Highly thermal conductive and electromagnetic shielding polymer nanocomposites from waste masks

A groundbreaking review in Nano-Micro Letters by Zhang, Gao, Song and co-workers from Beijing Forestry University, Nanjing Forestry University and University of Southern Queensland presents a closed-loop upcycling strategy that transforms COVID-era polypropylene (PP) mask waste into high-performance PP@G nanocomposites—delivering record thermal conductivity and electromagnetic shielding while cutting environmental impact and cost.

Why This Research Matters
• Overcoming Global Waste Crisis: > 950 billion masks (3.8 Mt) have been discarded since 2020; incineration releases dioxins, landfilling persists for centuries. The work converts this hazardous stream into strategic thermal-management and EMI-shielding feedstock.
• Enabling Next-Gen Electronics: High-power, high-density chips and 5G/6G modules demand lightweight, low-cost materials that simultaneously dissipate > 50 W m^-1 K^-1 of heat and block > 30 dB of EMI. PP@G surpasses both thresholds by 75 %, paving the way for greener data centers, EV powertrains and flexible wearables.

Innovative Design & Mechanisms
• Core-Sheath Nanostructure: Tannic-acid-decorated PP fibers (20 µm diameter) act as negatively charged “cores”; cationic PAE@GNP platelets (6 µm lateral size) electrostatically self-assemble into a continuous graphene “sheath” after 140 °C / 50 MPa hot-pressing, yielding meter-scale (1 m × 1 m) sheets.
• Aligned 3-D Phonon/Electron Highways: Face-to-face oriented GNPs create sub-100 K W^-1 contact resistance—two orders of magnitude lower than random dispersions—enabling 87 W m^-1 K^-1 in-plane thermal conductivity and 893 S m^-1 electrical conductivity at 66 wt % loading.
• Green & Scalable Process: Operates under atmospheric pressure, uses only water and food-grade tannic acid, and is fully compatible with roll-to-roll production—turning waste logistics into manufacturing assets.

Applications & Future Outlook
• Real-World Thermal Management: PP@G66 film cools 12 V LEDs by 60 °C versus commercial PI substrates; flexible PP@G heat-sinks outperform steel blocks in 1200-cycle on-off tests without delamination.
• EMI Shielding Champion: 88 dB total shielding effectiveness (1100 dB cm^-1) at 800 µm thickness—> 2× higher specific SE than MXene, CNT or rGO composites—validated by Tesla-coil LED extinction and X-band radar tests.
• Circularity & Profit: Life-cycle assessment shows 3.47 MJ fossil-fuel saving and 2.53 kg CO₂-eq reduction per kg vs landfill; techno-economic analysis projects $468 profit per ton of repurposed masks.
• Next-Gen Roadmap: Strategy is being extended to other fibrous plastic waste (PPE gowns, packaging films) and co-designed with 5G base-station, EV battery and aerospace thermal-EMI modules for 2026 pilot production.

Conclusions
By merging waste valorization with materials engineering, this work delivers a dual-function nanocomposite that turns pandemic pollution into a strategic resource—setting a new benchmark for sustainable thermal and EMI solutions in high-performance electronics while accelerating the transition to a circular economy.