Exceptional microwave absorption in soft polymeric nanocomposites facilitated by engineered nanostructures.

Multifunctional organophosphorus additives present opportunities to engineer epoxy networks with both enhanced mechanical properties and ultralow flammability. This paper describes a systematic investigation of the effect of dimethyl methylphosphonate (DMMP) on the mechanical and heat release properties of both conventional and inherently low flammability epoxy resins. The findings demonstrate that integration of DMMP into epoxy networks produces materials with outstanding flame retardance and increased stiffness. Thermogravimetric analysis of DMMP‐containing networks show that DMMP promotes considerable char formation, with char residue reaching very high levels, up to 55%, for DMMP‐containing deoxybenzoin networks. Microscale combustion calorimetry of all the DMMP‐containing networks exhibit 50% lower heat release capacity and total heat release rate values relative to formulations without DMMP. Moreover, vertical burn tests demonstrate that DMMP‐containing formulations burn slowly and self‐extinguish. Morphological analysis of the charred DMMP‐containing formulations shows a porous structure and mechanical characterization reveals 50% higher elastic modulus, and comparable yield stress, for networks containing DMMP relative to those without DMMP. Overall, this organophosphorus additive represents an opportunity to combine materials chemistry with mechanical enhancement mechanisms to achieve low heat release properties without the need for halogenated flame‐retardant additives.

This study demonstrates lightweight microwave absorber materials designed using polycarbonate (PC) nanocomposites containing multiwall carbon nanotubes (MWNTs) and "brick-like" lossy magnetic ferrite (Fe 3 O 4 ) nanoparticles encapsulated with carbon (Fe 3 O 4 @C). The designed nanocomposites manifested in exceptional microwave attenuation through absorption (89 %). The unique strategy, of encapsulating ferrites with C, adopted here prevents the disruption of conducting pathway facilitated through the network of MWNTs and overcomes the eddy current effects. In addition, this strategy further led to improved dispersion of ferrites in PC matrix which rather agglomerates during processing. Unlike classical electromagnetic interference (EMI) shielding materials, the PC nanocomposites containing MWNTs and Fe 3 O 4 @C resulted in exceptional microwave attenuation in a broad frequency range and mostly through ab-sorption. The absorption ability of these nanocomposites was further assessed by evaluating the reflection loss (RL). For instance, PC nanocomposites containing MWNTs and Fe 3 O 4 @C nanoparticles depicted in an exceptional RL of À41.3 dB at 17.7 GHz and with a remarkable bandwidth of 4.4 GHz for a thickness of 1 mm. Unlike previous studies where RL was improved by sacrificing dielectric losses, herein, the adopted strategy enhances both dielectric losses facilitating in enhanced total shielding effectiveness (SE T ) and RL through suitable impedance matching. This further result in excellent absorption. Therefore, this study provides comprehensive understanding about tailoring the complex microwave properties of the polymer nanocomposites in order to achieve enhanced microwave absorption.[a] S.

No abstract