Seaweed-Derived Alginate-Cellulose Nanofiber Aerogel for Insulation Applications.

Linn Berglund,Tuukka Nissilä,Kristiina Oksman,Deeptanshu Sivaraman,Ville-Veikko Telkki,Sanna Komulainen

doi:10.1021/acsami.1c07954

Abstract

The next generation of green insulation materials is being developed to provide safer and more sustainable alternatives to conventional materials. Bio-based cellulose nanofiber (CNF) aerogels offer excellent thermal insulation properties; however, their high flammability restricts their application. In this study, the design concept for the development of a multifunctional and non-toxic insulation material is inspired by the natural composition of seaweed, comprising both alginate and cellulose. The approach includes three steps: first, CNFs were separated from alginate-rich seaweed to obtain a resource-efficient, fully bio-based, and inherently flame-retardant material; second, ice-templating, followed by freeze-drying, was employed to form an anisotropic aerogel for effective insulation; and finally, a simple crosslinking approach was applied to improve the flame-retardant behavior and stability. At a density of 0.015 g cm–3, the lightweight anisotropic aerogels displayed favorable mechanical properties, including a compressive modulus of 370 kPa, high thermal stability, low thermal conductivity (31.5 mW m–1 K–1), considerable flame retardancy (0.053 mm s–1), and self-extinguishing behavior, where the inherent characteristics were considerably improved by crosslinking. Different concentrations of the crosslinker altered the mechanical properties, while the anisotropic structure influenced the mechanical properties, combustion velocity, and to some extent thermal conductivity. Seaweed-derived aerogels possess intrinsic characteristics that could serve as a template for the future development of sustainable high-performance insulation materials.

Highlights

The design of green insulation materials includes the use of renewable, bio-based raw materials and their eco-efficient and sustainable processing into next-generation building materials
The fibrillation process resulted in the separation of the cellulosic part into very fine nanofibers through the shearing forces applied to the sample by ultrafine grinding, resulting in a gel composed of alginate and cellulose nanofiber (CNF) (Figure 1c)
This resource- and eco-efficient approach of isolating nanofibers was combined with ice-templating and non-toxic CaCl2 crosslinking to produce a natural anisotropic aerogel with multifunctional properties such as lightweight, good mechanical properties, high thermal stability, low thermal conductivity, considerable flame retardancy, and self-extinguishing behavior

Summary

■ INTRODUCTION

The design of green insulation materials includes the use of renewable, bio-based raw materials and their eco-efficient and sustainable processing into next-generation building materials. The development of bio-based aerogel insulation materials that possess multifunctional properties such as mechanical stability, flame retardancy, and low thermal conductivity, combined with using eco-friendly and upscalable production approaches, remains a challenge. Uniaxial unconfined compression tests were performed at 25 °C using a dynamic mechanical analyzer (DMA Q800, TA Instruments, New Castle, DE, USA) to study the effect of crosslinking at different concentrations on the mechanical properties. The moisture resilience of the aerogels was evaluated before and after crosslinking at different concentrations by exposing samples (2 cm3) to 75% relative humidity for 48 h based on the average relative humidity for Europe 2016 reported by ERA-. Each sample was measured for 1 h with calibrations for equilibration and steady-state heat flow in the software.[24]

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES