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单螺杆挤出过程粒子熔融理论 总被引:2,自引:0,他引:2
基于宏观和亚宏观可视化实验观察到的单螺杆挤出过程粒子熔融现象,提出了与宏观熔融模型相结合的粒子熔融渗流模型,利用该模型计算了LDPE在熔融初期的熔融速率,并将计算结果与实验结果进行了比较。 相似文献
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在单螺杆挤出机中,通过螺杆的轴向振动将振动力场引入聚合物固体输送过程,提出振动力场强化固体输送过程的新概念.以螺槽中运动的物料为对象建立了振动力场强化固体输送过程的数学模型,并获得了物料沿螺槽方向输送的压力(密度)、速度的近似解析解.传统固体输送过程就是当螺杆轴向振动的振幅为零时的特例,此时的压力降与Darnell and Mol 理论一致,但不同的是物料速度及密度沿螺槽方向是变化的,从而修正了Darnell and Mol 固体输送理论.螺杆的轴向振动提高了固体输送平均压力,缩短了固体输送的长度,增加了固体输送角.透明料筒全程可视化实验挤出机证明了螺杆轴向振动确实缩短了物料固体压实输送所需的螺槽长度. 相似文献
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单螺杆挤出固体输送段非塞流的三层模型法 总被引:7,自引:0,他引:7
依据单螺杆挤出机固体输送段的非塞流现象,把固体塞分成上、中、下三层,通过应力—速度方程,推导出产量与压力降的三次方程;详细讨论了摩擦系数对最大产量的影响,并深入地分析了单螺杆挤出机固体输送段产量与末端压力的关系,通过这些分析计算,三层模型法能很好地预示单螺杆挤出机固体输送段的压力与产量,该方法不仅简单明晰而且精度高,是一个可使用的方法 相似文献
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运用Polyflow分别对聚乳酸(PLA)用3种不同结构类型单螺杆挤出机熔体输送段进行模拟,在流场分析的基础上,分析3种螺杆的混合性能。结果表明,在相同工艺条件下,普通型单螺杆和菠萝型单螺杆熔体轴向速度波动较大,且产生局部回流区域,不利于熔体的输送;菠萝型螺杆产生的流场速度和熔体黏度较高,使得物料在流场中受到更高的剪切速率,因此挤出产物的分散混合性能更好;挤出过程中,PLA熔体的黏度变化与流动速度变化存在一致性,随着流动速度逐渐增大,熔体受到的剪切作用逐渐增强,使黏度降低,流动性变好。 相似文献
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单螺杆挤出过程中固体粒子的变形,取向与熔融 总被引:2,自引:2,他引:0
在带有在线取样和在线显微观察系统的全程透明视窗单螺杆挤出机上,采用普通三段式螺杆和分离型螺杆,对LDPE和LLDPE等为物料进行了挤出实验,对实验过程中的固体床结构与变莆、固体粒子的变形现象和变形机理进行了描述和分析,针对固体粒子的粒间运动与变形现象,提出了固体粒子粒间有三个阶段的概念 相似文献
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阐述催化剂单螺杆挤条机挤出筒在结构、联接方式、冷却方式方面的设计:采用挤出机筒和进料机筒分体的组合衬套式,在挤出筒的内壁加工出提高输送效率的沟槽,使用便于更换的联接方式,在挤出筒的外围采用冷却水套,使物料在较低温度下成型,提高挤出筒的使用寿命和挤出效率,从而保证生产能力和提高催化剂挤条的质量. 相似文献
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选用五种含有多官能团的可反应单体和四种自由基引发剂,使用普通单螺杆挤出机作为连续的熔融反应器,研究了聚丙烯在自由基引发作用下与各种反应单体的反应规律.实验结果表明:二乙烯基苯(DVB)和过氧化二异丙苯(DCP)是聚丙烯熔体改性的最佳反应单体和引发剂.其最适宜用量:DVB为0.6%,DCP为0.04%;挤出机的最佳工艺条件为:螺杆转速45 r/mm,料膛反应区温度为190℃;经反应挤出产物的熔体强度达到14.1 kPa·s,比原料PP提高了7倍,熔体指数从5.0 g/10min降低到2.2 g/10min,熔垂从11.5 mm降低到3.2 mm. 相似文献
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Krzysztof Wilczyński 《Polymer-Plastics Technology and Engineering》2013,52(7-8):671-690
The ability of a screw to manufacture products of good quality with high productivity and low cost is called its performance. At the design stage of an extrusion process, evaluation of screw performance is very important and can be realized on the basis of experimental and theoretical investigations. 相似文献
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Krzysztof Wilczyński 《Polymer-Plastics Technology and Engineering》2013,52(3):449-477
A fully predictive computer model has been developed for a single-screw plasticating extrusion (with conventional screws). The model takes into account five zones of the extruder (hopper, solids conveying, delay zone, melting zone, melt conveying) and the die, and describes an operation of the extruder-die system, making it possible to predict a mass flow rate of the polymer, pressure and temperature profiles along the screw channel and in the die, solid bed profile, and power consumption. Moreover, mixing degree, temperature fluctuation and viscoelastic properties of the polymer are estimated. The simulation parameters are the material and rheological properties of the polymer, the screw, hopper and die geometry, and the operating conditions (screw speed and barrel temperature profile). Such a comprehensive approach to the modeling of extrusion creates the possibility of optimizing the process, for example, from the point of view of the quality of extrusion. The model has been verified experimentally for a low-density polyethylene on a 45 mm diameter single-screw extruder. 相似文献
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李晓翠;彭炯;陈晋南 《中国塑料》2010,24(2):109-112
用正交设计法设计了9组不同排布的销钉单螺杆。采用混合熵作为评价销钉单螺杆混炼段混合性能的指标,数值研究了不同销钉结构的单螺杆混炼段内聚丙烯熔体的等温流动过程,考察了一个导程内销钉排数、每排销钉个数和销钉高度对销钉单螺杆混炼段混合性能的影响。结果表明,在所设计的正交试验中,沿螺杆挤出方向各截面的混合熵逐渐增大,出口处该值达到最大;在销钉螺杆混炼段一个导程内安装5排,每排5个高度为12 mm的销钉时,其混合性能较优。 相似文献
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A novel kind of extruding machinery is proposed—a tri-screw extruder (TRISE), in which three intermeshed screws are arranged in the three corners of a triangle; three meshing regions and a center zone also comprise the special construction. The flow rate and the pressure-generating ability of the melt in the thread-zone flow field of the tri-screw extruder, especially the pumping formed by the action of taking in and sending out melt in the unique center zone, are also described. The results of simulation and experiments clearly show that the tri-screw extruder has stronger conveying capacity. The shear frequency of material in the tri-screw extruder is higher than that in the twin-screw extruder, which means that filler could be loaded to a much higher point in the TRISE than in the twin-screw. Results from the TRISE also show that energy consumption of the TRISE is lower than that of the twin-screw extruder. 相似文献
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