PC／ABS共混物接缝强度的研究

采用力学性能测试,应力—应变行为分析,以及流变学、DSC和显微切片等手段,对加入改性剂提高PC/ABS共混物接缝强度进行了较系统的研究。使用自行设计的模具,成型出含有不同类型接缝的标准试样,测试了改性剂加入量对共混物各种性能的影响。结果表明:含有接缝的缺口冲击强度由改性前的不足10kJ/m~2,增加到改性后的50kJ/m~2以上。并得出改性剂的加入量以7%为宜。另外,通过对改性前后共混物应力—应变行为的分析,探讨了不同类型接缝的断裂机理。并通过流变学和DSC测试,以及显微切片观察认为:共混物接缝强度的改进主要取决于两组分的分散程度和接缝界面的互渗性。     

高吸水树脂自养护湿接缝榫卯界面粘结性能

为了提高桥梁薄弱部分湿接缝的界面粘结性能，将高吸水树脂（SAP）作为自养护剂添加到湿接缝中，通过立方体抗压强度和抗弯拉强度试验对其力学性能进行分析，通过立方体劈裂抗拉强度试验对普通组和自养护组湿接缝的三种施工工艺界面粘结性能进行分析。结果表明：SAP的掺加质量分数为0.20%时，混凝土的力学性能最优。榫卯工艺有效改善了湿接缝界面的粘结性能，微凿毛榫卯工艺界面粘结性能最优，其次是普通榫卯工艺，最后是普通施工工艺，且微凿毛榫卯工艺劳动强度低，施工效率高。SAP的加入有效地改善了湿接缝的界面粘结性能，在同种施工工艺下，自养护组湿接缝界面粘结性能均大于普通组。     

有机硅在公路上的应用

简述了我国公路路面的主要类型与面临的主要问题，并扼要介绍了有机硅在水泥混凝土公路路面接缝以及有机硅改性乳化沥青在公路路面维修与养护方面的应用。     

挤出制品熔接缝形成的构象分析

从挤出制品熔接缝形成的原理进行细致的分析，制品的不良熔接缝有“V形槽及弱连接”两种形式。其中熔接缝的强度及物理机械性能远远低于产品其它部位。研究发现熔接缝的结构与材料的配方、挤出机头模具的结构和加工工艺参数均有关系。     

转炉接缝料研制与应用

研制的接缝料是以优质电熔镁砂和鳞片石墨为主要原料,加入适量的镁铝尖晶石和抗氧化剂,采用有机结合剂和有机调合剂按一定比例配制而成的适用于转炉接缝的不定形耐火材料。具有强度高、耐冲刷性好、施工性能和烧结性能优良等特点,经使用效果极好,达到了与炉衬材料材质相近、炉龄同步的目的。     

机场跑道接缝密封材料及密封工艺设计

阐述了机场跑道接缝密封剂和衬垫材料应具备的性能;通过对自流平型HM199室温硫化密封剂灌注工艺性能的研究,提出密封剂的灌注深度与接缝宽度的最佳比为1:2,灌注深度最小不低于6 mm,密封剂顶部与道面的距离为3～7 mm.     

热塑性塑料注塑件熔接缝影响因素分析

分析了热塑性塑料注塑件中熔接缝的分类和特征。从材料选择、制品结构设计、模具设计、成型工艺、热处理几个方面分析了影响熔接缝的因素；并针对不同因素，提出了相应的对策和改善熔接缝力学性能的方法。     

接缝施工技术在道路沥青路面中的运用

道路工程是我国基础设施建设的重要内容,随着我国社会发展水平的提升,道路总里程也在不断延长,成为社会交通运输不可或缺的工具之一。而接缝施工技术在道路施工有着广泛的运用,是影响道路寿命与质量的一项重要技术。文章以沥青道路路面为探究对象,分析接缝施工技术的运用策略,以便在面对不同类型接缝时运用科学的技术手段,实现接缝施工技术的科学、合理运用。     

建筑接缝用聚氨酯密封胶性能对比测试分析

通过将密封胶应用到装配式混凝土建筑外墙的拼接处，可以起到一定的防水作用，为了进一步提高密封胶防水效果，现以“聚氨酯密封胶”为研究对象，实验分析聚氨酯密封胶材料的适应性、强度等性能。结果表明：为保证工程施工质量，相关人员要重视对混凝土界面的清洁处理以及缝面的烘干处理，确保缝表面的整洁度和干净性；当干燥处理接收后，方可对聚氨酯材料进行接缝施工操作，最大限度地提高接缝防水性能。     

