外文翻譯--在先進的結構發(fā)泡成型中獲得一個有高間隙率方法的研究

1、<p>　　在先進的結構發(fā)泡成型中獲得一個有高間隙率方法的研究</p><p>　　John W. S. Lee, Jing Wang, Jae D. Yoon, and Chul B. Park</p><p>　　摘要：結構性泡沫提供比它們同類更多的優(yōu)點,包括更大的幾何準確性、最終產品的表面上沒有凹痕,較低的重量(由此延伸的需要以較低的材料),和更高的剛度與重量的比率。用傳統(tǒng)

2、的結構實現(xiàn)一個合適的空隙率在結構泡沫發(fā)泡成型方法已經有一些成功;這些方法允許小的控制和產量大的孔洞及非均勻的單元結構。本文章報告使用一種先進的結構發(fā)泡成型機以一個高的空隙率，達到一個統(tǒng)一的單元結構。我們研究以下方面:注塑工藝參數(shù)流量、吹氣的理論容量,和熔體溫度。在內部的剖面壓力不同的加工條件下的模腔內研究了塑料的成核和生長。通過優(yōu)化工藝條件,所有我們取得了一個統(tǒng)一的單元結構和非常高的空隙率(40%)。</p><p&

3、gt;<b>　　1.簡介：</b></p><p>　　結構成型是塑料成型所使用的一種傳統(tǒng)的注塑機。一種用物理吹劑(PBA),另一種用化工吹劑(CBA),或者兩者都被選用,在這個過程中,產生一種單元(泡沫)結構。這種結構性泡沫成型的優(yōu)點有缺乏凹痕的最后一個部分的表面上,一個減了體重,低背壓,更快捷的生產周期時間,具有相當高轉速.因為這獨特的優(yōu)勢,低壓預塑式結構發(fā)泡成型技術中得到了廣泛的應用

4、制造大產品,需要幾何精度。</p><p>　　實現(xiàn)一個適當?shù)目障堵试诮Y構泡沫使用傳統(tǒng)的注塑機并沒有證明是非常成功的,但由于這些成型方法允許小的控制和產量大的孔洞及非均勻的細胞結構。獲得一種統(tǒng)一的單元結構具有高空隙率、機器必須能先具有一張完全溶解和均勻的氣體混合物的沒有任何氣體的口袋。如果一個統(tǒng)一的單一氣體解決方案不是達到前發(fā)泡,將很難獲得一種統(tǒng)一的細胞結構發(fā)泡制品。在決策中，為滿足這一需求，要求一種先進的結構發(fā)

5、泡成型技術與連續(xù)聚合物發(fā)展,該技術有利于均勻的離散和溶解氣體的聚合物熔體在成型過程中,從而保護的產生對難溶氣體大口袋。在一個我們展示了以前的工作,用一個定制的可行性小注塑系統(tǒng)組成的一個微型注射單位和發(fā)泡擠出機，基于這種新技術。然而,除了改善硬件技術,它也是必要開發(fā)適當?shù)奶幚聿呗砸钥刂萍毎L成核和模具型腔內。</p><p>　　在此背景下,當前一些探討處理策略需要獲得一個統(tǒng)一的高間隙先進的結構發(fā)泡成型工藝單元結

6、構。我們調查了下列重要參數(shù):吹劑含量、注入流量、熔體溫度。使用我們的結構性泡沫獲得先進的成型技術進行表征方面的空隙率、細胞密度、細胞三維地形尺寸分布;x射線用來描寫的三維結構泡沫細胞的組織形態(tài)。內部的壓力剖面下模具型腔也被記錄在案，為了更好的理解不同加工條件下細胞的形核、長大的行為。</p><p><b>　　2.研究背景：</b></p><p>　　近年來,泡沫

7、塑料注射成型的優(yōu)勢已經引發(fā)了改進結構發(fā)泡成型技術。Trexel公司開發(fā)了一種微往復式注射成型技術的基出上,對預塑式注塑機進行了大量的工作。以進一步改善質模板在微孔發(fā)泡過程中使用了微結構成型。Turng，蘇達權等, ,研究了改變工藝條件的影響上,特別是在當前國內外微孔結構的例子, 混合成型用結構.何振平，高慶宇報道的創(chuàng)造與微孔發(fā)泡細胞的結構和表面質量良好使用了共聚物聚碳酸脂(PC).尹恩惠，孫俐，在當前國內外微孔形貌控制的聚丙烯(PP)等

