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A sol–gel film transformation and spraying approach has been developed to fabricate double-layered PBO nanofiber (PNF) nanocomposite paper nanocomposite paper. The construction of stable double-layered structures and nanofiber networks with extensive hydrogen bonds and coordination bonds led to ultraflexibility and excellent folding endurance of the nanocomposite paper. In addition, the nanocomposite paper possessed high wave-transparent coefficient, super-hydrophobicity, and self-cleaning performances. [Display omitted] Poly(p -phenylene-2,6-benzobisoxazole) nanofiber (PNF) paper is facing unprecedented challenges in enhancing the interaction between the PNFs and improving its hydrophobicity. In this work, a sol–gel film transformation approach was developed to fabricate high-strength PNF paper. Iron ions formed coordination bonds between PNFs to obtain a preforming three-dimensional, interconnective nanofiber network. Subsequently, polytetrafluoroethylene (PTFE) particles were sprayed onto the surface of the paper, followed by thermal treatment to obtain double-layered PTFE-P/PNF nanocomposite paper. The nanocomposite paper presents incredible tensile strength (271.6 MPa, increased by 52.9%), folding endurance, super-hydrophobicity, and self-cleaning performances. Moreover, it exhibits low dielectric constant (2.06) and dielectric loss tangent (0.0133) values. According to the wave-transparent model for a double-layered dielectric established by Maxwell's equations, the wave-transparent coefficients of electromagnetic waves incident from both sides of the paper are 97.6% (PNF side) and 96.0% (PTFE/P(S- co -BCB- co -MMA) side), respectively. The PTFE-P/PNF nanocomposite paper possesses great potential in the fields of wave-transparent applications. [ABSTRACT FROM AUTHOR]

1.6 Million metric tons of spent carbon electrodes modify carbon-rich solid wastes from aluminum electrolysis are produced annually, threatening ecosystems by cyanide and fluoride pollution. Here, we review carbon-rich solid wastes with focus on sources and hazards, detoxification, separation, recovery, recycling and disposal. Treatment techniques include roasting, calcination, vacuum distillation, flotation, water leaching, acid leaching, alkali leaching, complexation leaching, and alkali fusion. Waste can be disposed of alone or in combination with other waste such as cooper slag, sludge, red mud, and coal gangue. Recovery of fluorides and applications of recycled carbon are presented. Fluoride and carbon materials are separated based on differences in hydrophobicity, volatility, flammability, acidity, and alkalinity. The fluorides prepared from the solution are mainly aluminum hydroxyfluoride hydrate and cryolite. [ABSTRACT FROM AUTHOR]

Epoxy-capped polyhedral oligomeric silsesquioxane (EP-POSS) is performed to modify bisphenol A cyanate ester (BADCy) to regulate its dielectric constant and thermal resistance. EP-POSS can be incorporated in the cross-linked network of BADCy via covalent bonds, which catalyzes BADCy self-polymerization to decease the initial temperature of forming triazine rings. EP-POSS is distributed in the BADCy matrix uniformly and there is no aggregation and phase separation between EP-POSS and BADCy matrix at a micrometer scale. The dielectric constant values of EP-POSS/BADCy are decreased with the addition of EP-POSS, but increased slightly when the mass fraction of the EP-POSS is more than 2 wt%. The thermal resistance of EP-POSS/BADCy is increased slightly with the addition of EP-POSS. [ABSTRACT FROM AUTHOR]

Surface initiated reversible addition–fragmentation chain transfer polymerization (RAFT) of glycidyl methacrylate (GMA) was conducted on ceramic particles (ZNT). Then the ZNT@PGMA particles were introduced into cyanate ester (CE) matrix to prepare the ultra low dielectric loss ZNT@PGMA/CE composites. The ZNT@PGMA particles can be well dispersed in the CE matrix, resulting in the improvement of glass transition temperature by 40 °C and the increase of storage modulus by 130% in comparison to that of pure CE resins. The introduction of ZNT@PGMA particles can obviously decrease dielectric loss value of the ceramic/CE composites by one order of magnitude, which possesses potential in wave transparent composites and structures. [ABSTRACT FROM AUTHOR]

Quartz fibers (QFs) and two polyhedral oligomeric silsesquioxane (POSS) (epoxy-POSS and hydroxy-POSS) are performed to regulate the dielectric properties, heat resistance, and mechanical properties of cyanate ester (CE) resins. With the introduction of POSS, the dielectric constant and dielectric loss tangent values of the POSS/QFs/CE laminated composites are decreased obviously. The heat resistance properties and flexural strength values of the laminated composites are increased, but the interlaminar shear strength values of the laminated composites are decreased slightly. The EP-POSS/QFs/CE laminated composites have relatively better dielectric, heat resistance, and mechanical properties than those of HO-POSS/QFs/CE laminated composites. POLYM. COMPOS., 36:2017-2021, 2015. © 2014 Society of Plastics Engineer [ABSTRACT FROM AUTHOR]

Graphene sheets were covalently functionalized with poly(1-vinylimidazole) (PVI) type poly(ionic liquid), by utilizing a diazonium addition reaction and the subsequent grafting of PVI polymers onto the graphene sheet surface by a quaternarization reaction. The resultant modified graphene sheets showed improved dispersion property when being dissolved in DMF and ethanol. FTIR, XPS, XRD and TEM observations confirmed the success of the covalent functionalization, and thermogravimetric analysis revealed that the grafting ratio of PVI was ∼12 wt%. The obtained PVI-functionalized graphene showed a high capability for removing anionic dyes such as methyl blue (MB) from water solution. The experimental data of isotherm fitted well with the Langmuir adsorption model. The adsorption capacity of 1910 mg g −1 for methyl blue (MB) dye was observed for functionalized graphene sheets with poly(ionic liquid)s, which was higher than that of unmodified graphene. The high adsorption capacity observed in this study emphasizes that poly(ionic liquid)s-modified graphene materials have a great potential for water purification as they are highly efficient and stable adsorbents for sustainability. [ABSTRACT FROM AUTHOR]

The surface of high modulus poly( p-phenylene-2,6-benzobisoxazole) (HMPBO) fibers were treated by the combination method of oxygen plasma/polyhedral oligomeric silsesquioxane (POSS). The chemical compositions and surface morphologies of HMPBO fibers were characterized by Fourier transform infrared, X-ray photoelectron spectroscopy, thermogravimetric analyzer, and scanning electron microscopy. The interfacial shearing strength (IFSS) of the HMPBO/cyanate ester (HMPBO/CE) micro-composites was measured by single fiber pull out test. Results showed that the POSS was grafted on the surface of HMPBO fibers, and the grafting amount was about 0.82 wt%. After the treatment, the HMPBO fibers became coarser and the diameter was also increased. Compared with that of pure HMPBO/CE micro-composites, the IFSS of treated HMPBO/CE micro-composites was increased by 20.7%. POLYM. COMPOS., 34:2026-2030, 2013. © 2013 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

The development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero‐structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)‐(AgNWs@BNNS)‐(BNNS/ANF) (denoted as BAB) composite films by "filtration self‐assembly, air spraying, and hot‐pressing" method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in‐plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015 Ω ⋅ cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds. [ABSTRACT FROM AUTHOR]

The development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero‐structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)‐(AgNWs@BNNS)‐(BNNS/ANF) (denoted as BAB) composite films by "filtration self‐assembly, air spraying, and hot‐pressing" method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in‐plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015 Ω ⋅ cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds. [ABSTRACT FROM AUTHOR]

