Hence, compared with neat epoxy resin, the total heat release and total smoke production of the EP-7 wt% DOPT composite decreased by 14.0% and 25.3%, respectively. Moreover, owing to the excellent compatibility and the strong interface effect between DOPT and epoxy resin, the addition of DOPT also enhanced the mechanical and fire resistance properties of the epoxy resin composite. Therefore, it is proposed that DOPT could be exploited as an economical and high-efficiency flame retardant, and it has considerable prospects in flame retardant epoxy resin composites.

In this study, the thermal conductivity, thermal degradation and mechanical properties of the perlite added epoxy materials were investigated. Perlite was added into the epoxy resin (EP) at the rate of 2%, 4%, 6%, 8% and 10% compared to the total mass. For the analysis of these epoxy materials, the thermal conductivity, density, hardness, X-ray diffraction (XRD), FTIR spectra, thermogravimetric analysis (TGA), tensile strength, flexural strength, limit oxygen index (LOI) and vertical burning tests were carried out. With the added perlite (PER10), a decrease of 24.03% occurred in the thermal conductivity coefficient compared to the pure EP material. A maximum decrease of 6.86% was detected in its density. It gained fire retardant feature as it increased from 6.15% to 28.71% in V-0 and carbon residue as inflammability class. Despite the decrease of tensile stress, tensile modulus increased. The maximum increase PER02 was 36.9%. It did not provide any improvement in terms of other mechanical properties.

Constructing polymer composites containing zero-dimensional (0D) nanoparticles and two-dimensional (2D) lamellae is a simple and effective strategy to obtain high energy storage performance. Although the hexagonal boron nitride nanosheets (BNNSs) are widely used in energy storage areas, the low yield hinders their application. This work employed Al2O3 (AO) nanoparticles and thick hexagonal boron nitride (h-BN) lamellae to fabricate poly (vinylidene fluoride) (PVDF)-based films. An expected synergy effect on the breakdown strength ( E b) is achieved as the filler content and ratio change. A high E b (450 MV/m), which is 110 MV/m higher than the pure PVDF (340 MV/m), was acquired with a small loading (4 wt.%). The analysis suggests multiple synergy effects between AO and h-BN on leakage current, crystallinity, melting point, and Young’s modulus contribute to the high E b. However, a desirable low leakage current is an indispensable part of these properties. In addition to this, the mechanisms behind these synergy effects were discussed. A comprehensive comparison indirectly proves that the AO particles can increase the dispersibility of h-BN lamellae. Besides, the dielectric behavior and energy storage performance were comprehensively examined.

Si3N4 whiskers were modified with triethoxysilane as a means to improve the interfacial interaction with a poly-amide imide (PAI). The Si3N4/PAI composites were prepared by in-situ polymerization as an approach to improve the friction behavior and mechanical properties in order to meet the performance needs of electrical transformers and motors in harsh environments. 4,4′-diamino diphenyl ether, m-phenylenediamine, triethylamine, trimellitic anhydride chloride, and Si3N4 whiskers were used to manufacture Si3N4/PAI composite, which was then characterized for friction and mechanical behavior. The research showed that the addition of Si3N4 whiskers improved the mechanical properties and friction properties of PAI. When the whisker content was 10 wt%, the tensile strength of the composite was 137.5 MPa, which is 15% higher than pure PAI, and the wear rate was 0.69 × 10-8 g/N·m, which is 57% lower than pure PAI, and the friction coefficient was 0.47, which was an increase of 9%. In aerospace, machinery, and transportation applications, these materials may have better performance due to their improved combination of properties.

The conventional electromagnetic interference (EMI) shielding materials are being gradually replaced by a new generation of supported conducting polymer composites (CPC) films due to their many advantages. This work presents a contribution on the effects of silane surface–modified flexible polypyrrole-silver nanocomposite films on the electromagnetic interference shielding effectiveness (EMI-SE). Thus, the UV-polymerization was used to in-situ deposit the PPy-Ag on the biaxial oriented polyethylene terephthalate (BOPET) flexible substrates whose surfaces were treated by 3-aminopropyltrimethoxysilane (APTMS). X-ray Photoelectron Spectroscopy (XPS) analyzes confirmed the APTMS grafting procedure. Structural, morphological, thermal, and electrical characteristics of the prepared films were correlated to the effect of substrate surface treatment. Thereafter, EMI-SE measurements of the elaborated films were carried out as per ASTM D4935 standard for a wide frequency band extending from 50 MHz to 18 GHz. The obtained results confirmed that the APTMS-treated BOPET film exhibit higher EMI shielding performance and better electrical characteristics compared to the untreated film. In fact, a 32% enhancement of EMI-SE was noted for the treated films compared to the untreated ones. Overall, these results put forward the role played by the surface treatment in strengthening the position of flexible PPy-Ag supported films as high-performance materials in electronic devices and electromagnetic interference shielding applications.

