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Environmental stress cracking of polyethylene high density (PE‐HD) induced by liquid media – Validation and verification of the full‐notch creep test (FNCT)
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M. Schilling M. Böhning H. Oehler I. Alig U. Niebergall 《Materialwissenschaft und Werkstofftechnik》2017,48(9):846-854
The full‐notch creep test (FNCT) is widely used to characterize the slow crack growth (SCG) behavior of polyolefin materials in “inert” media as well as effects of environmental stress cracking (ESC) in which the medium has decisive influence on damage mechanism and time to failure. The test is of greatest importance for pipe and blow molding types of polyethylene, high density (PE‐HD). Usually the full‐notch creep test is applied as a standardized testing method (ISO 16770) using a few universal liquid media, such as solutions of Arkopal N 100. In our study, selected relevant polyethylene, high density materials are investigated also in real media – practical formulations as well as representative pure chemicals – and influences of temperature and geometry of specimen and notch are explicitly addressed. Furthermore, the investigations comprise also the environmental stress cracking behavior of polyethylene, high density in media that are sorbed to a significant extent – examples are diesel and biodiesel – based on comparison with samples previously saturated with those media. Thus, also the underlying diffusion controlled sorption process has to be assessed before. The investigations were performed using a full‐notch creep testing device with 12 individual sub‐stations, each equipped with individual electronic stress and temperature control and continuous online monitoring of the specimen elongation. 相似文献
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用自制增韧母料(E-TMB)分别与2200J型高密度聚乙烯(PE-HD)(HE1)和2911型PE-HD(HE2)热机械共混制得HE1/E-TMB和HE2/E-TMB共混物,用力学性能测试法和扫描电子显微镜研究了两类共混物的脆韧转变和断面形态。结果表明,HE1/E-TMB共混物比HE2/E-TMB共混物在弹性体含量较低的情况下发生脆韧转变,二者的脆韧转变区分别是共混物弹性体质量分数的3%~10%和10%~14%;弹性体质量分数为8%时,HE1/E-TMB共混物的冲击断面为韧性断裂,HE2/E-TMB共混物的冲击断面为脆性断裂,二者属于不同的断裂机理。 相似文献
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基于复合共挤成型原理,建立了高密度聚乙烯(PE–HD)/玻璃纤维(GF)复合共挤有限元模型,采用有限元软件Polyfl ow对流道内熔体的三维等温非牛顿流动行为进行了数值模拟,给出了GF以不同速度移动时流道内熔体压力和速度的分布特点及变化规律。根据数值模拟结果确定了挤出工艺参数,研制了共挤模具,制备了PE–HD/GF复合带,并进行了力学性能测试。结果表明,随着GF移动速度的提高,流道内压力减小,熔体在复合成型段挤出速度明显增加;GF移动速度达到一定值时熔体挤出速度均匀,移动速度过大则导致熔体速度分布不均匀。研制的PE–HD/GF复合带拉伸强度保留率可达GF的82%。 相似文献
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针对400丝以上大规格斜拉索高密度聚乙烯(PE-HD)防护套存在着易开裂及外观质量差等质量缺陷问题,在挤出成型防护套的过程中,通过合理设计口模结构尺寸以增加模具压力、合理调控机头温度、调整好口模中内外模的间隙、对原材料PE-HD进行增韧改性等方法,使PE-HD均匀地包覆在裸索上,并紧密地粘附成一体,形成的防护套厚度均匀、无银纹且其与裸索之间没有间隙。通过以上措施,制备的大规格斜拉索防护套在生产制造、张拉检测、卷盘运输、施工安装环节中,当其受到挤压、弯曲、拉伸等应力的作用时,没有开裂等隐患现象发生。 相似文献
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分别以木粉、竹粉、稻壳粉三种木质纤维为填料,高密度聚乙烯(PE–HD)为基体,采用模压成型法制备木塑复合材料,对复合材料的热膨胀性能和热失重特性进行了研究。结果表明,三种木质纤维填充PE–HD复合材料的线性热膨胀系数顺序为:PE–HD/木粉复合材料PE–HD/竹粉复合材料PE–HD/稻壳粉复合材料;PE–HD/木粉复合材料的线性热膨胀系数随着木粉含量的增加和木粉粒径的减小而减小,木粉质量分数为65%、粒径为150μm时,复合材料的线性热膨胀系数最小。PE–HD基木塑复合材料的热分解过程分为两个阶段,第一阶段主要为木质纤维分解阶段,第二阶段主要是PE–HD分解阶段;PE–HD/木粉复合材料起始失重温度高于竹粉和稻壳粉填充的复合材料;且PE–HD/木粉复合材料中木粉含量越高,第一阶段分解速率及失重量越大;木粉粒径越小,复合材料起始分解温度越低。 相似文献
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