Wood

Abstract

Along with stone, wood is the oldest material utilized by man. Originally it was indubitably used for fuel, for weapons and in construction of buildings and bridges. It was even used for keys by the Ancient Egyptians 4000 years ago. Wood can be considered both to be a natural cellular composite material and a hierarchical structure constituted from micro-fibrils of several organic polymers: cells made of cellulose (~40–50%), a polymer consisting of 5000–10,000 mers or repeat units run along the trunk or branch held together in a matrix of hemicellulose (which constitutes from ~20% in deciduous trees to ~30% in conifers) and lignin (which constitutes from ~23% in deciduous tress to ~27% in conifers). The lignin is a complex polymer that provides rigidity to the wood and also does not easily decompose.