Rheological, mechanical, and X‐band microwave absorption properties of nickel and nickel‐coated carbon‐filled cyclo‐olefin copolymer composites

Abstract

Cyclo‐olefin copolymer (COC) composites containing different amounts of nickel (Ni) and/or nickel‐coated carbon (NiC) hybrid fillers were prepared, and their morphological, rheological, mechanical, dielectric, and X‐band microwave absorption properties were examined. Rheological percolation thresholds for Ni and NiC fillers were determined to be in the range of 45 to 60 and 60 to 75 phr, respectively. Both fillers caused no significant increase in melt viscosity at low shear rates. The minimum filler concentrations to obtain acceptable reflection loss (RL) values (RL < −10 dB) were determined as 60 and 45 phr for the Ni and NiC series of samples, respectively. The minimum RL value (RLmin) and the broadest absorption bandwidth were determined as −52.5 dB and 8.2 to 12.5 GHz, respectively, for the composite sample containing 75 phr of Ni, whereas a similar performance could be obtained by the sample containing 45 phr of NiC. Considerable enhancement in the RLmin value could not be provided by the use of hybrid NiC fillers; however, the absorption bandwidth was enlarged, and the minimum sample thicknesses to obtain an acceptable absorption bandwidth were reduced significantly.

Evaluation of morphological, rheological, mechanical, and dielectric properties of aluminum dross filled polyoxymethylene (POM) composites

“…[ 62 ] However, σ relax is not observed at frequencies on the GHz level, and the ε ″ values change based on σ ac . [ 63 ] Therefore, increasing the conductive content (metallic aluminum powder for Al‐dross) in the composite structure led to an increase in the ε ″ values. As expected, the ε” values also increased with the increasing Al‐dross concentration, but the ε ″ values were much lower than the ε’ values due to the lower Al content of the Al‐dross powder.…”

A modified blister mixing element for generating extensional flow in a twin‐screw extruder: Process characterization and dispersion state of carbon nanotubes in cyclo‐olefin polymer

“…COP is a relatively new class of amorphous olefin-based thermoplastic polymers and demonstrates outstanding transparency, thermal stability, and mechanical properties. [20][21][22] SWCNTs with excellent mechanical properties and electrical conductivity have a higher aspect ratio of length to diameter and specific surface area than multiwalled CNTs. [20] Although adding SWCNTs into COPs can improve the mechanical properties and electrical properties, [21,22] achieving a good SWCNT dispersion in COPs is challenging because COPs have hydrophobic chemical structures, [23] and SWCNTs strongly aggregate due to their high specific area.…”

Effect of in situ fibrillation on polyethylene/poly(ethylene terephthalate)/multiwalled carbon nanotube electromagnetic shielding foams

“…[ 3 ] Nevertheless, different processing methods restrict the prospect of certain studies. For aerogel [ 4 ] and chemical vapor deposition [ 5,6 ] approaches, the less single yield and poisonous gas make safety and environmental protection difficult. The mechanical approach [ 7,8,9 ] adopts continuous equipment, such as ultralengthy diameter‐ratio extruder [ 10,11 ] and microfoaming injection molding machine, [ 12–14 ] as well as reduces carbon agglomeration, thus satisfying commercial requirements.…”