Ag@BN/phthalonitrile resin composites were prepared using highly thermally conductive BN modified by Ag plating. The effects of different contents of Ag@BN particles on the dynamic mechanical properties, thermal stability, and thermal conductivity of composites were examined. The results of Fourier-transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy analyses showed that Ag was successfully deposited on the surface of BN. The prepared Ag@BN was subjected to KH550 grafting treatment. With the increase in the content of Ag@BN/KH550, the storage modulus, thermal stability, and thermal conductivity of the composite increased. The storage modulus, decomposition temperature, and thermal conductivity of the Ag@BN/phthalonitrile composite with 20 wt.% Ag@BN/KH550 were 5.0 GPa, 539°C, and 0.80 W/(mK), respectively, which are 1.35, 1.18, and 3.33 times higher than those of pure resin, respectively. The compatibility and dispersibility of BN modified by Ag plating in phthalonitrile resin were effectively enhanced, thereby providing a potential candidate to be used at high-temperature devices with high thermal conductivity.

Three azine oligomeric esters were synthesized, characterized by IR, UV, 1H, 13C{1H} and GPC technique, and applied to chemosensor application. The sensitivity response of the oligomers towards the metal ion was evaluated for a metal ion series. The results have shown selective and sensitive “turn off” fluorescence response towards Fe3+ ion in DMF/H2O (1:1, pH: 7.4, fluorophore: 5 μM) solution. The binding stoichiometry and binding constant of the fluorophores were calculated using the Stern–Volmer equation and Benesi–Hildebrand plots, respectively. The quenching of fluorophores on the addition of Fe3+ ion indicates the capability of fluorophore towards quantitative analysis of Fe3+. The dimer of oligomers was theoretically studied using DFT, B3LYP/6-311G level basic set to support and explain the quenching mechanism of LMCT, PET process and to explain the DC, AC electrical studies results. The electrical conductivity measurements of solid-state, I2 doped and undoped oligomers were carried out and the conductivity gradually increases with increase in iodine vapor contact time of oligomers. The electrical conductivity was related with band gap and charge density values of imine nitrogen obtained by Huckel calculations. The dielectric measurements at different temperatures and frequencies were made by two probe method. Among the oligomers, EBHAP has recorded a high dielectric constant at the low applied frequency of 50 Hz at 373 K due to loosely attached π bonds resulting good polarization.

Polyimide composites (PETI-340M) were fabricated and subjected to high-temperature aging and thermal cycling to evaluate resistance to degradation. Mechanical-degradation mechanisms and kinetics depended on aging temperature. Aging at 232°C resulted in strength loss due to polymer degradation, while intra-tow cracking was the dominant mechanism during aging at 288°C. Composite panels subjected to thermal-cycling fatigue (−54°C to 232°C) retained mechanical properties without microcracking. However, in regions containing pre-existing fabrication-induced defects (primarily voids), intra-tow microcracks were observed after thermal cycling. Unlike some polyimide composites (PMR-15), oxidative aging effects during thermal cycling were negligible. The thermo-oxidative stability and the retention of mechanical performance after thermal cycling indicates potential for long-term, high-temperature structural applications.

With increased public awareness of fire-safety, flame retardant materials have been widely used and developed. Among them, a polyester called CPET, synthesized by the copolymerization of polyethylene terephthalate and 2-carboxyethyl (phenyl) phosphinic acid, has a good fire-safety and has been employed in the manufacture of synthetic fibers. However, the fabricated fiber made of CPET simultaneously possessing good flame retardancy and mechanical properties is a dilemma. Herein, we resolve this problem through the reactive blending of CPET with a type of thermotropic liquid crystal copolyester (PPDT) and subsequently solid-state polymerization (SSP). Thus, the fire-safety of the CPET/PPDTSSP blend improves greatly. The peak heat release rate, total heat release, and total smoke release decrease by 31.2%, 16.3%, and 11.0%, respectively, compared with those of CPET. Meanwhile, the CPET/PPDTSSP shows better crystallization and mechanical properties than CPET. The strength at yield and Young’s modulus of CPET/PPDTSSP increase by 20.0% and 15.8%, respectively. This blend shows great potential in the fabrication of fire-safety fibers with high strength.

In this article, an ultrafiltration membrane was fabricated from phenolphthalein polyethersulfone (PES-C) modified with emodin using a phase-inversion method. ATR-FTIR and UV-vis analysis showed that emodin had good compatibility with the PES-C ultrafiltration membrane. SEM showed that the prepared ultrafiltration membranes consisted of a porous skin layer and a macroporous support sublayer. The contact angle value of the pure PES-C ultrafiltration membrane was 77.71° and that of the PES-C ultrafiltration membrane blended with 0.105 wt.% emodin decreased to 65.71°, which explained the fact why its pure water flux significantly increased from 190 L/m2·h to 387 L/m2·h. The antifouling properties of the obtained ultrafiltration membranes were assessed by static protein adsorption, bacterial adhesion, antibacterial tests, and filtration experiments with BSA. The PES-C (13.895 wt.%)/emodin (0.105 wt.%) ultrafiltration membrane presented the lowest protein adsorption rate (1.44%), the highest flux recovery ratio (57%), and the largest inhibition zone diameter (3.0 ± 0.06 mm). Compared with that of the pure PES-C ultrafiltration membrane, the bacterial adhesion effect of the PES-C/emodin (0.105 wt.%) ultrafiltration membrane was significantly reduced. In addition, PES-C incorporated into the emodin ultrafiltration membrane had excellent stability in a deionized water system.