铜止水技术在堆石坝混凝土面板接缝止水中的应用分析

利用铜止水技术，对面板堆石坝的混凝土面板接缝进行止水施工，分别从止水结构、止水盖板、止水带的布设安装方面，实现接缝止水施工；安装波形止水带，进一步密封表面接缝，使流动止水长度增加。并利用高精度激光计米器测量出接缝宽度与止水长度，结果显示：采用该止水结构后的流动止水长度在最佳流动止水长度范围内，最大限度地保障坝体的抗渗性能。     

Weldline strength in injection molded HDPE/PA6 blends: Influence of interfacial modification

Most injection molded objects contain defects known as weldlines. This defect may introduce an element of weakness affecting the object's performance. Weldlines are particularly problematic in multiphase materials where the situation may be exaggerated by component mismatch on the two sides of the interface that results in additional weakening when the two components do not adhere well to each other. In addition, weldline behavior is influenced by orientation and morphological effects. This paper deals with relationships between the structure and the mechanical properties in injection molded high density polyethylene polyamide-6 blends. The weldline effect is investigated in detail. Two molds were used to generate weldlines: a double-gated tensile bar cavity in which the weldline results from the meeting of two melt fronts flowing into each other from opposite directions, and a film-gated rectangular plaque mold with a circular insert that divides the melt front in two. Following the recombination of the fronts, there is additional flow as the melt fills the mold cavity. Two preparations containing 75 vol % of polyamide-6 and 25 vol % of polyethylene with and without compatibilizer were studied. In the first case, a compatibilizer was incorporated into the polyethylene prior to compounding with the polyamide-6. In the directly molded tensile bar the minor phase is strongly oriented parallel to flow. Only in the core, which represents about 10% of the sample thickness, do the dispersed phase particles assume spherical shape. The morphology of the weldline is closely related to that of the skin: the elongated structures are oriented parallel to the weldline plane. The effect of the compatibilizer on the mechanical properties (without the weldline) of the directly molded tensile bars is minor: It is overshadowed by the flow-induced morphology. The weldline strength loss is about 40% in the noncompatibilized blend. The introduction of the compatibilizer has restored the material's ability to yield and the properties are close to those measured without the weldline. For the second type mold, the effect of the weldline is less pronounced and the effect of the distance from the insert is negligible. The anisotropy is quite pronounced in the noncompatibilized blend. In compatibilized blends, all tensile properties are unaffected by the presence of weldline, except for the 2-mm-thick plaque in the position close to the insert. The properties in the direction parallel to flow are similar to the type I mold and not affected by the increase of plaque thickness. Consequently one may question the utility of the directly molded tensile specimens in studying various aspects of the mechanical behavior of multiphase materials where the flow-generated structure is very different from that found in “real” injection molded parts. © 1995 John Wiley & Sons, Inc.     

材料性质对注塑件熔接痕外观及性能的影响

概述注塑件熔接痕的分类、特点及形成,分析了材料性质如结晶度、松弛时间、特征温度、取向、粘度及所用添加剂对熔接痕处外观和性能的影响及其造成影响的原因,具体分析了影响粘度的因素和添加剂的种类、形态、用量对熔接痕的影响,并从材料性质方面提出了减小熔接痕损害的方法。     

Weldline integrity of reinforced plastics: Effect of filler shape

The paper is a preliminary report on glass fiber and glass flake orientation in the weldline zone of injection molded reinforced polypropylene. Two types of weldlines were studied using simple shape molds: one where two melt streams meet head-on and become immobilized, the other where the weldline formation is followed by additional flow. In the weldlines of the first type, which are characteristic of current standard molds used to test weldline strength, the anisometric particles are almost perfectly oriented perpendicular to flow. As a result, the weldlines of this type tend to be weak and brittle. In the second case when the weldline is formed by merging of melt streams separated by an insert, particle orientation in the weldline area remains different from other areas of the sample for long distances from the insert. It is shown that in molds where the weldline formation is followed by laterally expanding flow the change of particle orientation is faster than for unidirectional flow.     

Effects of filler contents and processing parameters on the weldline strength of compression molded natural rubber

The presence of weldlines in rubber products is regarded as a one of the most undesirable phenomena, since it results in poor mechanical properties. Compression molding of large or complicated products are prepared by multiple charges, which produces weldlines once the melt fronts are joined by the impingement flow. In this work, the effects of curing systems, processing parameters, filler types, and contents on weldline strength of compression molded natural rubber (NR) were investigated. Furthermore, the effects of curing systems on the aging properties of NR vulcanizates were studied in details. The results show that an increased amount of calcium carbonate does not affect the weldline strength. However, the difference in tensile strength between weldline and nonweldline specimens becomes larger with the high loading of silica and carbon black. In addition, for the factors selected in the experiments, clamping pressure, and curing system were found to be the principal factors affecting the weldline property of vulcanizates. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Evaluation of mechanical properties of adjacent flow weldline

