Microstructure, Thermal Conductivity, and Flame Retardancy of Konjac Glucomannan Based Aerogels.

Ying Kuang,Qinjian Xiao,Junjun Zhai,Lijun Chen,Kao Wu,Dongling Qiao,Si Zhao,Fatang Jiang

doi:10.3390/polym13020258

Ying Kuang, Qinjian Xiao + Show 6 more

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https://doi.org/10.3390/polym13020258

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Journal: Polymers	Publication Date: Jan 14, 2021
Citations: 11	License type: CC BY 4.0

Affiliation: Hubei University of Technology, University of Nottingham

Abstract

With abundant renewable resources and good biodegradability, bio-based aerogels are considered as promising insulating materials for replacing the conventional petroleum-based foam. In this study, konjac glucomannan (KGM)-based aerogels were prepared as thermal insulation materials via a convenient sol–gel and freeze-drying progress with different content of plant polysaccharides, proteins, and wheat straw. The morphology, thermal conductivity, and flame retardancy of KGM-based aerogels were determined. The KGM-based aerogels showed a uniform three-dimensional porous microstructure. The addition of wheat straw could significantly reduce the pore size of aerogels due to its special multi-cavity structure. KGM-based aerogels showed low densities (0.0234–0.0559 g/cm−3), low thermal conductivities (0.04573–0.05127 W/mK), low peak heat release rate (PHRR, 46.7–165.5 W/g), and low total heat release (THR, 5.7–16.2 kJ/g). Compared to the conventional expanded polystyrene (EPS) and polyurethane (PU) foam, the maximum limiting oxygen index (LOI) of KGM-based aerogels increased by 24.09% and 47.59%, the lowest PHRR decreased by 79.37% and 94.26%, and the lowest THR decreased by 76.54% and 89.25%, respectively. The results demonstrated that the KGM-based aerogels had better performance on flame retardancy than PU and EPS, indicating high potential applications as heat insulation in the green advanced engineering field.

Highlights

With the continuous economic development, people’s living standards have been improved
Compared with konjac glucomannan (KGM)-based aerogels, expanded polystyrene (EPS) has more closed pores and the pores were arranged in an orderly manner
After the addition of starch, the total pore numbers of K1A1S1, K1G1 S1, and K1AL1S1 aerogels significantly increased to 472, 622, and 651, and the ratio of pore numbers below 50 μm of K1A1S1, K1G1S1, and K1AL1S1 aerogels increased to 92.1%, 83.0%, and 90.0%, respectively, indicating the decrease of pore sizes of KGM-based aerogels

Summary

Introduction

With the continuous economic development, people’s living standards have been improved. The rapid increase in the skyscrapers lead to a significant increasing in energy consumption, and the carbon emissions of buildings have increased year by year [1]. To effectively slow down energy loss and reduce building carbon emissions, thermal insulation materials are commonly used as the external wall insulation layer [2]. Thermal conductivity is a very important physical index to indicate the heat insulation ability of materials [3], which refers to the heat quantity transferred along with the heat flow to the unit area of the material under the unit temperature gradient in unit time. The thermal insulation material with lower thermal conductivity had a better energy-conservation effect. The thermal conductivity of heat insulation materials mainly depends on the chemical compositions, temperature, molecular structures, density, porosity, humidity, and other factors [4]

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