Highlights: m-BN/PNF nanocomposite paper with nacre-mimetic layered structures prepared via sol–gel film transformation approach presents excellent thermal conductivity, incredible electrical insulation, outstanding mechanical property and thermal stability. When the mass fraction of m-BN is 50 wt%, m-BN/PNF nanocomposite paper exhibits excellent thermal conductivity and electrical insulation. The λ∥ and λ⊥ are 9.68 and 0.84 W m−1 K−1, and the volume resistivity and breakdown strength are as high as 2.3 × 1015 Ω cm and 324.2 kV mm−1, respectively. The m-BN/PNF nanocomposite paper with 50 wt% m-BN also presents outstanding mechanical properties (tensile strength of 193.6 MPa) and thermal stability (thermal decomposition temperature of 640 °C). With the rapid development of 5G information technology, thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming prominent. In this work, "high-temperature solid-phase & diazonium salt decomposition" method is carried out to prepare benzidine-functionalized boron nitride (m-BN). Subsequently, m-BN/poly(p-phenylene benzobisoxazole) nanofiber (PNF) nanocomposite paper with nacre-mimetic layered structures is prepared via sol–gel film transformation approach. The obtained m-BN/PNF nanocomposite paper with 50 wt% m-BN presents excellent thermal conductivity, incredible electrical insulation, outstanding mechanical properties and thermal stability, due to the construction of extensive hydrogen bonds and π–π interactions between m-BN and PNF, and stable nacre-mimetic layered structures. Its λ∥ and λ⊥ are 9.68 and 0.84 W m−1 K−1, and the volume resistivity and breakdown strength are as high as 2.3 × 1015 Ω cm and 324.2 kV mm−1, respectively. Besides, it also presents extremely high tensile strength of 193.6 MPa and thermal decomposition temperature of 640 °C, showing a broad application prospect in high-end thermal management fields such as electronic devices and electrical equipment. [ABSTRACT FROM AUTHOR]

A series of polymeric shape memory system of chemically cross-linked poly(styrene-b-butadiene-b-styrene) triblock copolymer(SBS) and linear low density polyethylene(LDPE) blends were developed and characterized. The chemically cross-linked SBS/LDPE blends were prepared by varying the amount of initiator (DCP) between 0 and 1.5 wt.% and the ratio of SBS/LDPE ranges from 90/10 to 60/40. The cross-linked SBS/LDPE blends were fully characterized by gel content, tensile test, dynamic mechanical analysis (DMA), differential scanning calorimeter (DSC) and shape memory behavior. Results demonstrate that the cross-linking degree increases with the increment of the DCP content, leading to reductions in tensile strength and elongation at break. The transition temperature of cross-linked SBS/LDPE blends is tunable through changing SBS/LDPE ratio and DCP content. DMA test shows that the melt strength of the blends is influenced by the DCP and LDPE content. The chemically cross-linked SBS/LDPE blends have excellent shape memory effect when the cross-linking degree between 46 and 77 %. The shape recovery time decreases as the test temperature increases and the shape recovery rate decreases with cycle times increasing. [ABSTRACT FROM AUTHOR]

A new series of liquid crystal (LC) monomers – not only contain a double bond but also contain an azo group – were designed and synthesised. The length of side groups in the LC monomers containing azobenzene ester varied from 1 to 2 methylene units, and the length of the substituted groups in the main chain varied from 1 to 3 methylene units. The molecular structures of the intermediates and target compounds were confirmed by Fourier transform infrared, ultraviolet and visible spectrum and nuclear magnetic resonance (NMR) spectroscopy. The thermal phase behaviour of the LC monomers was investigated by polar optical microscopy coupled with hot stage and differential scanning calorimetry (DSC). In this paper, the effect on the LC zone with the substituents were investigated, and with the increased methylene of main chain, the melting point and the phase transition temperature of the substance will be lowered and LC regions will be narrower. [ABSTRACT FROM AUTHOR]

Abstract: Shape-memory polymers (SMPs) have the capacity to return large strains by external stimuli. Among various SMPs, shape-memory epoxy has received considerable attention because of its superior mechanical and thermal properties as well as excellent shape-memory performance. In this study, short glass fibre-reinforced shape-memory hydro-epoxy composites are developed to improve further the mechanical property of shape-memory epoxy resin. The thermomechanical and shape-memory properties of the developed composite materials are investigated by dynamic mechanical analysis, bend test and shape recovery test. The results indicate that the glass modulus and bend strength of the developed composite materials initially increase and then slightly decrease with increasing short glass fibre content. The glass transition temperature of the developed composite materials does not change with increasing short glass fibre. When the short glass fibre content is less than 4.5wt.%, full recovery can be observed after only several minutes at different temperatures. The shape-memory property of the composite materials is not affected greatly. However, when the short glass fibre content is more than 4.5wt.%, the material would be destroyed after deformation. [Copyright &y& Elsevier]

