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研究了线型低密度聚乙烯(PE–LLD)/超高分子量聚乙烯(PE–UHMW)共混物的超临界CO2微孔发泡行为,探讨了PE–UHMW含量、发泡温度和饱和压力对泡孔形貌的影响。采用差示扫描量热仪和旋转流变仪对PE–LLD及其共混物的热性质和流变性质进行了测试和表征,并通过扫描电子显微镜表征和分析了发泡样品的泡孔形貌。结果表明,少量PE–UHMW的加入可以显著降低PE–LLD发泡样品的孔径,增加孔密度。随着发泡温度的升高,PE–LLD样品的泡孔结构会发生塌陷现象,而加入少量PE–UHMW可以提高基体的黏度,起到支撑孔壁防止塌陷的作用,并最终得到均匀的开孔结构。另一方面,当温度一定时,饱和压力升高可以降低孔径并且得到开孔形貌的泡孔结构。 相似文献
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以超临界CO_2为发泡剂,采用釜压法在不同发泡工艺条件下制备了聚苯乙烯(PS)发泡试样,通过扫描电子显微镜对PS发泡试样的泡孔形貌进行了表征,探讨了不同发泡工艺对PS发泡试样发泡性能的影响。结果表明,随发泡温度的升高,PS发泡试样泡孔尺寸增大,泡孔密度下降,而泡沫密度呈现先降低后升高的趋势,发泡倍率与此相反;增大保压时间和保压压力,可提高试样的发泡效果。当发泡温度为136℃,保压压力为20 MPa,保压时间为4 h时,PS发泡试样的发泡效果最好,其泡沫密度为0.043 g/cm~3,发泡倍率为24.4,泡孔尺寸为59.8μm,泡孔密度为6.20×107个/cm~3。 相似文献
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超临界二氧化碳协助双单体接枝聚丙烯 总被引:2,自引:0,他引:2
采用氧化法制备氢过氧化聚丙烯(HPP),然后用超临界二氧化碳(SC CO2)将单体苯乙烯(St)和季戊四醇三丙烯酸酯(PETA)溶胀到HPP颗粒内,再通过热引发将单体接枝到HPP上.考察了溶胀温度、压力、接枝反应温度、时间及单体用量对产物接枝率与单体接枝效率的影响,并采用红外光谱(FT-IR)、热重-差热分析(TG-DTA)、扫描电子显微镜(SEM)对接枝共聚物进行了表征.结果表明,合适的反应条件为30 g聚丙烯和0.5 g过氧化苯甲酰(BP0)在80℃反应2 h生成HPP,HPP与9 g苯乙烯(St)和季戊四醇三丙烯酸酯(PETA)的混合物(St与PETA物质的量之比为1:1)在37℃,8.5 MPa的超临界CO2中溶胀3 h,再在80℃常压下反应8 h,得到双单体接枝聚丙烯,接枝率达到28%,接枝效率大于90%,且PETA和St同时接枝到了PP分子链上,聚合物的耐热性增强. 相似文献
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天然香料植物的超临界CO2萃取及应用问题 总被引:1,自引:0,他引:1
本文结合我国天然香料植物资源的利用情况及超临界流体技术在天然香料植物提取方面的应用和存在的问题进行讨论。提出为加快我国天然香料资源的利用 ,发展边远地区的经济和香料经济作物的种植 ,应充分发挥联合的优势 ,应用新技术 ,开发新产品 ,提高资源的利用率和经济效益 相似文献
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Column Fractionation of Canola Oil Deodorizer Distillate Using Supercritical Carbon Dioxide 总被引:1,自引:0,他引:1
Özlem Güçlü-Üstündağ Feral Temelli 《Journal of the American Oil Chemists' Society》2007,84(10):953-961
Semi-continuous column fractionation of canola oil deodorizer distillate using supercritical CO2 (SCCO2) was carried out to determine the feasibility of value-added processing of this feed material for the recovery of bioactive
components such as sterols and tocopherols and to determine the effect of operating conditions [pressure (20, 25 MPa using
a temperature gradient of 70–100 °C), temperature (70, 100 °C) and a linear temperature gradient (70–100 °C at 25 MPa)] on
extract yield and separation efficiency. Total extract yield increased significantly (p ≤ 0.05) with pressure, whereas at isobaric conditions (25 MPa) the highest yield was obtained at the lowest temperature tested
(70 °C). Fractionation efficiency was reflected in the composition of fractions and was affected by operating conditions.
