【正文】 然而，隨著時(shí)間的推移，這一猜想已經(jīng)成為一個(gè)神話，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。是以往任何時(shí)候都沒有致命的缺陷大小的定量信息，也不是支持的假說中提出的任何財(cái)產(chǎn)數(shù)據(jù)。 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。本章中的國家的藝術(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。 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的第一項(xiàng)專利被授予 1984年。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。 這將是合理的，說的微孔泡沫的潛力尚未得到實(shí)現(xiàn)。 MuCell技術(shù)的物理過程與化學(xué)發(fā)泡劑，有沒有溫度的限制，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的聚合物分類回收并允許重新研磨材料重新輸入流程。 通過更換包裝和保持細(xì)胞的生長階段，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。 MuCell 技術(shù)工藝使材料墻體厚度為功能和注塑成型過程優(yōu)化塑料零件設(shè)計(jì)。本刊物的副本，請(qǐng)聯(lián)系Trexel 公司。這 25 頁的加工手冊(cè)涵蓋的過程中設(shè)置的所有方面，解決問題，以優(yōu)化的結(jié)果。一個(gè)關(guān)斷噴嘴保持單相溶液，而注塑螺桿在任何時(shí)候都保持足夠的背壓，以防止過早發(fā)泡或虧損的壓力，這將使單相溶液返回到兩個(gè)階段解決方案。關(guān)鍵系統(tǒng)的修改，涉及精密 SCF輸送系統(tǒng)的使用，提供超臨界質(zhì)量流量計(jì)量的原則為基礎(chǔ)的特殊的注射器。創(chuàng)建的空隙或核結(jié)果作為均相成核時(shí)所發(fā)生的單相溶液聚合物和氣體（常用的氮?dú)?，但偶爾二氧化碳）通過注射進(jìn)入模具門傳遞。 MuCell 技術(shù)注塑成型工藝包括氣體高度控制在超臨界狀態(tài)使用（ SCF）在薄壁成型件（小于 3mm）微米大小的空隙創(chuàng)造了數(shù)百萬。誰是制造或正在計(jì)劃使用 MuCell 技術(shù)注塑成型工藝制造零件的公司主要是有用的。 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) 2033％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。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。 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 5075％。 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。 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。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 。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]。 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，醫(yī)療植入物，多孔聚合物，聚氨酯。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。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)查用以說明工藝參數(shù)對(duì)孔形態(tài)的影響。 the mold A showed the porediameter 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 pared with mold A. It was clear that the standard deviationfrom mold B was also significantly smaller than the values from mold A. Figure 6 shows the interconnective pore size 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。nster, Germany). 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 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 ofimplants from mold A, for a higher biological requirement andprospective production. Figure 2. Different mold designs. Two molds have similar gate, runner, and sprues. The mold B has ashorter polymer melt flow of mold cavity and the L/D (length/thickness)of , whereas this L/D for mold A is . This means the molded partfrom mold B is relatively thicker but shorter. The advantage of mold B 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, and so on, could be expected. On the other hand the mold B hasa bigger capacity which means more possibilities of parameter disadvantage of mold B is that relative thicker molded part will leadto an inplete filling of the cavity of mold B, a long cooling time, andsignificant shrinkage of molded part, in normal injection moldingprocess. These problems could be partially or wholly resolved if thefoaming process is applied due to the expansion of foamed polymer. Experimental Strategy The choice of the changeable parameters was made based on theknowledge given by nucleation theory and literature search [5,7]. Theranges of variable 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 performed on two molds implants from two molds, which were used to be pared,were produced at exactly same process parameters, so that the effects of different molds were shown. Characterization of Macro and Microstructures Scanning electron microscopy (SEM。 although recently there is much interest in creating opencell, porous structures that have cells in this size range. The microcellular process that sparked the growth in this field over the past two decades was invented at Massachusetts Institute of Technology, USA, in early eighties [1], in response to a challenge by food and film packaging panies to reduce the amount of polymer used in their industries. As most of these applications used solid, thinwalled plastics, reducing their densities by traditional foaming processes that produced bubbles larger than mm was not feasible due to excessive loss of strength. Thus was born the idea to create microcellular foam, where we could have, for example, 100 bubbles across one mm thickness, and expect to have a reasonable strength for the intended applications. 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 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 mercial enterprises on every continent are in a global race to harness the potential benefits. Much has been learned about the processing and properties of microcellular foams since the first patent was granted in 1984 [2]. An early review of the subject appeared in 1993 [3]. In this chapter the stateofthe art of processing will be reviewed in the next section, followed by a discussion of structure and properties. This chapter will conclude with a look at some of the current research directions involving microcellular technology. Although inno