The recent global energy context has been recognized as evidence for the need to reduce our energy consumption, to prolong fossil fuel supplies and minimize shortage, and to decelerate greenhouse gas transpiration. Over the past few years, using an insulator and decreasing its thermal conductivity have been recognized as the most effective way to reduce energy consumption. Aerogels as superinsulating materials permit reduction of the heat exchange between two environments while producing facile sol−gel and diverse drying routes. Aerogels have intrigued scientists and engineers due to their unique nanocharacteristics, such as low density, fine internal void spaces, and openpore geometry, which originate from sol particles in a 3D random network. Noteworthy are aerogel-based materials that have a supreme potential as thermal insulation owing to their very low thermal conductivity based on trapped air in the meso-/ nanoporous structure. Indeed, aerogels have great appeal in terms of their thermal efficiency, producing simplicity and performance reliability as compared with a traditional insulator. In this work, we will review the main milestones along with the concept of aerogels and then discuss some new trends, strategies, and opportunities in employing various morphological and nanostructural control methods to improve the performance of aerogels, especially enhancing insulation efficiency or decreasing thermal conductivity. The focus will be on (I) tailoring the porous structure of a carbon-based aerogel such as graphene oxide and reduced graphene oxide to accommodate high thermal behavior and (II) designing strategies to achieve intrinsically superinsulating materials in synthesized polymer and bio-based materials, with/without embedding an additional component.
Plastics offer several advantages, but their production and disposal processes have severe environmental implications. To overcome these issues, there is a need to switch from the linear to a circular economy by recycling plastic waste and by utilizing renewable resources to create bioplastics. However, this is challenging in the case of nonbiodegradable polyolefins (POs), which form the largest fraction of produced polymers and the least recycled one. Mechanical recycling, chemical recycling, and PO bioplastics are the three pillars of PO circular economy. Although mechanical recycling is an environmentally and economically viable option, it often results in the degradation and downgrading of POs. Nonetheless, innovations in mechanical recycling, such as the use of (nano)fillers or compatibilization with olefin block copolymers, attempt to mitigate these issues. Furthermore, the development of covalent adaptable networks improves the mechanical properties of recycled PO thermoplastics and provides recyclable PO elastomers. If mechanical recycling fails to meet the desired characteristics of the recyclate PO, chemical recycling to other chemicals is a potential alternative. Although retrieving the monomer is ideal for achieving a closed-loop circular economy, traditional approaches for the noncatalytic chemical recycling of POs are energy-intensive and lack specificity. This has been tried to be addressed by advancements in catalytic approaches. Finally, biobased polyolefins, especially those produced through emerging nonbiochemical approaches, offer attractive alternatives that can be integrated into existing petrochemical plants. With this comprehensive perspective on POs circular economy academic and industrial researchers of the field can better contribute to a more sustainable future.
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