Thermal insulation Behavior of Functionally Graded Aerogel: The Role of Novolac Molecular-Weight

Publication date: Available online 15 June 2019Source: PolymerAuthor(s): Mina Noroozi, Mahyar Panahi-Sarmad, Ahmad Reza BahramianAbstractIn this research, a novel aerogel with a functionally-graded (FG) structure as a thermal insulator has been fabricated without interfaces through sol-gel polymerization. The effects of molecular-weight (Mw) and initial-solvent concentration as decisive parameters in the microstructure of phenol-formaldehyde aerogels are systematically studied. The results show that a broad spectrum of Mw created via the precise control of the cross-linking (CL) process of the resin. Moreover, the sol-size have been remarkably augmented when increasing the Mw. The porousness structure assessment illustrated that the porosity decreases with enhancing the amount of solvent, but increasing Mw has no significant effect on the porosity of specimens. In FG-aerogel microstructure, more homogeneous distribution in the sol-size and significant decrement in pore size is observed while the Mw and solution concentration are simultaneously increased throughout the structure. Therefore, FG-aerogel structure contains a wide range of porosity, thermal conductivity (0.029 - 0.422 (W⁄(m.K))) and pore size (200-2000 nm) that leads to unique structural features of aerogels.Graphical abstract

Source: Polymer - June 16, 2019 Category: Chemistry Source Type: research