Accelerated aging of elastomeric composites with vulcanized ground scraps

The aim of this work is to study the effect of thermal aging on the mechanical, dynamic‐mechanical, and chemical properties of SBR (styrene‐butadiene rubber) composites filled with SBR industrial rubber scraps. Eight composites with varying proportions (10–80 phr) of the SBR ground scraps (SBR‐r) were prepared and subjected to accelerated aging in an air‐oven. The composites were evaluated, and the results were compared with a control sample (base formulation with 0 phr of SBR‐r), before and after thermal aging. The accelerated aging led to a decrease in the mechanical properties as a result of an increase in the stiffness of the material, related to an increase in the crosslink density. However, these properties were not affected by the addition of rubber scraps up to 50 phr, either before or after aging. The increase in the glass transition temperature of the composites after aging, measured using dynamic mechanical analysis, confirmed the occurrence of a postcrosslinking process. Fourier transform infrared spectroscopy and crosslink density revealed that the aging mechanism was dependent on the SBR‐r content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of epoxidized natural rubber on thermal properties,fatigue life,and natural weathering test of styrene butadiene rubber/recycled acrylonitrile‐butadiene rubber (SBR/NBRr) blends

The utilization of waste rubber powder in polymer matrices provides an attractive strategy for polymer waste disposal. Addition of recycled acrylonitrile‐butadiene rubber (NBRr) in rubber compounds gives economic (lowering the cost of rubber compounds) as well as processing advantages. In this study, the properties of styrene butadiene rubber (SBR)/NBRr blends with and without epoxidized natural rubber (ENR‐50) as a compatibilizer were determined. The results such as thermal gravimetric analysis (TGA), fatigue life, and natural weathering test of SBR/NBRr blends with and without ENR‐50 were carried out. Results showed that TG thermograms of SBR/NBRr blends with ENR‐50 show lower thermal stability compared blends without ENR‐50. The incorporation of ENR‐50 into SBR/NBRr blends has reduced char residue compared SBR/NBRr blends without ENR‐50. The incorporation of ENR‐50 in SBR/NBRr blends has increased the rigidity of the blends thus lowering the fatigue life. The increment in tensile properties retention of SBR/NBRr blends with ENR‐50 indicated the enhancement on weathering resistant. The surfaces of SBR/NBRr blends with ENR‐50 after 6 months exposure showed a minimal severity of crack compared with SBR/NBRr blends without ENR‐50. It revealed that the scale of cracks has reduced indicating well‐retaining interfacial adhesion between SBR and NBRr with the presence of ENR‐50 as a compatibilizer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

冷端加速分离辊道设计电机选型分析探讨

对浮法玻璃生产线冷端加速分离辊道配置电机进行了理论计算,以寻求对系统的参数优化,研究结果可以为传动系统设计提供依据。     

Accelerated and real-time creep and creep-rupture results for aramid fibers

This article presents results from conventional creep tests (CCT) and two accelerated test methods (the stepped isothermal method (SIM) and the stepped isostress method (SSM)) to determine the creep and creep-rupture behavior of two different aramid fibers, Kevlar 49 and Technora. CCT are regarded as the true behavior of the yarn, but they are impractical for long-term use where failures are expected only after many years. All the tests were carried out on the same batches of yarns, and using the same clamping arrangements, so the tests should be directly comparable. For both materials, SIM testing gives good agreement with CCT and gave stress-rupture lifetimes that followed the same trend. However, there was significant variation for SSM testing, especially when testing Technora fibers. The results indicate that Kevlar has a creep strain capacity that is almost independent of stress, whereas Technora shows a creep strain capacity that depends on stress. Its creep strain capacity is approximately two to three times that of Kevlar 49. The accelerated test methods give indirect estimates for the activation energy and the activation volume of the fibers. The activation energy for Technora is about 20% higher than that for Kevlar, meaning that it is less sensitive to the effects of increasing temperature. The activation volume for both materials was similar, and in both cases, stress dependent. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

