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Research On Steam Explosion Treating Three Non-wood Fiber Materials

Posted on:2015-10-29Degree:MasterType:Thesis
Country:ChinaCandidate:L YueFull Text:PDF
GTID:2191330503951100Subject:Wood science and technology
Abstract/Summary:PDF Full Text Request
In this paper, palm fiber as raw material, the research studied the effects of acids, alkalis and steam explosion treatment on the fiber surface silica and the length of solution fiber. Steam explosion pressure, retention time, presoaking effect on the fiber physical structure, chemical composition and crystallinity. Due to the advantage of steam explosion treatment, further study was done on the reed and bamboo, analyzing the surface contact angle, ash and salica content, chemical composition, physical and mechanical properties, etc. The main conclusions are as follows:(1)The palm fibers surface was covered silica, by acid and alkali treatment, the silica was almost unchanged, and the length and chemical composition of fiber would not changed very much. While the silica component was removed, fiber length was significant reduced. It indicated that the acid and alkali failed to enter into the fiber inside, and the role of steam explosion treatment can penetrate into the interior of the fiber. The steam explosion treated fiber occurred machinery faulting. The cellulose content increased from 28.1% to 56.87%, while the lignin content decreased from 44.07% to 28.46% and hemicellulose from 20.60% to 9.20%.(2)When the steam pressure came to 2.0MPa and 2.5MPa, the palm fibers arranged closed regularly and small dispersion of the fiber bundle; when the steam pressure increased to the 3.0MPa and 3.5MPa, the fiber bundle became loose, the gap between the fibers increasing, and the fiber bundle separation occurred. Fibrillated phenomenon appeared and the fiber surface had a lager number of cracks lobes. When the steam pressure reached 3.5MPa, it occurred slightly burnt phenomenon. After steam explosion process, palm fiber had no new functional groups occurred. The lignin peak intensity of absorption increased and the hemicellulose peak intensity of absorption with the steam pressure and retention time, indicating that degradation of hemicellulose and dissolved lignin covering the fiber surface after treatment. The degree of crystallinity increased with the strength of explosion. When the pressure of 3.0MPa and retention time of 180 s, the degree of crystallinity reached 58.8%, compared with the untreated palm fiber crystallinity increased 71.9%, the effect is significant, and when the steam pressure of 3.5MPa, the crystallinity started to fall.(3)Steam explosion treatment reduced the reed size. With the steam pressure and retention time increased, the unseparated reed scrap fiber bundles material decreased. To 2.8MPa and 2min handling conditions, the reed almost was separated into uniform fibrous state. When the steam pressure increased, the contact angle of the traeted reed fibers decreased, and the contact angle was 40°under 2.8MPa/2min condition. With the strength of steam explosion increased, the relative cellulose content increased. Steam explosion traetment can significantly reduce reed ash and silica content and improve the surface wettability.(4)When the steam explosion pressure came to 180 s, a part of fibers occurred slightly burnt phenomenon. The surface of bamboo fibers without steam explosion treatment were smooth and neat, and there were no significant damage or porosity. It was observed that the surface of steam-exploded bamboo fibers(SEBF) was rough. Fibers and fiber bundles were damaged and separated, and appeared curly fold, loose and messy. The surface of SEBF covered with many particles, suggesting that those particles are hemicellulose degradation products and lignin liberated from cell wall by steam explosion treatment. The highest MOR value of 15.9 MPa was determined for the board made by the 3.0/180 SEBF, and the lowest MOR value, 3.6 MPa, was determined for the boards with extracted 3.0/120 SEBF. With the increase of the steam explosion retention time, the boards improved the rupture strength. The TS and WA of the panels decreased with increasing steam explosion retention time. By increasing the retention time from 60 s to 180 s, the thickness swelling was reduced by 73%, and the water absorption decreased by 44%. Only the TS of 3.0/120 and 3.0/180 was not more than the 12%.
Keywords/Search Tags:non-wood fiber, steam explosion, physical structure, chemical composition, crystallinity
PDF Full Text Request
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