Specific Gravity of Inner and Outer Larch Bark

Günther Kain,Marco Morandini,Marius-Catalin Barbu,Jan Tippner,Alexander Petutschnigg

doi:10.3390/f11111132

Abstract

Larch bark is an interesting resource for the production of insulation panels. As it consists of a sugar-rich inner bark and an outer bark containing more durable components, there is the requirement to separate these compartments. Additionally, bark is often mixed with wooden pieces after industrial debarking processes. In this study, the wet density, dry density, and specific gravity of wood, whole bark, and inner and outer bark are investigated using the pycnometer method, which has been proven to be adequate for the volume measurement of irregularly shaped, light objects such as bark flakes. Soaked with water, the density of the inner bark is highest, followed by wood, and the lightest is the outer bark. Because of different moisture contents, the wet density is not directly comparable. The outer bark sucked up less water than the inner bark. Focusing on the specific gravity, the wood is the heaviest, followed by the outer bark and the inner bark. The differences are significant for both methods, displaying a promising physical basis for separation methods based on density differences. These might be a means to pick out more durable and less hygroscopic outer bark particles from a bark mixture in order to produce optimized bark composites.

Highlights

Tree bark is cellular tissue that is built as a peripheral layer outside of a tree’s cambium as a shell of the xylem
It was shown that the pycnometer method is well suited for the wet volume determination of bark pieces, which is in accordance with
It was shown that the pycnometer method is appropriate for the volume determination of larch bark with its flake periderm

Summary

Introduction

Tree bark is cellular tissue that is built as a peripheral layer outside of a tree’s cambium as a shell of the xylem. Phelloderm, phellogen, and phellem make up the periderm, which is long-lasting with some trees (e.g., Fagus sylvatica) and is short-lived with most European trees (e.g., Larix decidua) [2]. In this case, it dies off after some time and is replaced by a new one on its inner side. The phloem consists primarily of conducting, sclerenchymatic, and parenchymatic cells and contains the conducting system for the assimilates of a tree. For this reason, it is predominantly made up of sieve elements [1]. Outlying the respective new periderm, suberin is stored in the cells, making them impervious to water [4]

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