NER: Process for Increasing the Exfoliation and Dispersion of Nano-particles into Polymeric Matrices Using Supercritical Carbon Dioxide

摘要-0507995 VA理工学院&州立大学NER：使用超临界二氧化碳增加纳米颗粒在聚合物基质中的剥离和分散的方法背景：将纳米颗粒添加到聚合物基质中将奇迹般地导致优异的机械、阻隔、电和热稳定性性能的所有承诺和声明都没有完全实现，因为当达到约4wt%的水平时，性能的改善似乎趋于平稳。 仅对于尼龙6，由于酰胺基团和纳米粘土颗粒之间的氢键，在性能平台之前达到7重量%的水平。性能的平台归因于当浓度增加时不能保持纳米颗粒剥离。 用于合成纳米粘土复合材料的三种最常见的方法，即合适单体的插层和随后的原位聚合、聚合物从溶液的插层和聚合物熔体插层，在导致大于约4wt%的负载水平方面尚未成功。 然而，达到10重量%数量级的纳米粘土颗粒水平可能导致模量增加5倍或更多，而不是1.5至2.0倍（在4重量%下）。 目标：本研究的目的是探索使用超临界二氧化碳（sc CO2）来增加纳米粘土颗粒的水平的可能性，所述纳米粘土颗粒以大于5wt%并且优选地高达10wt%的水平保持剥离。 几个先前的研究提供的证据表明，SC CO2可以溶胀层状硅酸盐，从而可以提高聚合物插层到粘土的画廊的容易性。 提出了一种连续的方法，用于溶胀纳米粘土和剥离它们与SC CO2，然后随后将混合物注入熔融聚合物流。 此外，预期因为sc CO2在许多聚合物中高度可溶，所以它将有助于剥离的粘土颗粒的分散，并且同时降低熔体的粘度。一旦混合完成，就可以从系统中提取二氧化碳，留下分散在热塑性塑料中的颗粒。除了使用显微镜和流变学技术来确定剥离程度外，还将确定热塑性复合材料的机械性能。 智力优势：一种新的，高风险的，环境友好的剥离和分散纳米颗粒到聚合物熔体的过程的概念将从这项工作中发展出来，这应该是适用于一系列的纳米颗粒系统超出纳米粘土和toother聚合物基体。 更广泛的影响：这里提出的方法是新颖的，应该导致提交专利申请。 它有可能导致纳米颗粒水平的显著增加，从而显著增加性能。 性能的提高将扩大纳米复合材料的使用范围，特别是在汽车工业和快速成型领域。 该项目最初为期一年，因此，必须仔细规划学生的教育。 然而，至少有一名本科生（来自代表性不足的群体）和一名研究生，他们是我们聚合物计划的一部分，将接触到纳米复合材料领域和使用环境友好的方法来生产改进的材料。 此外，作为跨学科研究团队的一部分，他们将学习团队合作在解决技术问题方面的重要性。 研究主题（制造工艺）：提出一种新型的环境清洁制造工艺，用于生产具有显着改善性能的热塑性纳米复合材料。

ABSTRACT - 0507995VA Polytechnic Institute & State University NER: Process for Increasing the Exfoliation and Dispersion of Nano-particles into Polymeric Matrices Using Supercritical Carbon Dioxide Background: All the promises and claims that the addition of nano-particles to polymer matrices will miraculously lead to exceptional mechanical, barrier, electrical, and thermal stability properties have not been completely fulfilled because the improvements in properties seem to plateau when reaching levels of about 4 wt%. Only for nylon 6 have levels of 7-wt% been reached before the properties plateau because of hydrogen bonding between the amide groups and the nano-clay particles. The plateau of properties is attributed to the inability to keep the nano-particles exfoliated as the concentration is increased. The three most common methods used to synthesize nano-clay composites, i.e. intercalation of a suitable monomer and subsequent in situ polymerization, intercalation of polymer from solution, and polymer melt intercalation, have not been successful in leading to loading levels greater than about 4 wt%. However, reaching nano-clay particle levels of the order of 10 wt% could lead to a modulus increase of the order of a factor of 5 or more rather than a factor of 1.5 to 2.0(at 4 wt %). Goal: The Goal of this research is to explore the possibility of using supercritical carbon dioxide (sc CO2 ) to increase the level of nano-clay particles which remain exfoliated at levels greater than 5 wt% and preferably as high as 10 wt%. Several previous studies provide evidence that sc CO2 can swell the layered silicates, which thereby may enhance the ease of polymer intercalation into the galleries of the clay. A continuous method is proposed for swelling nano-clays and exfoliating them with sc CO2 and then subsequently injecting the mixture into a molten polymer stream. Furthermore, it is expected that because sc CO2 is highly soluble in a number of polymers it will aid dispersion of the exfoliated clay particles and at same time lower the viscosity of the melt. Once mixing is complete sc CO2 can be extracted from the system leaving the particles dispersed within the thermoplastic. In addition to using microscopy and rheological techniques to identify the degree of exfoliation, mechanical properties of thermoplastic composites will be determined. Intellectual Merit: The concept of a novel, high risk, environmentally benign process for exfoliating and dispersing nano-particles into polymer melts will evolve from this work which should be applicable to a range of nano-particle systems beyond nano-clays and toother polymer matrices. Broader Impact: The approach proposed here is novel and should lead to the filing of a patent application. It has the potential to lead to a signficant increase in the level of nano-partilces and, hence, a significant increase in properties. The increase in properties will extend the range of use of nano-composites especially in the automotive industry and rapid prototyping. The project will initially be one-year duration and, hence, the education of students will have to be planned carefully. However, at least one undergraduate (from an underrepresented group) and a graduate student, who are part of our polymer program, will be exposed to the field of nano-composites and the use of environmentally benign methods for generating improved materials. Furthermore, as part of an interdisciplinary research team, they will learn the importance of a cooperative team effort in solving technical problems. Research Theme (Manufacturing Process): A novel environmentally clean manufacturing process is proposed for generating thermoplastic nano-composite materials with signficantly improved properties.