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With the development of science and technology and electronic industry, electromagnetic wave pollution has become the fifth largest pollution in the world today, so it is very important to develop a material with good wave absorbing properties. In this study, polyaniline was loaded onto the surface of carbon nanotubes (CNTs) bundles in Buckypaper by electropolymerization, and epoxy resin was used as the matrix to prepare a polyaniline (PANI)/Buckypaper/EP composite absorber with integrated structure and function. The research shows that the CNTs are prepared into Buckypaper with a three‐dimensional porous structure by vacuum filtration. This three‐dimensional porous structure ensures that CNTs can be added at a high content and uniformly dispersed in epoxy resin. PANI adjusts the impedance matching of Buckypaper and adds more loss mechanisms. Under the optimal matching thickness of 1.5 mm, the optimal reflection loss reaches −29.31 dB, and the absorption bandwidth is 3.12 GHz. At the same time, the interaction between the π–π noncovalent bond of PANI and the delocalized π electrons on the surface of CNTs improves the mechanical strength of Buckypaper. The tensile strength reached 42.17 MPa, an increase of 92.82% compared with pure BP/EP. The research in this article is expected to provide a feasible idea for the preparation of structure–function integrated materials. [ABSTRACT FROM AUTHOR]

A new addition curable silicone resin (ASiR) system with excellent dielectric and thermal properties was developed, which consists of only two components: poly (methylphenylvinylsiloxane) (PMPVSi) and an end-capped hydrogen-functionalized hyperbranched polysiloxane (EHFHPSi). PMPVSi is synthesized by a green and controllable process; EHFHPSi is first synthesized via [A.sub.2] + [B.sub.3] approach, and then end-capped by hexamethyldisiloxane (HMDS). Three formulations were designed to investigate the optimum stoichiometry. Results show that cured ASiR resins have greatly different dielectric and thermal properties because of the different chemical structure of cured networks resulting from the different stoichiometrics. The resin with a suitable stoichiometry has not only excellent dielectric properties including extremely low dielectric constant (2.96 at 1 Hz) and loss (0.0003 at 1 Hz) as well as good stability on frequency, but also outstanding thermal resistance, exhibiting great potential to be used as a new kind of high-performance resins for many cutting-edge industries, especially the microelectronic and insulation fields. POLYM. ENG, SCI., 52:259-267, 2012. © 2011 Society of Plastics Engineers, INTRODUCTION Addition curable silicone resins are known to be cross-linked semi-inorganic polymers with the Si-O-Si chains as backbones and some organic groups as side chains, which possess combined properties of [...]

High curing temperature is the key disadvantage of cyanate esters. A novel catalyst system was developed, which is a hybrid catalyst system (HC) consisting of UV activated tricarbonyl cyclopentadienyl manganese (Catalyst I) and Catalyst II derived from dibutyl tin dilaurate. The effect of HC on the reactivity of 2, 2'-bis(4-cyanatophenyl) isopropylidene (BADCy) monomer, and that on the dielectric and thermal properties of cured resin were investigated. Results show that HC displays an attractive synergy effect on catalyzing BADCy over its two components. Compared with the curing exothermic peak of BADCy, that of BADCy/HC system appears at significantly lower temperature (which is at least 120°C lower than the former). In addition, cured BADCy/HC resin also exhibits interesting synergy effect in integrated performance, that is, it has much better thermal resistance and dielectric properties than cured BADCy, BADCy/Catalyst I, and BADCy/Catalyst II resins. The BADCy/HC resin can be used as high performance matrices for advanced composites and adhesives. POLYM. ENG. SCI., 51:22362244, 2011. @ 2011 Society of Plastics Engineers, INTRODUCTION Cyanate ester (CE) resins have excellent integrated properties, such as outstanding dielectric property, thermal resistance as well as good processing etc, so CE resins have been regarded as the [...]