Weldlines occur at the interface of two adjacent flows of material behind an obstructive pin in a cavity in injection molding (meldline or hot weldline). Tensile strength of such “adjacent flow weldline” in injection molded polystyrene plates was evaluated by a mechanical step‐by‐step milling technique. The strength when the milling depth was 1/5 of the thickness from each surface was about the same and independent of the distance from the pin. In contrast, the strength without milling decreased once and then increased along the flow direction. This demonstrates that the strength of a weldline is predominantly dependent on the properties of the surface layer of the weldline. The depth of the surface layer was defined as the depth of the weld, D_w. D_w reduced monotonously along the flow direction and faded away with the V‐notch, resulting in an increase of strength along the direction. On the other hand, it was considered that the farther from the pin, the flow‐induced molecular orientation in the surface layer is greater. It caused a decrease of the strength along the flow direction. The sequence of decrease and increase in tensile strength of adjacent flow weldline is due to the complex effect of these two contradictory factors. POLYM. ENG. SCI., 45:1180–1186, 2005. © 2005 Society of Plastics Engineers     

Physico-chemical Causes of the Extent of Water Resistance of Linearly Welded Wood Joints

A change in linear welding conditions, namely higher vibration frequency (150 Hz) and lower displacement (2 mm) during welding, produced a quicker rise in temperature of the weldline. This allowed a much shorter welding time (1.5 s). X-ray microdensitometry mapping showed a progressive increase in broadening and average density of the weldline as the welding time lengthens. As the welding time lengthens the maximum temperature reached at the end of welding is progressively higher. This causes increasingly greater degradation. This effect was confirmed also by CP-MAS ¹³C NMR and it was found that the lower is the degree of deterioration of the weldline of the wood joint the shorter is the welding time. Monitoring of the temperature of the weldline showed that the temperature reached in wood joints during welding was inversely correlated to its water resistance. Furthermore, the increase in weldline temperature is markedly quicker at a vibration frequency of 150 Hz than at 100 Hz. Thus, the shorter is the welding time the lower is the degree of deterioration of the weldline of the wood joint. This appears to be due to welding occuring when water vapour is still present in the joint, hence providing a less damaging welding environment.     

Weldline strength in injection molded glass fiber-reinforced polypropylene

Weldlines are inescapable byproducts of the injection molding process. They represent potentially fatal flaws particularly in multiphase materials. In this work weldlines in injection molded glass fiber-reinforced polypropylene (0 to 40wt%) were studied as a function of the cavity shapes and depths. It was found that the weldline is a zone between 2 and 8 mm wide extending throughout the thickness in which the fibers are oriented almost perfectly in a plane parallel to the weldline. While the strength of moldings without weldlines depends on the mold shape and on the fiber concentration, the weldline strength is a function of fiber content only. A simple model based on the assumption of complete debonding of the fiber-matrix interface when failure occurs can be used to predict the strength loss in the weldline.     

Performance prediction of weldline structure in amorphous polymers

The presence of a weldline generally reduces the mechanical strength of injection molded parts. A typical remedy to eliminate the problem of weak weldline structure has been to increase the melt temperature. This, however, is not an acceptable solution in some situations. A general solution to the weak weldline problem requires an in-depth understanding of the thermomechanical history of the injection molding process. A theoretical model for the strength of weldlines is presented that provides a comprehensive physical insight of the bonding process at the weldline interface. The model is based on the self-diffusion of molecular chains across the polymer-polymer interface and the frozen-in orientation that remains parallel to the interface. Both factors are analyzed separately and then superimposed to predict the strength of weldlines from known processing conditions and geometry. Experimental results show good correlation with predictions.     

Influence of Weldling Parameters on Weldline Density and Its Relation to Crack Formation in Welded Scots Pine Joints

Exterior use of welded wood laminates without further treatment is not recommended. Frictional welded joints have poor resistance to moisture variation, especially to drying. Therefore, application of welded woods is limited to interior use without exposure to highly variable air humidity. Influences of some welding and wood parameters such as welding pressure, welding time and heartwood/sapwood on weldline density of Scots pine (Pinus sylvestris) joints were investigated. Interdependence between density and water resistance of weldline (in terms of crack time) was also studied by comparing the results of this investigation with those of the earlier studies. Specimens composed of two wood pieces, each measuring 20 mm × 20 mm × 200 mm, were welded together to form a specimen measuring 40 mm × 20 mm × 200 mm by a vibration movement of one wood surface against another at a frequency of 150 Hz. An X-ray Computerized Tomography scanner was used to measure weldline density. Weldlines of sapwood produced by 1.3 MPa welding pressure and 1.5 s welding time showed the highest density. No correlation between weldline density and crack time was evident.