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中國(guó)地質(zhì)大學(xué)長(zhǎng)城學(xué)院
本科畢業(yè)設(shè)計(jì)外文資料翻譯
系 別： 工程技術(shù)系
專 業(yè)： 機(jī)械設(shè)計(jì)制造及其自動(dòng)化
姓 名： 李 江
學(xué) 號(hào)： 05208307
2012 年 4 月 20 日
外文資料翻譯譯文
塑料工業(yè)是與國(guó)民經(jīng)濟(jì)發(fā)展和社會(huì)文明建設(shè)息息相關(guān)的重要產(chǎn)業(yè)。塑料工業(yè)的機(jī)械和裝備的水平對(duì)該工業(yè)的發(fā)展起著關(guān)鍵作用。比起傳統(tǒng)的塑料擠出機(jī)，單螺桿塑料擠出機(jī)有他積極的優(yōu)勢(shì)，通常他能加工出高分子量、高粘度熱塑性好的塑料。其中有高生產(chǎn)率低熔點(diǎn)、高熔體強(qiáng)壓力的塑料有利于化學(xué)降解，產(chǎn)品質(zhì)量高，品，因此是最佳的塑料生產(chǎn)這使得單螺桿塑料擠出機(jī)生產(chǎn)經(jīng)濟(jì)，特別適用于穩(wěn)定的擠壓。
螺桿的回轉(zhuǎn)航程和固定筒壁的相互作用是擠出機(jī)的泵出過(guò)程中必要的參數(shù)。為了運(yùn)輸塑料材料，其摩擦在螺桿的表面要低，但在固定的筒壁要高。如果達(dá)不到這個(gè)基本標(biāo)準(zhǔn)，塑料可能會(huì)隨著螺桿旋轉(zhuǎn)，而不是在軸向/輸出方向上移動(dòng)。在輸出區(qū)域，螺桿和機(jī)筒的表面通常都覆蓋著的溶解物以及來(lái)自溶解物和螺桿通道之間的外力，而其除了 處理有極高粘性的材料時(shí)都是無(wú)效的，如硬質(zhì) PVC 材料和有超高分子量的聚乙烯。溶解物流在輸出部分是 受內(nèi)摩擦系數(shù)（粘度）影響，尤其是當(dāng)模具提供了一個(gè)高阻力的熔體流時(shí)。
常見且更多使用的單螺桿型使用的是傳統(tǒng)設(shè)計(jì)，即機(jī)筒和螺桿保持基本一致的直徑，包括具有例如減小螺 桿通道體積，有連續(xù)可變速度、壓力控制，和通風(fēng)（揮發(fā)）系統(tǒng)的擠出機(jī)。一些特殊的設(shè)計(jì)使用了圓錐或 拋物線外形的螺桿，用以達(dá)到特殊的混合和捏合效果。它們可以包含偏心的核心，根據(jù)不同坡度變化的動(dòng) 程，揉捏轉(zhuǎn)子，適應(yīng)性的核心環(huán)，和間歇的軸向運(yùn)動(dòng)。桶內(nèi)可能有螺紋，可伸縮的螺桿形狀以及進(jìn)料設(shè)備。
一個(gè)成功的擠出操作需要密切注意很多細(xì)節(jié)，如（1）進(jìn)給材料的質(zhì)量和在適當(dāng)溫度下的物質(zhì)流，（2）足以 融化、但不會(huì)分解聚合物的溫度曲線，以及（3）不會(huì)分解塑料的啟動(dòng)和關(guān)機(jī)。
應(yīng)采取措施，防止促進(jìn)塑料表面上水分的膠合和濕氣的吸收凝結(jié)，如顏料濃縮物中的色素。表面凝結(jié)，可 通過(guò)儲(chǔ)存于密封的塑料容器（吸濕性塑料）中在使用前約 24 小時(shí)與工作區(qū)域保持同溫來(lái)避免。如果懷疑顏 色母料有吸濕，可以在 250 至 300 ℉（ 120 -150 ℃）加熱 8 至 16 小時(shí)，烘箱應(yīng)充分干燥。料斗干燥機(jī)已被 證明在干燥塑料中非常有用。它們還可以在操作中提高擠出機(jī)受加熱和熔解能力限制的輸出的能力。圖 顯示了與加熱輸入擠出機(jī)所需的熔化塑料，有或沒(méi)有料斗干燥機(jī)作為預(yù)熱器時(shí)相關(guān)的不同。擠出機(jī)使塑料 熔體均勻熔化，并使之通過(guò)與產(chǎn)品的橫截面形狀關(guān)聯(lián)的模具口。所形成的 TP 的熔體（擠出的）是冷了卻的，或是加熱的TS熔體，因?yàn)樗窍蛳路胖玫倪M(jìn)而得以遠(yuǎn)離模具出口或是通過(guò)下游設(shè)備拔出。
外文原文
Plastic industry is an industry relation to national economy development 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 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 particularly stable extrusion so that output, pressure and melting temperature surges are prevented.
The essential parameter in the extruder’s 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 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 between 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 die 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 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 internal 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 startup 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 container (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 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 product’s 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.