Residue composition was determined by extract yield in addition to selectivity. Use of the thermal gradient (70–100 °C) decreased
the content of volatiles, free fatty acids and tocopherols while increasing sterol content significantly (p ≤ 0.05) to a level of 40% (GC area %) in the residue obtained at 25 MPa. The findings indicate the potential of canola oil
deodorizer distillate as a source of sterols and warrant further research on the countercurrent column fractionation to improve
the separation efficiency. 相似文献
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在半连续式实验设备中分别测定了苯甲醇-2-苯乙醇和苯甲酸酯-苯甲醇的等摩尔混合物与超临界CO2三元系相平衡数据。实验温度分别为308.2K和318.2K,压力范围为8~20MPa。实验结果表明:对第一个三元系,两种液体在超临界CO2中的溶解度与CO2在液相中溶解行为密切相关;对第二个三元系,较高压力下,超临界流体相中苯甲酸甲酯浓度突然增大,而苯甲醇浓度变化不明显。通过引入考虑分子体积差别的二元作用参数,用Peng-Robinson方程对气液平衡数据进行了关联。 相似文献
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Dilek Büyükbeşe Emine Elçin Emre Ahmet Kaya 《Journal of the American Oil Chemists' Society》2014,91(1):169-177
Supercritical carbon dioxide was used to fractionate anhydrous milk fat. Six fractions were produced at 40, 50 and 60 °C using pressure values of 10, 20, 25, 30, 33 and 36 MPa. The fractions were analyzed for fatty acids, thermal behavior, iodine and color values. Composition and yield of fatty acid methyl esters were evaluated at different fractionation conditions in relation to the original milk fat values. Short chain fatty acids (C4–C8), medium chain fatty acids (C10–C14) and total saturated fatty acids were decreased from fraction obtained in the order of 10–36 MPa, while long chain fatty acids (C16–C18:2) and total unsaturated fatty acids were increased. Fractions obtained in the raffinate stage of the fractionation exhibited higher melting behavior that obtained at the low CO2 pressures. The higher iodine value of raffinate fraction indicated that fraction was richer in oleic acid. Fractions produced at low pressures had lower melting behavior than those obtained at high pressures. Yellowness Index and b* values increased in raffinate fraction due to concentration of carotenoids. 相似文献
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超临界二氧化碳萃取蛋黄油实验研究 总被引:2,自引:2,他引:2
介绍了超临界二氧化碳萃取技术提取蛋黄洫的工作原理及工艺流程。设计了正交实验.考察萃取压力、萃取温度、萃取时间等参数对萃取率的影响,确定了最佳工艺条件。 相似文献
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在挤出发泡过程中聚合物/超临界CO2发泡体系的形成是气体在剪切混合作用下,通过对流扩散,完全溶解进聚合物形成物理性质均一的均相体系的过程。剪切作用对均相体系的形成具有重要的影响,为了研究剪切对均相体系形成的影响,成功设计了微孔发泡模拟实验机,研究了不同剪切速率作用下均相体系的形成。研究结果表明,随着剪切速率的增加,聚合物和气体的混合程度明显增强,泡孔分布变得均匀,泡孔密度增大。 相似文献
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Michael Eisenmenger Nurhan Turgut Dunford 《Journal of the American Oil Chemists' Society》2008,85(1):55-61
Wheat germ oil (WGO) is a specialty product with a very high nutritional value. The chemical composition of both commercial
and pilot scale supercritical carbon dioxide (SC-CO2) processed WGO was examined. This study showed that methods used for oil extraction and refining did not have a significant
effect on the fatty acid composition of the oil. SC-CO2 extracted oil had a higher tocopherol content than that of commercially hexane extracted oil. The phospholipid content of
the SC-CO2 extracted oil was very low indicating that the SC-CO2 extraction method could eliminate the degumming step from edible oil refining processes. Although the conventional chemical
oil refining technique reduced the tocopherol content of the WGO, it was possible to concentrate tocopherols in WGO by using
physical refining methods such as molecular distillation.
Published with approval of the Director, Oklahoma Agricultural Experiment Station. 相似文献
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超临界二氧化碳萃取器萃取分离香茅油 总被引:1,自引:0,他引:1
本文介绍了利用现有150L高压釜(压力20MPa)改造的超临界二氧化碳萃取器萃取分离香茅油,探讨了压力、温度、时间对萃取分离效果的影响。结果表明,采用超临界二氧化碳萃取器萃取分离香茅油时应选择一个适宜的压力、温度和萃取时间,产品的色、香味、纯度均优于常规的减压蒸馏法。 相似文献