微纳米木质素颗粒在酸碱溶液中的溶解行为

通过测试粒径,研究了具有微纳米尺寸的木质素颗粒在酸碱溶液中的溶解行为。结果显示:木质素在碱性溶液中的溶解无规律,但在酸性溶液中的溶解却首先是溶胀然后才是溶解,而这两者的分水岭似乎是在80min(25℃条件下),与酸液浓度无关。但值得关注的是这两者引起木质素颗粒的外型从球状改变为长方体。红外光谱显示木质素在酸性溶液中的溶解主要是其芳香环的断裂即分子量降低而无结构变化。     

防除藕田浮萍的药剂筛选及安全性评价

[目的]筛选安全有效防除藕田浮萍的除草剂,为藕田浮萍的防治提供理论依据。[方法]以18种常用除草剂对浮萍进行室内活性测定,筛选出活性高的药剂对3种莲藕进行安全性评价。[结果]扑草净、西草净及莠去津对青萍和紫萍防治效果明显,且不同质量浓度处理对3种莲藕安全。[结论]扑草净、西草净及莠去津可有效防治藕田浮萍,进一步研制合适的剂型可达到高效防除藕田浮萍的目的。     

发酵藕笋护色工艺研究

研究鲜藕笋的护色工艺。正交试验表明最佳护色复配液配方为Vc浓度为0.20%、亚硫酸钠浓度为0.15%、柠檬酸浓度为0.20%、EDTA浓度为0.25%。发酵后的藕笋保留了天然脆性、自然色泽和优良口感。     

MPS立磨辊子体工作面的一种修复方法

淮海中联公司MPS非凡原料立磨辊子体与磨辊皮配合部位长期使用，磨损严重，辊子体部分位置磨损不均匀，多处出现明显裂纹、剥落等缺陷，径向最大单边磨损深度为25-30mm，弧长大约2860mm，其余部分磨损5-6mm，已经严重影响正常运行。该磨辊组件重约33吨，外型尺寸约φ2180mm×1980mm，属大型部件。购买备件从订购到发货需要2年时间，     

道化学公司扩大乙二醇醚生产

美国道(Dow)化学公司最近完成了对其在路易斯安那Plaquemine的乙二醇醚装置的扩建,使其在美国的乙二醇醚生产能力增加而达到约12万t/a。该公司在全球的生产能力约为23.5万t/a(包括丙二醇醚类)。据称这一扩充显示了该公司要长期承担乙二醇醚的经营业务,并增加其生产的灵活性,以满足未来的     

雷达罩产品外型的反演算法

宽频带雷达罩设计经常从气动外型通过电性能设计得到蜂窝夹层厚度为变厚度的雷达罩的内型。加工后雷达罩成型阳模往往与产品的内型相比产生偏差,从而导致电厚度的不准确。从有偏差的阳模外型出发,通过雷达罩内型面点处的法线、位置角度及相关点附近的厚度函数,形成将内型面点处的法线转换成外型面对应点处的法线的转换矩阵,通过反演循环逐步逼近外表面的数据点。随着循环的进行,转换矩阵的数值及相应点的坐标数值将逐步稳定,当相邻两次矩阵及坐标值变化满足精度时,则循环终止。利用循环终止时的外型面点的坐标、法线及变厚度蜂窝的厚度公式,便可得到夹层结构雷达罩的内外层蜂窝外型面。这样,在模具有偏差时,也能得到符合电厚度要求的雷达罩结构。     

油田抽油机用防滑V带

本文介绍了油田抽油机用防滑节能型Ｖ带的制备，主要在Ｖ带的包覆层使用了改性氯丁橡胶，从而使其具有了疏水性和提高耐磨性。同时在外型设计上有其独到之处。     

4月全球氧化铝产量环比减少1.1%

<正>国际铝业协会数据显示:2019年4月全球氧化铝产量约为1 018万t,环比减少约1. 1%,同比小幅增加0. 6%。2019年1—4月全球氧化铝产量累计约为4 039万t,较2018年同期增加约1. 6%。数据还显示:2019年4月中国氧化铝产量约为576万     

L型集装架的使用情况

党的三中全会后,我们在国家建材总局、铁道部指导下,进行玻璃包装革新.通过反复试运,不断完善改进,使L型集装架装运玻璃基本获得成功.其外型见照片.目前,已有L型集装架11792个,计投资329万元.加上配套设备的投资总额为457万元.     

