基于DOE实验设计方法的聚丙烯焊接工艺优化

采用DOE实验设计方法,对聚丙烯(PP)材料焊接工艺进行了研究,确定了影响PP材料焊接强度的关键因素是气压夹紧力、焊接功率和样品厚度。通过全因子正交试验,对焊接强度和焊接工艺参数进行量化分析,通过优化器结果确定对共聚PP(牌号M60RHC)为原材料,样品厚度为2 mm,控制气压夹紧力为0.3 MPa,焊接功率控制在40 W,得到PP材料的最佳焊接工艺,降低了实验的次数,在该最大工艺条件下,焊接强度达到19.475 MPa。这将有助于其他原材料体系进行高效激光焊接工艺的筛选。     

振动注塑PP的拉伸蠕变研究

分别通过改变机械振动注塑机的频率(5~25 Hz)和压力(10~18 MPa)获得不同条件下成型的PP样条,然后在各种成型条件下的PP样条上分别施加相同的拉伸力(F=125 N),进行24 h拉伸蠕变实验.结果表明,在相同的振动频率(10 Hz)和不同的振动压力下成型的PP试样,其24 h蠕变量随着压力的增大而减小;在相同振动压力(12 MPa)和不同的振动频率下成型的PP试样,其24 h蠕变量随着频率的增大而增大.当振动频率达到f=10 Hz的时候,其24 h拉伸蠕变量的变化趋于平缓.同时,也对不同振动条件下注塑的PP试样进行拉伸实验,冲击实验和动态力学性能测试,讨论了成型条件对性能的影响.     

狼尾草特性及狼尾草/PP复合材料性能研究

对狼尾草茎秆进行拉伸性能测试和长径比测量、并进行X射线衍射图谱、红外光谱和热重分析,分别以三种粒径(40目、60目、80目)狼尾草茎秆纤维为填充材料,以聚丙烯(PP)为基体材料,使用模压成型工艺制备三种不同粒径的狼尾草/PP复合材料。对制备的复合材料进行了接触角测量、吸水性能和力学性能测试,并用扫描电子显微镜(SEM)观察了复合材料拉伸断面微观结构。结果表明:狼尾草茎秆纤维素类型为I型,相对结晶度为44%;40目、60目和80目三种目数狼尾草/PP复合材料24h吸水厚度膨胀率分别为7.7%、4.2%和4.4%;其中40目狼尾草/PP复合材料有较好的结合界面和较好的力学性能,其拉伸强度、弯曲强度、弯曲模量和冲击强度分别为10.47MPa、15.98MPa、1.9GPa和3.7kJ/m~2。由此得知,40目狼尾草/PP复合材料力学性能最好,但吸水性较强;60目狼尾草/PP复合材料具有较好的力学性能和一定的抗吸水性,综合性能最佳。     

超细聚酰胺6粒子增韧聚丙烯体系的研究

采用磨盘形力化学反应器室温下制备了聚丙烯 (PP) /聚酰胺 6 (PA6 )超细粉体 ,研究了其粒度、粒度分布及PA6超细粒子填充对PP力学性能的影响 .结果表明 ,磨盘形力化学反应器可有效实现PP/PA6的粉碎 ,所得粉体平均粒径达微米级 ,初级粒子尺寸甚至可达纳米级 ,粒度分布呈双峰分布状态 .在PA6和PP熔点之间的温度下加工可制得PA6超细粒于填充的PP/PA6共混体系 ,其力学性能明显好于PP/PA6简单共混体系 ,30 %PA6用量下 ,拉伸强度由 2 3 .2MPa提高至 2 9 3MPa ,Izod缺口冲击强度由 4.6 2kJ/m2 提高到6 .34kJ/m2 .形貌分析结果表明 ,由于基本保持了PA6超细粉体的原始尺寸 ,填充体系中PA6相区尺寸小、分布均匀 ,与使用增容剂得到的相区结构类似 .     

磨盘碾磨制备PA6/PP/SBS共混物的结构与性能

采用磨盘形力化学反应器,在室温下制备了PA6/PP超细混合粉体,与SBS共混制得PA6/PP/SBS共混物,测定了材料的力学性能并用TEM研究了材料在不同加工温度下相结构的变化.结果表明,通过固相力化学粉碎制备的PA6/PP混合微粉,改善了PA6与PP和SBS的相容性,促进了PA6及PP的分散和与SBS的相界面结合.在微粉填充量为4%～8%(质量分数)时,材料的拉伸强度大幅度提高,扯断伸长率保持不变.加工温度变化引起材料相结构的变化对材料性能产生显著影响.在PP熔融温度下加工,PP粒子产生粘连形成链状结构,可提高材料的力学性能.     

