张立群院士团队：聚氨酯（PU）热固性塑料的回收与升级再造技术路径

Core Viewpoint - The article emphasizes the importance of developing recycling and upcycling technologies for polyurethane (PU) thermosetting plastics to transition from a linear consumption model to a circular economy, highlighting the potential for bio-based materials in achieving sustainability [7][11]. Group 1: Market Overview - Polyurethane is the sixth largest plastic globally, with a market size of $83.2 billion in 2024, projected to exceed $108 billion by 2029 [8]. - As of 2022, global solid PU production surpassed 22 million tons, but the recycling rate remains below 30%, leading to significant environmental concerns due to landfill and incineration practices [8]. Group 2: Technological Innovations - The article discusses various technological pathways for recycling PU, including physical, chemical, and biological methods, which aim to convert waste PU into higher-value products [7][19]. - Innovations in smart material design, such as incorporating reversible covalent bonds, are proposed to enhance the recyclability of PU, allowing for efficient reprocessing and self-healing capabilities [29]. Group 3: Bio-based Polyurethane - Bio-based PU, derived from renewable resources like vegetable oils and starch, offers better biodegradability and lower carbon footprints compared to fossil-based PU [11]. - Research indicates that sugar-based PU can achieve significant mass loss (up to 35%) within 30 days under enzymatic degradation while maintaining thermal stability above 235°C [14]. Group 4: Recycling and Upcycling Strategies - The article outlines various recycling methods, including mechanical recycling, pyrolysis, solvolysis, hydrolysis, and biodegradation, each with distinct advantages and limitations [22][25]. - Chemical recycling techniques can selectively recover polyols and isocyanates, enabling the synthesis of new high-performance polymers, thus promoting a closed-loop system [19][22]. Group 5: Future Directions - The future of PU recycling hinges on making technologies more universal and cost-effective, advancing smart polymer designs from laboratory to industry, and improving waste classification and characterization systems [33].