Search

The radar absorbing materials composited of activated carbon fibers (ACF) as wave-absorber and glass fibers (GF) as impedance modifier were successfully prepared. The structure parameters of rectangular ACF felt screen, the influences of GF-piece and the reflection properties were investigated. It was observed that the effective bandwidth (the reflection loss below −10 dB) increased with the aspect ratio ( a / b ) increasing, but decreased with aperture spacing ( δ ) increasing. A double absorption peak (16.1 dB and 14.2 dB) for the optimized configuration ( a / b = 3, δ = 5 mm, a = 30 mm) appeared at 5.8 GHz and 16.9 GHz, and a wide absorption bandwidth (4–17.6 GHz) could be achieved. When a 30 mm × 15 mm rectangular aperture was filled by GF-piece of 20 mm × 10 mm, the effective bandwidth was improved to 12.1 GHz. The composites with a wide absorption bandwidth could be achieved via designing the proper element parameters and adjusting the composition of ACF and GF. [ABSTRACT FROM AUTHOR]

As the need for renewable and high-performance alternative elastomer grows, efforts have been made to develop bio-based elastic polymers for engineering applications. Herein, bio-based elastomers poly(dimethyl itaconate- co -butadiene)s (PDMIBs) were successfully synthesized by emulsion copolymerization of renewable monomer dimethyl itaconate (DMI) with partially petroleum-derived butadiene under mild conditions. It is an effective strategy to tailor PDMIB properties by comonomers with different feed ratios and to adjust the compositions and sequence distributions. The structure and thermal stability were investigated by FTIR, NMR, DSC analyses, etc. In terms of properties: (1) the vulcanizates showed excellent tensile strength (10.2 MPa), elongation at break (1146%) and toughness (37.6 MJ m−3) without filler reinforcement, which were obviously superior to the mechanical properties of most traditional petroleum-based synthetic rubbers; (2) Nanosilica-filled PDMIBs exhibited good mechanical properties, excellent abrasion resistance and oil resistance due to strong polarity in molecular chains; (3) Epoxy-functionalized poly(dimethyl itaconate- co -butadiene- co -glycidyl methacrylate) PDMIBG showed better silica dispersion and excellent dynamic mechanical properties. In summary, this new kind of bio-based elastomer PDMIBs can be used in multiple engineering applications, such as bio-based gloves, conveying belts, oil-resistant products and high-performance tire tread materials, etc. This study opens the door to the use of emulsion copolymerization and functionalization modification technology in the synthesis of new high-performance bio-based elastomer nanocomposites for the rubber industry. Novel sustainable elastomers nanocomposites with versatile properties are constructed based on bio-based dimethyl itaconate. [Display omitted] [ABSTRACT FROM AUTHOR]