A new series of nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesized via the Steglich esterification reaction. Length of the side groups varied from 1 to 2 methylene units. The molecular structures of the intermediates and the LC monomers were confirmed by Fourier transform infrared spectrum, elemental analysis, and nuclear magnetic resonance spectroscopy. The thermal phase behavior of the LC monomers was investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. All of these LC monomers showed only one nematic mesophase at room temperature during the cooling process. [ABSTRACT FROM PUBLISHER]

A novel shape-memory hydro-epoxy resin system was prepared from hydro-epoxy, poly(propylene glycol) diglycidyl ether, and menthane diamine. The relationships between the thermomechanical properties of the system and structural changes were investigated by differential scanning calorimetry, dynamic mechanical analysis, and bending tests. The shape-memory behavior of the hydro-epoxy resin was also characterized by performing a U-type shape-memory test. The results indicate that this novel shape-memory hydro-epoxy resin has good shape-memory performance, its shape recovery ratio ( R) is almost 100 %, and full recovery is observed after just a few minutes. The glass transition temperature ( Tg) of the resin was determined using dynamic mechanical analysis, and the results indicate that Tg decreases from 107 to 65 °C as the poly(propylene glycol) diglycidyl ether content is increased, which means that the Tg of the polymer can be modulated within a certain range by varying the poly(propylene glycol) diglycidyl ether content in order to meet different requirements. [ABSTRACT FROM AUTHOR]

Two nematic liquid crystal (LC) monomers containing double bonds in the side chain were designed and synthesised. Length of the side groups varied from 1 to 2 methylene units. The side-chain polymers were synthesised by hydrosilylation reaction. The molecular structures of the intermediates and the LC monomers were characterised by Fourier transform infrared, elemental analysis and nuclear magnetic resonance spectroscopy. The thermal phase behaviour of the monomers and polymers were investigated by differential scanning calorimetry and polar optical microscopy coupled with hot stage. The LC monomers showed only one nematic mesophase in the cooling process. And, the two polymers exhibit an enantiotroppic nematic mesophase either in the heating or in the cooling process. [ABSTRACT FROM AUTHOR]

[Display omitted] • The uniform organic–inorganic hybrid coating is formed on the surface of PBO fibers. • PBO@P-Ce 0.8 Ca 0.2 O 1.8 fibers present the excellent interfacial bonding strength with resin matrix. • The functionalized PBO fibers coated by the hybrid coating possess excellent UV resistance. Poly(p -phenylene-2,6-benzobisoxazole) (PBO) fibers display weak outdoor stability and reliability due to their poor UV resistance and chemically inert surface. In this work, calcia-doped ceria (Ce 0.8 Ca 0.2 O 1.8) nanoparticles was fabricated via chemical co -precipitation method, and the novel Ce 0.8 Ca 0.2 O 1.8 /P(S- co -BCB- co -MMA) organic–inorganic hybrid coating was then designed and prepared for surface functionalization of PBO fibers (PBO@P-Ce 0.8 Ca 0.2 O 1.8). Organic-inorganic hybrid coating presents high surface roughness and excellent UV resistance. When the concentration of Ce 0.8 Ca 0.2 O 1.8 nanoparticles with the particle size of about 50 nm is 0.6 wt%, PBO@P-Ce 0.8 Ca 0.2 O 1.8 –3 fibers (sample 4, 0.6 wt%) present the best interfacial bonding strength with modified bisphenol A cyanate (BADCy) resins, the single fiber pull-out strength between sample 4 and modified BADCy resins reaches the maximum value of 4.6 MPa, 48.4% higher than that of pristine PBO fibers (sample 0, 3.1 MPa). Meanwhile, the tensile strength of sample 4 after 288 h UV aging is increased from 1.4 GPa (PBO fibers) to 4.1 GPa. Overall, functionalized PBO fibers in this work demonstrate higher surface activity, excellent UV resistance and improved interfacial bonding strength with modified BADCy resins, which provides a new idea for functionalizing the surface activity and UV resistance of high-performance polymer fibers. [ABSTRACT FROM AUTHOR]

