模具設(shè)計(jì)外文翻譯（中文）--模具設(shè)計(jì)對(duì)微孔泡沫注塑技術(shù)mucell生產(chǎn)的聚合物孔結(jié)構(gòu)的影響

1、<p>　　編號(hào)： </p><p><b>　　中文6400字</b></p><p>　　畢業(yè)設(shè)計(jì)(論文)外文翻譯</p><p><b>　?。ㄗg文）</b></p><p>　　學(xué) 院： 機(jī)電工程學(xué)院 </p>&l

2、t;p>　　專(zhuān) 業(yè)：機(jī)械設(shè)計(jì)制造及其自動(dòng)化</p><p>　　學(xué)生姓名： </p><p>　　學(xué) 號(hào)： </p><p>　　指導(dǎo)教師單位： 藝術(shù)與設(shè)計(jì)學(xué)院 </p><p>　　姓 名： </p>

3、<p>　　職 稱(chēng)： 講師 </p><p>　　2012年 5 月 15 日</p><p>　　出處：JOURNAL OF CELLULAR PLASTICS Volume 46 — November 2010</p><p>　　The Effects of Mold Designon the Pore Mo

4、rphology ofPolymers Produced withMuCell_ Technology</p><p>　　ABSTRACT: </p><p>　　In this study two molds were designed and used in MuCell_technology to generate implants with a porous structure.

5、 To arrive the desiredpore structure many process parameters were investigated for indicating theeffects of process parameters on the pore morphology. This process parameterinvestigation was performed on each mold respec

6、tively, so that the influencesof the mold design on the pore morphology have been researched by the sameprocess parameter setting. It was found that the mold design al</p><p>　　KEY WORDS: mold design, cell m

7、orphology, MuCell_, injection molding,medical implant, porous polymer, polyurethane.</p><p>　　INTRODUCTION</p><p>　　MuCell technology, as an effective microcellular injection moldingprocess, is

8、widely used in automobile and furniture industries.In most cases, MuCell_ technology is used to save raw materials, but itis also used to produce implants with closed porous structure [1]. It usesCO2 as blowing agent, wh

9、ich is injected in the plasticization section ofthe injection molding machine (Figure 1). The blowing agent is injectedinto the polymer melt through the gas supply line and injector, in itssuper critica</p><p&

10、gt;　　The MuCell Microcellular Foam injection molding technology is a complete process and equipment technology which facilitates extremely high quality and greatly reduces production costs.  The MuCell Process invol

11、ves the controlled use of gas in its supercritical state to create a foamed part. The MuCell Technology is targeted at precision and engineered plastic components with maximum wall thicknesses of less than 3mm.The MuCell

12、 Process generally offers a 50-75% improvement in key quality measures</p><p>　　reduction and design for functionality often results in material and weight savings of more than 20%. </p><p>　　By

13、 replacing the pack & hold phase with cell growth, lower stress parts are produced which have enhanced dimensional stability and substantially reduce warpage. Cell growth also results in the elimination of sink marks

14、.</p><p>　　Unlike chemical foaming agents, the physical MuCell process has no temperature limitation and does not leave any chemical residue in the polymer; making consumer products perfectly suitable for re

15、cycling within the original polymer classification and allowing re-grind material to reenter the process flow. </p><p>　　The numerous cost and processing advantages have led to rapid global deployment of the

16、 MuCell process primarily in automotive, consumer electronics, medical device, packaging and consumer goods applications.Microcellular foams refer to thermoplastic foams with cells of the order of 10 µm in size. Typ

17、ically these foams are rigid, closed-cell structures; although recently there is much interest in creating open-cell, porous structures that have cells in this size range. The microcellular process t</p><p>

18、　　It would be reasonable to say that the potential of microcellular foams has yet to be realized. These materials have not yet appeared in mass produced plastic items, and the promised savings in materials and associated

19、 costs have yet to materialize. This is largely due to manufacturing difficulties encountered in scaling up for large scale production. However, enthusiasm for these materials remains high, and today researchers and comm

20、ercial enterprises on every continent are in a global race to </p><p>　　Much has been learned about the processing and properties of microcellular foams since the first patent was granted in 1984 [2]. An ear

21、ly review of the subject appeared in 1993 [3]. In this chapter the state-of-the art of processing will be reviewed in the next section, followed by a discussion of structure and properties. This chapter will conclude wit

