Mathematical modeling of photoinitiated coating degradation: Effects of coating glass transition temperature and light stabilizers

A mathematical model, describing coating degradation mechanisms of thermoset coatings exposed to ultraviolet radiation and humidity at constant temperature, was extended to simulate the behavior of a coating with a low glass transition temperature. The effects of adding light stabilizers (a UV absorber and a radical scavenger) to the coating were also explored. The extended model includes photoinitiated oxidation reactions, intrafilm oxygen permeability, water absorption and diffusion, reduction of crosslink density, absorption of ultraviolet radiation, a radical scavenger reaction, and simulates the transient development of an oxidation zone. Simulations are in good agreement with experimental data for a fast degrading epoxy-amine coating with a glass transition temperature of −50 °C. It was found that the degradation rate of the non-stabilized coating was influenced significantly by the diffusion rate of oxygen in the oxidation zone, whereas light absorption by the photoproducts formed was only a secondary effect. On the other hand, the degradation rate of the stabilized coating was mainly influenced by the light absorption capability of the coating and in this case there was no oxygen diffusion resistance. Finally, simulations showed that the rate constants of the photoinitiating and oxidation reactions, taking place within the epoxy-amine family of coatings, are strong functions of the specific crosslinker used and must be estimated, in each case, by calibration of the model against adequate experimental data series.     

能量色散X射线荧光光谱仪进行ROHS测试的不确定度评估

研究了能量色散X荧光光谱仪进行RoHS测试的不确定度来源.以PE塑胶样品中的Cd为例子,探索不确定度评估的模式,为产品的合格判定提供依据.     

材料近代分析测试方法课程教学改革的实践与探索

材料近代分析测试方法是材料学相关专业的专业必修课,课程内容丰富、知识面宽.文章从教学内容、教师队伍、教学方法和实验教学等几个方面,对材料近代分析测试方法教学改革进行实践和探索,以期激发学生的学习兴趣和积极性,达到提高教学质量和学生的综合素质的目的.     

无缝管荧光磁粉探伤方法讨论

对无缝管荧光磁粉探伤方法进行了简述,详细介绍了无缝管荧光磁粉探伤的基本原理、检测装置、检测方法、检测步骤、以及缺陷的分析评判方法,最后提出了无缝管荧光磁粉探伤的注意事项并对该方法进行了总结。     

基于MicroCANopen协议栈的CANopen从节点设计

提出一种基于MicroCANopen开源协议栈的CANopen从节点解决方案,给出以单片机STC90C514RD、CAN控制器SJA1000和CAN总线驱动模块CTM1050为核心的硬件结构;着重介绍结合MicroCANopen的软件设计方案以及具体实现方法.搭建CANopen网络测试平台测试所设计的CANo-pen从节点,实验结果证实了该方案及其实现方法的正确性和有效性.     

建筑用水基型胶粘剂中水分含量的测定研究

首先建立了建筑用水基型胶粘剂中水分含量的测定方法;然后以取样量、加热炉的加热温度和混合时间等为试验因素,采用单因素试验法优选出测定水基型胶粘剂中水分含量的最佳工艺条件。结果表明:当取样量为20 mg、加热炉的加热温度为170℃和混合时间为60 s时,水基型胶粘剂中水分含量的测定结果具有良好的重现性(平均回收率为93%¹00%,相对标准偏差为1.6%100%,相对标准偏差为1.6%⁵.3%);应用该方法和标准推荐的方法测定不同类型水基型胶粘剂的水分含量,两者结果相近,并且前者的操作更简单、更快速且取样量更少。     

弹性漆喷涂工艺

介绍了弹性漆的特性及应用,不同材质工件的涂装工艺、操作要点、注意事项、弹性漆漆膜检验标准等。对涂装过程中出现的一些常见故障进行了分析,并提出纠正措施。     

HEDP的热分解特性及其阻垢性能评价

研究了有氧、无氧条件以及不同pH条件下羟基亚乙基二膦酸(HEDP)在模拟工业锅炉炉水中的热分解特性,采用电导法和静态阻垢法对HEDP阻碳酸钙垢的性能进行了评价。实验结果表明,有氧和无氧条件下的HEDP热分解特性有较大的区别,pH对HEDP的热分解影响较小;电导法与静态阻垢法对阻垢剂阻CaCO3垢的评价结果具有一致性;溶液中加入5 mg/L HEDP即可达到较高的阻垢率;温度对阻垢剂的阻垢性能有较大的影响;在较低的钙离子和碳酸氢根离子浓度下,HEDP有较好的阻垢效果。     

电磁场频率对CaC03型污垢结晶的影响

基于自制的变频电磁水处理装置,研究不同频率的电磁场对碳酸钙结晶过程的影响。针对溶液电导率与加磁时间的关系特性,采用最小二乘法拟合出不同频率下其斜率与频率之间的多极值关系曲线;采用静态滴定法获得了钙离子浓度和碱度与频率之间的多极值关系曲线。为CaCO3污垢形成机理与电磁抑垢方法的完善提供了实验依据。     

On the ‘curiosity’ of electrical self‐heating,static charge and electromagnetic shielding effectiveness from carbon black/aluminium flakes reinforced epoxy‐resin composites

This paper shows the wide application range (such as electrical self‐heating and electromagnetic shielding effectiveness) of composites consisting of conductive carbon black/aluminum flakes (CBA) filler and epoxy insulative matrix. The effect of CBA content on the network structure of epoxy matrix was investigated in detail. Static electrical conductivity increases linearly with the increase of filler concentration at the interface in epoxy composites. The large decrease of the conductivity as a function of the temperature is analyzed in terms of the negative temperature coefficient of conductivity (NTCC) effect. The influence of viscosity, surface energy and barrier highest energy on the NTCC behaviour in the composite is also considered. Based on these results, a new interpretation is proposed to explain the NTCC phenomena by computing the swelling force among conductive phases. The correlations of conductivity during the temperature cycling and activation energy were analyzed. The effects of dynamic ageing at various temperatures on the resistivity are reported. Current–voltage–temperature characteristics for epoxy with different contents of CBA were examined in detail. A model based on the law of energy conservation is proposed to calculate the specific heat and amount of heat dissipation. The static charge of the epoxy–CBA composites was estimated. The correlation between electromagnetic wave‐shielding effectiveness (EMS), conductivity and frequency of epoxy composites with different filler contents is also discussed. Furthermore, the effect of annealing on EMS of epoxy composites was examined. © 2002 Society of Chemical Industry