共查询到20条相似文献,搜索用时 171 毫秒
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以聚丙烯(PP)/聚苯乙烯(PS)/纳米黏土(nano-clay)为研究对象,采用单螺杆连续发泡挤出机系统进行发泡,并用扫描电镜观察了发泡样品的泡孔结构。通过比较泡孔形态、发泡膨胀率、泡孔密度、泡孔直径等分析了PP/PS/nano-clay共混物组分配比对泡孔结构的影响。结果表明,将PP与PS共混,可以改善PP的发泡性能;同时,nano-clay的加入进一步改善了共混体系的发泡性能。随着nano-clay用量的增加,泡孔平均直径减小,泡孔密度增加,当nano-clay用量为5%(质量分数)时,制得了泡孔密度达到2.16×108个/cm3的微孔泡孔塑料。 相似文献
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采用正交实验设计法对聚丙烯(PP)/丁烷挤出发泡的工艺参数(成核剂添加量、注气量及机头压力)进行了研究,通过扫描电子显微镜,得到了不同工艺条件下的泡孔结构,并借此分析了各工艺参数对材料发泡倍率、平均泡孔直径和泡孔密度的影响程度及机理;进一步利用Design Expert软件对PP的发泡工艺进行了优化,并通过实验验证了优化工艺的预测值。结果表明,在成核剂用量为1.4 %、机头压力为4.66 MPa、发泡剂注入量为7 %时,材料的发泡倍率高、泡孔密度大、泡孔直径小;通过实验验证,实验结果与预测值的偏差小于5 %,证明了预测的可靠性。 相似文献
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发泡工艺对超临界CO_2/PLA微孔发泡泡孔形态的影响 总被引:1,自引:0,他引:1
研究了超临界CO2/PLA微孔发泡过程中,发泡温度、饱和压力、剪切速率对聚合物PLA泡孔形态的影响。结果表明,发泡温度对泡孔形态影响很大,温度降低,熔体强度增加,泡孔塌陷和合并减少,发泡材料的泡孔密度增大,泡孔尺寸减小,但温度太低时,熔体黏度和表面张力增加,发泡样品泡孔密度较低,泡孔壁较厚;压力对发泡形态的影响也是很显著的,压力太低,CO2的溶解度小,泡孔壁厚,泡孔分布不均匀。随着压力升高,CO2的溶解度增加,发泡样品的泡孔密度增加,泡孔更加均匀;随着转子转速增加,泡孔尺寸减小,气泡成核密度增大。但是转子转速过快,泡孔沿剪切的方向被拉长,泡孔取向严重,泡体质量变差。 相似文献
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选择不同拓扑结构的无机成核剂纳米二氧化硅和有机蒙脱土,研究其对PVC增塑糊涂覆发泡制品泡孔形态、结构的影响。通过扫描电子显微镜(SEM)观察样品泡孔形态,采用图像分析手段计算泡孔直径、发泡倍率及泡孔密度,以探明成核剂对泡孔形态结构的影响规律及机制。结果表明:与大多数聚合物熔融体系物理发泡不同,球型纳米二氧化硅对偶氮二甲酰胺(AC发泡剂)主导下的PVC增塑糊涂覆工艺化学发泡过程影响不明显,而插层、团聚分散于PVC增塑糊发泡体系中的有机蒙脱土会增加涂覆制品的泡孔直径,并降低发泡倍率及泡孔密度。 相似文献
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用单螺杆挤出装置,以CO2为发泡剂,对聚丙烯(PP)/CaCO3复合材料进行挤出发泡;采用正交法设计实验,利用Design-Expert统计软件对实验数据进行统计处理,观察制品纵截面上泡体的形态变化,从而得到加工工艺参数对泡体形态的影响规律,回归拟合得到泡孔平均直径、面密度、形变程度和倾向角的预测模型,并进行实验验证;最后用回归模型求解出较合适的加工参数范围。结果表明,转速为46~52 r/min、机头温度为170 ℃、熔体温度为180~189 ℃、CaCO3含量为6.67 %~7.9 %时,可得到较好的PP/CaCO3发泡制品。 相似文献
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Research on formation mechanisms and control of external and inner bubble morphology in microcellular injection molding 下载免费PDF全文
Gui‐long Wang Guo‐qun Zhao Jia‐chang Wang Lei Zhang 《Polymer Engineering and Science》2015,55(4):807-835
This study investigates the formation mechanisms and control of external and inner bubble morphology in MIM. First, the related theories about foaming and filling flow are analyzed. Second, the assumptions for the formation of inner bubble morphology, external bubble morphology, and the compact skin layer in MIM process are proposed based on theoretical analysis. Finally, experiments of MIM process are conducted to verify the theoretical assumptions. In addition, gas counter pressure (GCP) and rapid mold heating and cooling (RMHC) technology are used for control of bubble morphology. It is found that foaming process in MIM can be divided into foaming during filling and foaming during cooling. Foaming during filling produce oriented and deformed bubbles while foaming during cooling produce spherical or polygonal bubbles. As the bubbles formed by foaming during filling can reach melt flow front, they will be pushed to the cavity surface where they are stretched further and frozen to generate the silver or swirl marks. The compact skin layer is formed due to the redissolution of the gases within bubbles into polymer melt and also restraint of foaming by high cavity pressure. GCP and RMHC are two effective methods for controlling external and inner bubble morphology. POLYM. ENG. SCI., 55:807–835, 2015. © 2014 Society of Plastics Engineers 相似文献
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分别以水/二甲基亚砜(H2O/DMSO)、超临界二氧化碳为介质,将偶氮二甲酰胺(AC发泡剂)插层到蒙脱土(MMT)层间,制备得到AC/MMT复合发泡剂。通过红外光谱、热失重、X射线粉末衍射、扫描电子显微镜等方法对产品进行表征,考察反应介质对AC/MMT复合发泡剂中AC发泡剂插层量、AC发泡剂分解温度以及MMT形貌的影响。研究表明,两种介质均能成功制备得到AC/MMT复合发泡剂,以超临界二氧化碳为介质时钠基蒙脱土(Na-MMT)中AC发泡剂插层量最大,为14.34%;Na-MMT中AC发泡剂的分解温度主要受反应介质的影响且以H2O/DMSO为介质时AC发泡剂的集中分解温度由226℃降低至173.21℃;两种反应介质均能够改善MMT的团聚结构,以超临界二氧化碳为介质时更能够使得MMT结构变得蓬松、无序。应用于聚丙烯发泡材料中效果良好。 相似文献
