Mechanically Strong, Low Thermal Conductivity and Improved Thermal Stability Polyvinyl Alcohol-Graphene-Nanocellulose Aerogel

Abstract

Porous aerogel materials have advantages of a low density, low thermal conductivity and high porosity, and they have broad application prospects in heat insulation and building energy conservation. However, aerogel materials usually exhibit poor mechanical properties. Single-component aerogels are less likely to possess a good thermal stability and mechanical properties. It is necessary to prepare multiple-composite aerogels by reinforcement to meet practical application needs. In this experiment, a simple preparation method for polyvinyl alcohol (PVA)-graphene (GA)-nanocellulose (CNF) ternary composite aerogels was proposed. This is also the first time to prepare ternary composite aerogels by mixing graphene, nanocellulose and polyvinyl alcohol. A GA-CNF hydrogel was prepared by a one-step hydrothermal method, and soaked in PVA solution for 48 h to obtain a PVA-GA-CNF hydrogel. PVA-GA-CNF aerogels were prepared by freeze drying. The ternary composite aerogel has advantages of excellent mechanical properties, a low thermal conductivity and an improved thermal stability, because strong hydrogen bonds form between the PVA, GA and CNF. The composite aerogels were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffractometry, Brunauer-Emmett-Teller analysis, dynamic thermal analysis, thermogravimetry and thermal constant analysis to characterize the properties of the ternary composite aerogels. The lightweight, low-density and porous PVA-GA-CNF composite aerogels withstood 628 times their mass. The thermal conductivity of the composite aerogels was 0.044 ± 0.005 W/mK at room temperature and 0.045 ± 0.005 W/mK at 70 °C. This solid, low thermal conductivity and good thermal stability PVA-GA-CNF ternary composite aerogel has potential application in thermal insulation.

Keywords: cellulose; graphene; graphene aerogel; polyvinyl alcohol; ternary composite aerogel.

Figure 1

SEM micrographs of (a,b) PVA–GA–CNF-2 aerogel, (c,d) PVA–GA–CNF-4 and PVA–GA–CNF-5 aerogels, respectively.

Figure 2

Infrared spectra of GO, CNF, PVA–GA aerogels and PVA–GA–CNF-(1, 3, 5) aerogels.

Figure 3

XRD patterns of PVA–GA aerogels and PVA–GA–CNF-(1, 2, 3, 4, 5) aerogels.

Figure 4

Pore size distribution and specific surface area of composite aerogels. (a,b) BET diagrams of PVA–GA and PVA–GA–CNF-5 aerogels, respectively. (c) Specific surface areas of PVA–GA and PVA–GA–CNF-(1, 2, 3, 4, 5) aerogels.

Figure 5

Compression test images of PVA–GA aerogel and PVA–GA–CNF-(1–5) aerogel. (a) Appearance of PVA–GA aerogel and PVA–GA–CNF-(1, 2, 3, 4, 5) aerogel. (b–m) Height changes of PVA–GA aerogel and PVA–GA–CNF-(1–5) aerogel under 300 g mass, respectively.

Figure 6

(a) Height diagram, (b) height change diagram after pressure, (c) stress–strain curve and (d) density numerical diagram of PVA–GA aerogel and PVA–GA–CNF-(1–5) aerogel.

Figure 7

Thermogravimetric analysis of PVA–GA aerogels and PVA–GA–CNF-(1, 3, 5) aerogels.

Figure 8

(a) Thermal conductivity of PVA–GA aerogels and PVA–GA–CNF-(1–5) aerogels. (b) Thermal diffusivity of PVA–GA aerogels and PVA–GA–CNF-(1–5) aerogels.

Figure 9

Preparation process of PVA-GA-CNF aerogels.