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111.
用动力学方法对Li2O·nB2O3-20%LiCl-H2O体系(n=1,2,3)20℃过饱和溶液结晶过程进行研究,结果表明每一种溶液只析出一种固相,Li2O∶B2O3=1∶1、1∶2和1∶3的氯化锂溶液分别结晶出Li2O·B2O3·4H2O, Li2O·2B2O3·3H2O和Li2O·5B2O3·10H2O,拟合并给出结晶动力学方程,同时对这三种固相的结晶反应机理进行了探讨。 相似文献
112.
本文介绍了尼龙1010的结晶过程与动力学、晶体的熔融与转化;并论述了其稀溶液、热降解与动态力学性质及共聚、共混、填充、增强、交联改性方面的研究进展。 相似文献
113.
114.
Wei-ping Gao Yu Bai Er-qiang Chen~ 《高分子科学》2005,(3):275-284
Small fixed aggregates of a poly(ethylene oxide)-block-polybutadiene diblock copolymer(PEO-b-PB)in THFsolution were obtained by adding a selective solvent for PB blocks,followed by cross-linking the PB shells.Themorphologies of the nanostructured particles with a cross-linked shell were investigated by atomic force microscopy andtransmission electron microscopy.The average behaviors of the PEO crystallization and melting confined within thenanostructured particles were studied by using differential scanning calorimetry experiments.For the deeply cross-linkedsample(SCL-1),the crystallization of the PEO blocks was fully confined.The individual nanoparticles only crystallized atvery low crystallization temperatures(T_cs),wherein the homogenous primary nucleation determined the overallcrystallization rate.For the lightly cross-linked sample(SCL-2),the confinement effect was T_c dependent.At T_c(?)42℃,thecrystallization and melting behaviors of SCL-2 were similar to those of the pure PEO-b-PB diblock copolymer.At T_c>42℃,SCL-2 could form PEO lamellae thicker than those of the pure PEO-b-PB crystallized at the same T_c. 相似文献
115.
116.
René Androsch 《European Polymer Journal》2007,43(1):93-108
The melt-crystallization of an oligo[(R)-3-hydroxybutyrate] with five repeating units has been analyzed using standard and temperature-modulated calorimetry, optical microscopy, and atomic force microscopy. Specimens of different crystallinity and supermolecular structure were generated by variation of the rate of cooling of a quiescent melt, or by variation of the temperature of isothermal crystallization. Completely amorphous samples can be obtained by cooling of the melt at a rate of 40 K min−1, or faster, to a temperature lower than the glass transition. The crystallinity depends on the crystallization temperature. The maximum enthalpy-based crystallinity of about 40-45% is obtained by crystallization at temperatures lower than the temperature of the maximum crystallization rate, which is between 310 and 320 K. Analysis of the apparent heat capacity in metastable structural equilibrium reveals reversible melting at temperatures between 320 and 370 K by observation of an excess heat capacity above the level of the vibrational heat capacity, i.e., in the temperature range of irreversible reorganization and melting. The reversible melting is discussed in the context of coupling of the crystalline and amorphous phases, and compared to earlier studies on oligoethylene and oligo(oxyethylene). The presence of crystals causes formation of a rigid amorphous fraction of about 30% at a crystallinity of 40%. Optical and atomic force microscopy reveal spherulitic crystallization. At relatively high crystallization temperature, and in the early stage of the crystallization process, dendrites are observed which finally yield spherulites of decreased perfection. Larger spherulites of higher perfection grow at relatively low crystallization temperature, as deduced from the appearance of the Maltese cross, and the regularity of banding. The band spacing is less than 5 μm, as is accurately determined by atomic force microscopy. The temperature dependence of the spherulitic growth rate is in accord with the calorimetric analysis of the crystallization rate. 相似文献
117.
聚丙烯/纳米蒙脱土复合材料的结晶动力学研究 总被引:5,自引:1,他引:5
徐笑非 《分析测试技术与仪器》2002,8(1):26-30
采用热分析方法,研究了聚丙烯/纳米蒙脱土复合材料(PP/CLAY)的等温结晶行为,并分别用Avrami方程和赵志英方法对所得数据进行了分析,研究结果表明,纳米蒙脱土微粒对聚丙烯等温和非等温结晶行为均有不同程度的影响,可提高聚丙烯的结晶速率并改善结晶结构。 相似文献
118.
Mingbi Qi Fengying Yao Jun Zheng Renyuan Qian 《Journal of Thermal Analysis and Calorimetry》1993,40(2):783-789
In this paper two LLDPE samples with their own structural parameters were studied by means of DSC. Experimental results show
that DSC was good for revealing slight structural difference between these two samples. Furthermore, the effect of thermal
history on crystallization and melting behaviour of LLDPE was observed clearly through varying conditions of thermal treatment.
Zusammenfassung Mittels DSC werden zwei LLDPE-Proben mit ihren eigenen Strukturparametern untersucht. Die Versuchsergebnisse zeigen, da\ sich DSC gut eignet, um gering fügige Unterschiede dieser zwei Proben nachzuweisen. Weiterhin wurde unter verschiedenen Bedingungen der Einflu\ der thermischen Vorgeschichte auf das Kristallisations-und Schmelzverhalten von LLDPE untersucht.相似文献
119.
聚(丁二酸丁二酯-co-丁二酸丙二酯)的等温结晶行为研究 总被引:1,自引:0,他引:1
以1,4-丁二酸、1,4-丁二醇和1,3-丙二醇为原料通过直接熔融缩聚法合成了聚丁二酸丁二酯(PBS),聚丁二酸丙二酯(PPS)和聚(丁二酸丁二酯-co-丁二酸丙二酯)(PBSPS)等脂肪族聚酯.利用1H-NMR,WAXD,DSC和POM等研究了聚酯的结晶结构和结晶动力学过程等结晶行为.PBSPS的结晶晶型与PBS一致,说明只有丁二酸丁二酯(BS)单元结晶而丁二酸丙二酯(PS)单元处于无定形区.聚酯等温结晶后,在升温熔融过程中出现了多重熔融峰.分析表明多重熔融峰主要来自于聚酯升温过程中的熔融-重结晶行为.利用Avrami方程分析了聚酯的等温结晶动力学,Avrami指数n为2.2~2.8,说明聚酯等温结晶时主要以异相成核的三维生长方式进行;随着PS单元的增多,聚酯的表观结晶活化能升高,也就是说BS单元的结晶变得困难.POM观察到聚酯等温结晶时都出现了环带球晶现象,球晶形态会随着结晶温度和化学结构差异而改变. 相似文献
120.
Amphiphilic biodegradable poly(CL-b-PEG-b-CL) triblock copolymers have been successfully prepared by the ring-opening polymerization of ε-caprolactone (CL) employing yttrium tris(2,6-di-tert-butyl-4-methylphenolate) [Y(DBMP)3] as catalyst and double-hydroxyl capped PEGs (DHPEG) as macro-initiator. The triblock architecture, molecular weight, thermal and crystallization properties of the copolymers were characterized by NMR spectra, SEC, DSC and WAXD analyses. The isothermal crystallization behavior of the copolymers was investigated by POM analysis in detail, which is greatly influenced by the length of PCL and PEG blocks. On the POM micrograph of PEG10,000-(PCL8600)2, a unique morphology of concentric spherulites was observed due to the sequent crystallization of the PCL and PEG blocks. 相似文献