CAREER: Pathways of Microplastics Creation: Multi-physics Study of Macroplastic Fragmentation, Foliation, and Fibration

职业：微塑料的产生途径：大塑料破碎、叶状和纤维化的多物理研究

• 批准号: 2145137
• 负责人: Maryam Shakiba
• 金额: $ 51.66万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-05-01 至 2022-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2145137&HistoricalAwards=false
• 关键词: CAREER; Pathways; Microplastics; Creation; Multi

This Faculty Early Career Development (CAREER) grant supports research to understand the degradation mechanisms of macroplastics into microplastics under coupled effects of weathering and mechanical stresses. It is well-established that microplastics exist in our oceans in ever-increasing numbers and cause great ecological harm. Physical, mechanical, and chemical properties of macroplastics change during the degradation process and make it challenging to detect microplastics and estimate their lifetime in water. To address this challenge, it is critical to understand the formation mechanisms of microplastics and the rates at which they are produced. The objective of this research project is to discover the mechanics of degradation and develop predictive models which can estimate the fate of macroplastics. The outcome can help ocean environmental scientists and the manufacturing practices and recycling processes. The research activities will be complemented with a series of integrated educational activities to train the next generation of engineers and researchers in the multi-physics and mechanics of soft polymers through combinations of undergraduate and graduate students training and outreach to high-school students. The award will also be used to contribute to public knowledge infrastructure and create workshops for the polymer industry. Separate models exist for studying how polymers degrade due to two or three factors among mechanical loading, temperature, oxygen, salt-water, and UV irradiations. The principal emphasis of this project is on the nonlinear coupling effects of all these factors. Physics-based equations for degradation in microstructural properties will be established based on polymers' network statistics, chemistry kinetics, as well as stored and dissipative energies. The critical internal stress at which micro-cracks form in thin polymers will be determined using polymer statistics and conservation laws. A non-affine multiscale framework will be built upon the deformation and breakage in chains and crosslinks to predict heterogeneous damage initiation and propagation. A physics-guided machine learning algorithm will assist the development of the framework. The damage mechanisms, threshold, and transition from brittle to ductile under multi-physics conditions will be described. The particular questions to be answered include (1) effects of the microstructural morphology of macroplastics on the degradation process and the choice of a specific fracture pathway -- fragmentation, foliation, or fibration, (2) changes in mechanical properties due to thermo-chemo-UV internal stresses in soft polymeric materials, and (3) failure mechanisms in semi-crystalline and amorphous polymer under coupled conditions at different scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

该学院早期职业发展（Career）基金支持研究在风化和机械应力的耦合作用下，宏观塑料到微塑料的降解机制。众所周知，微塑料在我们的海洋中数量不断增加，并造成了巨大的生态危害。宏观塑料的物理、机械和化学性质在降解过程中会发生变化，这使得检测微塑料和估计它们在水中的寿命变得具有挑战性。为了应对这一挑战，了解微塑料的形成机制及其产生速度至关重要。这个研究项目的目的是发现降解的机制和发展预测模型，可以估计宏观塑料的命运。研究结果可以帮助海洋环境科学家、生产实践和回收过程。这些研究活动将辅以一系列综合教育活动，通过对本科生和研究生的联合培训以及对高中生的拓展，培养软聚合物多物理场和力学方面的下一代工程师和研究人员。该奖项还将用于为公共知识基础设施做出贡献，并为聚合物工业创建研讨会。存在单独的模型来研究聚合物如何由于机械负荷、温度、氧气、盐水和紫外线照射等两三个因素而降解。本项目的主要重点是所有这些因素的非线性耦合效应。微观结构性能退化的物理方程将建立在聚合物网络统计、化学动力学以及存储和耗散能量的基础上。利用聚合物统计和守恒定律确定薄聚合物中微裂纹形成的临界内应力。非仿射多尺度框架将建立在链和交联的变形和断裂上，以预测非均质损伤的发生和扩展。物理引导的机器学习算法将协助框架的开发。将描述在多物理场条件下的损伤机制、阈值和从脆性到韧性的转变。需要回答的具体问题包括：(1)宏观塑料的微观结构形态对降解过程的影响以及特定断裂途径的选择——破碎、叶理或纤维化；(2)软聚合物材料中热化学uv内应力引起的机械性能变化；(3)半晶和非晶聚合物在不同尺度耦合条件下的失效机制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。