ABSTRACT Phosphorous flame retardants (PFRs) are common halogen-free flame retardants. However, the flame retardancy of PFRs has not been fully exploited. Herein, the synergistic flame retardant effect of a typical phosphorous compound, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), and organoclay on epoxy is studied. Results show that the peak of heat release rate (pHRR) and smoke production rate of modified epoxy resin (EP) with both 2.0 wt % phosphorus and 4.0 wt % organoclay are only 40% and 46% of that of neat EP resin, respectively, while the sole use of 2.0 wt % phosphorus only decrease the pHRR to 59% of that of neat EP resin. The structure and thermal decomposition behavior of as-prepared nanocomposites are analyzed, and a synergistic flame retardant mechanism is proposed. This investigation opens a new approach to obtain halogen-free EPs with higher flame retardancy and better overall properties than the EPs loaded with DOPO only. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43367. [ABSTRACT FROM AUTHOR]

Graphene is regarded as a prominent multi-functional flame retardant for use in halogen-free flame retardant polymers with simultaneously improved integrated properties and special functionalities. However, its flame retardant efficiency is not impressive enough due to the weak resistance to thermo-oxidative decomposition. In order to overcome this problem, the surface of graphene oxide was covered with large amounts of non-flammable silicas through a sol–gel and surface treatment process, and then used to modify the epoxy (EP) resin. Results show that the incorporation of the as-prepared nanosilica/graphene oxide (m-SGO) hybrid into EP resin not only obviously increases the flame retardancy, mechanical, and thermal stability properties, but also endows EP resin with high thermal conductivity, low dielectric loss, and high dielectric constant. Specifically, the peaks of the heat release rate and total heat release of the modified EP resin with 1.5% m-SGO decrease by 39% and 10% of those of neat EP resin, respectively. These attractive features of m-SGO/EP nanocomposites are attributed to the unique structure and high resistance to oxidative degradation of m-SGO as well as its good interactions with EP resin. The investigation provides a new approach for the preparation of novel core–shell flame retardants through surface wrapping with other flame retardants on SGO and related high performance flame retardant resins. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) printing of continuous fiber-reinforced composites has been developed in recent decades as an alternative means to handle complex structures with excellent design flexibility and without mold forming. Although 3D printing has been increasingly used in the manufacturing industry, there is still room for the development of theories about how the process parameters affect microstructural properties to meet the mechanical requirements of the printed parts. In this paper, we investigated continuous carbon fiber-reinforced polyphenylene sulfide (CCF/PPS) as feedstock for fused deposition modeling (FDM) simulated by thermocompression. This study revealed that the samples manufactured using a layer-by-layer process have a high tensile strength up to 2041.29 MPa, which is improved by 68.8% compared with those prepared by the once-stacked method. Moreover, the mechanical–microstructure characterization relationships indicated that the compactness of the laminates is higher when the stacked CCF/PPS are separated, which can be explained based on both the void formation and the nanoindentation results. These reinforcements confirm the potential of remodeling the layer-up methods for the development of high-performance carbon fiber-reinforced thermoplastics. This study is of great significance to the improvement of the FDM process and opens broad prospects for the aerospace industry and continuous fiber-reinforced polymer matrix materials. [ABSTRACT FROM AUTHOR]

A novel hyperbranched polysiloxane containing epoxy and phosphaphenanthrene groups (EP-HPSi) was synthesized through a ring-open reaction between P-H bond of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and epoxy group of a hyperbranched polysiloxane. EP-HPSi was used to modify cyanate ester (CE) resin. The influences of the content of EP-HPSi in modified CE resin system as well as the molar ratio between DOPO and epoxy group on the structure and integrated performance of the EP-HPSi/CE system were systematically studied. Results show that EP-HPSi is a multi-functional flame retardant, which endows CE resin with not only outstanding flame retardancy, but also significantly increased toughness and stiffness. For example, EP-HPSi/CE system has a 40–80oC lower curing temperature than CE; moreover, the impact and flexural strengths of EP-HPSi/CE system are about 1.6–2.2 and 1.3 times higher than that of CE resin, respectively. These attractive integrated performances of EP-HPSi/CE system are attributed to the special structure of EP-HPSi, and its influence on the cross-linked network. This investigation suggests that the method proposed herein is a new approach to develop high performance flame retardant resins for cutting-edge industries, especially those that simultaneously have outstanding thermal resistance, toughness, and stiffness. [Supplementary materials are available for this article. Go to the Publisher's online edition of Soft Materials for the following free supplemental resource: Figure S1] [ABSTRACT FROM AUTHOR]