22、h a look at some of the current research directions involving microcellular technology. </p><p>　　Although innovations in processing have developed at a rapid pace, the property data on microcellular foams h

23、as been slow in coming. The early publications on microcellular foams conjectured that the microcellular structure, believed to be on a scale that was smaller than the ‘critical flaw size’ for polymers, would enable thes

24、e foams to retain their mechanical properties even as the density was reduced. No quantitative information on the critical flaw size was ever presented, nor was any proper</p><p>　　The tensile property data

25、[4] shows that the tensile strength of microcellular foams decreases in proportion to the foam density, and can be approximated quite well by the rule of mixtures. Thus a 50% relative density foam can be expected to have

26、 50% of the strength of the solid polymer. Figure 11.5 shows relative tensile strength as a function of relative foam density for a number of microcellular polymers. In this figure the relative tensile strength, is obtai

27、ned by dividing the tensile streng</p><p>　　Fatigue and creep behaviours of microcellular polycarbonate foams have been investigated [8-10]. An interesting result from fatigue studies is that introduction of

28、 very small bubbles in PC, with less that 1% reduction of density, led to a thirty-fold increase in fatigue life compared to the solid PC. This might suggest a process similar to heat treatment of metals, where a PC part

29、 may be saturated with carbon dioxide at 5 MPa and then heated to say 60 ºC to introduce the microcellular structure </p><p>　　The tensile data for all gas-polymer systems investigated falls on one redu

30、ced plot where relative tensile strength can be plotted against the relative density, as is shown in Figure 11.5. However, energy absorption measures, such as an impact test, are more sensitive to variations from polymer

31、 to polymer, and the results cannot be generalized. Gardner Impact Strength for PVC foams [11] with relative densities of 0.5 and higher. It is seen that the impact strength decreases linearly with foam de</p><

32、;p>　　Some studies have investigated the relations between the key processparameters in MuCell_ technology and produced cellular foam structure[1,5,6]. It was found that the pore morphology in MuCell_ process couldbe a

33、djusted through varying the process parameters. However, there iscurrently no literature regarding the effects of mold design on the poremorphology by MuCell_ technology.</p><p>　　In this study two molds wer

34、e designed and used in MuCell_ process togenerate implants with a porous structure for medical use. The researchof process parameters was independently performed on these two molds.By comparing the pore structure of impl

35、ants made from two molds atthe same process parameter setting, the influences of the mold design onthe porous structure were investigated.</p><p>　　Figure 1. Draft of the MuCell_ technology</p><p&

36、gt;　　MATERIALS AND METHODS</p><p>　　Polymer ProcessingMedical grade thermoplastic polyurethane TPU (Texin_ 985, Bayer,Pa, USA) was chosen as raw material for the implant. An injectionmolding machine (KM 125-

37、520C2, KraussMaffei Technologies GmbH,Munich, Germany) with a temperature control unit for cooling the mold(90S/6/TS22/1K/RT45, Regloplas, St. Gallen, Switzerland) was used forthe production of the samples. The injection

38、 molding machine wasequipped with a MuCell_ package by the Trexel Inc., Woburn, MA, USA.The MuCell_ package i</p><p>　　CO2 was used as blowing agent (CO2 protective gas DIN-32525-C1,Westfalen AG, Mu¨nst

39、er, Germany).</p><p>　　In order to produce the implant, two particular molds were designedand used. The technical drawings of molded parts from mold A and moldB are shown in Figure 2. The mold A had six ring

40、 shaped implantsand was just used for the preliminary test of the feasibility of thefoaming process and parameter research. The mold B was designed withsix solid disk shaped implant based on the results of in vivo test o

41、fimplants from mold A, for a higher biological requirement andprospective production.</p><p>　　Figure 2. Different mold designs.</p><p>　　Two molds have similar gate, runner, and sprues. The mol

42、d B has ashorter polymer melt flow of mold cavity and the L/D (length/thickness)of 2.8, whereas this L/D for mold A is 4.7. This means the molded partfrom mold B is relatively thicker but shorter. The advantage of mold B

43、 isthat the energy loss of melt flow, which dominates the cell nucleationand growth, is reduced due to the shorter flow path (low L/D). As aresult better pore morphology, such as bigger mean pore size, higherporosity, an

44、d so</p><p>　　Experimental Strategy</p><p>　　The choice of the changeable parameters was made based on theknowledge given by nucleation theory and literature search [5,7]. Theranges of variable