接枝受阻酚聚氨酯泡沫抗老化性能研究

对比研究了分别采用化学接枝受阻酚抗氧剂与物理共混四甲基[β-(3,5-二叔丁基-4-羟基苯基)丙酸]季戊四醇酯制备的两类室温固化聚氨酯泡沫在湿热及干热老化条件下的抗老化性能。结果表明:接枝受阻酚抗氧剂的聚氨酯泡沫初始拉伸强度为0.31MPa,在湿热老化条件下材料1周及52周龄期拉伸强度分别为0.42MPa和0.40MPa,而在干热老化条件下材料1周及52周拉伸强度分别为0.38MPa和0.32MPa。湿热老化52周,接枝受阻酚抗氧剂的聚氨酯泡沫强度保持率为129%,添加传统抗氧化剂的物理共混聚氨酯泡沫强度保持率为90%。无论是接枝型还是物理共混型聚氨酯泡沫的拉伸强度降低速率均低于无抗氧剂的纯聚氨酯泡沫,接枝受阻酚抗氧剂的聚氨酯泡沫的抗老化性能得到显著提高。     

单向热拉伸对聚丙烯透光率的影响

通过对PP进行不同条件下的单向热拉伸,研究了热拉伸条件对PP透光率的影响.由拉伸后试样透光率、结晶性能、晶体结构以及力学性能变化分析表明:在23℃拉伸时,PP透光率远远低于未拉伸的试样,而在120℃拉伸后,PP透光率大大高于未拉伸的试样,拉伸速度的变化对透光率的影响不大,由此可见:温度对PP热拉伸透光率提高的影响远远大...     

注塑工艺对高抗冲聚苯乙烯力学性能的影响

通过正交实验和单因素变量实验研究了射胶压力、射胶速度、保压压力、保压时间和冷却时间对高抗冲聚苯乙烯缺口冲击强度、弯曲强度、弯曲模量、拉伸屈服应力等力学性能的影响。结果表明,射胶速度、保压时间和冷却时间对高抗冲聚苯乙烯力学性能影响较小,而射胶压力、保压压力对高抗冲聚苯乙烯力学性能有显著影响,特别是缺口冲击强度和拉伸屈服应力。     

动态固化聚丙烯/环氧树脂共混物的研究

将动态硫化技术应用于热塑性树脂 热固性树脂体系 ,制备了动态固化聚丙烯 (PP) 环氧树脂共混物 .研究了动态固化PP 环氧树脂共混物中两组分的相容性、力学性能、热性能和动态力学性能 .实验结果表明 ,马来酸酐接枝的聚丙烯 (PP g MAH)作为PP和环氧树脂体系的增容剂 ,使分散相环氧树脂颗粒变细 ,增加了两组分的界面作用力 ,改善了共混物的力学性能 .与PP相比 ,动态固化PP 环氧树脂共混物具有较高的强度和模量 ,含 5 %环氧树脂的共混物拉伸强度和弯曲模量分别提高了 30 %和 5 0 % ,冲击强度增加了 15 % ,但断裂伸长率却明显降低 .继续增加环氧树脂的含量 ,共混物的拉伸强度和弯曲模量增加缓慢 ,冲击强度无明显变化 ,断裂伸长率进一步降低 .动态力学性能分析 (DMTA)表明动态固化PP 环氧树脂共混物是两相结构 ,具有较高的储能模量 (E′)     

热处理工艺对静电纺丝制备PVDF/PMMA复合膜的力学性能的影响

利用热处理工艺对静电纺丝制备复合膜聚偏氟乙烯/聚甲基丙烯酸甲酯(PVDF/PMMA)进行改性,研究不同温度与不同压力对复合膜力学性能的影响,并与商用膜Celgard 2400在力学性能、离子电导率、循环性能方面进行对比。结果表明:在温度145℃,压强0.05 MPa时,PVDF/PMMA复合膜的拉伸强度为19.0 MPa,是未加压处理时其拉伸强度的10倍;PVDF/PMMA复合膜室温下的离子电导率为1.180mS/cm,比商用膜室温下的离子电导率高出187%;由PVDF/PMMA复合膜组装的纽扣电池在0.2C倍率下的放电比容量为140 (mA·h)/g,在1C倍率下的放电比容量为130(mA·h)/g,与商用膜同倍率下的放电比容量相同;在5C倍率下PVDF/PMMA复合膜的循环性能更优。     

Particle Emission from Welding of Painted Steel

The particulate emission caused by welding of steel plates covered with 29 diversified shop primers has been investigated. The investigation includes the determination of particle mass, particle size distribution, and of the contents of heavy metals such as lead and cadmium. The results show that all investigated primers except those with high concentration of zinc pigment produce mass emissions which are very low in comparison to manual arc welding with covered electrode and CO₂-welding on uncoated steel. The emitted particles of the primers are smaller than 1 μm particle diameter and therefore respirable. Lead and cadmium was found in particles emitted during the welding process of all investigated primers. The highest amount was found in particles of primers with high contents of zinc and ferric oxide.     