Abstract: Surface modification of nano-β-SiC whiskers with titanate coupling reagent of NDZ-105 was performed to prepare β-SiCw/celluloid nano-composites via powder blending method. The surface performance of modified nano-β-SiC whiskers was characterized and analyzed using Zeta potential, XPS, FTIR and TGA. The results indicated that a chemical bonding of NDZ-105 to β-SiC whiskers film and a layer of organic single molecule membrane were formed, and the maximum mass fraction of NDZ-105 coated on the surface of β-SiC whiskers measured was only about 1.88%. Meantime, mechanical tests revealed that the tensile, flexural and impact properties of the nano-composites obviously enhanced with the increase mass fraction of NDZ-105 modified β-SiC whiskers, and these properties were optimal with 5% mass fraction of β-SiC whiskers which was modified by 3% mass fraction of NDZ-105. [Copyright &y& Elsevier]

Bisphenol A dicyanate ester (BADCy) was utilized as the matrix, poly (p -phenylene-2, 6-benzobisoxazole) (PBO) fibers as the reinforcement, and synthesized fluorine-containing linear PBO precursor (pre FLPBO) as the interfacial compatibilizer to prepare PBO fibers/FLPBO- m -BADCy wave-transparent laminated composites. The fluorine groups and PBO-like structures could respectively improve the dielectric properties of BADCy matrix and the interfacial compatibility between the BADCy matrix and PBO fibers. Additionally, the partly interpenetrating network formed between pre FLPBO and BADCy could significantly improve the mechanical properties. PBO fibers/FLPBO- m -BADCy wave-transparent laminated composites with 7 wt% pre FLPBO displayed the optimal comprehensive performances. Dielectric constant (ε) and dielectric loss (tan δ) were respectively 2.90 and 0.0042, and the corresponding theoretical wave-transmittance (| T |2) at 1 MHz was 93.3%, higher than that of PBO fibers/BADCy wave-transparent laminated composites. The minimum percentage of simulated electromagnetic wave-transparent energy (E T (simulation)) of the PBO fibers/FLPBO- m -BADCy (1 mm) wave-transparent laminated composites at 0.3~40 GHz was 87.3%, also better than PBO fibers/BADCy wave-transparent laminated composites (85.9%). The flexural and interlaminar shear strength (ILSS) of PBO fibers/FLPBO- m -BADCy wave-transparent laminated composites were increased from 587.4 and 36.7 MPa to 628.0 and 44.8 MPa, respectively. In addition, the corresponding volume resistivity and breakdown voltage were 2.7 × 1015 Ω·cm and 19.12 kV/mm, respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Novel compound (AEAF) with both cage-type adamantanes and fluorine-containing structures was synthesized from bisphenol AF, 1-adamantyl chloride and epichlorohydrin through successive esterification and O-alkylation reaction, which was then introduced into the curing networks of bisphenol A cyanate ester (BADCy) resins through copolymerization, to obtain AEAF- co -BADCy resins. AEAF presented low polarizability & dipole density, rigid cage adamantane, and stable CF 3 group. When the mass fraction of AEAF was 6 wt%, AEAF- co -BADCy resins displayed the minimum real part (ε′ r), imaginary part (ε" r) of complex permittivity, and dielectric loss tangent (tanδ) values, which were 2.49, 0.012, and 0.0048, respectively. And the corresponding wave transmission efficiency (T) was 92.3%, significantly higher than that of pure BADCy (86.6%). AEAF- co -BADCy resins also possessed excellent mechanical properties and better interfacial compatibilities with poly(p -phenylene-2,6-benzobisoxazole) (PBO) fibers. The corresponding flexural strength (126.5 MPa) and impact strength (15.2 kJ m−2) were increased by 16.6% and 47.6%, in comparison to pure BADCy (flexural strength of 108.5 MPa and impact strength of 10.3 kJ m−2). Meantime, the single fiber pull-out strength of PBO fibers/AEAF- co -BADCy (6 wt% AEAF) micro-composites also displayed an increase from 3.1 MPa (PBO fibers/BADCy) to 3.4 MPa. [ABSTRACT FROM AUTHOR]