纳米涂料市场价值2020年将达81．7亿美元

根据美国Grand View研究公司的最新研究显示,全球纳米涂料市场价值2020年有望达到81.7亿美元。纳米涂料正在替代传统聚合物涂料被广泛应用于汽车、建筑、医疗和卫生保健产品领域,由于其相比其他目前商业化应用的涂料产品具有更优越的性能和低VOC等特性,市场需求将不断增长。根据该研究显示,2013年全球纳米涂料市场总量约为30.95万t,到2020年有望达到126.29万t,2014-2020年的年复合增长率约为22.3%。     

聚丙烯腈原丝中毛丝的结构与性能研究

采用扫描电子显微镜和纤维强伸度仪研究了聚丙烯腈（PAN）原丝中毛丝的微观结构和力学性能。结果表明,与正常原丝相比,毛丝直径较细,表面缺陷较多,力学性能较差;纺丝过程中的机械损伤是导致毛丝产生的直接原因;但导致毛丝产生的根本原因是因为PAN原丝本身纤度不均匀。指出从减少机械损伤和提高纤度均匀性两方面着手控制PAN原丝中毛...     

莲纤维的形态研究

莲纤维是从农业废弃物荷秆中提取的纤维,是一种环保型天然纤维。通过生物显微镜及扫描电子显微镜观察,研究了莲纤维的基本形态特征。结果表明,经物理方法提取的莲纤维细长柔软,纵向有横节,外观乳黄。扫描电镜观测发现,单根莲纤维是由数根直径约4μm的微细纤维横向缔合而成,间距3～5μm。纵向呈带状螺旋转曲,横截面有中腔和孔洞。     

几种天然纤维素纤维的物理结构研究

对竹纤维等几种天然纤维素纤维的物理结构进行了系统的比较研究。实验结果表明:竹纤维聚合度远高于粘胶、稍低于苎麻;结晶度高、取向度高,属于大分子排列整齐、紧密型超分子结构,接近于苎麻纤维;在形态结构上,横截面为腰圆形,有中腔,壁上有裂纹,截面有孔隙,TEM结果表明,次生层为单层次结构,与苎麻相仿。总之,竹纤维从微观的大分子链结构到聚集态结构,到宏观的纤维形态结构,各种物理指标特征均表明其与苎麻纤维有着非常的相似性。     

Energy filtered low voltage “in lens detector” SEM and XPS of natural fiber surfaces

Most analyses of natural fibers give the average composition of the fiber and not the nature and distribution of surface species present. The nature of the fiber surface is important since it governs interfacial adhesion between fiber and matrix and the transfer of stress to the fiber in composite materials. The surface of caustic treated flax fibers is analyzed using X‐ray photoelectron spectroscopy (XPS) and a low voltage scanning electron microscopy (SEM) technique that uses a filtered in‐lens electron detector. XPS shows that the fiber surface is not composed of a single polymer but is a mixture of materials, probably degraded lignin and hemicellulose and extractives. The SEM technique shows patches of material on the surface with different contrast and this contrast is shown to result from different average atomic number (Z). The variation in surface composition has obvious implication in variable interfacial properties in composites made using natural fibers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39572.     

Utilization of bowstring hemp fiber as a filler in natural rubber compounds

The cure characteristics and physicomechanical properties of natural rubber (standard Nigerian rubber) vulcanizates filled with the fiber of bowstring hemp (Sansevieria liberica) and carbon black were investigated. The results showed that the scorch and cure times decreased, whereas the maximum torques increased, with increasing filler loadings for both bowstring hemp fiber and carbon black filled vulcanizates. The tensile strength of both bowstring hemp fiber and carbon black filled vulcanizates increased to a maximum at a 40 phr filler concentration before decreasing. The elongation at break and rebound resilience decreased, whereas the modulus, specific gravity, abrasion resistance, and hardness increased, with increasing filler contents. The carbon black/natural rubber vulcanizates had higher tensile strength, which was about 1.5 times that of bowstring hemp fiber/natural rubber vulcanizates. This superiority in the tensile strength was probably due to the higher moisture content and larger particle size of the bowstring hemp fiber. However, the bowstring hemp fiber/natural rubber vulcanizates showed superior hardness. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of different fiber loadings and sizes on pultruded kenaf fiber reinforced unsaturated polyester composites

