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

摘要-0507995VA理工学院和州立大学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：所有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、电气和热稳定性性能的承诺和声称尚未完全实现，因为当达到约4wt%的水平时，性能的改善似乎停滞不前。只有尼龙6由于氨基和纳米粘土颗粒之间的氢键作用，在性能平台之前达到了7-wt%的水平。性能的平台化归因于纳米粒子不能随着浓度的增加而保持剥离。三种最常用的合成纳米粘土复合材料的方法，即合适的单体插层和随后的原位聚合、从溶液中插层聚合物和聚合物熔融插层，都不能成功地导致负载量超过约4wt%。然而，达到10wt%量级的纳米粘土颗粒可以导致弹性系数增加5倍或更多，而不是1.5到2.0倍(4wt%)。目标：这项研究的目标是探索使用超临界二氧化碳(Sc CO2)来增加纳米粘土颗粒水平的可能性，这些纳米粘土颗粒保持在高于5wt%的水平，最好高达10wt%。以前的几项研究提供了证据，表明超临界二氧化碳可以膨胀层状硅酸盐，从而可能增加聚合物插入粘土走廊的难度。提出了一种连续的方法来膨胀纳米粘土，并用sc CO2剥离它们，然后将混合物注入熔融的聚合物流中。此外，由于超临界二氧化碳在许多聚合物中高度溶解，预计它将有助于剥离的粘土颗粒的分散，同时降低熔体的粘度。一旦混合完成，就可以从体系中提取sc二氧化碳，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。智力价值：将纳米粒子剥离和分散到聚合物熔体中的新的、高风险的、对环境无害的过程的概念将从这项工作中发展出来，它应该适用于除纳米粘土之外的一系列纳米粒子系统，以及其他聚合物基质。更广泛的影响：这里提出的方法是新颖的，应该会导致专利申请的提交。它有可能导致纳米粒子水平的显著增加，从而显著提高性能。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中。该项目最初为期一年，因此，学生的教育必须仔细规划。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，并使用环境友好的方法来产生改进的材料。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)：提出了一种新的环境清洁制造工艺，以制备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.