8、課程教學中存在的報道說,有一個高慶宇甲級的表面和高空隙率可以達到通過使用一個透氣通道.發(fā)泡等,綜述了最近高慶宇的微孔復合材料的新型高分子材料和鋼筋與礦物填料及自然光纖。</p><p>　　Shimbo報道, 在典型的結構成型工藝另一種微孔發(fā)泡過程中注塑機，使用了一個預塑式注塑機被用來塑化螺柱塞聚合物,是用來注入聚合物進入模具腔,另一個替代方案泡沫注射成型工藝是在發(fā)達的德國亞琛的一個系統(tǒng),在這個系統(tǒng)中,氣體注射在

9、一個特別設計的噴油嘴，它安裝在塑化單元之間的，可對噴嘴關閉的常規(guī)射出成型機。此外,它達到更好的分散性之氣, 靜態(tài)混合元素被安裝之間的氣體噴油嘴和關閉噴嘴。這項技術后來為商業(yè)化專利。</p><p>　　在2006年, 有人提出了一個結構,經過在先進的高慶宇發(fā)泡成型技術的基礎上,預塑式注射機傳統(tǒng)的結構發(fā)泡技術這樣就提高了注入氣體會完全溶解在聚合物。由一個強化技術的齒輪油泵及附加蓄能器使聚合物/氣體混合物形成一步連續(xù)

10、不斷的成型操作。換句話說,更新的設計完全解耦,氣體溶解步驟的注塑操作使用一個主驅動泵。這一先進的結構發(fā)泡的細節(jié) 技術概述在下一節(jié)。</p><p>　　3.先進的成型結構:</p><p>　　先進的成型機。經過先進的發(fā)泡成型機器.這種技術促進統(tǒng)一的氣體色散和完整(或實質)溶解在聚合物熔體,盡管是穩(wěn)定成型工藝。但是它認識到連續(xù)成型行為不可避免地引起不一致的氣體充填、這種結構使得流動但是聚合

11、物熔體和天然氣是連續(xù)的(即不停止在注射時期)。</p><p><b>　　圖1</b></p><p><b>　　圖3-4</b></p><p>　　圖1顯示的原理圖結構,經過先進的泡沫成型機在發(fā)達的Toronto大學的這臺機器包含了一主驅動泵(例如:一個齒輪泵)和額外的蓄電池、附于擠壓桶和之間的關斷閥。(一個位于前

12、關閉閥門柱塞,另一種是位于噴嘴處。)此設計完全減弱氣體溶解步驟的注塑操作使用和維護主動驅動泵齒輪泵的穩(wěn)態(tài)氣體溶解作用。在注塑業(yè)務,橡膠壓片機壓出的螺桿轉動,而生成聚合物/氣體混合物收集在加時賽的蓄電池。后兩者混合遭受到注塑和收集到的,它移動通過柱塞機制進入到下一個周期。這項技術確保了壓力,在擠壓桶內保持相對穩(wěn)定,達到一致的氣體充填是這樣一個統(tǒng)一的聚合物/氣體混合物是取得了不管壓力波動柱塞。這項技術已經成為商業(yè)專利。</p>

13、<p>　　均勻分布和完全溶解吹塑過程保持一致的氣體充填的聚合物和替代或近乎溶解所有的氣體在聚合物熔體,螺桿必須保持相對穩(wěn)定的自轉時，在螺桿的優(yōu)點是恒轉速移動一倍。首先,一致的氣體充填是容易實現(xiàn):由于壓力波動的擠壓桶內減至最低。第二,維持一個高壓力下確保解散的注入氣體進入聚合物熔體。一個統(tǒng)一的聚合物/氣體混合物,其中的氣體已經完全(或實質上)溶解, 為改善制品塑料結構。</p><p>　　就需要有一

14、個常數(shù)溶氣/重量配比提供理論依據(jù)。</p><p><b>　　表1</b></p><p><b>　　圖5</b></p><p><b>　　圖6</b></p><p>　　圖7 .瓦斯含量的影響和注入流量等泡沫的形態(tài)</p><p>　　一個齒

