EFRI E3P: Supercritical Extraction for the Elimination of End-of-Life Plastics (SCE3P)

多层塑料包装对于保持各种食品，包括肉类、果汁袋、奶酪和预制食品在运输和储存过程中的安全至关重要。为了发挥作用，多种材料一起使用以满足单个材料无法满足的要求。然而，大多数多层食品包装最终都被填埋了，因为目前的回收过程无法分离各种成分。在这个项目中，研究人员将使用高压和高温将气体转化为超临界流体，从而分离典型多层食品包装中使用的材料。由此产生的更纯净的材料流的更高价值将提高多层结构回收的经济性。该过程将被设计成允许在现有回收厂常见的设备上直接实施。这项工作将包括对多层包装提高回收率的经济和环境影响进行全面评估。如果成功，该项目将产生新的技术，提高塑料垃圾的可回收性，减少进入垃圾填埋场的塑料垃圾数量，并限制食品包装对环境的影响。该项目还将结合大型四年制大学、传统黑人大学和两年制社区大学的努力，以高度跨学科的方式解决研究问题，从而提高教育、多样性和劳动力发展。参与研究的研究生和本科生将在合作机构进行交叉培训，并开展有关聚合物、回收和相关科学的社区外展活动，用于开放日和区域教室。该项目旨在通过设计从多层食品包装中回收高价值屏障聚合物并同时回收聚烯烃的工艺来实现多层聚合物废物流的价值。研究人员假设：1)超临界CO2与助溶剂结合，通过提高聚合物在溶剂相中的浓度和增强溶剂通过塑化渗透多层结构的能力，将改善多层体系中乙烯基醇（EVOH）和聚己二酰胺（MXD6）的萃取；2)改造挤出设备以使用超临界流体有几个优点，包括加强层分离和溶解动力学，降低成本，包括总体回收能源和回收设施改造费用；3)该过程回收的材料将适合用于闭环回收；4)拟议的技术将提高总体回收率，对环境有积极的净影响。这项工作将增加我们对商业上重要的塑料及其混合物在超临界CO2和共溶剂中的相行为的热力学和动力学理解。基本了解如何选择溶剂，加工条件（例如，温度和压力），挤出机螺杆设计影响分配系数和聚合物萃取动力学将获得。将采用技术经济分析、生命周期评价以及经济和环境影响分析相结合的方法来确定回收多层食品包装对环境的潜在影响，并确定是否需要政策工具来促进这些材料的回收。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。

Multilayer plastic packaging is critical to keeping a wide range of food products, including meats, juice pouches, cheeses, and prepared foods, safe during transportation and storage. To function, multiple materials are used together to meet requirements that individual materials cannot. However, most multilayer food packaging winds up in landfills because current recycling processes cannot separate the various components. In this project, researchers will use high pressure and high temperature to turn gases into supercritical fluids that enable separating the materials used in typical multilayer food packaging. The higher value of the resulting purer material streams will improve the economics of recycling multilayer structures. The process will be designed to allow straightforward implementation on equipment commonly found at existing recycling plants. The work will include a thorough assessment of both the economic and environmental impacts of increased recycling rates for multilayer packaging. If successful, the project will result in new technology that increases the recyclability of plastic waste, reduces the amount of plastic waste entering landfills, and limits the environmental impact of food packaging. The project will also enhance education, diversity, and workforce development by combining efforts from a large four-year university, a historically black university, and a two-year community college in a highly interdisciplinary approach to addressing the research questions. Graduate and undergraduate students participating in the research will cross-train at the partner institutions and develop community outreach activities on polymers, recycling, and related science for use at open houses and area classrooms.This project aims to valorize the multilayer polymer waste stream through a process designed to reclaim high-value barrier polymers from multilayer food packaging and simultaneously recycle the polyolefins. The investigators hypothesize: 1) supercritical CO2, in combination with cosolvents, will improve the extraction of ethylene vinyl alcohol (EVOH) and polyxylylene adipamide (MXD6) from multilayer systems by increasing the polymer concentration in the solvent phase and enhancing the solvent's ability to penetrate the multilayer structure via plasticization, 2) modifying extrusion equipment to use supercritical fluids offers several advantages including enhanced layer separation and dissolution kinetics and reduced costs including overall recycling energy and recycling facility retrofitting expenses, 3) the materials reclaimed by this process will be suitable for use in closed-loop recycling, and 4) the proposed technology will increase overall recycling rates, having a net positive environmental impact. The work will increase our thermodynamic and kinetic understanding of the phase behavior of commercially important plastics and their mixtures in supercritical CO2 with cosolvents. Fundamental understanding of how solvent choice, processing conditions (e.g., temperature and pressure), and extruder screw design impact partition coefficients and polymer extraction kinetics will be gained. A combination of techno-economic analysis, life-cycle assessment, and economic and environmental impact analysis will be used to establish the potential impact of recycling multilayer food packaging on the environment and determine the need for policy instruments to promote the recycling of these materials.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.