NiFe layer double metal hydroxide nanosheets (NiFe LDHs) have been extensively investigated as one of the best promising candidates to construct efficient bifunctional catalysts. In this research, element (vanadium) doping into NiFe LDHs grown in nickel foam were synthesized by the one-step method and applied in overall water splitting. The content and structure of the composites were adjusted to regulate the catalyst's electronic structure and reduce the onset potential and achieved unprecedented electrocatalysis for OER and HER. The V-NiFe-LDH/NF showed perfect OER and HER activities with low Tafel slopes of 31.3 and 89.8 mV dec−1, and small overpotentials of 195 and 120 mV at 10 mA cm−2 in 1.0 m KOH solution, respectively. Electrochemical analysis indicated that the efficient catalytic activity of V-NiFe-LDHs/NF mainly benefited from V doping, which optimized the electronic structure and produce defects, thereby resulting in an enhanced conductivity, facile electron transfer, and adequate active sites. [ABSTRACT FROM AUTHOR]

Abstract Combining method of dopamine/polyhedral oligomericsilsesquioxane (DA/POSS) was firstly performed to functionalize the surface of Kevlar (POSS- g -Kevlar@PDA, f -Kevlar) cloth. And then the corresponding f -Kevlar cloth/bisphenol A cyanate ester (BADCy) matrix wave-transparent laminated composites were successfully fabricated by the method of impregnation, lamination followed by mould pressing. The obtained wave transmission efficiency (T) of 92.0% for f -Kevlar cloth/BADCy wave-transparent laminated composites was higher than that of pristine Kevlar cloth/BADCy wave-transparent laminated composites (T of 88.4%). Flexural strength and interlaminar shear strength (ILSS) of the f -Kevlar cloth/BADCy wave-transparent laminated composites were also significantly increased to 236.3 MPa and 28.5 MPa, increased by 28.8% and 73.7%, in comparison to that of pristine Kevlar cloth/BADCy wave-transparent laminated composites (flexural strength of 183.5 MPa and ILSS of 16.4 MPa), respectively. And the corresponding glass transition temperature (T g) and heat resistant index (T HRI) of the f -Kevlar cloth/BADCy wave-transparent laminated composites was 226.3 °C and 232.8 °C, respectively. [ABSTRACT FROM AUTHOR]

In this paper, a novel interfacial compatibilizer of soluble epoxy-terminated poly ( p -phenylene-2, 6-benzobisoxazole) precursor (epoxy- pre PBO) was synthesized to modify bisphenol A cyanate ester (BADCy) resin via copolymerization. Compared to PBO fibers/BADCy wave-transparent composites, the obtained PBO fibers/epoxy- pre PBO modified BADCy (PBO fibers/PBO- co -BADCy) wave-transparent composite with 7 wt% epoxy- pre PBO showed ultra-low dielectric constant ( ε, 2.68) and dielectric loss tangent (tan δ, 0.0061) values, excellent mechanical properties (flexural strength, 658.5 MPa) and interlaminar shear strength (48.4 MPa), and outstanding thermal stability ( T Heat-resistance index , 262.9 °C). These properties proved its potential in applications, such as in radomes and antenna system of aircrafts. [ABSTRACT FROM AUTHOR]

