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A strong shear flow was imposed on the melt of polycarbonate (PC) microfibril reinforced high density Polyethylene (HDPE) during a secondary melt flow process, i.e. gas assisted injection molding (GAIM). Classic shish-kebabs and typical transcrystallinity were simultaneously observed in the entire thickness of the GAIM HDPE/PC microfibril composites, which were closely related to the strong shear flow that was further amplified and distributed by incorporated PC microfibrils. Interestingly, some nano-sized ultrafine PC microfibril inclined to absorb extended chain bundles to form shish nuclei on its surface first, which subsequently evolved into hybrid shish-kebab superstructures. It was deemed that the induced formation of hybrid shish-kebab superstructures on nano-sized ultrafine PC microfibril was due to the absorbing of extended chain bundles for hybrid shish nuclei with the strong shear flow serving as the driving force. Importantly, large scale formation of these highly oriented crystalline superstructures can bring significant mechanical reinforcement in GAIM HDPE/PC microfibril composite. For GAIM HDPE/PC microfibril composites, its yield strength is increased by 68% and 66%, compared to the GAIM HDPE parts and the common injection molded (CIM) HDPE/PC composites, respectively; meanwhile, the Young's modulus is enhanced by 253% and 17%, compared to the GAIM HDPE parts and the CIM HDPE/PC composites, respectively. 相似文献
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以魔芋葡甘聚糖(KGM)为原料,结合聚丙烯酰胺(PAAM),运用微流体纺丝技术制备KGM/PAAM微纤丝膜。研究KGM/PAAM溶胶的流变性。采用傅里叶红外光谱(FT-IR)、热重分析(TGA)、扫描电镜(SEM)、X射线光电子能谱(XRD)方法,表征微纤丝膜。将氧氟沙星颗粒负载于微纤丝膜中做抗菌试验。研究表明:(1)制备KGM/PAAM纺丝溶胶的最佳比例为:KGM∶PAAM(质量比)=1∶1;(2)制得的KGM/PAAM微纤丝膜形成有序的网状结构,纤维直径100μm,膜的热稳定性增强;(3)抗菌试验结果表明KGM/PAAM微纤丝膜具有良好的抑菌特性,对副溶血性弧菌有明显的抑菌效果,对大肠杆菌、金黄色葡萄球菌的抑菌圈直径分别为39.6,31.5 mm。本试验结果为开发新型食品包装材料,提供理论参考。 相似文献
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黑麦小孢子母细胞核基质的超显微结构观察 总被引:1,自引:1,他引:0
把黑麦的幼穗剪下插入含5%二甲基亚砜(DMSO)的Banner's盐溶液中。室温下培养24小时后,解剖出花药,按常规的超薄切片法制片。透射电子显微镜下观察发现小孢子母细胞核内出现类似微丝的微纤丝结构。这种结构粗约6-7nm,集合成微纤丝束,特异性地出现在凝线期的小孢子母细胞核中。在凝线期,染色质向核的一极集中,靠近核膜的区域由于染色质的转移变为透明区。微纤丝束通常分布在这种透明区。微纤丝束位于染色质附近,并与细胞核的长轴和染色质向极端运动的方向平行。在未经DMSO处理的小孢子母细胞中偶尔也可看到这种结构。文章讨论了黑麦小孢子母细胞核中微纤丝结构的生化本质和可能的作用。 相似文献
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《Journal of Natural Fibers》2013,10(4):19-37
Abstract Characterization of hemp fibers was carried out to investigate the mild defibration with Phlebia radiata Cel 26, a fungus which selectively degraded the epidermis and the lignified middle lamellae. Thin fiber bundles could thereby be produced. The single fiber S2 layer consisted of 1-5 mm thick concentric layers constructed of ca. 100 nm thick lamellae. The microfibril angle showed values of 0-10 for the main part of S2 and 70-90 for SI. The low S2 microfibril angle resulted in fiber bundles with high tensile strength (960 MPa) decreasing to 850 MPa after defibration due to degradation of non cellulosic components. The elastic modulus of the hemp fibers within composites was similar to glass fibers (75 GPa). 相似文献
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Han Do Ghim Jae Pil Kim Ick Chan Kwon Chul Joo Lee Jinwon Lee Sam Soo Kim Sung Min Lee Won Sik Yoon Won Seok Lyoo 《应用聚合物科学杂志》2003,87(9):1519-1524
Iodination of syndiotacticity‐rich high molecular weight poly(vinyl alcohol) (PVA) microfibril, which was obtained from the saponification of poly(vinyl pivalate) without a spinning procedure, was conducted before and after zone drawing at various conditions. The resulting PVA microfibrils were characterized by differential scanning calorimetry and scanning electron microscopy. Surface morphologies of these PVA microfibrils showed some differences between PVA microfibrils iodinated after and before drawing. Crude shapes of PVA microfibrils iodinated after drawing indicated that iodine decreased the structural regularity severely. On the other hand, PVA microfibrils iodinated before drawing showed relatively ordered surfaces. This was ascribed to the enhanced molecular ordering of PVA microfibrils due to zone drawing. Iodinated PVA microfibrils showed a decrease in the crystal melting temperature of about 100°C compared to the untreated sample. PVA microfibrils drawn after iodination showed a relatively higher crystal melting temperature than those of microfibrils iodinated after drawing. These results were considered as proof of the changes in the crystalline lattice of the PVA microfibrils by iodine absorption. Effects of the drawing temperature on the sublimation of iodine were also evaluated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1519–1524, 2003 相似文献
