Peng-Gang Ren

Improved mechanical and barrier properties of low-density polyethylene nanocomposite films by incorporating hydrophobic graphene oxide nanosheets

The high hydrophilicity of graphene oxide nanosheets (GONSs), arising from their abundant oxygen-containing functional groups, gravely restricts their application in non-polar polymer nanocomposites. In the present study, alkylated GONSs were fabricated by facile refluxing of GONSs and octadecylamine (ODA), thus giving rise to the selective dispersion of ODA–GONSs in non-polar xylene rather than in polar water. Fourier-transform infrared spectroscopy, atomic force microscopy, and X-ray diffraction results demonstrated the occurrence of the nucleophilic substitution reaction between the primary amine groups of ODA and the epoxide groups of GONSs during the refluxing. In the low density polyethylene (LDPE) nanocomposites, ODA–GONSs were uniformly and randomly dispersed, exhibiting excellent compatibility with the LDPE matrix. As a result, when adding 4.0 wt% ODA–GONSs, the Youngs modulus was improved by 58.9%; O2 permeability was reduced by 37.0%; and initial decomposition temperature was elevated by 15.9 °C. Besides, the inclusion of ODA–GONSs could effectively block the transmission of UV light in the nanocomposite films and serve as heterogeneous nucleating agents for LDPE crystallization. These results confirm that such long alkane chain modification holds great value or potential to design and prepare LDPE nanocomposite films for packaging applications with excellent integrated performance.

Efficient electromagnetic interference shielding of lightweight carbon nanotube/polyethylene composites via compression molding plus salt-leaching

Carbon nanotube/high density polyethylene (CNT/HDPE) foam composites with high electrical conductivity and electromagnetic interference (EMI) shielding performance were developed by means of compression molding plus salt-leaching. The uniform porous structure and interconnected CNT networks throughout the cell backbones endowed the as-prepared foam composites with a significantly lower electrical percolation threshold (0.22 vol%) than that of the solid composites (0.84 vol%). Owing to the multiple reflections and scattering between the cell–matrix interfaces, the foam composites presented a superior specific EMI shielding effectiveness (EMI SE) of 104.3 dB cm3 g−1, 2.2 times higher than that of their solid counterpart. Besides this, the pore sizes of the CNT/HDPE foam composites could be easily tuned by controlling the particle size of the porogen. Also, the electrical conductivity and specific EMI SE increased with an increase in the cell diameter, which was attributed to the formation of a more perfect conductive network in the cell backbones. Our approach provides a novel idea for fabricating new lightweight EMI shielding materials, especially for aircraft and spacecraft applications.

Cyanate Ester Resin Filled with Graphene Nanosheets and NiFe2O4–Reduced Graphene Oxide Nanohybrids for Efficient Electromagnetic Interference Shielding

An effective electromagnetic interference (EMI) shielding cyanate ester (CE) composite has been fabricated with a combination of graphene nanosheets (GNSs) and nickel ferrite (NiFe2O4) particles. NiFe2O4 particles were loaded on the reduced graphene oxide (RGO) to improve the dispersibility while the composites were synthesized via solution blending method. Scanning electron micrographs (SEM) showed good dispersion of GNSs and RGO–NiFe2O4 in CE. Electromagnetic properties and EMI shielding effectiveness (SE) of the nanocomposites were determined over X-bands (8.2–12.4GHz). It was observed that the EMI shielding performance of composites was improved by increasing the filler loading of composites and absorption was found to be the dominant shielding mechanism. The total EMI SE is almost reaching 50dB for samples with thicknesses of ∼2.7mm, which suggests that the GNSs/RGO–NiFe2O4/CE could be good candidates for highly efficient EMI shielding materials in the whole X-band.

Resistivity Relaxation of Anisotropic Conductive Polymer Composites

The electrical properties of anisotropic carbon nanotubes (CNTs)/polycarbonate (PC)/ polyethylene (PE) (ACPC) strongly depended on the CNTs’ concentration. When the ACPC was subjected to isothermal treatment (IT), the resistivity variation in both the parallel and perpendicular directions had the characteristics of a relaxation as a function of temperature. During the IT the orientation of the PC microfibrils was gradually damaged and CNTs/PC microfibrils were deformed and changed to short fibers, leading to a transition from anisotropy to isotropy. The velocity of the conductive network reconstruction could be characterized by the relaxation time, and the resistivity of the composite during the IT process can be instantaneously predicted based on the relaxation equation. The relaxation time and the equilibrium resistivity of the composite during IT were determined by the IT temperature and CNT content.

Facile preparation of 3D regenerated cellulose/graphene oxide composite aerogel with high-efficiency adsorption towards methylene blue

Composite aerogels consisting of graphene oxide (GO) and regenerated cellulose (RCE) were prepared via a solution mixing-regeneration and freeze-drying process. The prepared RCE/GO composites aerogel exhibited 3D network thin-walled pore structure with large specific surface area, also favorable compression recovery capability, outstanding dye elimination efficiency and reusability after the addition of GO. With addition of only 0.5 wt% GO, the methylene blue (MB) elimination efficiency of RCE/GO aerogel reached 99.0% and still remained at 90.5% after five-time reused under oscillation adsorption. In addition, our research indicates that the excellent MB adsorption of RCE/GO composite aerogel was driven by electrostatic interactions and followed a pseudo-second-order adsorption kinetic and monolayer Langmuir adsorption isotherm. This investigation provides the guidance for the development of green environmental adsorbents to remove organic dye from sewage water.