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1、中国地质大学长城学院本科毕业设计外文资料翻译系 别： 工程技术系 专 业： 机械设计制造及其自动化 姓 名： 李 江 学 号： 05208307 2012 年 4 月 20 日 外文资料翻译译文塑料工业是与国民经济发展和社会文明建设息息相关的重要产业。塑料工业的机械和装备的水平对该工业的发展起着关键作用。比起传统的塑料挤出机，单螺杆塑料挤出机有他积极的优势，通常他能加工出高分子量、高粘度热塑性好的塑料。其中有高生产率低熔点、高熔体强压力的塑料有利于化学降解，产品质量高，品，因此是最佳的塑料生产这使得单螺杆塑料挤出机生产经济，特别适用于稳定的挤压。螺杆的回转航程和固定筒壁的相互作用是挤出机的泵出
2、过程中必要的参数。为了运输塑料材料，其摩擦在螺杆的表面要低，但在固定的筒壁要高。如果达不到这个基本标准，塑料可能会随着螺杆旋转，而不是在轴向/输出方向上移动。在输出区域，螺杆和机筒的表面通常都覆盖着的溶解物以及来自溶解物和螺杆通道之间的外力，而其除了 处理有极高粘性的材料时都是无效的，如硬质 PVC 材料和有超高分子量的聚乙烯。溶解物流在输出部分是 受内摩擦系数（粘度）影响，尤其是当模具提供了一个高阻力的熔体流时。 常见且更多使用的单螺杆型使用的是传统设计，即机筒和螺杆保持基本一致的直径，包括具有例如减小螺 杆通道体积，有连续可变速度、压力控制，和通风（挥发）系统的挤出机。一些特殊的设计使用了
3、圆锥或 抛物线外形的螺杆，用以达到特殊的混合和捏合效果。它们可以包含偏心的核心，根据不同坡度变化的动 程，揉捏转子，适应性的核心环，和间歇的轴向运动。桶内可能有螺纹，可伸缩的螺杆形状以及进料设备。 一个成功的挤出操作需要密切注意很多细节，如（1）进给材料的质量和在适当温度下的物质流，（2）足以 融化、但不会分解聚合物的温度曲线，以及（3）不会分解塑料的启动和关机。 应采取措施，防止促进塑料表面上水分的胶合和湿气的吸收凝结，如颜料浓缩物中的色素。表面凝结，可 通过储存于密封的塑料容器（吸湿性塑料）中在使用前约 24 小时与工作区域保持同温来避免。如果怀疑颜 色母料有吸湿，可以在 250 至 30
4、0 （ 120 -150 ）加热 8 至 16 小时，烘箱应充分干燥。料斗干燥机已被 证明在干燥塑料中非常有用。它们还可以在操作中提高挤出机受加热和熔解能力限制的输出的能力。图 显示了与加热输入挤出机所需的熔化塑料，有或没有料斗干燥机作为预热器时相关的不同。挤出机使塑料 熔体均匀熔化，并使之通过与产品的横截面形状关联的模具口。所形成的 TP 的熔体（挤出的）是冷了却的，或是加热的TS熔体，因为它是向下放置的进而得以远离模具出口或是通过下游设备拔出。 外文原文Plastic industry is an industry relation to national economy developm
5、ent and social civilization.The level of working equipment plays a pivotal role in the development of the plastic industry.The processing of very high-molecular-weight and high-viscosity thermoplastics in single-screw extruders today is usually done only in extruders with a positive-advantages over
6、conventional extrusion. Among these are high output at low melting temperatures and high melt pressures; reduced shear of the plastics, which makes this system energy-saving and very economical; gentle plastic of the plastics; on thermal or chemical degradation, hence optimum product quality; and pa
7、rticularly stable extrusion so that output, pressure and melting temperature surges are prevented.The essential parameter in the extruders pumping process is the interaction between the rotating fights of the screw and the stationary barrel wall. For the plastic material to be conveyed, its friction
8、 must be low at the screw surface but high at the barrel wall. If this basic criterion is not met, the plastic will probably rotate with the screw and not move in the axial/output direction. In the output zone, both screw and barrel surfaces are usually covered with the melt, and external forces bet
9、ween the melt and the screw channel walls have no effect except when processing extremely high viscosity materials such as rigid PVC and ultrahigh molecular weight PE. The flow of the melt in the output section is affected by the coefficient of internal friction (viscosity), particularly when the di
10、e offers a high resistance to the flow of the melt. The usual and more popular single screw types use conventional designs with basically uniform diameters of the screw and barrel. Examples include extruders that have decreasing screw channel volume, continuous variable speed, pressure control, and
11、a venting (devolatilization) system. Special designs use conical or parabolic screws for special mixing and kneading effects. They can include eccentric cores, variable pitch superimposed flights of different pitch, kneading rotors, fitted core rings, and periodic axial movement. Barrels may have in
12、ternal threads,telescopic screw shapes, and feeding devices. A successful extrusion operation requires close attention to many details, such as (1) the quality and flow of feed material at the proper temperature, (2) a temperature profile adequate to melt but not degrade the polymer, and (3) a start
13、up and shutdown that will not degrade the plastic. Care should be used to prevent conditions that promote surface condensation of moisture on the plastic and moisture absorption such as by the pigments in the color concentrates. Surface condensation can be avoided by storing the sealed plastic conta
14、iner (for hygroscopic plastics) in an area at least as warm as the operating area for about 24 h before use. If color concentrate moisture absorption is suspected, heating for 8 to16h in a 250 to 300 (120 to 150 ) oven should permit sufficient drying. Hopper dryers have proven very useful in drying
15、plastics. They can also enhance extruder capacity in operations where the output is limited by the heating and melting capacity of the extruder. The relative difference in heat input required from the extruder to melt the plastic, with and without the hopper dryer used as a preheater. The extruders form a homogeneous plastic melt and force it through a die orifice that is related to the shape of the products cross section. The formed TP melt (extrudate) is cooled or the TS melt heated as it is being dropped downward away from the die exit or drawn through downstream equipment.