15、輪油泵是一種最基本的組成部分,因為它提供了一份改進工藝恒體積流率對聚合物/氣體混合物;泵上的壓力,從而控制的擠壓,并允許一個一致的連續(xù)性桶重量比為粘性聚合物熔體,壓力在擠壓酒桶保持相對穩(wěn)定,因為這種積極的位移的齒輪泵。由于氣體流量壓力取決于在桶顯著,恒氣流量可以通過保持固定的壓力,在擠壓桶。聚合物/氣體混合物能夠控制的變轉速的齒輪泵。通過獨立控制的流動速率兩種氣體與聚合物/氣體混合物,這種聚合物流量也可以被控制住。因此,既有一致的重量比

16、”,并獲得統(tǒng)一流動聚合物/氣體混合物可以很容易地實現(xiàn)與齒輪泵。這些優(yōu)勢不能被輕易的做到了,用一個關閉或止回閥。背后的基本原理與裝備新模型具有額外的蓄能器來源于需要適應這個混合物在每個周期的注射期間使螺桿可以勻速旋轉和煤氣可以不斷的注入melt.4不斷旋轉螺桿是一種重要的差異,從以前所有的結構發(fā)泡成型技術是基于低壓塑料注塑系統(tǒng)。一旦是壓力相對穩(wěn)定的擠出桶,它會變得更容易控制的流量,注入氣體的高分子,和氣體即可更為均勻散布到融化</p

17、><p>　　圖8 .細胞密度測量的地點A-C(0.3硅油%氮氣)。</p><p>　　當一個一致的氣體聚合物量比,實現(xiàn)了注入氮氣,有一個非常低的溶解性,可完全溶化,如果一個足夠高的壓力保持在這兩種擠壓桶和累加器?！白銐蚋叩膲毫Α币馕吨垠w壓力遠高于溶解性的壓力進行了給定的氣體的注入聚合物熔體。此外,保持了足夠高的壓力后的油已經完全溶解,防止形成第二階段在聚合物熔體在積累階段。因為溶解性的壓

18、力進行了瓦斯含量要求產生一個fine-celled結構[例如,為0.1-1.0% N2期的140-1400 psi的高密度聚乙烯(HDPE)在200°C]17號低比壓極限存在的低壓預塑式結構性泡沫成型機(最大許用壓力≈3000 psi),一個足夠高的壓力就可以很容易地保持先進的結構發(fā)泡成型機。</p><p><b>　　4.結果和討論：</b></p><p&

19、gt;　　加工參數(shù)的影響程度,充模。圖4顯示了吹劑的影響(氮氣)和溫度對泡沫融化程度充滿了模具。卒中是用于不同的注入不同數(shù)目的N2為了達到不同的空泡內餾份:60,50,和40毫米,和0.5 ，0.1,0.3硅油%氮氣,分別。這些注入中風占期末無效的分數(shù)占17%,31%和45%,分別。</p><p>　　很清楚,氮氣含量和噴射流量中起到了至關重要的作用,在確定充填型腔的程度。充填型腔的程度隨氮氣含量和注入流量而增

20、加。因為低壓結構發(fā)泡成型使用一種近程注射,在這個過程中,依靠泡沫膨脹以填充模子腔。</p><p>　　一個更高的氮氣含量增加的程度,從而提高了泡沫膨脹模具，也是值得注意是由高細胞密度增加氮氣含量是另一個推動力的創(chuàng)作中較大的空系率。 注射充模流動速率也受到了影響。因為在何種程度上的不同,熔體冷卻流量、更高注射注塑流動速度下降冷卻速率在注射過程中,這導致熔融粘度較低,同時,也增加了聚合物的力學性能。此外,因為熔體溫

21、度比較高,在高注入流量、時間較長的細胞形核、長大。應該指出的是,晶核的成核和生長在模具型腔熔體溫度降低會了停一下下面的結晶溫度。</p><p><b>　　5.總結:</b></p><p>　　在這項研究中，實驗對各種材料的低壓注塑成型加工條件進行了調查，注射流量和模腔平均壓力在注塑中起到了至關重要的作用，它也發(fā)現(xiàn)氮氣的數(shù)量對形成致密的單元結構很重要。當?shù)獨夂刻?/p>

22、低(即,0.1硅油%),空腔壓降成核率會下降并導致制品的密度過低。另一方面,當?shù)獨夂孔銐蚋?例如,0.3硅油%及以上),會導致制品密度過高。我們還發(fā)現(xiàn),沒有一個合適的阻力，我們不可能獲得一個統(tǒng)一的制品結構和較高的制品精度。通過優(yōu)化所有的壓力加工條件,我們就能實現(xiàn)一個統(tǒng)一的細單元結構和較高的制品精度(接近40%)。</p><p><b>　　參考文獻</b></p><