Welding immiscible polymers with a supercritical fluid

Polymer adhesion between two immiscible polymers is usually poor because there is little interpenetration of one polymer into the other at the interface. Increasing the width of the interfacial zone can enhance adhesion and mechanical properties. In principle, this can be accomplished by exposing heterogeneous polymer materials to a high-pressure fluid. The fluid can act as a common solvent and promote interpenetration. It also increases chain mobility at the interface, which helps to promote "welding" of the two polymers. A combination of the gradient theory of inhomogeneous systems and the Sanchez-Lacombe equation of state was used to investigate this phenomenon, especially the effect of the high compressibility of supercritical (SC) fluid on the compatibilization of two incompatible polymers. We calculate the interfacial density profile, interfacial thickness, and interfacial tension between the two polymers with and without the SC fluid. We find that the interfacial tension is decreased and the interfacial thickness is increased with high-pressure SC fluid for the ternary systems we have investigated. As the critical point is approached and the SC compressibility becomes large, no enhancement or deleterious effects on compatibilization were observed.     

Catalyst Control of Interfacial Welding Mechanical Properties of Vitrimers

Chinese Journal of Polymer Science - Interfacial welding of thermosetting polymers has been a challenge, but vitrimers with dynamic covalent networks open numerous opportunities for welding and...     

激光诱导击穿光谱法分析焊丝样品

采用激光诱导击穿光谱法(LIBS)对焊丝样品中的硅、锰、磷、硫、铬及镍元素进行测定。采用扫描电子显微镜和激光共聚焦显微镜观察了样品经激光脉冲烧蚀后的形貌,并考察了各元素的谱线强度与激光脉冲个数之间的关系,从而确定了预剥蚀激光脉冲个数。通过分析标准样品建立了单个元素的谱线强度与其质量分数之间的标准曲线,相关系数在0.989~0.999之间。本方法对焊丝样品的分析结果与经典的电感耦合等离子体原子发射光谱法和高频红外硫碳分析方法的测定结果相吻合,其精密度稍差于经典的分析方法。     

大面积功率器件软钎料的焊接失效分析

针对大面积功率器件软钎料的失效问题,运用扫描电子显微镜(SEM)分析了SnPb软钎料的微观结构并运用能谱仪对其进行成分分析,找出了失效的主要原因:对软钎料进行刚玉抛光后,未能将残留在软钎料内的Al2O3成分完全去除,以至于器件的可焊性变差.根据分析提出了改进意见,较好地解决了SnPb软钎料的失效问题.     

Sealing Anticorrosion Pastes for Resistant Spot Welding of Aluminum Alloys

This article investigates the application of PSP-2M and KSP-2AK pastes modified by Laproxid 603 for protection of the internal cavity of welding overlap of aluminum alloys. It has been demonstrated that, upon resistant spot welding of 1913 and 1370 aluminum alloys over such modified coatings, the weld joints are characterized by superior mechanic and corrosion properties.     

Welding of gold nanoparticles on graphitic templates for chemical sensing

Controlled self-assembly of zero-dimensional gold nanoparticles and construction of complex gold nanostructures from these building blocks could significantly extend their applications in many fields. Carbon nanotubes are one of the most promising inorganic templates for this strategy because of their unique physical, chemical, and mechanical properties, which translate into numerous potential applications. Here we report the bottom-up synthesis of gold nanowires in aqueous solution through self-assembly of gold nanoparticles on single-walled carbon nanotubes followed by thermal-heating-induced nanowelding. We investigate the mechanism of this process by exploring different graphitic templates. The experimental work is assisted by computational studies that provide additional insight into the self-assembly and nanowelding mechanism. We also demonstrate the chemical sensitivity of the nanomaterial to parts-per-billion concentrations of hydrogen sulfide with potential applications in industrial safety and personal healthcare.     

SiC陶瓷与金属Ta连接的残余应力

碳化硅陶瓷与金属的焊接结构应用于一些高技术领域, 而金属钽常被作为实现与其他金属焊接的过渡材料.焊接残余应力降低连接强度和结构的稳定性.采用弹性有限元方法计算了SiC-Ta连接试样的残余应力, 并采用四点弯曲试验检验了计算结果.     

Numerical Simulation of Metal Vapour Behavior in Double Electrodes TIG Welding

Metal vapour from the weld pool in double electrodes tungsten inert gas welding is taken into account by a unified numerical model including the arc plasma and the weld pool. The thermodynamic properties and transport coefficients of the arc plasma are dependent on both the local temperature and the mass fraction of the metal vapour. A second viscosity approximation is used to describe the diffusion coefficient of the metal vapour in the arc plasma. The temperature and the flow fields of both the arc plasma and the weld pool are calculated together with the metal vapour concentration. The simulated results are presented for the cases of 3 and 9 mm electrode separation, respectively. It is shown that the metal vapour behavior is much different in these two cases. In the case of 3 mm electrode separation, the metal vapour above the mass fraction of 0.2% is concentrated just above the weld pool surface, while in the case of 9 mm electrode separation, the metal vapour is diffused to the most region of the arc plasma for the same range of mass fraction. In addition, the arc plasma temperature as well as the heat flux at the weld pool is constricted by the presence of the metal vapour. The constricted heat flux at the weld pool results in an increase in the temperature of the weld pool about 100 K or less but a slight shrinkage of the weld pool shape.