45、parameters and the values of fixed parameters arepresented in Table 1. The experiments were done by varying one of variable parameters while keeping the others constant. The wholeprocess parameters investigation was perf

46、ormed on two molds respectively.The implants from two molds, which were used to be compared,were produced at exactly same process p</p><p>　　Characterization of Macro- and Microstructures</p><p>

47、;　　Scanning electron microscopy (SEM; Jeol JSM-6060LV, JEOL Ltd.,Tokyo, Japan) was used for the observation of the pore morphology ofthe cross section of implant. The samples were sliced with a scalpel andthen coated wit

48、h a thin gold layer by using a sputter-coater (SCD 005,BAL-TEC AG, Balzers, Lichtenstein) under high vacuum with a voltagerange between 5 and 15 kV. Characteristics of porous structure such aspore size and porosity can b

49、e calculated by counting the average cellnumber and size of sev</p><p>　　One cut area with certain size was chosen and all pores were measuredmanually with the help of software of digital microscope (VHX-500

50、, Keyence Corporation, Osaka, Japan). The average diameter ofpores was calculated as Dmeasured. Due to the fact that the pores shownin the micrographs are 2D projections of 3D objects, their maximumdiameter may not be re

51、presented in the image. Following equation wasused for determination of the maximum spherical diameter, namedcorrected median pore diameter, from </p><p><b>　?。?）</b></p><p>　　MicroC

52、T (SkyScan 1172, SkyScan, Kontich, Belgium) was used toquantitatively measure the porous interconnectivity of implants – three8mm_11mm cylindrical samples from each implant (n3) at 7 mmresolution using a voltage of 59 kV

53、, and a current of 167 mA. Imagereconstruction and analysis were conducted using the software packageprovided by SkyScan. Samples were rotated 1808 around their long axisand three absorption images were recorded every 0.

54、400o of rotation.These raw images of the samples were </p><p>　　The image analysis of the reconstructed axial bitmap images wasperformed using the standard SkyScan software (CTan and CTvol).First, a threshol

55、ding analysis was performed to determine the thresholdvalue for which the greyscale tomograms of scaffolds were mostaccurately represented by their binarised counterparts in terms ofporosity. The threshold value was set

56、between 65 and 225 for this study.Additional noise was removed by the ‘despeckling’ function. All objectssmaller than 500 voxels and not </p><p><b>　　（2）</b></p><p>　　All images unde

57、rwent 3D analysis, followed by the quantification ofinterconnectivity using the ‘shrink-wrap’ function, which allows measuringthe fraction of pore volume in a scaffold that was accessible fromthe outside through openings

58、 of a certain minimum size [8]. A shrinkwrapprocess was performed between two 3D measurements to shrinkthe outside boundary of the VOI in a scaffold through openings the sizeof which was equal to or larger than a thresho

59、ld value (0–280 mm wereused in this study). I</p><p><b>　　（3）</b></p><p>　　RESULTS AND DISCUSSION</p><p>　　The SEM images (Figure 3) show the pore structures of foamedim

60、plants from two molds in the injection speed variation with value of30 mm/s, when the other process parameters were kept unchanged(weight reduction of 35%, plasticizing temperature of 1808C, plasticizingpressure of 180 b

61、ar, mold temperature of 258C, and gas content of 2%). Itwas found that the left image, which came from the foamed implantfrom mold B, showed a significant larger pore size than right image frommold A. The interconnecti&l

62、t;/p><p>　　Figure 3. Different pore structures of mold B (left) and mold A (right) at the injectionspeed of 30 mm/s.</p><p>　　Figure 4. Differences of the porosity at injection speed variation.<

63、/p><p>　　It was found from Figure 4 that the implants from mold B at everydifferent injection speed had a higher porosity than the implants frommold A. The porosity range of implants from mold B was between 73%

64、and 79%, whereas by mold A this porosity range was between 60% and67%. At the same time the standard deviation of the porosity from moldB was significantly smaller than the deviation by mold A.</p><p>　　Figu

65、re 5. The mean pore size from two molds at different injection speeds</p><p>　　Figure 5 shows the mean pore size of two molds by different injectionspeeds. The pore size decreased with rise of the injection

66、speed for twomolds. The same result was also found by other study [11]. The porediameter of the implants from mold B decreased from 340_17 mm to246_20 mm with injection speed increase; the mold A showed the porediameter

