Cork Structure And Chemical Composition Analysis

Cork is the outer bark of trees such as Quercus variabilis B., it is a kind of natural macromolecule material, with the property of abrasion proofing, waterproofing, anti-aging, good elasticity, low density, heat insulation, sound absorbing, aseismatic. The character of major structure and main chemical composition is the theosetic base of manufacturing, using, property modification, developing new product and secondary fine machining. This paper analyzed the basic structural characteristics and chemical composition and its content of cork from Quercus variabilis B., then compared with Phellodendron amurense and Euonymus phellomanus. Main conclusions are as follows:Macro-structural characteristics: the phellem distributed continuously around trees, and the outer bark is dust-colour, with deeper trench in virgin cork than reproduction cork and after; there are sclereids in cork and forms a brown belt around the region; there are pores in bark, which looks like lip. The colours of cork from Phellodendron amurense, Euonymus phellomanus, Quercus variabilis B. varys deeper and deeper. There were no sclereids found in cork from Phellodendron amurense, Euonymus phellomanus.Micro-structural characteristics: Observeing the three sections of cork from Quercus variabilis by SEM, it can be seen that cork is formed by one kind of cell, with thin cell wall, internal hollow and full of gas; cells arranged and accumulated along the radial; In the tangential section, cork cells are seen in a honeycomb-like arrangement. In the transverse and radial section, cork cells are in brick-like arrangement. Ideal cork cell is a 14-faces-polyhedron, formed with 8 hexagonal and 6 quadrangular faces. The average dimensions of cork cells depend appreciably on the season in which they are formed. Cells formed in the early growing season are larger and have thinner wall than the cells formed in the late growing season. The lateral faces of cork cells from Quercus variabilis are corrugated. No pit was found but pore connect cells. The shape and arrangement of Phellodendron amurense and Euonymus phellomanus are similar to which of Quercus variabilis, and the dimensions of cells also depend on season. The drape in cork cell wall from Phellodendron amurense are more and distinct than Quercus variabilis; the cell wall from Euonymus phellomanus are straight, without drape.Main chemical composition and its content: The main chemical components of cork include extract, suberin, lignin and polysaccharides. The content of chemical composition is affected with trees species, the environment it grows, age and so on. The average content of main chemical composition are: extract12%, suberin 40%, lignin 20%, polysaccharide 20%. Virgin cork from sprout Quercus variabilis B. have a higher suberin content, and fewer lignin content than other cork from Quercus variabilis B. Among Quercus variabilis B., Phellodendron amurens and Euonymus phellomanus , suberin content form Phellodendron amurens is the highest one, more than 50%, and Euonymus phellomanus is the lowest one, less than 4.9%.Suberin and monosaccharides component of polysaccharide analyse: Suberin extract from cork in this experiment is segments of the whole suberin molecule. It is obtained by alcoholysis. Through Infrared Ray spectrogram analysis, it can be seen that Suberin is composed of fatty acids and hydroxybenzene acids. Analysised by ion chromatography, monosaccharides component of polysaccharide in cork from Quercus variabilis B. are: xylose (30%), glucose (12%), fructose (45%), mannose (4%), galactose (12%). Monosaccharides content of polysaccharide have some difference from different corks from Quercus variabilis B.. Monosaccharides composition of polysaccharide from Phellodendron amurense and Euonymus phellomanus are same to Quercus variabilis B., with little difference in content.