Xulin Yang

Cross-linkable nitrile functionalized graphene oxide/poly(arylene ether nitrile) nanocomposite films with high mechanical strength and thermal stability

To develop high performance graphene-based nanocomposites, precise interface control and dispersal of graphene in the polymer hosts are challenging due to its strong interlayer cohesive energy and surface inertia. Here, we firstly report an efficient and novel method to functionalize graphene oxide with 4-aminophenoxyphthalonitrile and successfully compound them with poly(arylene ether nitrile)(PEN) to prepare nanocomposite films. Fourier transforms infrared spectra (FTIR), Raman spectra, and atomic force microscopy (AFM) were employed to examine the surface functionalization of the graphene oxide. The resulting PEN nanocomposite, with 0.75 wt% nitrile functionalized graphene oxide (G-CN), revealed an approximate 27% and 68% increase in tensile strength and Youngs modulus, respectively, compared to that of neat PEN. The onset thermal degradation temperature (Td5) and the maximum decomposition temperature (Td,max) of the composite with 0.75 wt % of G-CN were increased by 21 and 25 °C compared to those of neat PEN. More importantly, the mechanical and thermal properties of the PEN composite films were further enhanced by the chemical cross-linking reaction of nitriles, which opens a new route to optimize the interface structures and improve the comprehensive performances of graphene–polymer nanocomposites.

Controllable synthesis, magnetism and solubility enhancement of graphene nanosheets/magnetite hybrid material by covalent bonding

Hybrids of Fe(3)O(4) nanoparticles and surface-modified graphene nanosheets (GNs) were synthesized by a two-step process. First, graphene nanosheets were modified by SOCl(2) and 4-aminophenoxyphthalonitrile to introduce nitrile groups on their surface. Second, the nitrile groups of surface-modified graphene nanosheets were reacted with ferric ions on the surface of Fe(3)O(4) with the help of relatively high boiling point solvent ethylene glycol to form a GNs/Fe(3)O(4) hybrid. The covalent attachment of Fe(3)O(4) nanoparticles on the graphene nanosheet surface was confirmed by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectrometer (EDS) and scanning electron microscopy (SEM). TEM and HRTEM observations indicated that the sizes of the nanoparticles and their coverage density on GNs could be easily controlled by changing the concentration of the precursor and the weight ratio to GNs. Magnetic measurements showed that magnetization of the hybrid materials is strongly influenced by the reaction conditions. Chemically bonded by phthalocyanine, the solubility of as-synthesized GNs/Fe(3)O(4) hybrid materials was greatly enhanced, which was believed to have potential for applications in the fields of composites, wastewater treatment and biomaterials.

Synergetic effect of cyanogen functionalized carbon nanotube and graphene on the mechanical and thermal properties of poly (arylene ether nitrile)

Cyanogen functionalized carbon nanotube and graphene/poly (arylene ether nitrile) (CNT-CN/GN-CN/PEN) nanocomposite films were prepared by a facile solution casting method. The weight ratio of CNT-CN/GN-CN was varied from CNT-dominated to GN-dominated for the purpose of investigating their synergetic effects on the mechanical and thermal properties of PEN nanocomposites. Consequently, GN-CN/PEN composites demonstrated better mechanical and thermal properties than CNT-CN/PEN composites due to larger contact area between GN-CN and PEN matrix. Nevertheless, all CNT-CN/GN-CN/PEN composites exhibit enhanced mechanical properties than those of GN-only nanocomposites. With the increasing of CNT-CN/GN-CN weight ratio, the mechanical properties of CNT-CN/GN-CN/PEN composites increase, then decrease, and reach their maximums when CNT-CN/GN-CN weight ratio is around 4/4. From scanning electron microscope images, it is found that around that point GN-CN is flatly dispersed and CNT-CN is penetrated into GN-CN, capable of transferring stress load and thus decreasing interface loss. Thermal properties of CNT-CN/GN-CN/PEN composites once again confirmed the joint effect of CNT-CN and GN-CN, leading to improved thermal properties. In short, a synergistic effect between one-dimensional (1-D) CNT and two-dimensional (2-D) GN on the mechanical and thermal properties of nanocomposites have been demonstrated in these systems.

Preparation and properties of bisphenol A-based bisphthalonitrile polymers

The nitrile groups of 2,2-bis [4-(3,4)-dicyanophenoxy phenyl] propane (bisphthalonitrile; BAPh) can be cured by the nucleophilic phenol groups. Bisphenol A (BPA) can react with 4-nitrophathalonitrile to synthesize BAPh. Therefore, BPA was used as a novel curing agent to react with BAPh. The BAPh/BPA prepolymers and polymers were prepared by heat polymerization. The curing behaviors were characterized using differential scanning calorimetry, dynamic rheological analysis, and thermogravimetric analysis. The results indicate that BPA can decrease the melting temperature of BAPh, shorten the curing time of BAPh with lower curing temperature at 243°C, and widen the processing windows of BAPh to 95–120°C. Meanwhile, BAPh/BPA polymers could withstand temperatures up to 443°C under nitrogen atmosphere and 420°C in air when cured at 240°C for 10 h. The mechanical properties of BAPh/BPA polymers were investigated, and it exhibits a flexural strength of 75 to 122 MPa. Dynamic mechanical analysis was used to evaluate the dynamic mechanical properties of BAPh/BPA polymers. The polymers show glass transition temperature ranging from 244 to 299°C heating and cured to 240°C. Herein, the BAPh/BPA polymers can be a good candidate resin for high-performance polymeric materials.

Designing a Phthalonitrile/Benzoxazine Blend for the Advanced GFRP Composite Materials

High performance resin must be used in the high performance glass fiber-reinforced plastic (GFRP) composites, but it is sometimes difficult to balance the processabilities and the final properties in the design of advanced thermoset GFRP composites. In this study, a phthalonitrile/benzoxazine (PPN/BZ) blend with excellent processability has been designed and applied in the GFRP composite materials. PPN/BZ blend with good solubility, low melt viscosity, appropriate gel condition and low-temperature curing behavior could enable their GFRP composite preparation with the prepreg-laminate method under a relatively mild condition. The resulted PPN/BZ GFRP composites exhibit excellent mechanical properties with flexural strength over 700 MPa and flexural modulus more than 19 GPa. Fracture surface morphologies of the PPN/BZ GFRP composites show that the interfacial adhesion between resin and GF is improved. The temperatures at weight loss 5% (T5%) and char residue at 800 °C of all PPN/BZ GFRP composites are over 435 °C and 65% respectively. PPN/BZ GFRP composites with high performance characteristics may find applications under some critical circumstances with requirements of high mechanical properties and high service temperatures.