不同干热环境对聚苯乙烯老化的严酷度差异

将聚苯乙烯(PS)材料在吉达和吐鲁番2种典型干热自然环境中进行自然暴晒,对PS材料在自然老化过程中的黄色指数、光泽度、雾度等光学性能和表面形貌进行了测试与表征,研究了PS在吉达和吐鲁番的老化行为差异。通过对吐鲁番和吉达两地的太阳辐照和温度2种关键环境条件的量化比较,计算出了2种干热环境的相对严酷度。结果表明,PS材料在干热环境自然老化的过程中出现了光学性能下降,表面颜色变黄,样品发生明显的老化失效的现象,此外,样品在吉达的光学性能下降幅度和颜色变黄程度均高于吐鲁番。通过比较PS材料在2个试验地点的光学性能差异,验证了吐鲁番相对吉达的环境严酷度为0.66。     

Micro-Analysis of ＂Sulfate Salt Weathering Distress on Concrete＂： I. Cement Paste

在多孔材料内部检测发现硫酸盐晶体是证明盐结晶破坏最直接的证据。运用环境扫描电子显微镜、扫描电子显微镜、能谱仪和X射线衍射等微观分析手段,研究了稳定环境和变化环境中,硫酸钠溶液对半浸泡纯水泥净浆和水泥粉煤灰净浆的破坏作用,结果表明：在破坏的净浆试件中并没有发现硫酸钠晶体,反而发现大量的混凝土硫酸盐化学侵蚀产物（钙矾石和石膏等）晶体,硫酸盐化学侵蚀依然是引起净浆试件破坏的主要原因。     

Micro-Analysis of ＂Sulfate Salt Weathering Distress on Concrete＂：Ⅱ.Concrete

运用环境扫描电镜、能谱仪和X射线衍射等微观分析手段研究了稳定环境中,半浸泡混凝土试件在硫酸钠和硫酸镁溶液中的劣化破坏特征,以及混凝土碳化对＂混凝土硫酸盐结晶破坏＂的影响。结果表明：粗骨料界面过渡区生成的大量钙矾石和石膏等晶体是引起混凝土试件劣化的原因;在碳化混凝土内发现了硫酸钠结晶破坏现象。     

Effect of accelerated aging on properties of biobased polymer films applicable in printed electronics

The growing interest in sustainable, lightweight, bendable roll-to-roll manufactured printed electronics applied to packaging, textiles or medical healthcare has led to the need for materials that can withstand various environmental conditions. In this work, the studied materials were polyethylene terephthalate (PET), typically used as a substrate for printed electronics, and it was compared to biobased polymeric substrates bio-PET, polylactic acid (PLA), cellulose acetate propionate (CAP) and regenerated cellulose film Natureflex™. Films were exposed for 500 h to heat (50.5°C); heat and humidity (50 RH%); heat, humidity, and light (UV-A 300–400 nm, 42 W/m²) and temperature cycles in the range of −45°C to 65°C. Changes in film transparency and mechanical properties were analyzed. The main findings were that during the exposure to only elevated temperature and temperature with humidity, the analyzed properties were retained in all film materials. UV-A caused less or no changes in Natureflex™, bio-PET and PLA. The most stable in thermal cycling was Natureflex™, CAP, and PET. These results may open new possibilities for biopolymers in printed electronics applications.     

磷矿的风化反应与酸解活性的关系

通过对磷矿风化水解反应的分析，说明风化反应与磷矿的化学组成及微观结构有着密切的联系。磷矿中碳酸盐的含量及在磷矿晶体中的存在状况对磷矿的酸解反应活性有着较大的影响。由磷矿酸解反应活性与磷矿晶体微观结构的关系，指出易风化的磷矿具有较好的酸解反应活性。     

聚甲醛加速老化试验研究

对聚甲醛（POM）进行了光加速老化试验和湿热老化试验研究。利用电子显微镜，差示扫描量热仪和X光电子能谱对材料在老化过程中的物理和化学性能进行了分析。结果表明，POM在老化过程中物理力学性能下降的主要原因是表面无定形区域的光氧化。