Achieving Theoretical Property Limits in Polymer Nanofibers: Stiffness, Strength and Thermal Conductivity

该奖项的目的是确定纳米级聚合物纤维样品的热性能和机械性能达到理论极限的程度。 聚合物材料被用于数百万种消费品中，尽管它们的机械性能相对较差并且它们的导热性较低。 这是因为长的分子链往往是无序的。 然而，聚合物的固有刚度、强度和热导率由于其碳-碳主链而高。 使用超高拉伸比技术，现在可以制造具有高度有序性的聚乙烯纳米纤维。 在这项工作中的方法将采用微机械步进电机测试超拉伸聚合物的机械性能。 对于热导率的测量，将使用最近开发的六线平台。这项工作的好处是，它将使许多应用的聚合物导热系数的评估。 由于超拉伸纤维是高度有序的，因此可能获得接近理论极限的性能。 同时具有高刚度、高强度和高导热性的材料将反过来促进广泛的研究。 这将是在制造技术，如大规模的热塑性塑料生产，并在应用，如散热器，热交换器，防弹衣和复合材料。 在教育方面，调查人员将扩大卡内基梅隆大学的两个课程。 其中一个将集中在力学和纳米试样的测试方法。 第二个将集中在热性能和开发超材料的方法来控制它们。 学生在调查本科课程将介绍微机械设备通过讲座和便携式“类芯片”系统。 6-9年级的学生将学习通过图标驱动的界面编程微机械设备。 博士学位学生和两名硕士论文的学生将获得机械和热测量技术的专业知识。

The objective of this award is to determine the degree to which the thermal and mechanical properties of nanoscale polymer fiber specimens can attain theoretical limits. Polymer materials are used in millions of consumer products even though their mechanical properties are relatively poor and their thermal conductivity is low. This is because long molecular chains tend to be disordered. However, the intrinsic stiffness, strength and thermal conductivity of polymers are high due to their carbon-carbon backbone. Using an ultra-high draw ratio technique, it now is possible to fabricate polyethylene nanofibers with a high degree of order. The approach in this work will be to employ a micromachined stepper motor to test ultra-drawn polymer mechanical properties. For the thermal conductivity measurements, a recently-developed six wire platform will be used.The benefit of this work is that it will enable assessment of polymer nanofiber for many applications. It is possible that properties near theoretical limits will be attained because the ultra-drawn fibers are highly ordered. Simultaneous high stiffness, strength and thermal conductivity values will in turn stimulate broad research. This will be in manufacturing techniques such as large scale nanofiber production, and in applications such as heat sinks, heat exchangers, body armor and composites. With regard to education, the investigators will expand two courses at Carnegie Mellon University. One will focus on mechanics and test methods of nanoscale specimens. The second will focus on thermal properties and develop metamaterial approaches to control them. Students in the investigators undergraduate course will be introduced to micromachined devices through a lecture and a portable "Class on a Chip" system. Grade 6-9 students will learn to program a micromachined device through an icon-driven interface. A Ph.D. student and two Master's Thesis students will gain expertise in both mechanical and thermal measurement techniques.