Abstract
The desire for lightweight nanoporous materials with high-performance thermal insulation and efficient anti-ablation resistance for energy conservation and thermal protection/insulation has greatly motivated research and development recently. The main challenge to synthesize such lightweight materials is how to balance the relationship of low thermal conductivity and flame retardancy. Herein, we propose a new concept of lightweight “rime-like” structured carbon-phenolic nanocomposites to solve this problem, where the 3D chopped network-structured carbon fiber (NCF) monoliths are incorporated with nanoporous phenolic aerogel to retain structural and functional integrity. The nanometer-scaled porous phenolic (NP) was synthesized through polymerization-induced phase separation and ambient pressure drying using phenolic resin (PR) solution as reaction source, ethylene glycol (EG) as solvent and hexamethylenetetramine (HMTA) as catalyst. We demonstrate that the as-prepared NCF-NP nanocomposite exhibits with a low density of 0.25–0.35 g/cm3, low thermal conductivity of 0.125 Wm−1K−1 and outstanding flame retardancy exceeding 2000 °C under arc-jet wind tunnel simulation environment. Our results show that the synthesis strategy is a promising approach for producing nanocomposites with excellent high-temperature heat blocking property.
Highlights
Traditional carbon fiber reinforced phenolic resin (C-Ph) composites have played an important and strategic role in the field of energy efficiency for buildings and thermal protection/insulation[1,2,3,4,5]
Inspired by “rime-like” structure in nature, we describe lightweight (0.25–0.35 g/cm3), highly porous network-structured carbon fiber (NCF)-nanometer-scaled porous phenolic (NP) composites that are produced by impregnating nanostructured NP sol into 3D porous NCF framework by polymerization-induced phase separation of phenolic resin (PR), ethylene glycol (EG) and HMTA (Fig. 1a), and subsequent ambient pressure drying
The cured NCF-NP composite was conducted to immerse in IPA to exchange redundant EG and directly dried under ambient pressure, and the final NCF-NP composite had a relatively low density of 0.25–0.35 g/cm[3]
Summary
Traditional carbon fiber reinforced phenolic resin (C-Ph) composites have played an important and strategic role in the field of energy efficiency for buildings and thermal protection/insulation[1,2,3,4,5]. C-Ph composites have relatively high density and thermal conductivity, owing to its densified structure consisting of dispersive carbon fiber and thermosetting phenolic resin. Quasi-stable, low-density, three-dimensional assemblies of nanoparticles are referred to as aerogels and typically are derived from drying wet-gels by supercritical, subcritical or ambient pressure to remove the pore-filling solvent and retain its formed skeleton structure simultaneously[14,15]. Their large internal nanoporous void space is responsible for ultra-low thermal conductivity and thermal insulation application. The resultant nanocomposites exhibit sufficiently low thermal conductivity and show high flame retardancey
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