The mechanical properties and thermal conductivity of bamboo with freeze\u2013thaw treatment

Jieyu Wu,Xiang Xu,Xianke Wang,Hong Chen,Caiping Lian,Benhua Fei

doi:10.1186/s10086-021-01998-0

Abstract

The aim of this research was to investigate the effect of freeze–thaw treatment on bamboo with different initial moisture content (water-saturated, air-dried and oven-dried). Bamboo (Phyllostachys pubescens) were treated with two freeze treatments and its microstructure, chemical composition, mechanical properties and thermal conductivity were characterized by field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), mechanical testing machine and thermal conductivity tester, respectively. The results showed that the freeze–thaw treatment had little influence on the microstructure of bamboo, the chemical composition content and the cellulose crystalline structure of bamboo were also not altered. The crystallinity index was found to increase with the increase of initial moisture content. The bending strength and elastic modulus of the treated bamboo increased, the extent of the increase was dependent on the initial moisture content and the freezing temperature. The thermal conductivity of the treated bamboo increased remarkably, which might be possibly determined by the cellulose crystallinity, moisture content, and density of bamboo.

Highlights

With the increasing concerns about low carbon development, renewable biomass materials have attracted growing attention [1]
There was no significant change in the microstructure of fibers and parenchyma cells with different moisture contents after freeze–thaw treatment
In this study, bamboo with different moisture content was subjected to two freeze–thaw treatments to investigate the change in its material properties in terms of the microstructure, chemical composition, mechanical properties, and thermal conductivity

Summary

Introduction

With the increasing concerns about low carbon development, renewable biomass materials have attracted growing attention [1]. The density gradually decreased and formed a gradient structure as the distribution of vascular bundle decreased from the outer layer to the inner layer of bamboo [13, 14]. This unique structure of bamboo has a significant impact on its mechanical properties. There was limited information on the changes of mechanical properties and physicochemical of bamboo under low temperature In this regard, the studies on the change in materials properties of bamboo under freeze–thaw treatment might be important for its development and utilization in outdoor applications, for the use in extremely cold environments

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Results

Conclusion