67、from 234_90 mm to 152_34 mm by the same injection speedvariation. The mean pore size from mold B at every speed was alsohigher compared with mold A. It </p><p>　　Figure 6 shows the interconnective pore size

68、of foamed implants. Theinterconnective pore size is very important for the tissue in growth inBiology. The interconnective pore size of foamed implants from mold Bhad a range of 91_6 mm to 67_7 mm; by mold A this range w

69、as35_10 mm to 19_8 mm. This change was also corresponding to thefinding in the mean pore size of foamed implants from two molds.</p><p>　　It could be concluded from Figures 3–6 that the improved mold designo

70、f mold B could not affect the change tendency of pore structure, such asdecreased pore size with rise of the injection speed, but it could increasethe porosity and the mean pore size as well as the interconnective poresi

71、ze of the foamed implants. At the same time the standard deviation of pore structure was significantly decreased. In other words the porestructure of foamed implants from mold B had a higher porosity, a largerpo</p>

72、;<p>　　Figure 6. Size of interconnections of implants at different injection speeds.</p><p>　　Figure 7 shows the comparison of the maximal porosity at differentkinds of process parameter variations, i

73、ncluding the injection speed, fromtwo molds. In every kind of process parameter variations, the maximalporosity was always obtained at a same setting value for two molds, suchas 79% and 67% at 300 mm/s by mold B and mold

74、 A for the injection speedvariation. It was observed that mold B indicated a higher maximalporosity at every kind of parameter variation. The porosity at 35% weightreduction </p><p>　　The differences between

75、 the maximal pore sizes at different kinds ofprocess parameter variations of two molds are shown in Figure 8.Implants from two molds showed the maximal pore size also at the sameprocess parameters setting in every kind o

76、f variation. The mold B hasalways a larger maximal pore size than mold A. The minimal elevation ofmaxima pore size of mold B was 14% by the plasticizing temperaturevariation, whereas the maximal elevation of pore size wi

77、th value of 45%was found by the injec</p><p>　　Figure 7. Differences between the maximal porosity at different processing parametersfor two molds.</p><p>　　Figure 8. Differences between the maxi

78、mal pore size at different process parameters fortwo molds.</p><p>　　Figure 7 and 8 have indicated that the improvement of the porestructure, such as maximal pore size and porosity, induced by thechange of m

79、old design could be observed not only in variation of theinjection speed but also in all process parameters variations. Theshortened L/D by mold B led to a decreased energy loss which dominatesthe cell nucleation, during

80、 the polymer melt flow in the mold cavity. Therelative thicker implant from mold B needed also a longer cooling time,which was very important </p><p>　　CONCLUSION</p><p>　　This study was intent

81、to investigate the potential effect of the molddesign on the pore morphology. The improved pore morphology such asthe higher porosity, larger mean pore size, and smaller deviation wasfound by the foamed samples from mold

82、 B. This indicated that besidesthe effects of process parameters, the mold design, that is, productdesign has also a distinct influence on the foam behavior of foamingprocess, which has given the possibility to improve t

83、he pore morphologythrough a more suita</p><p>　　模具設(shè)計(jì)對(duì)微孔泡沫注塑技術(shù)</p><p>　　MuCell生產(chǎn)的聚合物孔結(jié)構(gòu)的影響</p><p><b>　　摘 要</b></p><p>　　在這項(xiàng)研究中，兩副模具都用微孔泡沫注塑技術(shù)MuCell設(shè)計(jì)和使用以生成具

84、有多孔結(jié)構(gòu)的植入物。為了到達(dá)所需孔隙結(jié)構(gòu)，對(duì)許多工藝參數(shù)進(jìn)行了調(diào)查用以說(shuō)明工藝參數(shù)對(duì)孔形態(tài)的影響。這個(gè)過(guò)程參數(shù)的調(diào)查分別在每個(gè)模具上進(jìn)行嚴(yán)格地實(shí)驗(yàn)，這樣模具設(shè)計(jì)對(duì)孔形態(tài)的影響可以通過(guò)相同工藝參數(shù)設(shè)置來(lái)研究。于是研究發(fā)現(xiàn)，模具的設(shè)計(jì)對(duì)MuCell技術(shù)的孔隙結(jié)構(gòu)確有影響。一個(gè)適當(dāng)?shù)哪＞咴O(shè)計(jì)能提高生成的孔隙結(jié)構(gòu)，比如孔隙率，孔徑等，并且互相影響。</p><p>　　關(guān)鍵詞: 模具設(shè)計(jì)，細(xì)胞形態(tài)，微孔泡沫注塑，注塑成型

