共查询到19条相似文献,搜索用时 562 毫秒
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采用自行研制的高熔体强度聚丙烯(PP),通过挤出片材发泡实验,研究了口模温度、挤出温度、螺杆转速等工艺条件以及PP熔体强度和发泡成核剂对片材发泡效果的影响。PP发泡片材最佳挤出工艺条件为:挤出温度210℃,口模温度160℃,螺杆转速40 r/min。PP熔体强度为13 cN,发泡成核剂用量为6 phr时,发泡片材密度最低(0.450g/cm~3),片材表面光滑平整,挤出发泡效果最好。 相似文献
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应用Polyflow软件对粘弹性聚合物熔体在气辅挤出口模内的流动进行了研究,得到了挤出物直径的挤出胀大比方程。模拟结果表明,熔体在滑移段的平均停留时间与材料松弛时间之比同挤出胀大比之间存在指数衰减关系。通过HDPE的气辅挤出成型实验,发现不同螺杆转速及挤出温度下挤出物直径的实验值与计算值达到很好的吻合,该计算方法可用于指导气辅口模设计。 相似文献
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《炭素技术》2018,(6)
采用熔融挤出成型工艺制备了石墨烯/聚乳酸复合线材,研究了模口温度、螺杆转速等工艺参数对复合线材导电性能的影响;研究了不同石墨烯含量对复合线材综合性能的影响;最后进行了石墨烯/聚乳酸复合线材3D打印实验。研究结果表明:只有当模口温度高于195℃时,才能获得表面光滑无气孔缺陷的线材;复合线材电导率随着模口温度和螺杆转速的增加,先增大后减小,合适的模口温度为200~210℃,螺杆转速为13~17 r/min。石墨烯/聚乳酸复合线材拉伸强度和断裂伸长率随着石墨烯含量增加而增大,当石墨烯质量分数为9%时,电导率最高,达到2.7×10~(-2) S/cm。在FDM打印实验中发现:添加石墨烯5%时,其抗弯强度提高了57.1%。与石墨烯/PLA复合线材相比,打印试样的电导率有所提高。 相似文献
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以淀粉和乙烯-醋酸乙烯共聚物(EVA)为原料制备生物质复合材料,研究了模口温度、螺杆转速及EVA含量对挤出胀大现象的影响,并应用人工神经网络技术建立双层BP神经网络模型,将正交实验结果作为样本带入模型进行训练。经反复训练,修正误差后对复合材料的挤出胀大比进行预测。结果表明,该神经网络模型能较为准确的预测复合材料的挤出胀大比;随着模口温度的升高,或螺杆转速的下降,或EVA含量的降低,复合材料的挤出胀大比逐渐减小。 相似文献
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A pulse pressure was superimposed on the melt flow in extrusion, called vibration extrusion. A die (L/D = 17.5) was attached to this device to study the rheological properties of an amorphous polymer (ABS) and semicrystalline polymer (PP, HDPE), prepared in the vibration field, and the conventional extrusion were studied for comparison. Results show that the melt vibration technique is an effective processing tool for improving the polymer melt flow behavior for both crystalline and amorphous polymers. The enhanced melt rheological property is also explained in terms of shear thinning criteria. Increasing with vibration frequency, extruded at constant vibration pressure amplitude, the viscosity decreases sharply, and so does when increasing vibration pressure amplitude at a constant vibrational frequency. The effect of vibrational field on melt rheological behavior depends greatly on the melt temperature, and the great decrease in viscosity is obtained at low temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5292–5296, 2006 相似文献
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借助流变测量和连续介质理论,不依赖已有的本构关系,对平行叠加正弦振动条件下高分子熔体经毛细管的动态挤出过程进行了理论分析。以低密度聚乙烯(LDPE)为原材料,实验测量LDPE熔体在一定振动频率和振幅下毛细管入口压力、体积流量和挤出胀大的瞬态值,即可得到动态成型过程中高分子熔体剪切应力、剪切速率和表观粘度的变化规律:随振幅和频率的变化,LDPE熔体的表观粘度呈非线性变化趋势;在不同的振幅和频率下动态挤出LDPE熔体,跟稳态挤出时一样,壁面剪切应力与壁面剪切速率也成非线性比例关系。 相似文献
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Javier Vera-Sorroche Adrian L. Kelly Elaine C. Brown Tim Gough Chamil Abeykoon Phil D. Coates Jing Deng Kang Li Eileen Harkin-Jones Mark Price 《Chemical Engineering Research and Design》2014
In this work, a highly instrumented single screw extruder has been used to study the effect of polymer rheology on the thermal efficiency of the extrusion process. Three different molecular weight grades of high density polyethylene (HDPE) were extruded at a range of conditions. Three geometries of extruder screws were used at several set temperatures and screw rotation speeds. The extruder was equipped with real-time quantification of energy consumption; thermal dynamics of the process were examined using thermocouple grid sensors at the entrance to the die. Results showed that polymer rheology had a significant effect on process energy consumption and thermal homogeneity of the melt. Highest specific energy consumption and poorest homogeneity was observed for the highest viscosity grade of HDPE. Extruder screw geometry, set extrusion temperature and screw rotation speed were also found to have a direct effect on energy consumption and melt consistency. In particular, specific energy consumption was lower using a barrier flighted screw compared to single flighted screws at the same set conditions. These results highlight the complex nature of extrusion thermal dynamics and provide evidence that rheological properties of the polymer can significantly influence the thermal efficiency of the process. 相似文献
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《塑料、橡胶和复合材料》2013,42(5):193-198
AbstractSingle screw extruders are used to generate a continuous flow of molten polymer in many industrial polymer processes. The melt velocity profile as extruded is important in determining the properties of the final product and influences process related phenomena such as die swell and the onset of sharkskin. The factors that influence the velocity profile would be expected to be the melt temperature (this affecting the viscosity of the melt), the screw and die geometry, and the output rate from the extruder. In the present work a thermocouple mesh sensor coupled with a cooled stainless tube has been used to determine velocity profiles in melts exiting from the screw of a single screw extruder. The results show that the technique can be used successfully to determine velocity profiles in the extrusion process.It was found that the main influence on the magnitude of the melt velocity was the extruder screw speed. Melt temperature, and hence melt viscosity, were found to have little effect on the velocity profiles measured. The flow in the centre of the duct was retarded slightly owing to the flow across the screw tip and no rotational component of flow was observed. The velocity profiles measured seemed to be reasonably stable, only small changes being observed in the velocity profiles as the melt flowed along a duct of uniform cross-section, although these changes were limited in nature. Die diameter and length had a limited effect on the velocity profiles generated, although the die entry angle did have a significant effect on the shape of the velocity profile at higher screw speeds. 相似文献
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聚合物动态挤出流变行为研究 总被引:30,自引:5,他引:25
本文论述聚合物材料毛细管动态流变行为的测量原理,介绍了自行研制成功的用于合物熔体挤出的毛细管动态流变仪。在该仪器上对LDPE进行了实验研究,发现熔体的粘度与振动源的频率、振幅呈非线性关系。在振动必场作用下LDPE熔体的粘度减小,随振动频率的变化有一最小值。这对矣合物动态塑化挤出工艺过程控制具有十分重要意义。 相似文献