A new hyperbranched polysiloxane containing maleimide (HPMA) was synthesized through the reaction between N-(4-hydroxyphenyl) maleimide and 3-glycidoxypropyltrimethoxysilane, which was then used to prepare cyanate ester (CE) resin-based hybrids (coded as HPMA x/CE, where x is the weight fraction of HPMA in the hybrid). The curing behavior of uncured hybrids and the typical properties (impact strength and dielectric properties) of cured hybrids were systemically investigated. Results show that the performance of hybrids is greatly related with the content of HPMA. Hybrids have obviously lower curing temperature than CE, overcoming the poor curing characteristics (higher curing temperature and longer curing time) of neat CE, for example, the curing peak temperature of HPMA20/CE is about 65°C lower than that of CE. In the case of cured resin and hybrids, the hybrids exhibit decreased dielectric constant and loss than CE resin; moreover, the former also exhibits lower water absorption than the latter. Specifically, the dielectric loss of HPMA15/CE hybrid is only about 27% of that of neat CE resin. In addition, the hybrids with suitable contents of HPMA have significantly improved impact strengths. The overall improved properties suggest that HPMA x/CE hybrids have great potential in applications needing harsh requirements of curing feature, dielectric properties, and toughness. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

An improved method is developed to synthesize octavinylsilsesquioxanes (VPOSS) with shorter time and higher yield, and then VPOSS is used to prepare new hybrids based on bismaleimide-triazine (BD/CE) resin, coded as VPOSS/BD/CE. The effect of the content of VPOSS on the key properties including curing behavior, thermal, mechanical, and dielectric properties as well as water resistance of VPOSS/BD/CE hybrids were systematically discussed. Compared with BD/CE resin, hybrids show similar curing behavior but different chemical structures and thus macro-performance. These key properties of hybrids are dependent on the content of VPOSS, all hybrids show significantly improved dielectric properties, water resistance, and dimensional stability; moreover, the hybrids with suitable content of VPOSS have bigger impact strengths. Specifically, with the addition of 7 wt% VPOSS to BD/CE resin, the dielectric constant decreases from 3.7 to 3.2, the dielectric loss decreases 55%, and the coefficient of thermal expansion reduces 23%; moreover, the glass transition temperature and initial decomposition temperature increase about 15°C. The attractive integrated properties suggest that VPOSS/BD/CE hybrids have great potential to be used as structural and functional materials for many cutting-edge fields. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The correlation between microstructure and dielectric properties of cyanate ester (CE)/hollow silicate tube (HST) hybrids was investigated by positron annihilation lifetime spectroscopy, coincidence Doppler-broadening spectroscopy, Fourier transform infrared spectra, and dynamic mechanical analyses. The addition of HST to CE resin brings a multi-aspect influence (cross-linked structure and density, free volume, and interfacial action) on the structure of the cross-linked network and thus results in significantly varied dielectric properties. There is an optimum content of HST in hybrids to get the lowest dielectric constant and loss. When the content of HST is smaller than the percolation threshold, the hybrid has decreased dielectric constant and loss; this mainly results in the reduced size of free volume and orthopositronium intensity ( I3), although when the content of HST is larger than the threshold, the increased I3 and the size of free volume as well as the interfacial polarization are responsible for the significantly enlarged dielectric constant and loss. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

