| Industrial hemp, a kind of fast growing annual fiber sources, is a specie of cannabis plants, which is harmless or even no harmful for human. And Yunma No. 1, as the raw material in this experiment, is a new kind of hemp species, systematically cultivated in Yunnan Agriculture Science Institution, whose tetrahydrocannabinol (THC) is less than 0.3%. Based on the advantages of fast growing, high yield and cultivated adaptability, this kind of hemp is a potentially raw biomass to develop various fiber-based-products.Firstly, this paper independently studied the morphology and the chemical composition of the stalk core and bast of Yunma No. 1, respectively. Secondly, it mainly analyzed the influence of different operating conditions used in soda-AQ chemical pulping and, subsequently, O-D-P sequence bleaching on the pulp properties of the stalk core and bast, respectively, and optimized the pulping and each step bleaching conditions for providing comparatively high-quality hemp pulp fibers applied to the next graft copolymerization experiment. Thirdly, it preliminary discussed the water-absorbing polymers prepared by graft-copolymerization of acrylic acid (AA) and acrylamide (AM) with these two kinds of bleaching pulps' cellulose of Yunma No. 1; and the water absorption behaviors of these resins, furthermore, were determined and compared in different media and related conditions.On the basis of study and analysis of the morphology and the chemical composition of the stalk core and bast of Yunnan 1~# industrial hemp, the results are as follows: the average length and width of the bast fiber is 14 mm and 30μm, respectively, and so it belongs to super-long-fiber raw materials; the average length and width of the core fiber is 0.6 mm and 30μm, respectively, and so it belongs to short-fiber raw materials. Moreover, the bast part of Yunma No. 1 contains 67.1% cellulose, 4.4% lignin, 6.8% semicellulose content, 2.5% organic-solvent abstractive content, 27.3% l%NaOH abstractive, 7.6% cold-water abstractive, 8.3% hot-water abstractive and 4.8% ash content. And the core part contains 46.8% cellulose, 23.2% lignin, 17.3% semicellulose content, 3.3% organic-solvent abstractive content, 26.5% l%NaOH abstractive, 4.1% cold-water abstractive, 5.5% hot-water abstractive and 2.6% ash content.After soda-AQ pulping and O-D-P bleaching, the final pulp properties of Yunma NO.1 are shown: 1) the core part: pulp SBD brightness of 85.3%, kappa number of 3.8, viscosity of 1031 ml/g; 2) the bast part: pulp SBD brightness of 80.2%, kappa number of 1.1, viscosity of 844 ml/g.In this experiment, the superabsorbent resins were successfully synthesized by means of ordinary radical copolymerization of AA, AM onto the hemp bleaching pulp cellulose of the core and bast respectively, using N, N -methylenebisacrylamide (MBAA) as crosslinking agent and sodium bisulfite and ammonium persulfate as initiator in aqueous slution. The structures of these two kinds of water-absorbent resins were determined by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electric Microsocopy (SEM) and X-Ray Diffraction (XRD). In order to thoroughly investigate and discuss the graft-copolymerization time affecting percentage of grafting (P_g), grafting efficiency (G_E), percentage of monomers grafting onto cellulose (P_m), and water-absorbent capacity of these resins, other factors were kept constantly: each monomer to dry pulp weight ratio of 8:1, ammonium persulfate to dry pulp weight ratio of 0.015:1, sodium bisulfite to ammonium persulfate weight ratio of 1:3, NMB A to two monomers weight ratio of .004:1, AA neutralization degree of 70%, reaction temperature of 65℃. Based on the analysis and comparison of the experimental results, P_g, G_E, and P_m increased with prolonging the reaction time from 5h to 10h and 15h. However, the water-absorbent capacity and rate of each super-absorbent resin did not increase but oppositely decreased with the increase of the reaction time. So, comparatively with other reaction time, the optimal water-absorbent capacity as well as 0.9% NaCl absorbent ability of both kind resins is at 5h. Furthermore, both water-absorbent capacity and 0.9% NaCl absorbent ability of the bast-cellulose-PAA (-PAM) resin are obviously better than these of the core-cellulose-PAA (-PAM) resin at the same graft-copolymerization conditions. The bast-cellulose-PAA(-PAM) resin with absorbent capacity of 572 times their own weight in distilled water and 154 times in 0.9% saline solution, and the core-cellulose-PAA(-PAM) resin with absorbent capacity of 246 times their own weight in distilled water and 71 times in 0.9% saline solution under optimized reaction time of 5h, were obtained. |
PDF Full Text Request