Irradiation of highly oriented polyethylene fibers in the atmosphere of some vinyl monomers: Effect on compressive strength

Highly oriented polyethylene fibers have been modified by γ‐irradiation in the presence of some vinyl monomer vapors, followed with further annealing in the atmosphere of the same monomer. Two types of vinyl monomers that are known to produce polymers with different glass transition temperatures, namely methyl methacrylate and vinyl acetate, were studied for their effect on the compressive strength of the fiber. It was found that a significant improvement in compressive strength, measured by tensile recoil test, was obtained. The level of improvement was affected by heat treatment and the presence of monomer during irradiation. Modification with vinyl acetate was found to be more effective than methyl methacrylate. These facts suggest that the improvement in compressive strength was attributable to several factors, including structural relaxation, the presence of graft copolymer, and energy dissipation ability of the graft copolymer. It is speculated that lateral integrity of the fiber is one of the key factors that prevents sliding of microfibril and possibly lateral or circumferential expansion of the fiber to accommodate kink band. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2494–2502, 2001     

Influence of surface treatment of carbon fibers on interfacial adhesion strength and mechanical properties of PLA‐based composites

In the present study C/PLA composites with different fiber surface conditions (untreated and with nitric acid oxidation for 4 h and 8 h) were prepared to determine the influence of surface treatment on the interfacial adhesion strength and mechanical properties of the composites. A chemical reaction at the fiber–matrix interfaces was confirmed by XPS studies. Nitric acid treatment was found to improve the amount of oxygen‐containing functional groups (particularly the carboxylic group, —COOH) on carbon fiber surfaces and to increase the surface roughness because of the formation of longitudinal crevices. The treated composites exhibited stronger interface adhesion and better mechanical properties in comparison to their untreated counterparts. There was a greater percentage of improvement in interfacial adhesion strength than in the mechanical properties. The strengthened interfaces and improved mechanical performance have been mainly attributed to the greater extent of the chemical reaction between the PLA matrix and the carbon fibers. The increased surface roughness also has had a slight contribution. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 367–376, 2001     

乳液型丙烯酸树脂改性阳离子淀粉增干强剂的制备及性能

淀粉与阳离子醚化剂在碱性介质和氧化剂存在下 ,搅拌加热至 6 5～ 70℃ ,进行氧化降解和阳离子化反应 ,反应时间为 2h。再加入丙烯酸及丙烯酸酯单体于 80～ 85℃进行接枝共聚 ,m (玉米淀粉 )∶m (改性单体 ) =1 0∶0 8时 ,得到的乳液型丙烯酸树脂接枝共聚阳离子淀粉增干强剂的增强效果最好 ,对增加纸张干强度和耐撕裂度有明显效果 ,用量为绝干浆质量的 0 4%～ 0 .5 %时 ,可使纸的干强度增加 15 %以上 ,耐撕裂度提高 8%以上。并用IR、SEM、DSC等手段对这种接枝共聚物的结构与性能进行了表征     

Al_2O_3/Cu_(70)Ti_(25)Zr_5/Nb界面结构及强度

本研究选用Cu70 Ti2 5 Zr5 活性钎料钎焊Al2 O3/Nb .通过对Al2 O3/Cu70 Ti2 5 Zr5 /Nb界面结构及接头性能研究 ,旨在进一步揭示Al2 O3/含Ti活性钎料间界面反应机制 ,并为指导工程应用提供最佳工艺参数 .借助扫描电镜、能谱、X射线衍射探讨了Al2 O3/Cu70 Ti2 5 Zr5 /Nb钎焊接头界面结构 ,并采用拉剪试验评价了接头强度 .研究结果表明 ,时间 0 .6ks ,温度小于 12 2 3K ,界面产生了 3种新相 :Cu2 Ti4O ,Ti0 .5 Zr0 .5 O0 .1 9,CuTi,界面结构为Al2 O3/Cu2 Ti4O +Ti0 .5 Zr0 .5 O0 .1 9/CuTi/Cu固溶体 +CuTi;温度大于 12 93K ,界面产生了Cu2 Ti4O ,Ti,CuTi 3种新相 ,界面结构为Al2 O3/Cu2 Ti4O/Ti固溶体 /CuTi/Cu固溶体 +CuTi.在 12 93K ,0 .6ks条件下 ,接头剪切强度最高达到 162MPa ,温度大于或小于12 93K ,强度下降     

Use of Self-assembled Monolayers at Variable Coverage to Control Interface Bonding in a Model Study of Interfacial Fracture: Pure Shear Loading