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以超临界二氧化碳(scCO2)为介质,将偶氮二甲酰胺(AC)发泡剂插层到蒙脱土(MMT)中,制备MMT/AC复合发泡剂;通过红外光谱、热失重、X射线衍射和扫描电子显微镜分析方法对复合发泡剂进行表征;探究了插层条件对复合发泡剂中AC插层效果及MMT形貌的影响,以得到最优插层条件;结果表明,40 ℃、20 MPa、100 r/min为最优插层条件,且在此条件下最有利于改善MMT的团状结构;MMT/AC复合发泡剂在聚丙烯中注塑发泡无需添加发泡助剂,当注塑温度为190 ℃时,泡孔尺寸较均匀,泡孔孔径约为250 μm。 相似文献
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Matthias Ahlhelm David Werner Johanna Maier Johannes Abel Thomas Behnisch Tassilo Moritz Alexander Michaelis Maik Gude 《Journal of the European Ceramic Society》2018,38(9):3369-3378
The so-called Freeze Foaming method aims at manufacturing ceramic cellular scaffolds for diverse applications. One application is dedicated to potential bone replacement material featuring open, micro and interconnected porosity. However, the main challenges of this foaming method is to achieve a homogeneous pore morphology. In a current project, the authors throw light on the bubble/pore and strut formation of this process by in situ computed tomography. This allows for evaluating varying process parameter’s effects on the growth of the ceramic foam during the foaming process. As first result and basis for CT analysis, a stable and reproducible model suspension was developed which resulted in reproducible foam structures. In dependence of selected process parameters like pressure reduction rate or air content in the ceramic suspension resulting Freeze Foams became adjustable with regard to their pore morphology. Pore size and distribution data as well as the porosity were characterized and evaluated accordingly. 相似文献
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利用超临界二氧化碳(sc-CO2)微孔发泡方法制备聚乳酸/磷酸钙(PLA/TCP)多孔材料,通过扫描电子显微镜(SEM)观察TCP颗粒分散和泡孔形态。结果表明,TCP质量分数为1 wt%和3 wt%时,微米级TCP颗粒均匀分布在PLA基体中,在发泡过程中起到异相成核的作用,减小泡孔尺寸同时增加泡孔密度。当TCP含量为5 wt%时,TCP颗粒出现团聚,异相成核作用减弱,泡孔密度下降。随着发泡温度升高,泡孔尺寸增大的同时泡孔壁变薄甚至破裂,发泡温度对泡孔密度影响不大。增加发泡压力,泡孔的数量急剧增加,同时泡孔的尺寸减少,泡孔壁变厚。 相似文献
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发泡剂对软质PVC发泡材料性能的影响 总被引:1,自引:0,他引:1
对发泡剂偶氮二甲酰胺(AC)及其共混物、碳酸氢钠(NaHCO3)进行了DSC分析,讨论了几种AC共混物对软质PVC发泡材料性能的影响。结果表明:当AC/NaHCO3/稳定剂的质量比为4/0.8/6.2时,材料的密度可以降至0.3g/cm3以下,但材料的泡孔直径增大,力学性能有所降低;当AC/NaHCO3/L/稳定剂为4/0.8/0.6/6.2时,材料的密度继续降低,泡孔直径减小,其强度、回弹性增大,但断裂伸长率减小;当AC/NaHCO3/L/Na-L/稳定剂为4/0.8/0.6/1.0/6.2时,复合发泡剂受热时分解平缓、放热适中,制得的材料性能最佳,泡孔均匀细密。 相似文献
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拉伸作用对采用超临界CO2发泡时气泡成核的影响 总被引:3,自引:0,他引:3
分析采用超临界CO2流体挤出发泡成型时拉伸作用对聚合物分子自由体积的影响,以及由此引起的对气泡成核的影响。利用具有不同入口收敛角的锥型挤出口模进行了验证,结果显示,拉伸作用可增加气泡的成核数目,减小气泡的平均直径。 相似文献
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This article is concerned with bubble growth dynamics in the CO2/polypropylene microcellular foaming process. The effect of the melt strength on the bubble growth was thoroughly investigated in theory for the first time. The theoretical results indicate that enhanced melt strength effectively restrains the bubble growth and stabilizes the bubble oscillation. Higher melt strength leads to lower bubble growth rate, shorter growth time, and smaller ultimate bubble size. Compared to the melt strength, the viscoelasticity and the gas pressure have less effect on the microcellular foaming process. The bubble growth varies a little as the viscoelasticity is varied. The bubble oscillation and growth rate are enhanced with increasing gas pressure, which leads to the augmentation of the bubble size. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献