CAREER: Post-Processing Polymer Nanofibers for Improved Mechanical Properties

该学院早期职业发展（CAREER）奖支持对后处理过程中纳米级纤维中发生的分子排列进行基本调查。高强度聚合物纤维是用于各种行业的轻质和高强度材料的基础材料。多年来，研究人员一直在研究和优化传统的微尺度纤维制造和后处理方法，以最大限度地提高纤维的刚度和强度。聚合物纳米纤维具有比较大的常规纤维更高的归一化强度的潜力，这归因于与它们的小纤维直径相关的物理学。然而，传统的后处理方法难以与纳米纤维方法（例如静电纺丝）整合，使得后处理对聚合物抗弯强度的影响没有得到很好的理解。静电纺丝常规后处理方法的实施、研究和优化具有实现超强、轻质聚合物纤维和聚合物衍生碳纤维材料的潜力。这些材料将有利于关键行业和我们的社会，降低能源成本，提高安全性，并使建造更大的结构和更快的车辆，船舶和航空/航天器成为可能。项目执行将为研究生和本科生提供纳米技术和材料科学与工程方面的高级培训。相关的外展活动将使小学和高中学生接触工程和科学，以促进对STEM教育和职业的追求。该奖项的目的是研究聚合物纳米纤维在拉伸过程中的大分子水平的结构转变以及由此产生的机械性能。将建立在独立控制的参数下加工单个纳米纤维和低密度取向聚合物预聚物的方法，所述参数包括拉伸前的固化时间、加工温度和拉伸速率。将建立过程/结构/性能关系，以研究聚合物链流动性、分子量和纤维直径对纳米纤维最大伸长率的影响。纤维-纤维连接对低密度非织造垫的应变的影响将被建模和实验测试，以确定后拉伸单个聚合物纳米纤维与纳米纤维组装的重要性。这些研究将为拉伸过程中聚合物抗拉强度的发展以及规模对聚合物纤维后处理的影响提供证据。

This Faculty Early Career Development (CAREER) award supports a fundamental investigation into the molecular alignment that occurs in nanoscale fibers during post-processing. Strong polymer fibers are the building blocks for lightweight and high strength materials useful in a wide variety of industries. Researchers have studied and optimized conventional microscale fiber manufacturing and post-processing methods for many years to maximize fiber stiffness and strength. Polymer nanofibers have the potential for higher normalized strength than larger conventional fibers due to the physics associated with their small fiber diameter. However, conventional post-processing approaches are difficult to integrate with nanofabrication methods such as electrospinning, making the effects of post-processing on polymer nanofiber strength not well understood. Implementation, investigation, and optimization of conventional post-processing methods for electrospinning have the potential to realize ultra-strong, lightweight polymer nanofiber and polymer-derived carbon nanofiber material. These materials would benefit key industries and our society by reducing energy costs, increasing safety, and making it possible to build larger structures and faster vehicles, vessels, and air/spacecraft. Project execution will provide advanced training in nanotechnology and materials science and engineering to graduate and undergraduate students. The associated outreach activities will expose elementary and high school students to engineering and science to promote the pursuit of STEM education and careers. The objective of this award is to investigate the macromolecular-level structural transition of polymer nanofibers during drawing and the resultant mechanical properties. Methodologies will be established to process both individual nanofibers and low density aligned polymer nanofiber mats under independently controlled parameters including cure time prior to stretching, processing temperature, and stretch rate. Process/structure/property relationships will be established to investigate the effects of polymer chain mobility, molecular weight and fiber diameter in relation to maximum elongation of the nanofibers. The influence of fiber-fiber junctions on strain for low density non-woven mats will be modeled and tested experimentally to determine the importance of post-stretching individual polymer nanofibers versus an assembly of nanofibers. These studies will provide evidence of polymer nanofiber strength development during drawing as well as the effect of scale on polymer fiber post-processing.