85、，醫(yī)療植入物，多孔聚合物，聚氨酯。</p><p><b>　　引言</b></p><p>　　MuCell技術(shù)，作為一種有效的微孔注塑加工，被廣泛應(yīng)用于汽車(chē)和家具等行業(yè)。采用微孔泡沫注塑技術(shù)在很多情況下可以節(jié)省原料，并且它可以用于生產(chǎn)具有多孔結(jié)構(gòu)的封閉的產(chǎn)品[1]。這項(xiàng)技術(shù)使用CO2作為發(fā)泡劑，并將其注入到注射機(jī)的塑化部分（圖1）。在供氣線路和噴油器的作用下，被注

86、入的發(fā)泡劑達(dá)到在其超臨界狀態(tài)在在注塑機(jī)的塑化部分成為熔體聚合物。經(jīng)過(guò)塑化的聚合物熔體和氣體混合并通過(guò)噴嘴注入到模具內(nèi)部，在模具內(nèi)快速壓降的影響下就變成了泡沫結(jié)構(gòu)。如今微孔泡沫注塑技術(shù)已經(jīng)可以生產(chǎn)接近蜂窩形狀的泡沫。</p><p>　　MuCell技術(shù)的微孔發(fā)泡注塑成型技術(shù)是一個(gè)完整的工藝和設(shè)備技術(shù)，有利于質(zhì)量非常高，大大降低了生產(chǎn)成本。 MuCell工藝涉及在其超臨界狀態(tài)下氣體的控制使用，以創(chuàng)建一個(gè)泡沫的一部分

87、。 MuCell技術(shù)是有針對(duì)性的技術(shù)精度和工程塑料元件，最大墻壁厚度小于3mm。MuCell工藝質(zhì)量的關(guān)鍵措施，如平整度，圓度和翹曲，也消除了所有的凹痕，一般都提供了一個(gè)提高50-75％。這些改進(jìn)的結(jié)果，在成型零件，而不是固體成型的非均勻應(yīng)力特性建立相對(duì)統(tǒng)一的應(yīng)力模式。作為被淘汰，因?yàn)槿盒鄄⒊钟谐尚椭芷陔A段的MuCell工藝的均勻應(yīng)力和收縮的直接結(jié)果（發(fā)生），所生產(chǎn)的零件往往更為密切的合作符合模具的形狀，大概，部分本身的尺寸規(guī)格。這意味

88、著，使用MuCell工藝時(shí)，需要較少的模具迭代產(chǎn)生一個(gè)標(biāo)準(zhǔn)的組成部分，節(jié)省時(shí)間和成本。MuCell工藝的質(zhì)量?jī)?yōu)勢(shì)，輔以一定的直接的經(jīng)濟(jì)優(yōu)勢(shì)，包括能夠產(chǎn)生一個(gè)給定的注塑機(jī)每小時(shí)20-33％以上，部分低噸位機(jī)器模具的能力，作為粘度減少和消除伴隨著使用超臨界氣體的包裝要求。這25頁(yè)的加工手冊(cè)涵蓋的過(guò)程中設(shè)置的所有方面，解決問(wèn)題，以?xún)?yōu)化的結(jié)果。誰(shuí)是制造或正在計(jì)劃使用MuCell技術(shù)注塑</p><p>　　通過(guò)更換包裝和

89、保持細(xì)胞的生長(zhǎng)階段，低應(yīng)力部件的生產(chǎn)，提高尺寸穩(wěn)定性，并大大減少翹曲。細(xì)胞的生長(zhǎng)，也導(dǎo)致在消除縮痕。</p><p>　　MuCell技術(shù)的物理過(guò)程與化學(xué)發(fā)泡劑，有沒(méi)有溫度的限制，不留任何化學(xué)殘留物在聚合物，使消費(fèi)產(chǎn)品的完美適合在原來(lái)的聚合物分類(lèi)回收并允許重新研磨材料重新輸入流程。</p><p>　　無(wú)數(shù)的成本優(yōu)勢(shì)和加工優(yōu)勢(shì)，已導(dǎo)致全球快速部署的MuCell技術(shù)過(guò)程主要是在汽車(chē)，消費(fèi)電子

