Chaobo Liang

Ideal dielectric thermally conductive bismaleimide nanocomposites filled with polyhedral oligomeric silsesquioxane functionalized nanosized boron nitride

Silane coupling reagent γ-glycidoxy propyl trimethoxy silane/polyhedral oligomeric silsesquioxane (KH-560/POSS) functionalized nanosized boron nitride (POSS-g-nBN) fillers were performed to fabricate thermally conductive bismaleimide/diallylbisphenol A (BMI/DABA) nanocomposites combining excellent dielectric properties and outstanding thermal stability. POSS molecules have been grafted on the surface of the nBN fillers. The POSS-g-nBN/BMI/DABA nanocomposite with 15.4 vol% POSS-g-nBN is an excellent dielectric composite material with high thermal conductivity and outstanding thermal stability; the corresponding dielectric constant e is 3.42, the dielectric loss factor tanδ is 0.0085, the thermally conductive coefficient λ is 0.607 W m−1 K−1 (increased by 266% compared to that of pure BMI/DABA), and the 5 wt% thermal weight loss temperature (T5) reaches up to 428 °C, which holds potential for use in the integration and the miniaturization of microelectronic devices.

A low loading of grafted thermoplastic polystyrene strengthens and toughens transparent epoxy composites

Transparent epoxy composites strengthened and toughened by thermoplastic polystyrene grafted with epichlorohydrin (g-PS) have been prepared at low loading levels. The polymer backbone of PS was manipulated by the epoxide and hydroxyl groups confirmed by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Contact angle and differential scanning calorimetry (DSC) tests indicated that the grafting process could decrease the surface tension and increase the compatibility between PS and epoxy resins. The effects of g-PS loading and the grafting process on both the viscosity of liquid epoxy resin suspensions as well as the physicochemical properties of cured epoxy composites have been systematically investigated. The cured g-PS/epoxy composites demonstrated an enhanced tensile strength (maximum of 97.4 MPa) compared to either cured pure epoxy (77.6 MPa) or PS/epoxy composites (79.1 MPa). The modulus of toughness for g-PS/epoxy composites reaches values of up to 355.9 MJ m−3, which is respectively 176.6 and 141.1% higher than those for cured pure epoxy and PS/epoxy composites. The uniform g-PS distribution in the cured g-PS/epoxy composites was observed by scanning electron microscope (SEM). The glass transition temperature (Tg) of cured g-PS/epoxy composites was shifted to a higher temperature (increased by 16.3 °C) in the dynamic mechanical analysis (DMA) compared with that of cured pure epoxy (111.7 °C). The strong interfacial interaction obtained between g-PS and the epoxy matrix was responsible for the enhanced mechanical and thermal mechanical properties. This work provides a new insight into the investigation of interaction and compatibility between thermoplastic and thermoset materials.

A review on thermally conductive polymeric composites: classification, measurement, model and equations, mechanism and fabrication methods

AbstractWith the fast-developing miniaturization and integration of microelectronics packaging materials, ultrahigh-voltage electrical devices, light-emitting diodes (LEDs), and in areas which require good heat dissipation and low thermal expansion, the investigations on the polymeric composites with highly thermal conductivities and excellent thermal stabilities are urgently required, which would be beneficial to transferring the heat to the outside of the products, finally to effectively avoid substantial overheating and prolong their working life. Our article reviews recent progress in the classification, measurement methods, model and equations, mechanisms, commonly used thermally conductive fillers, and the correlative fabrication methods for the thermally conductive polymeric composites, aiming to understand and grasp how to enhance the λ value effectively. And future perspectives, focusing scientific problems and technical difficulties of the present thermally conductive polymeric composites are also described and evaluated. Graphical abstractThermally conductive polymeric composites: classification, measurement, model and equations, mechanism and fabrication methods.

Fabrication of novel wave-transparent HMPBO fibre/BADCy laminated composites

The method of “impregnation–winding–lamination–mould pressing” was performed to fabricate novel wave-transparent high modulus poly(p-phenylene-2,6-benzobisoxazole) fibre/bisphenol A cyanate ester resin (HMPBO fibre/BADCy) laminated composites. The “two-step approach” of methanesulfonic acid/γ-glycidoxy propyl trimethoxy silane (MSA/KH-560) was also proposed to functionalize the HMPBO fibres’ surface. Results revealed that KH-560 was grafted on the HMPBO fibres’ surface successfully. The functionalized HMPBO fibre/BADCy laminated composites possessed better ILSS & flexural strength, lower e & tan δ, and higher heat-resistance index & Tg. The ILSS and flexural strength of the functionalized HMPBO/BADCy laminated composites were increased to 53.7 MPa and 753.7 MPa, respectively. The corresponding e and tan δ were decreased to 2.93 and 0.00097, respectively. The corresponding heat-resistance index and Tg were increased to 219 °C and 236 °C, respectively. The functionalized HMPBO fibre/BADCy laminated composites display potential application in radomes and the antenna systems of aircrafts.

