HEMP PULP WITH IMPROVED STRUCTURAL AND PHYSICAL-MECHANICAL CHARACTERISTICS

The method of obtaining high-viscosity hemp cellulose on the basis of sulfate treatment of fiber, which, unlike wood processing, is carried out in a relatively low temperature range (150-170° C), in an alkali solution, including surfactant and reducing agent, with the use of an environmentally friendly variant of bleaching using hydrogen peroxide solution, is considered. The developed method allows to use hemp fiber with the content of bark up to 13% and fiber breaking load - not less than 200 kgf as a source of cellulose. Due to the loose structure of hemp straw resulting from pretreatment, the cooking solution penetrates more easily into the raw material, which in turn accelerates delignification processes. Pre-treatment of raw materials increases the yield as well as the physical properties of the final product - cellulose, mainly from cereal crops (rye, wheat, etc.). Due to the loose morphology of cereal plants, oxygen easily penetrates inside the material, which in turn accelerates delignification processes. Dense structure of hemp fiber, heterogeneity of properties depending on the place and conditions of growth complicate the process of fiber processing. The proposed modified sulfate treatment of hemp fiber with lignin content of 9 wt% provides intensification of delignification processes of annual plant raw materials and fibrillation of cellulose fibers. In solving the problem, standard analytical methods were used to study the physicochemical properties of celluloses of different nature; FT-IR spectroscopy to study inter- and intramolecular interactions in the samples of the studied celluloses; supramolecular structure of hemp and flax cellulose of different kinds in comparison with samples of wood sulfite cellulose in the form of RB by X-ray diffraction method; quantitative assessment of quality and degree of pulverization of cellulose samples of different nature and kind; determination of physical and mechanical characteristics of castings from hemp cellulose samples in comparison with castings from hemp cellulose of foreign standard, as well as with samples from wood sulfite cellulose. The proposed method provides reduction of lignin content (0,7-0,9 %) and preservation of average degree of polymerization (DP = 1200 - 1600) due to selectivity of fiber delignification process, reduction of destruction process of high molecular weight fraction of cellulose, which allows obtaining high viscosity hemp pulp with improved structural and physical-mechanical characteristics.