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Abstract The effect of drying on wood cellulose crystallinity, crystallite size, and microfibril angle was investigated using wide angle X-ray diffraction. Forty replicated specimens of black spruce (Picea mariana) wood were dried at constant temperatures of 40°C and 80°C and relative humidities of 34% and 47% in attempts to attain samples possessing final moisture content of 15% and 8% at each temperature. X-ray evaluation of wood specimens, comparing individual samples pre- and post-drying, revealed that both the mass fraction of crystalline cellulose and crystallite width increased with drying. In contrast, mean microfibril angle of the wood was not significantly affected by drying. It was also apparent that the changes in wood ultrastructure resulting from drying were not influenced by the drying conditions, including temperature, relative humidity, and final moisture contents. 相似文献
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Plant cell wall production is a membrane-bound process. Cell walls are composed of cellulose microfibrils , embedded inside a matrix of other polysaccharides and glycoproteins. The cell wall matrix is extruded into the existing cell wall by exocytosis. This same process also inserts the cellulose synthase complexes into the plasma membrane. These complexes, the nanomachines that produce the cellulose microfibrils, move inside the plasma membrane leaving the cellulose microfibrils in their wake. Cellulose microfibril angle is an important determinant of cell development and of tissue properties and as such relevant for the industrial use of plant material. Here, we provide an integrated view of the events taking place in the not more than 100 nm deep area in and around the plasma membrane, correlating recent results provided by the distinct field of plant cell biology. We discuss the coordinated activities of exocytosis, endocytosis, and movement of cellulose synthase complexes while producing cellulose microfibrils and the link of these processes to the cortical microtubules. 相似文献
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Chan J 《Journal of microscopy》2012,247(1):23-32
In this review, I ask the question of what is the relationship between growth and the orientations of microtubules and cellulose microfibrils in plant cells. This should be a relatively simple question to answer considering that text books commonly describe microtubules and cellulose microfibrils as hoops that drive expansion perpendicular to their orientation. However, recent live imaging techniques, which allow microtubules and cellulose synthase dynamics to be imaged simultaneously with cell elongation, show that cells can elongate with nonperpendicular microtubule arrays. In this review, I look at the significance of these different microtubule arrangements for growth and cell wall architecture and how these resultant walls differ from those derived from perpendicular arrays. I also discuss how these divergent arrays in stems may be important for coordinating growth between the different cell layers. This role reveals some general features of microtubule alignment that can be used to predict the growth status of organs. In conclusion, nonperpendicular arrays demonstrate alternative ways of cell elongation that do not require hooped arrays of microtubules and cellulose microfibrils. Such nonperpendicular arrays may be required for optimal growth and strengthening of tissues. 相似文献
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Yael Abraham Carmen Tamburu Eugenia Klein John W. C. Dunlop Peter Fratzl Uri Raviv Rivka Elbaum 《Journal of the Royal Society Interface》2012,9(69):640-647
The sessile nature of plants demands the development of seed-dispersal mechanisms to establish new growing loci. Dispersal strategies of many species involve drying of the dispersal unit, which induces directed contraction and movement based on changing environmental humidity. The majority of researched hygroscopic dispersal mechanisms are based on a bilayered structure. Here, we investigate the motility of the stork''s bill (Erodium) seeds that relies on the tightening and loosening of a helical awn to propel itself across the surface into a safe germination place. We show that this movement is based on a specialized single layer consisting of a mechanically uniform tissue. A cell wall structure with cellulose microfibrils arranged in an unusually tilted helix causes each cell to spiral. These cells generate a macroscopic coil by spiralling collectively. A simple model made from a thread embedded in an isotropic foam matrix shows that this cellulose arrangement is indeed sufficient to induce the spiralling of the cells. 相似文献