【正文】 mold Bhad a range of 91_6 mm to 67_7 mm。 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％。這 25 頁(yè)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。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。 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。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。 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。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。 by mold A this range was35_10 mm to 19_8 mm. This change was also corresponding to thefinding in the mean pore size of foamed implants from two molds. It could be concluded from Figures 3–6 that the improved mold designof 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 poresize 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 largerpore size, and was more uniform than those from mold A. Figure 6. Size of interconnections of implants at different injection speeds. Figure 7 shows the parison of the maximal porosity at differentkinds of process parameter variations, including 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 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 from mold B showed a minimal elevation of ca. 6% while themaximal porosity elevation of 14% was found by injection speed variation. The differences between the maximal pore sizes at different kinds ofprocess parameter variations of two molds are shown in Figure from two molds showed the maximal pore size also at the sameprocess parameters setting in every kind of 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 with value of 45%was found by the injection speed variation. Figure 7. Differences between the maximal porosity at different processing parametersfor two molds. Figure 8. Differences between the maximal pore size at different process parameters fortwo molds. Figure 7 and 8 have indicated that the improvement of the porestructure, such as maximal pore size and porosity, induced by thechange of mold 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 the polymer melt flow in the mold cavity. Therelative thicker implant from mold B needed also a longer cooling time,which was very important for the cell growth in the mold. Consideringthe possibility of interaction of these factors, using formulae of cellnucleation theory to predict the change of final pore morphology is verydifficult in this study, but the effects of mold design on pore morphologysuch as porosity and mean pore size were successfully observed throughthe experiments. CONCLUSION This study was intent 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