Xiongwei Qu

Preparation and characterization of surface modified boron nitride epoxy composites with enhanced thermal conductivity

Hexagonal boron nitride (h-BN) microparticles, modified by surface coupling agent 3-aminopropyl triethoxy silane (APTES), were used to fabricate thermally conductive epoxy/BN composites, and the effects of modified-BN content on the thermal and insulating properties were investigated. It was found that incorporation of h-BN particles in the epoxy matrix significantly enhanced the thermal conductivity of the composites. With 30 wt% modified-BN loading, the thermal conductivity of the composites was 1.178 W m−1 K−1, 6.14 times higher than that of the neat epoxy. Fabricated epoxy/BN composites exhibited improved thermal stability, storage modulus, and glass transition temperature with increased BN content. The composites also possessed excellent electrical insulation properties. These results revealed that epoxy/BN composites are promising as efficient heat-releasing materials for thermal management and microelectronic encapsulation.

Preparation and properties of thermally conductive polyimide/boron nitride composites

Polyimide (PI) has been widely used as a preferred packaging matrix material due to its low dielectricity, outstanding insulation and excellent thermal stability. Hexagonal boron nitride (h-BN) microparticles were functionalized with a silane coupling agent, 3-glycidyloxypropyltrimethoxy silane (γ-MPS), to improve the interface action with the PI matrix. The modified h-BN (m-BN) particles were used to fabricate the PI/m-BN composites with enhanced thermal conductivity by in situ polymerization. The Fourier transform infrared (FTIR) spectra, thermo-gravimetric analysis (TGA), transmission electron microscopy (TEM) and contact angle test proved that γ-MPS coupling agent molecules had been chemically grafted onto the h-BN surface. In addition, the effects of the m-BN content on the thermal conductivity of PI/m-BN composites were investigated. The composite obtained with 40 wt% m-BN particle loading presented a thermal conductivity of 0.748 W m−1 K−1, 4.6 times higher than that of pure PI. Meanwhile, the fabricated PI/m-BN composites retained excellent electrical insulation and thermal stability. The glass transition temperature values of the PI/m-BN composites decreased slightly while the storage modulus improved with the increase of the m-BN content. These results showed that PI/m-BN composites may offer new applications in the microelectronic industry because future substrate materials require effective heat dissipation.

A novel high-temperature naphthyl-based phthalonitrile polymer: synthesis and properties

A novel naphthyl-based phthalonitrile monomer, 1,6-bis(3,4-dicyanophenoxy) naphthalene (1,6-BDCN), was prepared, and the phthalonitrile resin was cured with 4,4′-diaminodiphenyl ether (ODA) via two steps, namely, preparation of prepolymer and postcuring prepolymer at elevated temperatures. The 1,6-BDCN polymer might form triazine and phthalocyanine rings as demonstrated by FTIR spectra. The prepolymer shows fine solubility in organic solvents. The 1,6-BDCN polymer exhibits excellent structural integrity and superior thermal stability as indicated by thermogravimetric analysis (TGA). Dynamic mechanical analysis (DMA) revealed that the phthalonitrile resin has a high storage modulus and glass transition temperature (Tg). The water uptake is about 3% by weight after submersion in boiling water for 50 hours. The influence of curing processes on thermal stability and flame retardancy was also explored.

Synthesis and properties of a novel high-temperature diphenyl sulfone-based phthalonitrile polymer

A novel high-temperature diphenyl sulfone-based phthalonitrile polymer is prepared from bis-[4-(3,4-dicyanophenoxy)phenyl]sulfone (BDS) monomer synthesized with high yield by a simple nucleophilic displacement of a nitro-substituent from 4-nitrophthalonitrile (NPN). The structure of BDS polymer is investigated by Fourier transform infrared spectroscopy and wide-angle X-ray diffraction. Curing behavior of BDS monomer with 1,3-bis(4-aminophenoxy)benzene (APB) is recorded by differential scanning calorimetry. The properties of BDS polymer are evaluated by thermogravimetric analysis, dynamic mechanical analysis, and tensile test. The results reveal that the BDS polymer exhibits excellent thermal and thermo-oxidative stabilities, high glass temperature (Tg = 337°C), and outstanding mechanical properties (Young’s modulus: 4.02 GPa and tensile strength: 64.16 MPa). Additionally, the BDS polymer exhibits high flame retardance and low water uptake.

Flame retarding epoxy composites with poly(phosphazene-co-bisphenol A)-coated boron nitride to improve thermal conductivity and thermal stability

Based on the template-induced self-assembly characteristic of cyclomatrix polyphosphazene micro–nanometer materials, novel poly(cyclotriphosphazene-co-bisphenol A)-coated boron nitride (PCB-BN) was designed and synthesized by in situ condensation polymerization on the surfaces of boron nitride (BN) particles using the reaction of hexachlorocyclotriphosphazene (HCCP) with bisphenol A (BPA). It was found that the incorporation of PCB-BN particles in the epoxy matrix significantly enhanced thermal conductivity of the epoxy composites. With 20 wt% PCB-BN loading, the thermal conductivity of the EP/PCB-BN composites was 0.708 W m−1 K−1, which was 3.7 times higher than that of the neat epoxy. Meanwhile, the EP/PCB-BN composites possessed good electrical insulation and thermal stability simultaneously. The composites fabricated also exhibited improved flame retardation and superior dimensional stability during combustion.