Synchronously improved dielectric and mechanical properties of wave-transparent laminated composites combined with outstanding thermal stability by incorporating iysozyme/POSS functionalized PBO fibers

Modified bisphenol A dicyanate ester (m-BADCy) wave-transparent laminated composites reinforced with functionalized poly(p-phenylene-2,6-benzobisoxazole) (f-PBO) fibers were fabricated using an optimized method of impregnation-winding followed by lamination-molding. m-BADCy was synthesized from copolymerization between (2-((3-trifluoromethyl)phenoxy)methyl)oxirane and the BADCy matrix. f-PBO fibers were obtained by modifying with lysozyme followed by polyhedral oligomericsilsesquioxane (POSS). Lysozyme was coated on the surface of PBO fibers (PBO@lysozyme) and polyhedral oligomericsilsesquioxane (POSS) was grafted onto the PBO@lysozyme fibers (POSS-g-PBO@lysozyme, f-PBO fibers). The dielectric constant (e), 2.81, and dielectric loss (tan δ), 0.0028, for f-PBO fiber/m-BADCy wave-transparent laminated composites were lower than those of PBO fiber/m-BADCy wave-transparent laminated composites (e = 2.91 and tan δ = 0.0043). The interlaminar shear strength (ILSS) and the flexural strength of the f-PBO fiber/m-BADCy wave-transparent laminated composites were significantly increased to 47.6 and 805.8 MPa, increased by 23.0% and 33.5% in comparison to those of PBO fiber/m-BADCy wave-transparent laminated composites (ILSS = 38.7 MPa and flexural strength = 603.5 MPa), respectively. In addition, the corresponding heat resistance index (THRI, representing thermal stability) and glass transition temperature (Tg) of the f-PBO fiber/m-BADCy wave-transparent laminated composites were 228.3 and 252.1 °C, respectively.

Fabrication of modified bismaleimide resins by hyperbranched phenyl polysiloxane and improvement of their thermal conductivities

Synthetic terminal amine group hyperbranched phenyl polysiloxane (NH2-HBPSi) is introduced into a bismaleimide/diallylbisphenol A (BMI/DABA) prepolymer to fabricate NH2-HBPSi/BMI/DABA resins. Furthermore, functionalized silicon carbide particle/silicon carbide whisker (fSiCp/fSiCw) hybrid fillers are also used to fabricate fSiCp/fSiCw/NH2-HBPSi/BMI/DABA thermal conductivity composites. A NH2-HBPSi/BMI/DABA resin with 20 wt% NH2-HBPSi is an ideal dielectric material with excellent impact strength and outstanding thermal stability, the corresponding dielectric constant (e) is 3.12, dielectric loss (tanδ) is 0.0098, impact strength value is 18.7 kJ m−2, glass transition temperature (Tg) value is 281 °C and the 5 wt% thermal weight loss temperature (T5) value is 424 °C. The thermal conductivities of the fSiCp/fSiCw/BMI/DABA and fSiCp/fSiCw/NH2-HBPSi/BMI/DABA composites are both increased with the increasing mass fraction of fSiCp/fSiCw hybrid fillers.

A superfast hexavalent chromium scavenger: Magnetic nanocarbon bridged nanomagnetite network with excellent recyclability

In this work, a nanocarbon bridged nanomagnetite network (NC-NMN) is developed through the electrospinning of epichlorohydrin functionalized polystyrene (f-PS), followed by the direct calcination of f-PS and ferric nitrate, which is capable of superfast removing hexavalent chromium (Cr(VI)) from polluted water within only 15 s benefiting from its gridding framework, with an adsorption rate constant of 1.64 g mg-1 min-1 according to the pseudo-second-order kinetics. The well-fitted Langmuir isotherm model indicates a monolayer adsorption for Cr(VI) on NC-NMN. The thermodynamic parameters including negative ΔG° and positive ΔH° demonstrate that the Cr(VI) adsorption on NC-NMN is spontaneous and endothermic. The Cr(VI) adsorption retention, which is only 3.8%, is achieved for NC-NMN after five cycles, exhibiting a prominent stability and an excellent recyclability. X-ray photoelectron spectroscopy (XPS), zeta potential and energy-filter transmission electron spectroscopy (EFTEM) results illustrate that both the electrostatic attraction and the network structure of NC-NMN are responsible for the superior Cr(VI) adsorption performance. This work intends to provide a new method for designing the novel structure materials for polluted water treatment.

Design and Multi-body Dynamics Analyses on the Novel Force-bearing Structures for Variable Configuration Spacecraft

Abstract Novel variable configuration spacecraft (VCS) can change its configuration by on-orbit assembly or the motion of the mechanism according to the requirements and missions, and the multibody dynamics analysis is performed to obtain the corresponding theoretical lowest values of the mechanical properties of force-bearing structures for the VCS module. In the meantime, to meet the actual use requirements for VCS, novel force-bearing structures are designed optimally and fabricated successfully. The corresponding experimental values of the mechanical properties for the force-bearing structures are also tested and investigated, which are compared to the corresponding theoretical values via multibody dynamics analysis. This paper is part of a large project on the development and preparation of the novel force-bearing structures applied in the next generation of VCS.