In this paper, we presented a new strategy for fabrication of polymeric composites combined with low dielectric loss and desirable thermal conductivity. With the incorporation of hyperbranched polyborosilazane (hb-PBSZ) into bisphenol A cyanate ester (BADCy) matrix, the modified hb-PBSZ/BADCy resin with 4 wt% hb-PBSZ possessed a low dielectric constant (?) value of 2.37 and relatively low dielectric loss tangent value of 0.008 at 1MHz. Furthermore, by integrating micrometer boron nitride particles (mBN) into hb-PBSZ/BADCy matrix, the mBN/hb-PBSZ/BADCy composites presented relatively low ? of 3.09, desirable thermally conductive coefficient (? of 0.63 W/(m?K)) and thermal diffusivity (? of 0.42 mm2/s) values. It provides an important perspective for designing dielectric and thermally conductive polymeric composites for electrical packaging and energy storage fields. [ABSTRACT FROM PUBLISHER]

The hierarchically macro/micro-porous silicon-carbon-nitrogen (Si-C-N) hybrid material was presented with novel functionalities of totally selective and highly efficient adsorption for organic dyes. The hybrid material was conveniently generated by the pyrolysis of commercial polysilazane precursors using polydivinylbenzene microspheres as sacrificial templates. Owing to the Van der Waals force between sp-hybridized carbon domains and triphenyl structure of dyes, and electrostatic interaction between dyes and Si-C-N matrix, it exhibites high adsorption capacity and good regeneration and recycling ability for the dyes with triphenyl structure, such as methyl blue (MB), acid fuchsin (AF), basic fuchsin and malachite green. The adsorption process is determined by both surface adsorption and intraparticle diffusion. According to the Langmuir model, the adsorption capacity is 1327.7 mg·g−1 and 1084.5 mg·g−1 for MB and AF, respectively, which is much higher than that of many other adsorbents. On the contrary, the hybrid materials do not adsorb the dyes with azo benzene structures, such as methyl orange, methyl red and congro red. Thus, the hierarchically porous Si-C-N hybrid material from a facile and low cost polymer-derived strategy provides a new perspective and possesses a significant potential in the treatment of wastewater with complex organic pollutants. [ABSTRACT FROM AUTHOR]

Polydopamine hybrid zeolitic imidazolate framework-8 (PDA*ZIF-8) membrane, synthesized by zinc nitrate hexahydrate (ZnNO 3 •6H 2 O), 2-methylimidazole (2-MI), and dopamine (DA), uniformly grows on the surface of poly(p -phenylene-2, 6-benzobisoxazole) (PBO) fibers by heterogeneous nucleation method to obtain PBO@PDA*ZIF-8 fibers. PBO@PDA*ZIF-8 fibers are then applied as the reinforcement, bisphenol A dicyanate ester (BADCy) as the matrix, and PBO@PDA*ZIF-8 fibers/BADCy wave-transparent laminated composites are prepared by high-temperature molding. Results indicate that PDA*ZIF-8 membrane increases the surface roughness and chemical activity of PBO fibers. The interlaminar shear strength (ILSS) and flexural strength of PBO@PDA*ZIF-8 fibers/BADCy laminated composites are 45.3 and 656.3 MPa, respectively, which are increased by 23.4% and 11.7% compared with those of PBO fibers/BADCy composites (587.4 and 36.7 MPa). The dielectric constant and dielectric loss values at 1 MHz are 2.76 and 0.0046, respectively, lower than PBO fibers/BADCy (3.06 and 0.006). At 0.3–40 GHz, PBO@PDA*ZIF-8 fibers/BADCy laminated composites have excellent wave-transparent performance (The simulated wave-transparent rate is greater than 87%, d = 1.5–3.5 mm). Meanwhile, the corresponding volume resistivity and breakdown strength are 3.7 × 1015 Ω•cm and 23.61 kV/mm, higher than PBO fibers/BADCy composites (2.2 × 1015 Ω•cm and 17.69 kV/mm), respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: The regularity of ‘skin-core’ type of crystallinity distribution within the polyethylene cylindrical specimen crystallized under high pressure was investigated via modulated differential scanning calorimeter (MDSC), wide angle X-ray diffraction meter (WAXD), dynamic mechanical analyzer (DMA) and scanning electron microscope (SEM). The relationship between the gradient of high pressure stress field and the ‘skin-core’ structure of polyethylene was also established. The results indicate that there exists a distinguished difference of crystallinity, morphology and dynamical mechanical properties between skin layer and core region within the cylindrical specimen crystallized under 650MPa pressure. The measurement data of the non-reversible heat flow of MDSC and WAXD for both skin layer and core region are in accordance with that marked difference. According to the law of stress decay of high pressure stress field and the high pressure crystallization theory of polymers, it was found that the uneven distribution of high pressure stress field, especially, the high pressure decay effect at the edge of plunger and cylindrical channel of the mold is proposed as the principal factor to the formation of the ‘skin-core’ type of crystallinity distribution within the polyethylene cylindrical specimen crystallized under high pressure. [Copyright &y& Elsevier]

