CAREER: Understanding Process-Structure-Property Relations in Gas/Supercritical Fluid-Injected Polymer Coextrusion Foam Processes

这项教师早期职业发展计划（Career）资助将通过为制造轻型多材料泡沫结构的新制造工艺提供新知识来促进科学进步，这些结构在汽车、航空航天、生物医学、食品和电子包装行业有各种应用。大多数新的聚合物产品含有两种或两种以上的聚合物和功能性添加剂，从而从每个组分中获得所需的性能。该工艺在单步工艺中同时挤压多种材料，使用两种或更多种聚合物材料形成独特应用的多层结构。这些包括光学、机械和气体屏障膜，如用于电子屏幕的亮度增强过滤器，超强安全和安全窗膜，或用于运动鞋缓冲膀胱的弹性屏障膜。通过在加工过程中向塑料中引入气体或超临界流体，可以从任何塑料制备泡沫。该奖项支持基础研究，将为制造轻质复合材料的新型共挤泡沫制造技术提供所需的知识。该工艺还将通过减少材料使用，以及通过适当的材料微观结构工程提高性能重量比，显著降低生产成本。这一跨学科研究涵盖了制造、高分子化学、高分子物理和材料科学。制造增值塑料材料的公司将从中受益。来自弱势群体的学生将参与这项研究，并将与当地一家博物馆合作开发一个新项目，以激发K-12学生对聚合物材料的兴趣。在几何约束下，依赖于气体/超临界流体浓度的晶体成核/生长、晶片取向以及随后的气泡成核/生长行为对共挤泡沫过程构成了根本性挑战。此外，材料和工艺参数在很大程度上影响了微观结构和气泡形态。这些复杂的、耦合的现象影响最终复合材料的性能。本研究的目的是弥补在共挤泡沫过程中微观结构演变和气泡成核/生长机制理解方面的知识差距。研究小组将开发一个基于物理的模型，以了解和预测气体/超临界流体浓度和相间相容性对半结晶聚合物微观结构演变的影响，并将进行实验来验证该模型。该团队还将进行原子和宏观建模模拟，以了解气泡的成核和生长行为，并将使用新开发的介电方法测试不同应力状态影响溶解度和扩散率的假设。根据这些研究结果，将选择工艺参数，以获得满意的微观结构和泡沫形态，而无需耗时的试错过程。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。

This Faculty Early Career Development Program (CAREER) grant will promote the progress of science by contributing new knowledge related to a novel manufacturing process for fabricating lightweight multimaterial foam structures that have a variety of applications in the automotive, aerospace, biomedical, food and electronics packaging industries. Most new polymeric products contain two or more polymers and functional additives resulting in desired properties contributed from each component. The process extrudes multiple materials at the same time in a single-step process using two or more polymeric materials shaped to form a multilayer structure for unique applications. These include optical, mechanical, and gas barrier films, such as brightness-enhancing filters for electronic screens, ultra-strong safety and security window films, or elastomeric barrier films for cushioning bladders in athletic shoes. Foams can be prepared from any plastic by introducing a gas or supercritical fluid within the plastic during processing. This award supports fundamental research that will provide needed knowledge about a new coextrusion foam manufacturing technology for fabricating lightweight composites. This process will also significantly reduce production costs by decreasing material usage as well as increasing performance-to-weight ratios through proper engineering of the material microstructure. This interdisciplinary research encompasses manufacturing, polymer chemistry, polymer physics and materials science. Companies manufacturing value-added plastic materials will benefit from the results. Students from underrepresented groups will participate in the research and a new program will be developed with a local museum to inspire interest in polymer materials for K-12 students. The gas/supercritical fluid concentration-dependent crystal nucleation/growth, crystal lamellae orientation, and subsequent bubble nucleation/growth behaviors under geometric constraints pose fundamental challenges in the coextrusion foam process. Further, the materials and process parameters largely influence the microstructure and bubble morphologies. These complex, coupled phenomena affect the properties of the final composite. The objective of this research is to close the knowledge gap in the understanding of microstructural evolution and bubble nucleation/growth mechanisms in coextrusion foam processes. The research team will develop a physics-based model to understand and predict the effects of the gas/supercritical fluid concentration and the interphase compatibility on the microstructure evolution of semi-crystalline polymers and will conduct experiments to verify the model. The team will also perform atomistic and macroscopic modeling simulations to understand the bubble nucleation and growth behaviors, and will test the hypothesis that various stress states influence the solubility and diffusivity by using a newly developed dielectric method. Based on these research results, the process parameters will be selected to achieve satisfactory microstructure and foam morphologies without time-consuming trial-and-error procedures.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.