90、，醫(yī)療設(shè)備，包裝及消費(fèi)品應(yīng)用。這將是合理的，說(shuō)的微孔泡沫的潛力尚未得到實(shí)現(xiàn)。這些材料還沒(méi)有尚未出現(xiàn)在大規(guī)模生產(chǎn)的塑料物品，節(jié)省材料和相關(guān)費(fèi)用的承諾還沒(méi)有兌現(xiàn)。這主要是由于擴(kuò)大大規(guī)模生產(chǎn)中遇到的生產(chǎn)困難。然而，對(duì)這些材料的熱情仍然很高，今天在各大洲的研究人員和商業(yè)企業(yè)在全球競(jìng)爭(zhēng)中利用的潛在好處。</p><p>　　已經(jīng)有很多關(guān)于微孔泡沫材料的加工和性能了解到以來(lái)的第一項(xiàng)專(zhuān)利被授予1984年。一個(gè)主題的早期審查，出

91、現(xiàn)在1993年。本章中的國(guó)家的藝術(shù)處理，將在下一節(jié)審查，隨后的結(jié)構(gòu)和性質(zhì)的討論。本章結(jié)束時(shí)將在一些涉及微孔技術(shù)目前的研究方向。</p><p>　　雖然在處理創(chuàng)新發(fā)展迅速，微孔泡沫的屬性數(shù)據(jù)一直在緩慢。微孔泡沫的早期出版物推測(cè)，微孔結(jié)構(gòu)，認(rèn)為是比聚合物“臨界缺陷尺寸較小的規(guī)模，將使這些泡沫，以保留其機(jī)械性能，密度減少。是以往任何時(shí)候都沒(méi)有致命的缺陷大小的定量信息，也不是支持的假說(shuō)中提出的任何財(cái)產(chǎn)數(shù)據(jù)。這很可能是由

92、于重點(diǎn)放在發(fā)展過(guò)程，而不是早年在這一領(lǐng)域的發(fā)展，性能表征。然而，隨著時(shí)間的推移，這一猜想已經(jīng)成為一個(gè)神話(huà)，微孔材料是固體聚合物的強(qiáng)烈，但有一個(gè)較低的密度，從而提供了一個(gè)機(jī)會(huì)，以降低成本，沒(méi)有性能損失。</p><p>　　拉伸性能數(shù)據(jù)[表明，微孔泡沫材料的拉伸強(qiáng)度降低泡沫密度的比例，可以近似的混合物規(guī)則很好。因此可以預(yù)計(jì)將有50％的固體聚合物的強(qiáng)度50％的相對(duì)密度泡沫。顯示了作為一個(gè)相對(duì)泡沫密度微孔聚合物的功能相

93、對(duì)抗拉強(qiáng)度。在這個(gè)數(shù)字相對(duì)抗拉強(qiáng)度，得到的固體聚合物的拉伸強(qiáng)度除以泡沫的拉伸強(qiáng)度。同樣，相對(duì)密度除以固體聚合物密度的泡沫密度。我們策劃了一個(gè)特定的基礎(chǔ)上的強(qiáng)度數(shù)據(jù)。因此，具體為一個(gè)給定的相對(duì)密度的泡沫相對(duì)抗拉強(qiáng)度除以相對(duì)密度相對(duì)抗拉強(qiáng)度。顯示了一個(gè)特定的基礎(chǔ)上，微孔泡沫材料的拉伸強(qiáng)度，基本上是在整個(gè)泡沫密度范圍不斷。不幸的是，傳統(tǒng)的泡沫類(lèi)似的數(shù)據(jù)是不容易的與微孔foams.A獨(dú)特的一面數(shù)據(jù)直接比較，相對(duì)密度在0.1至0.5范圍內(nèi)，微孔泡

94、沫與性能的新型材料工程師代表以前沒(méi)有。最傳統(tǒng)的泡沫屬于低密度區(qū)域（相對(duì)密度小于0.1），或?qū)儆诮Y(jié)構(gòu)性泡沫類(lèi)（相對(duì)密度大于0.5）。微孔泡沫材料的彈性模量，可以合理地估計(jì)吉布森阿什比立方米的細(xì)胞模型[5]，預(yù)測(cè)相對(duì)拉伸模量，等于相對(duì)密度的平方。在細(xì)胞中的氣體成分，可能會(huì)影響長(zhǎng)遠(yuǎn)的泡沫導(dǎo)熱[6]。已審查通過(guò)威廉姆斯和Wrobleski的</p><p>　　顯微組織，抗拉強(qiáng)度和低密度泡沫的熱膨脹性能。聚碳酸酯微孔塑料

