Li Dunzhu, Li Peijing, Shi Yunhong, Sheerin Emmet D, Zhang Zihan, Yang Luming, Xiao Liwen, Hill Christopher, Gordon Conall, Ruether Manuel, Pepper Joshua, Sader John E, Morris Michael A, Wang Jing Jing, Boland John J
Jiyang College, Zhejiang A&F University, Zhuji, China.
AMBER Research Centre and Centre for Research on Adaptive Nanostructures and Nanodevices (CRANN), Trinity College Dublin, Dublin, Ireland.
Nat Commun. 2025 Apr 23;16(1):3814. doi: 10.1038/s41467-025-58898-w.
Residual stress is an intrinsic property of semicrystalline plastics such as polypropylene and polyethylene. However, there is no fundamental understanding of the role intrinsic residual stress plays in the generation of plastic pollutants that threaten the environment and human health. Here, we show that the processing-induced compressive residual stress typically found in polypropylene and polyethylene plastics forces internal nano and microscale segregation of low molecular weight (MW) amorphous polymer droplets onto the plastic's surface. Squeeze flow simulations reveal this stress-driven volumetric flow is consistent with that of a Bingham plastic material, with a temperature-dependent threshold yield stress. We confirm that flow is thermally activated and stress dependent, with a reduced energy barrier at higher compressive stresses. Transfer of surface segregated droplets into water generates amorphous polymer micropollutants (APMPs) that are denatured, with structure and composition different from that of traditional polycrystalline microplastics. Studies with water-containing plastic bottles show that the highly compressed bottle neck and mouth regions are predominantly responsible for the release of APMPs. Our findings reveal a stress-induced mechanism of plastic degradation and underscore the need to modify current plastic processing technologies to reduce residual stress levels and suppress phase separation of low MW APMPs in plastics.
残余应力是聚丙烯和聚乙烯等半结晶塑料的固有属性。然而，对于固有残余应力在威胁环境和人类健康的塑料污染物生成过程中所起的作用，目前尚无根本性的认识。在此，我们表明，在聚丙烯和聚乙烯塑料中通常发现的加工诱导压缩残余应力会迫使低分子量（MW）无定形聚合物液滴在塑料表面发生内部纳米和微米尺度的偏析。挤压流动模拟表明，这种应力驱动的体积流动与宾汉塑性材料的流动一致，具有与温度相关的屈服应力阈值。我们证实，流动是热激活且依赖于应力的，在较高压缩应力下能垒降低。表面偏析液滴转移到水中会产生变性的无定形聚合物微污染物（APMPs），其结构和组成与传统多晶微塑料不同。对装有水的塑料瓶的研究表明，高度压缩的瓶颈和瓶口区域是APMPs释放的主要原因。我们的研究结果揭示了一种应力诱导的塑料降解机制，并强调需要改进当前的塑料加工技术，以降低残余应力水平并抑制塑料中低MW APMPs的相分离。