23、p>　　(1) Hornsby, P. R. Thermoplastics Structural Foams: Part 2 Properties and Application. Mater. Eng. 1982, 3, 443.</p><p>　　(2) Ahmadi, A. A.; Hornsby, P. R. Moulding and Characterization Studies with P

24、olypropylene Structural Foam, Part 1: Structure-Property Interrelationships. Plast. Rubber Process. Appl. 1985, 5, 35.</p><p>　　(3) Hikita, K. Development of Weight Reduction Technology for Door Trip Using F

25、oamed PP. JSAE ReV. 2002, 23, 239.</p><p>　　(4) Park, C. B.; Xu, X. Apparatus and Method for Advanced Structural Foam Molding. U.S. Patent Application 11/219,309, filed Sep 2, 2005;</p><p>　　Str

26、ategies to Achieve a Uniform Cell Structure with a High Void Fraction in Advanced Structural Foam Molding</p><p>　　ABSTRACT：Structural foams offer numerous advantages over their solid counterparts, including

27、 greater geometrical accuracy, the absence of sink marks on the final product’s surface, lower weight (and, by extension, the need for less material), and a higher stiffness-to-weight ratio. The possibility of achieving

28、a suitable void fraction in structural foams using conventional structural foam molding methods, however, has been of limited success;these methods allow for little control and typically y</p><p>　　Introduct

29、ion</p><p>　　Structural foams are plastic foams manufactured using ，conventional preplasticating-type injection-molding machines. A physical blowing agent (PBA), chemical blowing agent，(CBA), or both are emp

30、loyed in the process to produce a cellular (foam) structure. The advantages of structural foam molding，include the absence of sink marks on the final part’s surface, a reduced weight, a low back pressure, a faster produc

31、tion cycle ，time, and a high stiffness-to-weight ratio.1-3 Because of this unique set </p><p>　　Background</p><p>　　In recent years, the advantages of foam injection molding have prompted improv

32、ements in structural foam molding technologies. Trexel Inc. developed a microcellular injection molding technology (MuCell technology) based on a reciprocating-type injection molding machine.6,7 A great deal of work has

33、been carried out to further improve the quality of the microcellular foams produced using the MuCell process. Turng et al., for example, investigated the impact of changing processing conditions on the </p><p&

34、gt;　　In 2000, Shimbo reported an alternative microcellular foam process that employed a preplasticating-type injection molding machine.14 A screw was used to plasticate the polymer, and a plunger was used to inject the p

35、olymer into the mold cavity as in typical structural molding. Another alternative foam injection molding process was developed at IKV, Aachen, Germany.In this system, gas was injected in a specially designed injection n

36、ozzle mounted between the plasticizing unit and the shut-off nozz</p><p>　　This technology was later commercialized by Sulzer Chemtech.</p><p>　　In 2006, Park et al. presented an advanced struct

37、ural foam molding technology based on a preplasticating-type injection molding machine.4,5 The conventional structural foaming technology was improved such that the injected gas would completely dissolve into the polymer

38、. The enhanced technology consisted of a gear pump and an additional accumulator to make the polymer/gas mixture formation step continuous regardless of the stop-and-flow molding operations. In other words, the newer des

39、ign complet</p><p>　　This technology4 promotes uniform gas dispersion and complete (or substantial) dissolution in the polymer melt, despite the non -steady molding process. Recognizing that stop and-flow m

40、olding behavior inevitably causes inconsistent gas dosing, this design allows the flows of the polymer melt and gas to be continuous (i.e., not to stop during the injection period</p><p>　　Figure 1 shows a s

41、chematic of the advanced structural foam molding machine developed at the University of Toronto.4 This machine comprises a positive-displacement pump (i.e., a gear pump) and an additional accumulator, which is attached b

42、etween the extrusion barrel and the shut-off valves. (One shut-off valve is located before the plunger, and the other is located at the nozzle.) The design completely decouples the gas dissolution step from the injection

43、 and molding operations using the positive</p><p>　　Homogeneous Distribution and Complete Dissolution of Blowing Agent. </p><p>　　To maintain consistent gas dosing of the polymer and to complete

44、ly or near-completely dissolve all of the gas in the polymer melt, the screw must rotate at a relatively constant speed.4 The advantages of having the screw move ata constant rotational speed are two-fold. First, consist