Application of the available natural resources became crucial for developing sustainability recently. The use of natural fiber as reinforced materials in polymer composite materials is gaining new interest from within industry. In this research, the effect of different fiber loadings and different types of kenaf yarns, used on the properties of Pultruded Kenaf Fiber Reinforced Composites (PKFRC), was studied. The pultruded composite samples were prepared with different fiber loadings and sizes (tex) of kenaf fiber. Three different fiber loadings, i.e., 60, 65, and 70% were used during the preparation of the PKFRC samples. Flexural and compression testing was performed, to study the effect of different fiber loadings and different kenaf fiber yarns, on the mechanical properties of kenaf fiber pultruded composites. The results show that the highest fiber loading of 70% gave more desirable flexural and compression properties to the PKFRC. The use of twist kenaf yarn fiber showed lower mechanical properties of PKFRC as compared to the single kenaf yarn. Damage configurations and accumulations for each loading case were examined. A morphological study, using optical microscopy (OM) revealed the type of fracture that occurred in the pultruded samples after mechanical testing. POLYM. COMPOS., 36:1224–1229, 2015. © 2014 Society of Plastics Engineers     

Interphase effects on the mechanical and physical aspects of natural fiber composites

The interaction and adhesion between the fiber and matrix has a significant effect in determining the mechanical and physical behavior of fiber composites. The effect of the interface and interphase depends on several factors such as chemical composition (functional groups), molecular structure characteristics (branching, molecular weight distribution, cross-linking), and details of its physical state (above or below T_g, nature and degree of crystallinity). Natural fibers have complex and varying chemical structures that have uneven surface topographies. This creates difficulties in using single fiber composite testing to accurately evaluate the interfacial shear strengths, except for comparisons. A review of our interphase related research in natural fiber composites is presented. When using coupling agents it is well known that the tensile and flexural strengths increase dramatically in natural fiber reinforced composites. However, in the case of modulus, the results are more complex. For two ethylene-propylene impact copolymers, the uncoupled systems had much higher Young's moduli than the coupled systems. The dynamic storage moduli of the uncoupled impact polymers were higher than the coupled composites at temperatures up to about 50°C. At higher temperatures the presence of the coupling agent resulted in higher storage moduli. Transcrystallinity may play an important role in this phenomenon. Creep and other long-term properties are also affected by the quality of the interphase, although the level of improvement decreases with an increase in the molecular weight of the matrix polymer. Coupling agents reduced the rate of water absorption and the moduli were less affected in blends with a higher concentration of coupling agents.     

Interfacial micromechanics and effect of moisture on fluorinated epoxy carbon fiber composites

Carbon fiber composites have witnessed an increased application in aerospace and other civil structures due to their excellent structural properties such as specific strength and stiffness. However, unlike other structural materials, carbon fiber composites have not been as widely studied. Hence, their increased application is also accompanied with a serious concern about their long‐term durability. Many of these applications are exposed to multiple environments such as moisture, temperature, and UV radiation. Composites based on conventional epoxies readily absorb moisture. However, recently synthesized fluorinated epoxies show reduced moisture absorption and hence potentially better long‐term durability. The aim of this project is to study the effect of moisture absorption on fluorinated‐epoxy‐based carbon fiber composites and their comparison with conventional epoxy carbon fiber‐based composites. Microbond tests are performed on fluorinated and nonfluorinated epoxy‐based single fiber samples before and after boiling water degradation. It is found that fluorinated epoxy‐based single fiber coupons showed relatively reduced degradation of interface when compared with the nonfluorinated epoxy single fiber coupons. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Flammability of natural plant and animal fibers: a heat release survey

With increased interest in sustainable materials for use in building materials and clothing, there is a renewal in the use of natural fibers (plant or animal‐based) versus synthetic fibers in a variety of applications. However, there is not as much information available on the flammability of these natural fibers especially when they are used in products where purification techniques used in conventional textile processing are not required. The literature to date suggests that all of the fibers can be grouped into two categories: cellulosic and animal, with the assumption that regardless of original species, the flammability is similar for fibers within each category. In this report, we have conducted a survey via microcombustion calorimetry to determine if all cellulose‐based and all protein‐based fibers are the same from a heat release perspective. Our findings show that this is not the case, and there are notable differences in fiber types within each genus. Further, how the natural fiber has been treated prior to use can have some dramatic effects on heat release caused by residual impurity content. The results in this paper suggest that there is more to be learned about these natural fiber types in regards to their inherent flammability. Copyright © 2016 John Wiley & Sons, Ltd.     

碳/玻混杂纤维的混杂效应及其受力性能研究

碳纤维与玻璃纤维进行层间混杂后用来进行混凝土结构的加固,可以产生较好的正向混杂效应．就混杂纤维的混杂方式．混杂效应和受力性能进行了研究,结果表明：较之单一纤维,混杂纤维复合材料表现出了明显的混杂效应,还可以降低加固成本,综台效益较好。并提出了混杂纤维复合材料在当前工程应用中存在的问题。