Synthesis, tensile, and thermal properties of polyimide/diamond nanocomposites

Polyimide/diamond nanocomposites were prepared using 4,4′-diaminoiphenyl ether and 3,3 ′,4,4′-benzophenonetetracarboxylic dianhydride. The structure of the polyimide/diamond nanocomposites was characterized by Fourier transform infrared, ultraviolet and transmission electron microscopy. Agglomeration of nano diamond particles is observed in polyimide matrix as revealed by transmission electron microscopy micrographs which is ascribed to the high surface free energy of particles. Both tensile strength and failure strain of polyimide are obviously enhanced with incorporation of nano diamond particles though tensile modulus only shows slight increase. The reinforcing effect of nano diamond on polyimide is discussed. Thermal stabilities of the polyimide/diamond nanocomposites are evaluated using a thermogravimetric analyzer. The thermal stability of nanocomposites is slightly reduced as indicated by a small decrease in onset degradation temperature.

The effect of nitrile-functionalized nano-aluminum oxide on the thermomechanical properties and toughness of phthalonitrile resin

Resorcinol-based phthalonitrile (R-CN)/nano-aluminum oxide (Al2O3) nanocomposites were prepared via a two-step approach. Firstly, Al2O3 was functionalized with nitrile groups on the surface of Al2O3 nanoparticles, which was confirmed by Fourier transform infrared spectroscopy, thermogravimetric analysis, and scanning electron microscopy (SEM). The effect of nano-Al2O3 particles on thermomechanical and flexural properties has been evaluated for different weight ratios ranging between 0% and 5%. Compared with pure nano-Al2O3, nitrile-functionalized Al2O3 (CN-Al2O3) particles showed a more significant enhancement effect on the properties of R-CN resin. The storage modulus of nanocomposite with 5 wt% CN-Al2O3 reaches 2679 MPa at 25°C, which is much higher than that of the pure R-CN resin. For 3 wt% CN-Al2O3-reinforced R-CN composites, it showed an increase of 54.84% in flexural strength and 21.48% in flexural modulus. SEM was employed to explore the fracture surface of composites. Micrographs of fracture surface analysis confirmed that the toughness of R-CN resin can be improved significantly by incorporating CN-Al2O3 nanoparticles.

Low temperature self-assembled synthesis of hexagonal plate-shape Mn3O4 3D hierarchical architectures and their application in electrochemical capacitors

There is an intense need for development in the field of hierarchically structured functional materials owing to their outstanding and peculiar properties. Herein, we report the 3D Mn3O4 hierarchical architectures synthesized based on a self-assembly approach via a hydrothermal synthesis route at low temperature, which is sparse in literature. The synthesized Mn3O4 hierarchical architectures were characterized with XRD, FE-SEM, HRTEM/SAED, and FTIR. Electrochemical studies show that the Mn3O4 hierarchical architectures exhibit acceptable specific capacitance and excellent electrochemical stability, making them promising electrode materials in electrochemical capacitors.

Preparation of a functionalized core–shell structured polymer by seeded emulsion polymerization and investigation on toughening poly(butylene terephthalate)

Poly(n-butyl acrylate)/poly(methyl methacrylate-co-methacrylic acid) (PBMMA), a core–shell structured modifier with controlled particle sizes, was prepared, and the toughening effects of PBMMA on poly(butylene terephthalate) (PBT) were investigated. The modifier was prepared at a solid content of 50 wt% by a two-stage sequential emulsion polymerization. Dynamic light scattering (DLS) was used to monitor the particle diameters, which showed that the particles grew without significant secondary nucleation occurring. The morphology was confirmed by means of transmission electron microscopy (TEM). According to the results on the mechanical properties of the PBT/PBMMA blends, a remarkable toughening effect of methacrylic acid (MA) on PBT resin was found. By means of scanning electron microscopy (SEM) observation, the toughening mechanism was proposed to be crazing caused by rubber particles and shear yielding of PBT matrix. The uniform dispersion of rubber particles in PBT matrix was attributed to the good compatibility between PBT and PBMMA modifier.

Synthesis and properties of high temperature phthalonitrile polymers based on o, m, p-dihydroxybenzene isomers

A series of high-temperature phthalonitrile monomers with o, m, p-dihydroxybenzene isomers, namely, 1,2-bis(3,4-dicyanophenoxy) benzene (o-BDB), 1,3-bis(3,4-dicyanophenoxy) benzene (m-BDB) and 1,4-bis(3,4-dicyanophenoxy) benzene (p-BDB), were synthesized via a facile nucleophilic displacement of a nitro-substituent from 4-nitrophthalonitrile. The structures of the monomers were characterized by FTIR, 1H NMR and WXRD. Curing behaviors of the monomers with 4,4′-diaminodiphenyl ether were recorded by DSC. The result shows that the processabilities of o-BDB and m-BDB are superior to p-BDB due to lower melting points and broader processing windows. The structures of the cured phthalonitrile polymers were characterized by FTIR and WXRD, and thermal stabilities were evaluated by TGA and all the polymers exhibit excellent thermal and thermal-oxidative stabilities. Dynamic mechanical analysis reveals that the polymers have high storage modulus and high glass-transition temperatures. Consequently, o-BDB and m-BDB polymers show more outstanding processability, thermal stability and mechanical properties than p-BDB polymers, which may be good candidates for high-temperature phthalonitrile polymers.