Poly (p -phenylene-2,6-benzobisoxazole) fibers treated by random copolymer P(S -co -BCB- co -MMA) membrane and UV etching (UV-PBO@P fibers) are performed as reinforcement, bisphenol AF/amantadine modified bisphenol A cyanate ester (AEAF- co- BADCy) resin as polymeric matrix, and the UV-PBO@P fibers/AEAF- co -BADCy wave-transparent laminated composites were then fabricated. When the P(S- co -BCB- co- MMA) membrane thickness is 62.3 nm and the UV etching time is 96 h, UV-PBO@P fibers display the best interfacial compatibility with AEAF- co- BADCy resin, and the corresponding wave-transparent laminated composites present the optimal comprehensive performance. Interlaminar shear strength (ILSS) and flexural strength are 50.2 and 745.6 MPa, 27.4% and 21.6% higher than those (ILSS of 39.4 MPa, flexural strength of 613.3 MPa) of pristine PBO fibers/AEAF-co-BADCy wave-transparent laminated composites, respectively. And the composites possess low complex permittivity and tan δ , corresponding | T |2 in the X band is 88.9–94.2%. High-frequency structural simulation (HFSS) results demonstrate that the radome from the composites displays high |T| 2 of 89.1–93.1% in the X-band, close to the theoretical calculation value. This work provides a certain theoretical guidance for fabricating lightweight, high strength, and high | T |2 polymer matrix wave-transparent composites, and further broadens the application of PBO fibers and cyanate ester resins in aviation/aerospace, 5G communication services, electronic information, and other fields. [Display omitted] • A novel way to improve the interfacial bonding strength between fibers and resins. • The wave transmission performances of composites were investigated. • A certain theoretical guidance for fabricating wave-transparent composites.. [ABSTRACT FROM AUTHOR]

Poly(p -phenylene-2,6-benzobisoxazole) (PBO) fibers can be applied as reinforcement to fabricate PBO/cyanate ester (CE) resin laminated composites with light weight, high specific strength & modulus, excellent dielectric properties, and extraordinary excellent thermal & humidity resistance for radome application. However, the surface of PBO fibers is extremely inert, resulting in poor interfacial compatibility to CE matrix. Besides, the toughness and wave-transparent performances of the cured CE resins need to be further improved. In this work, 2, 2-bis(3-amino-4-hydroxyphenyl) hexafluoropropane (6FAP) and terephthaloyl chloride (TPC) were performed to synthesize fluorine-containing epoxy-terminated PBO precursor (epoxy- pre FPBO) via condensation reaction followed by end-group functionalization with glycidol. Afterwards, epoxy- pre FPBO modified CE resins (FPBO- co -BADCy resins) were prepared by copolymerization of epoxy- pre FPBO and bisphenol A cyanate ester (BADCy). FPBO- co -BADCy resins with 7 wt% epoxy- pre FPBO displayed the optimal wave-transparent performances and mechanical properties. Dielectric constant (ε) and dielectric loss (tan δ) is respectively 2.48 and 0.0081, and the corresponding transmittance (|T| 2 ) at 10 MHz is 94.9%, higher than that of pure BADCy (92.7%). The corresponding flexural and impact strength was enhanced to 119.9 MPa and 12.3 kJ/m2, 21.4% and 24.5% higher than that of pure BADCy, respectively. In addition, FPBO- co -BADCy resins presented better interfacial bonding strength with PBO fibers than that of pure BADCy. [ABSTRACT FROM AUTHOR]