Study On Basic Properties And Board Manufacturing Of Hemp Core

Hemp is belong to Cannabaceae Cannabis which is annual herbal fiber crop, its Latin name is Cannabis sativa L., also known as many other Chinese names, whose include about 150 species, mainly plated in Asia and Europe, and hemp resources are rich in China. Hemp has important application value. Each part of hemp, especially its Phloem fibers, is developed and used significant in the textile industry, light industry, construction, chemical industry, transportation, defense industries and agriculture, animal husbandry, forestry and so on, other leaves, seeds and branches have been used to a certain extent, but hemp core who occupy a large volume as a whole are not be good utilized, so make good use of hemp core is an important positive meaning to multipurpose use of hemp, form hemp industry chain, increase income of farmers, relieve the situation of lacking timber resource and develop the green economy.Through the systemically research on the basis characters of hemp core material different parts to understand the features, and investigate hemp core maintaining its shape to manufacture man-made board, discuss different densities, material width and adhesive influence on the hemp core board.Study on the basic properties of hemp core and the results as followed:Hemp core is mainly consist of fiber, vessel, axial parenchyma and xylem ray. The length of hemp core fiber is between 362.77﹣938.01μm, the width is between 16.48﹣54.85μm; the length of vessel is between 128.65﹣807.03μm, the width is between 37.87μm﹣164.24μm. The wall thickness is only 2.45μm, the wall thickness-lumen ratio is 0.214 which belongs to very thin fiber. hemp core air-dried density is between 0.111﹣0.303g/cm3, and average value is 0.193g/cm3. The average value of oven-dried density is 0.186g/cm3, and the average value of basic density is 0.179g/cm3. the density of hemp core increase with height, bottom is minimum, middle is second, and top is maximum. Oven-dried and air-dried shrinkage ratio trend of hemp core is longitudinal<radical<tangential, which is as the same as wood. Hemp core has absorbent ability; its water absorption is reach 299.91% in 24 hours. The modulus of elasticity, bending strength, tensile strength parallel to grain and compressive strength is belong small level.The main chemical components of hemp core are cellulose, hemicellulose and lignin. The result shows holocellulose content is 79.91%, lignin content is 19.16%, hot water and cold water extractive content is 5.66% and 4.26%, alcohol benzene extractive content is 5.72% and 1%NaOH extractive content is 30.81%, ash content is 1.48%.Hemp core crystallinity is between 55﹣66%, according to FTIR, it mainly contain cellulose, hemicellulose and lignin typical infrared spectra absorption peaks as wood, and have a little Phosphorus compounds, the lignin structure is as the same as G,S type of hard wood. According to Thermal synthesize analyzer, thermal decomposition of hemp core is divided into three main stages, which including the drying and early evaporation stage, main thermal decomposition stage and the stage of residues thermal decomposition.Study on the board processing of hemp core as man-made material as followed: hemp core boards average moisture content are between 10﹣12%, and density of hemp core boards are between 0.141﹣0.351g/cm3. The 24 hours water absorption, thickness and volume swelling are between 90.56﹣153.47%, 5.94﹣31.77% and 14.36﹣39.33%. The bending strength, modulus of elasticity are increasing with density, the bending strength are between 3.77﹣12.33MPa, modulus of elasticity are between 1163.56﹣2534.89MPa, the internal conductivity is between 0.102﹣0.193MPa. hemp core board is very good heat preservation material, its thermal conductivity is only 0.061W/(m·K)of 0.25g/cm3 density board, and sound absorption coefficient is between 0.105﹣0.245.The 24 hours water absorption, thickness, volume swelling, sound absorption coefficient and thermal conductivity are decreasing with material width, but the mechanical property are increasing with material width.