45、ent gas dosing is easily realized because the pressure fluctuations inside the extrusion barrel are minimized. Second, maintaining a high pressure guarantees the dissolution of the injected gas into the polymer melt.<

46、/p><p>　　A gear pump is an essential part of the improved process because it provides a constant volume flow rate for the polymer gas mixture; the pump thereby controls the pressure in the extrusion barrel and

47、allows a consistent polymer-to-gas weight ratio to be maintained.4 For viscous polymer melts, the pressure in the extrusion barrel is relatively constant because of the positive displacement of the gear pump. Because the

48、 gas flow rate depends significantly on the barrel pressure, a constant gas flo</p><p>　　The rationale behind having outfitted the new model with an additional accumulator derives from the need to accommodat

49、e the mixture during each cycle’s injection period so that the screw can rotate at a constant speed and the gas can be continuously injected into the melt.4 The constantly rotating screw represents a significant differen

50、ce from all previous structural foam molding technologies that are based on the low-pressure preplasticating-type system. Once the pressure in the extrusion barre</p><p>　　Although the advanced structural mo

51、lding machine features modifications that allow for the complete dissolution of gas into a polymer melt while a constant gas-to-polymer weight ratio is maintained,4,5 this system design does not automatically guarantee t

52、he production of high-quality foams. To produce high quality foams with uniform cell structures and a large void fraction, a set of overall conditions must be satisfied; these conditions are described below.</p>&

53、lt;p>　　In addition to the formation of a foamable polymer/gas mixture with a uniform and constant polymer/gas weight ratio, the mold geometry including the gate shape should be designed properly.</p><p>

54、　　Once the hardware machinery has been properly designed and constructed, appropriate material compositions should be selected and fed into the system. Both the molecular weight and structure variation of the plastic res

55、in and the type and content of added materials, such as the nucleating agent, the blowing agent, and any other additives or fillers, should be prudently selected because all of these materials and their compositions affe

56、ct the cell nucleation and growth behaviors.</p><p>　　Results And Discussion. </p><p>　　It should be also noted that the measured void fractions inFigure 4 were higher than the set void fraction

57、. If the void fractions of the sprue, runner, and injection-molded parts had been uniform, the measured void fraction from the molded part would be the same as the set void fraction. However, in reality, the void fractio

58、ns of the spure and runner were observed to be lower than that of injection-molded part. This must have been caused by the higher pressure in the sprue and runner compared to</p><p>　　Some large bubbles were

59、 observed in the foam, however, when 0.5 wt % N2 was used. There might have been several reasons for this, as discussed earlier, but most likely, a content of 0.5 wt % was too high because of N2’s low solubility The cavi

60、ty pressure of a foaming mold has a significant influence on cell nucleation. If the cavity pressure is lower than the solubility pressure (or the threshold pressure22) of the injected gas and if the pressure before the

61、gate is high enough, cell nucleation </p><p>　　To achieve a high cell density and uniform cell structures in low-pressure structural foam molding, several requirements should be met with respect to the mold

62、pressure profile. Figure 13 shows the proper pressure profiles in low-pressure structural foam molding. First, the pressure before the gate should be kept higher than the solubility (or threshold) pressure to prevent pre

63、mature cell nucleation and growth. This pressure can be controlled by properly choosing the resistance of the gate and t</p><p>　　Conclusion</p><p>　　I n this study, experiments were conducted t

64、o investigate the effects of various materials and processing conditions on injection-molded foams in low-pressure structural molding. The injection flow rate played a critical role in the degree of filling and the cavit

65、y pressure profile. It was also found that the amount of N2 was important for achieving a high cell density. When the N2 content was too low (i.e., 0.1 wt %), the cavity pressure drop rate governed cell nucleation and le

66、d to the product</p><p>　　References </p><p>　　(1) Hornsby, P. R. Thermoplastics Structural Foams: Part 2 Properties and Application. Mater. Eng. 1982, 3, 443.</p><p>　　(2)

67、 Ahmadi, A. A.; Hornsby, P. R. Moulding and Characterization Studies with Polypropylene Structural Foam, Part 1: Structure-Property Interrelationships. Plast. Rubber Process. Appl. 1985, 5, 35.</p><p>　　(3)

68、Hikita, K. Development of Weight Reduction Technology for Door Trip Using Foamed PP. JSAE ReV. 2002, 23, 239.</p><p>　　(4) Park, C. B.; Xu, X. Apparatus and Method for Advanced Structural Foam Molding. U.S.