次磷酸铝对木粉/高密度聚乙烯复合材料阻燃及力学性能的影响

以次磷酸铝(AHP)为阻燃剂对高密度聚乙烯(HDPE)基木塑复合材料进行阻燃改性。采用锥形量热、垂直燃烧、极限氧指数(LOI)系统评价复合材料的阻燃性能。通过拉伸强度、无缺口冲击强度、弯曲强度等测试,探讨了复合材料的力学性能。并通过热失重分析、扫描电镜对AHP阻燃木粉/HDPE(WF/HDPE)复合材料的机理进行分析。结果表明,AHP、木粉(WF)及WF中的结合水构成膨胀阻燃体系,AHP质量分数为30%时,WF/HDPE复合材料达到垂直燃烧V-0级别,LOI值达到25.5%,阻燃性能显著提高。AHP的加入使WF/HDPE复合材料的力学性能有所下降。     

聚乙烯木塑复合材料的流变行为及阻燃性能

采用旋转流变仪研究了聚乙烯基木塑复合材料的动态流变性能。通过与基体树脂流变行为的比较,发现木塑复合材料呈现典型的热流变复杂行为,木塑样品的临界频率较之聚乙烯移向更低的频率值,且其弹性模量、损耗模量对温度敏感性均显著高于聚乙烯。Cole-Cole曲线和扫描电镜(SEM)照片发现,木塑复合材料呈现多相体系结构。利用锥形量热仪和极限氧指数(LOI)方法探索了木塑配方、阻燃剂用量对聚乙烯基木塑复合材料的阻燃性能的影响,研究发现聚磷酸铵(APP)有助于促进膨胀炭层的形成,从而显著改善复合材料的阻燃性能。     

玻璃纤维/木塑混杂复合材料及其协同增强效应

将固体废弃物中的高密度聚乙烯(HDPE)回收后与废弃的木纤维以及短切玻璃纤维进行复合,成功地制备出混杂型木塑复合材料。研究结果表明,采用长径比较大的L型玻璃纤维增强时,木塑复合材料的弯曲强度、弯曲模量以及冲击强度同时得到提高,而采用长径比较小的玻璃纤维增强时,弯曲性能和冲击强度均呈现下降趋势。玻璃纤维增强木塑复合材料的主要破坏模式为玻璃纤维的拔出、玻璃纤维断裂、界面脱粘等。在玻璃纤维/木纤维/HDPE混杂体系中由于组元之间的协同增强作用,形成了特殊的三维网络结构,木塑复合材料的力学性能得到显著改善。     

聚磷酸铵/纳米SiO_2阻燃水稻秸秆/聚乙烯复合材料的研究

采用聚磷酸铵(APP)与纳米SiO_2阻燃水稻秸秆/高密度聚乙烯(HDPE)木塑复合材料,通过力学性能、极限氧指数、垂直燃烧、热重分析(TGA)和扫描电镜等研究了复合材料的界面,力学,阻燃性能及热降解行为。研究结果表明,当添加17%(wt,质量分数,下同)的APP与3%的纳米SiO_2时达到V-0级,极限氧指数提高了30.8%。拉伸强度提高了42.8%,弯曲强度提高51.9%,冲击强度提高了73.9%。TGA与SEM研究表明,APP与纳米SiO_2对木塑复合材料具有阻燃协效效应,APP使秸秆粉碳化同时膨胀发泡,纳米SiO_2加固炭层是阻燃的主要原因。     

铝矾土改性竹粉/HDPE复合材料性能

为制备高性能的木塑复合材料,扩展其应用领域,采用A-171硅烷偶联剂对竹粉进行表面改性,并添加一定量的铝矾土,经热压成型制备了竹粉/高密度聚乙烯(HDPE)复合材料。分析了铝矾土用量对竹粉/HDPE复合材料力学性能、耐热性和摩擦性能的影响。采用XRD分析了铝矾土的结晶特性,利用SEM和EDS分析了竹粉/HDPE复合材料的断面形貌和表面元素分布情况。结果表明:加入适量铝矾土后,竹粉/HDPE复合材料的力学强度、耐热性及耐磨性能得以改善。铝矾土在竹粉/HDPE复合材料基体中分布均匀,可有效承担载荷,同时提高了竹粉/HDPE复合材料的结晶性能,降低了竹粉/HDPE复合材料在外在应力下引起的变形和破坏;但铝矾土用量过高,分布不均匀,容易形成团聚现象,导致竹粉/HDPE复合材料的力学强度和耐磨性降低,线性热膨胀系数增大。     

彩色木塑复合材料的老化性能

向桦木粉/高密度聚乙烯(HDPE)复合材料中添加白色、黄色和红色着色剂,采用热压成型工艺制备彩色木塑复合材料。研究着色剂种类及含量对木塑复合材料力学性能和表面颜色的影响,同时分别考察彩色木塑复合材料在户外自然老化和紫外光加速老化箱中的老化情况,分析讨论其老化机制。结果表明:添加着色剂可提高木塑复合材料的力学性能,改善材料的外观颜色;木塑复合材料的力学强度和总色差随着色剂用量的增加而逐渐增大,当着色剂用量为3.5wt%时,复合材料的性能达到最佳;木塑复合材料经老化实验后表面褪色明显且力学强度显著降低,但自然老化后其性能下降更明显。这主要是因为木塑复合材料在老化过程中,不仅受到紫外光的照射发生了光降解,而且长期被雨水冲刷导致材料表面的桦木纤维及着色剂大量剥落,降低了材料界面结合强度,从而导致材料性能明显下降。     

