Bark Thermal Insulation Panels: An Explorative Study on the Effects of Bark Species.

Günther Kain,Marius-Catalin Barbu,Eugenia Mariana Tudor

doi:10.3390/polym12092140

Günther Kain, Marius-Catalin Barbu + Show 1 more

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https://doi.org/10.3390/polym12092140

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Abstract

Tree bark is a byproduct of the timber industry which accrues in large amounts, because approximately 10% of the volume a log is bark. Bark is used primarily for low-value applications such as fuel or as a soil covering material in agriculture. Within the present study, thermal insulation panels made from larch, pine, spruce, fir and oak tree bark with different resins (urea formaldehyde, melamine formaldehyde, Quebracho, Mimosa) as a binder are discussed. Also, the properties of panels made from larch bark mixed with industrial popcorn are investigated. The physical-mechanical properties of the panels, which are dependent on panel density, bark species, resin type, resin content and particle size, are analyzed. The bark species has a minor effect on the mechanical characteristics of the panels, while the compression ratio is important for the panel strength, and hence, barks with lower bulk density are preferable. Under laboratory conditions, panels made with green tannin resins proved to have adequate properties for practical use. The addition of popcorn is a means to lower the panel density, but the water absorption of such panels is comparably high. The bark type has a minor effect on the thermal conductivity of the panels; rather, this parameter is predominantly affected by the panel density.

Highlights

Tree bark is the protective layer of a tree
The aim of this study is to investigate the mechanical, physical and thermal properties of composite panels made of five bark species bonded with conventional adhesives and green adhesives based on Mimosa and Quebracho tannins, and the influence of bark species, density and particle size on the tested panels
The equilibrium moisture content of bark samples at 20 ◦ C/65% relative humidity (RH) was determined to be up to 3% higher than that of wood, which is in good agreement with the findings of Standke and Schneider [28], who reported that MC variations in bark are twice as high as those in wood, and with

Summary

Introduction

Tree bark is the protective layer of a tree. It defends a tree’s vascular cambium from mechanical damage, frost, heat, fires and fungi attack [1,2], and provides partial structural support [3].Bark consists of secondary phloem, periderm and nonconductive rhytidome [4]. Tree bark is the protective layer of a tree. It defends a tree’s vascular cambium from mechanical damage, frost, heat, fires and fungi attack [1,2], and provides partial structural support [3]. The risk of forest fires and stem size was shown to explain a large part of the variation of bark thickness on a global scale [6]. The morphology of bark is influenced by other functions too, such as photosynthesis [7], water retention and the storage of nonstructural carbohydrates [1]. Bark functionalities are partly conflictive, i.e., the bark tissue has to prevent the excessive loss of water on the surface of a tree and should enable the exchange of CO2 and O2 for photosynthesis and respiration [8]

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