The relationships between fundamental interfacial interactions, energy dissipation mechanisms, and fracture stress or fracture energy in a glassy thermoset/inorganic solid joint are not well understood. This subject is addressed with a model system involving an epoxy adhesive on a polished silicon wafer containing its native oxide. The proportions of physical and chemical interactions at the interface, and the in-plane distribution, are varied using self-assembling monolayers of octadecyltrichlorosilane (ODTS). The epoxy interacts strongly with the bare silicon oxide surface, but interacts only weakly with the methylated tails of the ODTS monolayer. The fracture stress is examined as a function of ODTS coverage in the napkin-ring (nominally pure shear) loading geometry. The relationship between fracture stress and ODTS coverage is catastrophic, with a large change in fracture stress occurring over a narrow range of ODTS coverage. This transition in fracture stress does not correspond to a wetting transition of the epoxy. Rather, the transition in fracture stress corresponds to the onset of large-scale plastic deformation within the epoxy. We postulate that the transition in fracture stress occurs when the local stress that the interface can support becomes comparable to the yield stress of the epoxy. The fracture results are independent of whether the ODTS deposition occurs by island growth (T_dep = 10°C) or by homogeneous growth (T_dep = 24°C).     

惯性力作用下船用液化天然气储罐的应力分析

船用液化天然气储罐作为移动式压力容器,在运输过程中不仅承受静载荷,并且还承受一定惯性载荷的作用。相比传统的常规设计计算,使用有限元方法对于液化天然气储罐的结构强度分析将会更加准确方便。文中使用ANSYS软件对液化天然气储罐建立有限元模型,对于惯性载荷作用下的储罐进行了数值模拟,对于受到应力集中的局部进行应力分类和安全评定。仿真结果对于液化天然气储罐的设计制造提供参考和依据。     

快烧对磷石膏脱水相组成及胶凝性能的影响

去除可溶磷杂质和脱水是利用磷石膏制备胶凝材料必需的处理过程。通过改变快烧温度和时间对磷石膏进行处理,分别测定快烧磷石膏可溶磷含量、脱水相组成和胶凝性能,并对几种典型快烧条件下的磷石膏矿物组成和形貌进行分析,同时与经水洗后150℃煅烧4 h制备的磷石膏胶凝材料进行对比。结果表明:快烧后磷石膏为Ca SO4·2H2O、Ca SO4·1/2H2O和Ⅲ、Ⅱ型Ca SO4组成的复相石膏体系,可溶磷杂质含量随快烧温度提高和时间延长明显降低;800℃快烧30 s得到的磷石膏胶凝材料强度最高,2 h抗压强度达到3.79 MPa;经快烧处理磷石膏的颗粒尺寸明显减小。800℃快烧30 s能有效降低磷石膏中可溶磷杂质含量,并获得较高强度的磷石膏胶凝材料;虽然相比水洗后煅烧工艺,快烧制备的磷石膏胶凝材料强度和可溶磷杂质去除率稍低,但快烧是一种具有竞争力的处理工艺。     

含油污泥制煤的研究

研究了影响除油、脱水后的含油污泥与煤粉混合制备型煤的因素,以实现罐底泥、渣泥等的废物资源化。试验考察了油泥与煤的混合比例、混合时所用原煤粒度与成型率和抗压强度的关系,助燃剂的添加量和热能、未燃烬率的关系。结果表明:煤粒度在3.35 mm以下,滤饼添加量(w)在25%左右时成型率88%、抗压强度0.150 MPa、新煤热值20 962 k J/kg;助燃剂的添加量(w)1.5%时,热值能达到23 283 k J/kg,未燃烬率18.63%。     

氧化石墨烯与聚羧酸减水剂单体共聚物的制备与性能

通过氧化石墨烯(GO)与聚羧酸系减水剂单体甲基丙烯酸聚乙二醇单甲醚(MAAPEGME)、甲基丙烯酸(MAA)及甲基丙烯磺酸盐(SMAS)进行自由基共聚反应制备了氧化石墨烯与聚丙烯酸系减水剂(PCs)单体的共聚物(GO-PCs),旨在解决GO掺入水泥基材料时存在的分散不均匀及流动性降低的问题,制备GO-PCs时各组分的质量比为m(MAAPEGME)∶m(MAA)∶m(SMAS)∶m(GO)=17∶2∶1∶0.2。检测结果表明GO与单体之间发生了共聚反应,GO纳米片层均匀地分布在PCs中,达到了GO在水泥材料中分布均匀、不影响水泥流动性及增强增韧的目的,SEM形貌说明GO-PCs对水泥浆体的微观结构有较好的调控作用,研究结果对于制备高性能长寿命混凝土具有积极的意义。     

DQC602型催化剂在聚丙烯PPB-MM35-S开发中的应用

采用非对称外给电子体技术,在环管反应器中加入氢调敏感性好的外给电子体X用于生产丙烯均聚物,在气相反应器中加入共聚合性能较好的外给电子体Y用于生产乙丙橡胶相,在生产过程中不断优化工艺参数,调整两个环管反应器中氢气浓度和气相反应器中共聚聚丙烯中的乙烯含量,使用更适合生产抗冲共聚聚丙烯的DQC602型催化剂,成功开发出高熔体流动速率(MFR)、高抗冲击共聚聚丙烯PPB-MM35-S。采用直接加氢气的方法,PPB-MM35-S的MFR可达35.00 g/10 min。