95、泡沫材料的疲勞和蠕變行為進(jìn)行了研究。疲勞研究的一個(gè)有趣的結(jié)果是非常小氣泡在PC上推出，不到1％，密度降低，導(dǎo)致在疲勞壽命固體PC相比增加了三十倍。這可能表明一個(gè)類(lèi)似金屬，1電腦的一部分可飽和二氧化碳在5兆帕和再加熱說(shuō)60℃，以引進(jìn)無(wú)1可觀的密度變化的微孔結(jié)構(gòu)，增加了一個(gè)疲勞壽命的熱處理過(guò)程的一部分。由于加工溫度低，非常小的尺寸變化，在實(shí)驗(yàn)中觀察到。</p><p>　　拉伸所有天然氣聚合物系統(tǒng)數(shù)據(jù)調(diào)查跌倒在一個(gè)相

96、對(duì)拉伸強(qiáng)度可對(duì)相對(duì)密度的繪制減少積。然而，能量吸收的措施，如沖擊試驗(yàn)，從聚合物，聚合物的變化更加敏感，結(jié)果不能一概而論。圖11.7顯示加德納沖擊強(qiáng)度PVC泡沫0.5和更高的相對(duì)密度?？梢钥闯?，沖擊強(qiáng)度降低泡沫密度線性。這個(gè)結(jié)果是相反的民間信仰，只要沒(méi)有證據(jù)舉行的微孔結(jié)構(gòu)，始終將改善由于阻力增加的能量吸收行為，嚴(yán)厲打擊傳播提供微空洞。</p><p>　　已經(jīng)有研究人員研究過(guò)微孔泡沫注塑技術(shù)中的技術(shù)參數(shù)與所生產(chǎn)的蜂

97、窩泡沫結(jié)構(gòu)之間的關(guān)系[1,5,6]。結(jié)果發(fā)現(xiàn)，MuCell工藝的孔隙大小可以通過(guò)設(shè)置不同的工藝參數(shù)進(jìn)行調(diào)整。但是目前還沒(méi)有文獻(xiàn)記錄關(guān)于模具設(shè)計(jì)對(duì)微孔泡沫注塑技術(shù)的孔形態(tài)的影響。在該研究中，設(shè)計(jì)了兩款可以使用MuCell工藝設(shè)計(jì)和實(shí)施的模具來(lái)成型醫(yī)療用途的多孔結(jié)構(gòu)的產(chǎn)品。在這兩款模具上進(jìn)行實(shí)驗(yàn)時(shí)都使用了獨(dú)立的工藝參數(shù)。通過(guò)比較采用相同的工藝參數(shù)設(shè)置的兩款模具所成型的產(chǎn)品的孔隙結(jié)構(gòu)，來(lái)研究模具設(shè)計(jì)對(duì)多孔結(jié)構(gòu)的影響。</p>&

98、lt;p>　　圖1 微孔泡沫注塑技術(shù)示意圖</p><p><b>　　材料和方法</b></p><p>　　聚合物材料工藝成型產(chǎn)品的原料選用醫(yī)療級(jí)熱塑性聚氨酯TPU（Texin985，拜耳，美國(guó)賓夕法尼亞州）。選用德產(chǎn)的注射成型機(jī)（KM125-520C2，克勞斯瑪菲技術(shù)有限公司，慕尼黑，德國(guó)）和德產(chǎn)的模具的溫度控制單元（90S/6/TS22/1K/RT45，

99、萊格祿普拉司，圣加侖，瑞士）來(lái)生產(chǎn)樣品。選用來(lái)自美國(guó)馬薩諸塞州沃本Trexel公司的配備了微孔泡沫注塑模塊注塑機(jī)。示意圖如圖1所示。發(fā)泡劑被注入到注射機(jī)的塑化部分（圖1）。在供氣線路和噴油器的作用下，被注入的發(fā)泡劑達(dá)到在其超臨界狀態(tài)在在注塑機(jī)的塑化部分成為熔體聚合物。經(jīng)過(guò)塑化的聚合物熔體和氣體混合并通過(guò)噴嘴注入到模具內(nèi)部，在模具內(nèi)快速壓降的影響下就變成了泡沫結(jié)構(gòu)。二氧化碳被用作發(fā)泡劑（CO2保護(hù)氣體DIN-32525-C1，威斯特法倫公