New high performance insulating composites based on hollow silica tubes (mHST) and bismaleimide/diallylbisphenol A (BDM/DBA) resin, which exhibit improved toughness, dielectric properties, and flame retardancy, were successfully developed. The effect of the amount of mHST on the properties of composites was systematically studied. Results show that the impact strength of the composite with 0.5 wt% mHST is about 2.2 times that of BDM/DBA resin. In addition, compared with BDM/DBA resin, the composites show lower and stable dielectric constant, better frequency stability of dielectric loss, significantly improved flame retardancy, and similarly outstanding thermal resistance. The reasons behind these attractive integrated properties are discussed from the view of structure-property relationship. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A novel method is proposed to synthesize new mesoporous silica containing amine groups (MPSA), and it was further employed to modify bismaleimide-dialllyl bisphenol (BD)/cyanate ester (CE) resin to form novel MPSA/BD/CE hybrids; in addition, the typical properties of MPSA/BD/CE were systematically investigated. Results show that these hybrids have very low dielectric constant and loss as well as good thermal properties. Compared with BD/CE resin, all hybrids have not only decreased dielectric constant and loss but also similar dependence of dielectric properties on frequency over the whole frequency from 10 to 106 Hz. Specifically, with the addition of MPSA to BD/CE resin, the dielectric constant reduces from 3.5 to 3.0, and the dielectric loss is only 85% of that of BD/CE resin. Note that all hybrids show better thermal resistance (reflected by higher glass transition temperature, decreased maximum degradation rate, and higher char yield at 800°C) than BD/CE resin. All these differences in macro-properties are attributed to the different structure between MPSA/BD/CE hybrids and BD/CE resin. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Novel modified cyanate ester (CE) resins with decreased dielectric loss, improved thermal stability, and flame retardancy were developed by copolymerizing CE with hyperbranched phenyl polysiloxane (HBPPSi). HBPPSi was synthesized through the hydrolysis of phenyltrimethoxysilane, and its structure was characterized by 1H-NMR, 29Si-NMR, and Fourier transform infrared spectra. The effect of the incorporation of HBPPSi into CE resin on the curing behavior, chemical structure of cured networks, and typical performance of HBPPSi/CE resins were systemically evaluated. It is found that the incorporation of HBPPSi into CE network obviously not only catalyzes the curing of CE, but also changes the chemical structure of resultant networks, and thus results in significantly decreased dielectric loss, improved thermal stability, and flame retardancy as well as water absorption resistance. For example, in the case of the modified CE resin with 10 wt% HBPPSi, its limited oxygen index is about 36.0, about 1.3 times of that of neat CE resin, its char yield at 800°C increases from 31.6 to 35.4 wt%; in addition, its dielectric loss is only about 61% of that of neat CE resin at 1 kHz. All these changes of properties are discussed from the view of the structure-property relationship. The significantly improved integrated properties of CE resin provide a great potential to be used as structural and functional materials for many cutting-edges fields. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A novel kind of solventless silicone hybrids (SSiH) containing branched poly(methylphenylvinylsiloxane) (PMPVSi), end-capped hydrogen-functionalized hyperbranched polysiloxane (EHFHPSi), and octavinyl-polyhedral oligomeric silsesquioxane (OVPOS) was developed through a hydrosilylation reaction. Each of the three basic components was synthesized by harmless and recyclable methods. The new hybrids are considerably suitable for vacuum pressure impregnation process, and can serve as an excellent class C insulating material. The effect of differing stoichiometries of OVPOS and EHFHPSi on the performance of cured hybrids is discussed. Results show that SSiH hybrids possess excellent dielectric and thermal properties as well as low viscosity. The reduction in the dielectric constant and the improvement of thermal property of SSiH hybrids can be explained by the unique structure and morphology of hybrids resulting from the presence of OVPOS and EHFHPSi. The novel silicone hybrids exhibit great potential to be used for many cutting-edge industries, especially the microelectronic and insulation fields. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

High-performance thermosetting resins should have good toughness and stiffness, so simultaneously toughening and stiffening is the main target in developing high-performance resins. A novel modified cyanate ester resin with improved toughness and stiffness was developed by copolymerizing 2,2′-bis(4-cyanatophenyl)isopropylidene (CE) with hyperbranched polyphenylsilsesquioxane (HBPPSi). The mechanical properties and their nature were systematically investigated from the viewpoint of structure-property relations using positron annihilation lifetime spectroscopy and spectral analyses. It is found that a suitable content of HBPPSi in CE resin can effectively improve toughness and stiffness. In the case of the CE resin modified with 10 wt% HBPPSi, its impact and flexural strengths are 21 kJ m−2 and 148 MPa, respectively, about 2.6 and 1.4 times of those of neat CE resin. The flexural modulus increases from 3.0 (for neat CE resin) to 3.4 GPa. The results of dynamic mechanical analyses also corroborate the static mechanical properties. The improved toughness and stiffness of CE resin can be attributed to the synergistic effect resulting from changes of both polymer chain structure and aggregation state structure. These attractive features of HBPPSi/CE resins suggest that the method proposed herein may be a new approach for the development of high-performance resins for cutting-edge industries. Copyright © 2011 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Photosensitive resins used in three-dimensional (3D) printing are characterized by high forming precision and fast processing speed; however, they often possess poor mechanical properties and heat resistance. In this study, we report a photocurable bismaleimide ink with excellent comprehensive performance for stereolithography (SLA) 3D printing. First, the main chain of bismaleimide with an amino group (BDM) was synthesized, and then, the glycidyl methacrylate was grafted to the amino group to obtain the bismaleimide oligomer with an unsaturated double bond. The oligomers were combined with reaction diluents and photo-initiators to form photocurable inks that can be used for SLA 3D printing. The viscosity and curing behavior of the inks were studied, and the mechanical properties and heat resistance were tested. The tensile strength of 3D-printed samples based on BDM inks could reach 72.6 MPa (166% of that of commercial inks), glass transition temperature could reach 155 °C (205% of that of commercial inks), and energy storage modulus was 3625 MPa at 35 °C (327% of that of commercial inks). The maximum values of T-5%, T-50%, and Tmax of the 3D samples printed by BDM inks reached 351.5, 449.6, and 451.9 °C, respectively. These photocured BDM inks can be used to produce complex structural components and models with excellent mechanical and thermal properties, such as car parts, building models, and pipes. [ABSTRACT FROM AUTHOR]

