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

利用超临界二氧化碳背景增加纳米颗粒在聚合物基质中的剥离和分散的过程：所有的承诺和声称，将纳米颗粒添加到聚合物基质中，将奇迹般地导致特殊的机械、屏障、电和热稳定性性能，但这并没有完全实现，因为当达到约4 wt%的水平时，性能的改善似乎趋于平稳。由于酰胺基团和纳米粘土颗粒之间的氢键作用，只有尼龙6在达到7-wt%的水平时，性能才稳定下来。性能的平稳期归因于随着浓度的增加，纳米颗粒无法保持脱落。用于合成纳米粘土复合材料的三种最常用的方法，即插入合适的单体并随后进行原位聚合，从溶液中插入聚合物，以及聚合物熔体插入，都没有成功地导致负载水平大于约4 wt%。然而，达到10 wt%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到2.0倍（在4 wt%时）。目的：本研究的目的是探索使用超临界二氧化碳（sc CO2）的可能性，以增加纳米粘土颗粒的水平，这些颗粒在大于5 wt%，最好高达10 wt%时仍保持脱落。先前的几项研究提供了证据，表明sc CO2可以使层状硅酸盐膨胀，从而可以增强聚合物嵌入粘土画廊的便利性。提出了一种连续的方法来膨胀纳米粘土，用sc CO2将其剥离，然后将混合物注入熔融聚合物流中。此外，由于sc - CO2在许多聚合物中高度可溶，预计它将有助于脱落的粘土颗粒的分散，同时降低熔体的粘度。一旦混合完成，sc CO2可以从系统中提取出来，使颗粒分散在热塑性塑料中。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：一种新颖的、高风险的、环境友好的纳米颗粒剥离和分散到聚合物熔体中的过程的概念将从这项工作中发展出来，它应该适用于纳米粘土和其他聚合物基质以外的一系列纳米颗粒系统。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。它有可能导致纳米粒子水平的显著增加，因此，性能的显著增加。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方面。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，他们是我们聚合物项目的一部分，将接触到纳米复合材料领域和使用无害环境的方法来产生改进材料。此外，作为跨学科研究团队的一员，他们将了解合作团队努力解决技术问题的重要性。研究主题（制造工艺）：提出了一种新型的环境清洁制造工艺，用于生产性能显著改善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.