共查询到18条相似文献,搜索用时 62 毫秒
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聚乙烯压力管道在低温时易出现裂纹快速扩展,其破坏一般都具有突发性,难以预防。本文采用小尺寸稳态试验方法,测试了在不同温度下,裂纹扩展长度随压强的变化情况,同时也测试了在不同压强下,裂纹扩展长度随温度的变化情况。通过计算分析,确定了裂纹快速扩展的临界压强和临界温度。给出了影响该试验结果的因素如温度、压力、介质、裂纹扩展速度及裂纹尖端的流体减压等。并通过试验测试了焊缝以及套筒对塑料管道开裂的影响。最后给出了塑料管道在实际运行中的一些具体的止裂措施。 相似文献
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本刊讯(2007年1月23日)巴赛尔(Basell)已成功研制出改良版的Hostalen CRP 100黑色高密度聚乙烯牌号,客户可用其生产具备增强扰艮陛裂纹扩展的压力管。 相似文献
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简要介绍先进的埋地管道防腐工艺——管道三层PE防腐,在埋地天然气管道、给排水管道中的应用,三层PE管道防腐工艺逐渐取代传统的管道防腐工艺。 相似文献
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采用循环载荷裂纹圆棒(CRB)试验,测试了A~C 3种聚乙烯(PE)材料在载荷比(R)分别为0.1、0.3和0.5时,缺口圆柱棒试样的裂纹扩展速率(da/dt)与应强度因子(KI)的对应关系。通过结合聚合物材料线弹性断裂力学理论,外推至R=1(静载)条件,得到含缺陷PE管材的使用寿命(tf),并与全缺口蠕变试验(FNCT)评价结果进行了对比分析。结果表明,当A~C 3种PE管材内壁存在aini=0.4 mm的初始裂纹缺陷时,CRB试验外推得的管材的tf分别为44、53和65年;FNCT外推结果分别为53、59和79年;CRB和FNCT的寿命预测结果具有较好的正相关性,寿命预测结果偏差较小,试验结果证实了该方法的有效性。 相似文献
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稳态反应模型在气相聚乙烯反应器中的应用 总被引:1,自引:0,他引:1
通过对气相流化床聚乙烯工艺稳态反应模型的应用进行分析,讨论了中间控制参数温度、氢气乙烯摩尔比、共聚单体乙烯摩尔比、催化剂产率等输入变量对反应器输出变量树脂性能-熔体流动指数(MI)的影响。选择工业实例,对系统出现波动后人工调控MI与利用稳态反应模型的计算机调控MI的过程分别进行了计算,并对2种调控过程进行了比较,证明了稳态反应模型在工业质量控制中的优越性。 相似文献
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Cracks in polymer glasses can grow slowly preceded by a craze, a narrow zone of plastic cavitation. The craze widens by drawing more polymer from its surfaces into its fibrils but the fibrils themselves fail by local creep. When the crack tip moves at velocity v the loading at the crack tip can be described by a local stress intensity factor K which is the sum of the ‘apparent’ stress intensity factor KA and a plastic contribution Kp (usually negative). Kp is found to be where P(K) is an integral over the craze boundary displacement law. Fibril failure by local creep leads to a power law, v ∞ Km. From these relations K and v can be determined as a function of KA. The plot of K vs. KA is multiple-valued with a stable branch (at high K) and an unstable branch (at low K) separated by a minimum value of KA which represents a threshold for stable, steady state crack growth. There is also a v threshold, below which cracks will not grow steadily. These predictions, the form of the v?KA curve and implications for slip-stick crack growth are compared with recent experiments. 相似文献
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A mixture of formic acid/acetic acid makes it possible to electrospin polyamide 6.6 in steady state conditions. Steady state conditions are essential in nozzle electrospinning to generate a stable process which fabricates reproducible material, permitting industrial upscaling. This study shows that only a limited mixture range of formic acid/acetic acid allows electrospinning of polyamide 6.6 in steady state. Furthermore, the weight concentration in solution; the tip to collector distance and the flow rate have been changed to control the average diameter of the nanofibres. The average diameter increases by increasing weight concentration in solution, increasing volume fraction of acetic acid in the mixture, increasing tip to collector distance and increasing flow rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
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Sander De Vrieze Bert De Schoenmaker Özgür Ceylan Jara Depuydt Lieve Van Landuyt Hubert Rahier Guy Van Assche Karen De Clerck 《应用聚合物科学杂志》2011,119(5):2984-2990
Electrospinning is a process to generate a nanofibrous material. Although the working principle of electrospinning is rather straight forward, it is influenced by many parameters. There is still a serious lack of knowledge concerning the influence of the ambient parameters, for which preliminary knowledge reveals that the relative humidity is of primary importance. This article reports the influence of the relative humidity on electrospun polyamide 6 nanofibres. Mixtures of formic acid and acetic acid are used for steady state electrospinning of polyamide 6 nanofibres, for which a steady state table is determined. When the relative humidity increases, the average fiber diameter decreases and the fraction of the less stable γ‐phase crystals in the polyamide diminishes. This effect is explained by absorbed water acting as a plasticizer, reducing the Tg of the polyamide. This article shows the importance of working in climatized conditions during electrospinning to obtain reproducible nanofibres. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献