Key Takeaways & Executive Findings
- •• Fabricating low-cost, high-performance, scalable polypropylene (PP)@graphene (G) nanocomposites from recycled PP fibers in waste masks by a simple electrostatic self-assembly hot-pressing method. • The resultant PP@G presents a high thermal conductivity of 87 W m−1 K−1 and a high electromagnetic interference shielding effectiveness of 88 dB (1100 dB cm−1). • Life cycle assessment and techno-economic assessment demonstrate significant environmental and economic advantages over existing waste mask disposal methods. • This upcycling strategy offers a facile and promising approach to repurposing fibrous waste plastics for advanced thermal management and EMI shielding applications.
Abstract
Over 950 billion (about 3.8 million tons) masks have been consumed in the last four years around the world to protect human beings from COVID-19 and air pollution. However, very few of these used masks are being recycled, with the majority of them being landfilled or incinerated. To address this issue, we propose a repurposing upcycling strategy by converting these polypropylene (PP)-based waste masks to high-performance thermally conductive nanocomposites (PP@G, where G refers to graphene) with exceptional electromagnetic interference shielding property. The PP@G is fabricated by loading tannic acid onto PP fibers via electrostatic self-assembling, followed by mixing with graphene nanoplatelets (GNPs). Because this strategy enables the GNPs to form efficient thermal and electrical conduction pathways along the PP fiber surface, the PP@G shows a high thermal conductivity of 87 W m⁻1 K⁻1 and exhibits an electromagnetic interference shielding effectiveness of 88 dB (1100 dB cm−1), making it potentially applicable for heat dissipation and electromagnetic shielding in advanced electronic devices. Life cycle assessment and techno-economic assessment results show that our repurposing strategy has significant advantages over existing methods in reducing environmental impacts and economic benefits. This strategy offers a facile and promising approach to upcycling/repurposing of fibrous waste plastics.
1. Introduction
The frequent outbreaks of epidemic respiratory diseases have led to a significant increase in the use of disposable medical masks, primarily composed of polypropylene (PP), which accounts for more than 90% by weight [1–3]. Recent statistics indicate that due to the COVID-19 outbreak, the global consumption of waste masks has exceeded 950 billion units (about 3.8 million tons) in the last four years (Fig. 1a) [4]. Most of these waste masks are disposed of through incineration or landfill. Incineration of PP releases toxic gases and organic pollutants, such as dioxins and furans, contributing to air pollution [5–7]. Landfilled PP takes hundreds of years to fully degrade, generating microplastics and other environmental hazards.
Meanwhile, the development of high-power and highly integrated electronic devices in recent years has created an urgent demand for advanced polymer-based thermal management materials (TMMs) [15–18]. In this context, we hypothesize that PP fibers in waste masks can be used as a polymer fibrous matrix to prepare TMMs due to their low cost, ease of processing, and high aspect ratio [19–22]. Therefore, this upcycling process can not only solve the waste masks problem, but also provide new insights for the development of advanced TMMs.
In this study, we aim to repurpose waste masks to fabricate PP-based TMM nanocomposites (PP@G) with high electromagnetic interference (EMI) shielding performance by assembling thermally conductive filler graphene nanoplatelets (GNPs) on tannic acid (TA)-decorated PP fibers (Fig. 1c). The as-prepared PP@G shows a high thermal conductivity (TC) (87 W m⁻1 K⁻1) and a high electromagnetic interference shielding effectiveness (EMI SE) (88 dB) (1100 dB cm−1). The PP@G nanocomposites hold great potential for heat dissipation and EMI shielding applications (Fig. 1d). In addition, life cycle assessment (LCA) and techno-economic assessment (TEA) are also performed to evaluate the advantages of this upcycling strategy over existing methods [23, 24]. This work paves the way for a new upcycling strategy for waste masks and other plastics waste, contributing to creating a sustainable environment and circular economy.
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Xilin Zhang, Wenlong Luo, Yanqiu Chen, Qinghua Guo, Jing Luo, Paulomi Burey, Yangyang Gao, Yonglai Lu, Qiang Gao, Jingchao Li, Jianzhang Li, Pingan Song (2025). Highly Thermal Conductive and Electromagnetic Shielding Polymer Nanocomposites from Waste Masks. Nano-Micro Letters. https://doi.org/10.1007/s40820-025-01796-z
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Frequently Asked Questions
What is the main innovation of this study?
The study introduces a novel upcycling strategy to convert waste polypropylene masks into high-performance thermally conductive and electromagnetic shielding nanocomposites (PP@G) via a simple electrostatic self-assembly hot-pressing method, achieving a thermal conductivity of 87 W m−1 K−1 and EMI shielding effectiveness of 88 dB.
How are the waste masks recycled in this process?
The waste masks are first cleaned and processed to extract polypropylene fibers. These fibers are then decorated with tannic acid via electrostatic self-assembly, followed by mixing with graphene nanoplatelets and hot-pressing to form the final nanocomposite.
What are the key performance metrics of the PP@G nanocomposites?
The PP@G nanocomposites exhibit a high thermal conductivity of 87 W m−1 K−1 and an electromagnetic interference shielding effectiveness of 88 dB (1100 dB cm−1), making them suitable for heat dissipation and EMI shielding in advanced electronic devices.
What are the environmental and economic benefits of this upcycling strategy?
Life cycle assessment and techno-economic assessment show that this repurposing strategy significantly reduces environmental impacts compared to incineration or landfill, and offers economic benefits by converting waste into valuable materials.
What potential applications do the PP@G nanocomposites have?
The PP@G nanocomposites are potentially applicable for heat dissipation and electromagnetic shielding in advanced electronic devices, such as smartphones, laptops, and 5G communication equipment.
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