Chemical Composition of Cork from <i>Quercus Variablis</i>
Keywords:Cork, <i>Quercus variablis</i>, chemical composition, properties
AbstractCork is a natural and renewable raw material harvested from the outer bark of oak (Quercus spp.) trees. Unique and valuable properties of cork include low density, low permeability, high elasticity, good heat and acoustic insulation properties, and resistance to chemical and microbial attack. Chemical composition of cork is affected by many factors including the Quercus species and the number of times that cork has been harvested from the tree (ie virgin vs reproduction cork). Differences in chemical composition can significantly influence cork properties. In this study, chemical composition of virgin and reproduction cork from Quercus variablis trees in Shaanxi Province, China, was investigated. Cork samples were sequentially extracted with dichloromethane, ethanol, and water in a Soxhlet extractor. Eluted fractions were analyzed using ion chromatography. Chemical composition of virgin Q. variablis cork was 34.3% suberin, 20.6% lignin, 17.4% extractives, and 15.2% polysaccharides. Composition of reproduction cork was 36.9% suberin, 19.9% lignin, 12.7% extractives, and 12.0% polysaccharides. These results show that composition of virgin and reproduction Q. variablis cork was similar. Virgin Q. variablis cork had greater extractives and polysaccharides content than reproduction cork but a little less suberin. Chemical composition of Q. variablis cork from China is significantly different from that of Quercus suber L. cork from Europe.
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