Aerogels are lightweight materials with extensive microscale pores, which could be used in thermal insulation, energy devices, aerospace structures, as well as emerging technologies of flexible electronics. However, traditional aerogels based on ceramics tend to be brittle, which limits their performance in load-bearing structures. As a result of restrictions posed by their building blocks, recently developed classes of polymeric aerogels can only achieve high mechanical strength by sacrificing their structural porosity or lightweight characteristics.
A research team led by Dr Lizhi Xu and Dr Yuan Lin from the Department of Mechanical Engineering of the Faculty of Engineering of the University of Hong Kong (HKU), has developed a new type of polymer aerogel materials with vast applicational values for diverse functional devices.
In this study, a new type of aerogels was successfully created using a self-assembled nanofiber network involving aramids, or Kevlar, a polymer material used in bullet-proof vests and helmets. Instead of using millimetre-scale Kevlar fibres, the research team used a solution-processing method to disperse the aramids into nanoscale fibrils.
The interactions between the nanofibers and polyvinyl alcohol, another soft and “gluey” polymer, generated a 3D fibrillar network with high nodal connectivity and strong bonding between the nanofibers, similar to a microscopic 3D truss network. The team managed to weld the trusses firmly together, resulting in a very strong and tough material that can withstand extensive mechanical loads, outperforming other aerogel materials.
The team has also used theoretical simulations to explain the outstanding mechanical performance of the developed aerogels. They constructed a variety of 3D network models in computer, which captured the essential characteristics of nano fibrillar aerogels, said Dr Lin, who led the theoretical simulations of the research.
It was noted that the nodal mechanics of fibrillar networks are essential to their overall mechanical behaviours. The team’s simulations revealed that the nodal connectivity and the bonding strength between the fibres influenced the mechanical strength of the network by many orders of magnitudes even with the same solid content.
The team not only developed a new type of polymer aerogels with excellent mechanical properties but also provided insights into the design of various nanofibrous materials. The simple fabrication processes for these aerogels also allow them to be used in various functional devices, such as wearable electronics, thermal stealth, filtration membranes, and other systems.
The research was published in Nature Communications, in an article entitled “Ultrastrong and multifunctional aerogels with hyperconnective network of composite polymeric nanofibers”.
The global aerogel market size was valued at US$818.9 million in 2020 and is expected to grow at a compound annual growth rate (CAGR) of 15.1% from 2020 to 2028. The rapid development of the aerogel for high-temperature insulation primarily in the oil & gas industry, due to low thermal conductivity is expected to drive the market over the forecast period.
The COVID-19 pandemic had an impact due on the market in 2020. Lockdowns imposed across various regions led to the delay of the new construction related to insulation in the oil & gas industry and led to limited growth of the market. However, product usage in critical applications for critical MRO activities was responsible for the market growth in 2020.
Polymer aerogel products are expected to witness the fastest CAGR of 20% during the forecast period on account of their superior chemical and physical properties as compared to their silica counterparts. Polymer aerogels have applications in various end-use industries including defence, electrical & electronics, building and construction, and several others.