木质素-木粉/高密度聚乙烯复合材料的制备及阻燃性能

将生物质可再生资源木质素（Lig）和一种P-N-B系阻燃剂单独或复配使用添加到木粉/高密度聚乙烯（WF/HDPE）混合物中,通过挤出成型的方式制备Lig-WF/HDPE复合材料,探究了Lig对阻燃型Lig-WF/HDPE复合材料阻燃性能的影响。锥形量热仪测试结果表明,Lig的加入能有效降低Lig-WF/HDPE复合材料的热释放速率,提高残余物质量。Lig添加量为15wt%时Lig-WF/HDPE复合材料的阻燃效果最佳,但发烟量较大。Lig与P-N-B系阻燃剂复配使用可使（P-N-B）-Lig-WF/HDPE复合材料的发烟量明显降低,阻燃性能进一步提高。Lig添加量为5wt%、P-N-B系阻燃剂添加量为10wt%时,（P-N-B）-Lig-WF/HDPE复合材料的极限氧指数从未添加阻燃剂WF/HDPE复合材料的24.3提高到27.3,且力学性能较两种阻燃剂单独使用时有提升。      

基于数字图像相关技术的木纤维/高密度聚乙烯复合材料界面力学行为

以木纤维/高密度聚乙烯(WF/HDPE)复合材料界面应变为研究对象,采用数字图像相关技术(DIC)探究WF(质量分数为10wt%~40wt%)及改性聚磷酸铵(mAPP)阻燃剂(质量分数为10wt%~25wt%)对WF/HDPE复合材料应变分布及传递的演变规律,并结合力学性能测试和SEM对其拉伸性能、冲击性能、界面结合进行分析。结果表明:随着WF添加量从10wt%增至30wt%,WF/HDPE复合材料应变传递较为平稳,由受力两端向复合材料轴中心均匀传递,当WF添加量为30wt%时,高应变在复合材料上约1/2区域得到了有效传递,此时,复合材料的拉伸强度和冲击强度分别达21.5 MPa和10.22 kJ/m2。但当WF添加量增加至40wt%时,WF/HDPE复合材料的拉伸承载端部出现应力集中,阻碍了其内部应变的均匀传递。mAPP阻燃剂加剧了WF与HDPE界面间的脱粘行为,削弱了WF与HDPE之间的机械啮合作用力。当mAPP阻燃剂添加量从10wt%增加至25wt%时,WF/HDPE复合材料开始出现多个分散的高应变区域,全场应变传递出现不规则分布。当mAPP阻燃剂添加量达25wt%时,WF/HDPE复合材料应变分布呈两极化趋势,导致复合材料的拉伸强度和冲击强度分别降低为15.5 MPa和5.49 kJ/m2。      

亚临界流体挤出法制备高密度聚乙烯/木粉复合材料

采用亚临界流体挤出法制备高密度聚乙烯(HDPE)/木粉复合材料,研究了亚临界流体种类(去离子水、正丙醇和乙醇)与温度对木塑复合材料(WPC)综合力学性能的影响。实验利用傅立叶变换红外光谱、差示扫描量热分析和扫描电镜分别对复合材料的化学组成、热变形温度和界面形貌作了相应的研究。结果表明,亚临界流体的高温高压可以对木纤维起到很好的溶胀作用,一定程度上打破了木素、半纤维素对纤维素的包裹作用,明显促进基体与木纤维之间的机械捏合与酯化反应,增加界面强度。在亚临界流体条件下,尤其在亚临界乙醇条件下,木粉在HDPE树脂基体中具有优异的分散性,拉伸断面处的断裂形式主要以基体与纤维断裂为主,说明HDPE/木粉的WPC具有较好的界面结合强度。     

四种植物纤维/高密度聚乙烯木塑复合材料耐海水腐蚀性能比较

为比较桉木、杨木、竹粉和稻壳为改性相的高密度聚乙烯（HDPE）基四种木塑复合材料耐海水腐蚀性能,对其进行模拟海水加速腐蚀试验,测试四种HDPE基木塑复合材料腐蚀前后力学性能和色差值,分析其腐蚀前后微观形貌和官能团变化。结果表明:模拟海水腐蚀导致四种HDPE基木塑复合材料两相结合质量变差（裂隙和空洞增多）,力学性能下降,色差值变大（桉木/HDPE、杨木/HDPE和稻壳/HDPE复合材料趋于变白、变黄和变绿,竹粉/HDPE复合材料趋于变白、变蓝和变绿）,羟基含量增多。模拟海水腐蚀21天,四种HDPE基木塑复合材料弯曲强度和弯曲模量降幅为:桉木/HDPE复合材料分别为12.94%和23.18%;竹粉/HDPE复合材料分别为15.45%和23.20%;稻壳/HDPE复合材料分别为18.53%和25.15%,杨木/HDPE复合材料分别为18.52%和34.21%。模拟海水腐蚀后,力学性能下降和颜色变化及断面裂隙和孔洞缺陷最少的是桉木/HDPE复合材料,最多的是杨木/HDPE复合材料。      

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.