Using conventional mixing techniques, the mechanical properties of prepared carbon nanotube (CNT)/polymer composites are not impressive enough, because of their aggregation problem at a high loading of CNTs. In this article, high mechanical performance ultrahigh molecular weight polyethylene (UHMWPE) nanocomposites with high loading of multiwalled CNTs were successfully fabricated by a new manufacturing technique. Specifically, the tensile strength and storage modulus at 25 °C of UHMWPE nanocomposites with 32 wt % of nanotubes prepared by the novel technique reaches 107.6 MPa and 6.0 GPa, respectively, about 4.7 times and 5.0 times of that of pure UHMWPE resin, which are also very high experimental results compared with polyethylene nanocomposite prepared by traditional hot‐compression techniques. These attractive results suggest that the high‐loading CNTs without sacrificing their dispersion and the impregnation quality of polymer‐impregnated buckypapers are essential for fabricating CNTs/polymer composites with superior mechanical properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48667. [ABSTRACT FROM AUTHOR]

Highlights: [•] K2CuCl4·2H2O can be used as the mimic laccase to cure the dead lacquer. [•] Optimal cure conditions are 0.6% K2CuCl4·2H2O, stirring 90min, 75% relative humidity. [•] The dead lacquer film has good thermal stability and chemical resistance. [ABSTRACT FROM AUTHOR]

In this study, an experimental investigation on fabricating Ni-free CoCrW alloys by selective laser melting (SLM) for dental application was conducted in terms of microstructure, hardness, mechanical property, electrochemical behavior, and metal release; and line and island scanning strategy were applied to determine whether these strategies are able to obtain expected CoCrW parts. The XRD revealed that the γ-phase and ε-phase coexisted in the as-SLM CoCrW alloys; The OM and SEM images showed that the microstructure of CoCrW alloys appeared square-like pattern with the fine cellular dendrites at the borders; tensile test suggested that the difference of mechanical properties of line- and island-formed specimens was very small; whilst the outcomes from the electrochemical and metal release tests indicated that the island-formed alloys showed slightly better corrosion resistance than line-formed ones in PBS and Hanks solutions. Considering that the mechanical properties and corrosion resistance of line-formed and island-formed specimens meet the standards of ISO 22674:2006 and EN ISO 10271, CoCrW dental alloys can be successfully fabricated by line and island scanning strategies in the SLM process. [ABSTRACT FROM AUTHOR]

In order to improve the wear resistance and service life of the epoxy resin (EP)-bonded diamond abrasive tools, graphene oxide (GO) was incorporated through a green method without any organic solvents. A curing accelerator, 3-methyl-N,N-diethylbenzenamine (3-MBDEA) acts as a phase transfer agent which rapidly catches GO from water phase to epoxy phase, and the diamond/GO/EP abrasive tools were fabricated via in situ polymerization. The effect of GO on the structure of EP was characterized, and the grinding performances of as-prepared diamond/GO/EP abrasive tools were evaluated in the grinding of concrete. Results show that the service life of the diamond/GO/EP abrasive tools are significantly improved by the incorporation of GO. In the case of the diamond with the size of 50 μm (D50)/GO0.5/EP abrasive tool only with 0.5 wt% GO, its service life increases by 75% compares to that of the D50/EP abrasive tool. The excellent performance of diamond/GO/EP abrasive tools is attributed to the improvement of the wear resistance of EP and the enhancement of the interfacial adhesion between EP and diamond with the addition of GO. This work may provide a potential industrial application for graphene-related materials. Image 1 [ABSTRACT FROM AUTHOR]

The large-scale synthesis of high-purity SiC nanowires is a challenge. In this context, sponge-like graphene oxide (GO) was used as a carbon source as well as a reaction template for directly synthesizing SiC nanowires. GO was completely reacted with SiO to prepare high-purity 3C-SiC nanowires by thermal evaporation and carbothermal reduction without the use of any catalyst, rather than by epitaxy. Characterization was conducted using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and selected-area electron diffraction. The SiC nanowires had lengths of several tens of micrometers and a perfect single-crystalline structure with a bamboo-like morphology., Competing Interests: The authors declare no competing financial interest.