Analysis of the effects of the polymerization route of ethylene‐propylene‐diene rubbers (EPDM) on the properties of polypropylene‐EPDM blends

A comparative study of two ethylene‐propylene‐diene rubbers (EPDM) polymerized by both conventional (Ziegler–Natta catalysts) and new techniques (metallocene catalysts) is presented. For this purpose, thermoplastic elastomers based on isotactic polypropylene (iPP) and EPDM blends at different percentages were prepared and their properties examined. In particular, the processing behavior and mechanical properties are reported. So, the flow properties analyzed by torque value, melt index, and rheological study reveal that the blends containing EPDM synthesized by metallocene catalyst present a smaller viscosity, thus offering better processing behavior. On the other hand, the mechanical properties show that metallocene EPDM rubbers give rise to more elastic materials with a higher deformation at break and resilience as well as a lower compression set. Moreover, the effectiveness of these innovative EPDM rubbers as impact modifiers for PP is demonstrated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 25–37, 2002     

聚合物多元醇在聚氨酯微孔弹性体中的应用研究

对聚合物多元醇在聚氨酯微孔弹性体中的应用进行了研究。考察了聚合物聚醚多元醇及聚合物聚酯多元醇对聚氨酯微孔弹性体力学性能的影响。实验结果表明,该类聚合物多元醇的引入可使聚氨酯微孔弹性体制品的力学性能得到较大改善,因此该类聚合物多元醇在聚氨酯领域必将具有广阔的应用前景。     

环氧SBS开环制备顺酐化离聚体及其物化性能的研究

利用环氧化苯乙烯-丁二烯-苯乙烯嵌段共聚物（ESBS）的环氧基与顺丁烯二酸氢钾（HKM）在相转移催化剂和开环催化剂存在的条件下开环反应制得钾离聚体。研究了其反应条件，由于添加了助剂BM，环氧基开环率达到了95．2％，并用FTIR确定了离聚体的生成；通过对不同环氧值ESBS开环反应，研究了不同离子基团质量摩尔浓度对离聚体物化性能的影响。     

喷雾低水熄焦技术在济钢的应用

采用喷雾低水熄焦技术对原熄焦系统进行了改造,解决了喷嘴堵塞及喷淋效果不好等问题。熄焦时间缩短了50～80s,用水量减少了20%～40%,焦炭水分降低了1%。同时,还稳定了高炉操作,使焦比降低了1.2%。     

端氨基聚脲聚氨酯环氧树脂体系的固化反应及粘接性能

本文采用DTA和FT-IR研究了端氨基聚脲聚氨酯固化环氧树脂的反应特性,考察了被粘表面状态、偶联剂和促进剂、填料等对剪切强度性能的影响。并对该粘合剂耐化学腐蚀性进行了试验,说明具有好的耐腐蚀性。     

Tribological behavior of the polyamide composite coating filled with different fillers under dry sliding

The polyamide (PA) composite coating filled with the particles of microsized MoS₂, microsized graphite, and nano‐Al₂O₃, respectively, were prepared by flame spraying. The friction and wear characteristics of the PA coating and composite coating filled with the varied content of filler under dry sliding against stainless steel were comparatively investigated using a block‐ring tester. The morphologies of the worn surfaces and transfer films on the counterpart steel ring were observed on a scanning electron microscope. The result showed that the addition of fillers to the composite coatings changed significantly the friction coefficient and wear rate of the coatings. The composite coatings filled with a low level content of fillers showed lower wear rate than did pure PA coating under dry sliding; especially the MoS₂/PA composite coating had the lowest wear rate among these composite coatings. The composite coatings with a high level content of fillers had higher wear rate than did pure PA coating, except of the Al₂O₃/PA composite coating. The bonding strengths between the polymer matrix and fillers changed with the content of the fillers, which accounted for the differences in the tribological properties of the composite coatings filled with the varied content fillers. On the other hand, the difference in the friction and wear behaviors of the composite coatings and pure coating were attributed to the difference in their worn surface morphologies and transfer film characteristics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

PET／EPDM／蒙脱土复合材料的性能研究

以聚对苯二甲酸乙二醇酯（PET）为基体，以三元乙丙橡胶（EPDM）为弹性体，用熔融共混的方法制备了不同比例的PET／EPDM／蒙脱土（MMT）复合体系。用原子力显微镜、扫描电子显微镜研究了复合材料的微观结构，并测试了力学性能。结果表明MMT含量较低时，用熔融共混的方法能制得PKT／EPDM／MMT纳米复合材料EPDM及增容剂的引入都较大程度地改善了复合材料的缺口冲击强度。     

The influence of gun transverse speed on electrochemical behaviour of thermally sprayed Cr3C2-NiCr coatings in 0.5 M H2SO4 solution

In the present study, different types of 75% Cr₃C₂-25% NiCr coatings were applied on a steel substrate by means of high velocity oxygen fuel spraying (HVOF), and studied using ac and dc electrochemical measurements in an aerated and unstirred 0.5 M H₂SO₄ solution. Structural characterization was determined before and after electrochemical tests. Differences between all sprayed systems are related to the gun transverse speed and number of deposited layers, which strongly affected the electrochemical characteristics of the coated steels. The coating obtained with a higher torch speed showed better resistance against corrosion. The electrochemical impedance results were analyzed using an equivalent circuit where porosity of the coatings and substrate oxidation were considered.     

丁羟聚氨酯弹性体的老化规律研究

针对丁羟聚氨酯弹性体的老化及其对材料性能的影响,制备了丁羟弹性体胶片试样,对试样进行了加速老化试验,测试了不同老化阶段弹性体的密度、力学性能、交联密度及红外光谱.通过对测试结果的分析,指出了丁羟弹性体体系内部发生的化学反应及其对力学性能的影响,总结了丁羟弹性体的老化规律.研究发现在老化过程的前期,MAPO与TDI也发生了交联反应,使弹性体的交联密度有所增加,弹性体内的化学反应主要以降解断链为主,通过弹性体熵弹性的降低来影响其力学性能,该阶段弹性体的力学性能并不随交联密度而变化.在老化过程的后期,弹性体内部以氧化交联反应为主.     

汽雾冷却条件下转炉炉体瞬态温度场

通过有限元方法,对汽雾冷却条件下大型转炉炉体瞬态温度场进行了三维有限元仿真分析及宝钢300 t大型转炉热电偶数据实测,研究了该条件下炉体瞬态温度场的分布及变化规律.实测的炉壳温度及其变化规律与有限元仿真结果吻合较好,证实了炉体瞬态温度场有限元分析的可信性.研究结果表明,汽雾冷却条件下炉壳温度呈锯齿形波动(降温速度快,升温较慢),平均降温速度为2～2.5℃/min.运用汽雾冷却技术,可将炉壳温度控制在材料热蠕变温度(约400℃)以下,有效抑制了炉壳热蠕变变形.