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排序方式: 共有8181条查询结果,搜索用时 31 毫秒
91.
A series of poly(?‐caprolactone)‐b‐poly(ethylene glycol) (PCL‐b‐PEG) block copolymers with different molecular weights were synthesized with a salicylaldimine‐aluminum complex in the presence of monomethoxy poly(ethylene glycol). The block copolymers were characterized by 1H NMR, GPC, WAXD, and DSC. The 1H NMR and GPC results verify the block structure and narrow molecular weight distribution of the block copolymers. WAXD and DSC results show that crystallization behavior of the block copolymers varies with the composition. When the PCL block is extremely short, only the PEG block is crystallizable. With further increase in the length of the PCL block, both blocks can crystallize. The PCL crystallizes prior to the PEG block and has a stronger suppression effect on crystallization of the PEG block, while the PEG block only exerts a relatively weak adverse effect on crystallization of the PCL block. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
92.
The present work analyzes the effect of various factors on the hydration of pentasodium triphosphate. The experimental method
is based on application of the hydration test. Technical-quality products with different proportions of phase I and phase
II have been used. The variables studied are phase I/phase II ratio, initial temperature, particle size, stirring rate and
composition of the slurry (presence of hexahydrate crystals and water hardness). The results have been discussed according
to a kinetics model that includes a series of stages of a physical nature (dissolution of anhydrous salt and the crystallization
of the hexahydrate), as well as of a chemical nature (solvation of the ions in solution). Crystallization of the hexahydrate
may be the controlling stage in the process. 相似文献
93.
Natural amorphous polymer poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P3HB4HB) containing 41 mol % of 4HB was blended with poly(3‐hydroxybutyrate) (PHB) with an aim to improve the properties of PHB. The influence of P3HB4HB contents on thermal and mechanical properties of the blends was evaluated with differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy, stress–strain measurement and thermo gravimetric analyzer. Miscibility of PHB/P3HB4HB blends was mainly decided by the contents of P3HB4HB. When P3HB4HB exceeded 50 wt %, the two polymer phases separated and showed immiscibility. The addition of P3HB4HB did not alter the crystallinity of PHB, yet it diluted the PHB crystalline phase as revealed by DSC studies. DSC and FTIR results showed that the overall crystallinity of the blends decreased remarkably with increasing of P3HB4HB contents. Decreased glass transition temperature and crystallinity imparted desired flexibility for the blends. The ductility of the blends increased progressively with increasing of P3HB4HB content. Thus, the PHB mechanical properties can be modulated by changing the blend composition. P3HB4HB did not significantly improve the thermal stability of PHB, yet it is possible to melt process PHB without much molecular weights loss via blending it with suitable amounts of P3HB4HB. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
94.
涤纶切片的结晶性能及其对POY结构均匀性的影响 总被引:4,自引:0,他引:4
采用DSC等方法研究了几种涤纶切片的等速降温结晶性能,提出了用熔融结晶峰的半高宽/峰高的比值、过冷度和结晶度来定量表征的方法,并结合纺丝过程讨论了其对POY成形时结构均匀性的影响。结晶性能差的切片,易得到结构均匀的POY。 相似文献
95.
BHT结晶采用乙醇作为溶剂。对不同浓度的乙醇,改变溶质与溶剂的物料配比,测定了BHT溶液的出晶点温度。结果表明:在乙醇浓度一定的条件下,出晶点温度随BHT与乙醇配比的增大而降低;而在相同物料配比的条件下,乙醇浓度越低,出晶点温度越高。 相似文献
96.
1-环丙基-7-氯-6-(1-哌嗪基)-4-氧-1,4-二氢-3-喹啉羧酸盐酸盐为环丙沙星合成中主要的杂质之一,研究其物化性质对于改善环丙沙星的结晶分离提纯具有重要意义。本文研究了1-环丙基-7-氯-6-(1-哌嗪基)-4-氧-1,4-二氢-3-喹啉羧酸盐酸盐的熔化,分解特性,溶解度与离子强度,温度和pH值的关系,并测定了该物质的离解常数,估算了该物质在水溶液中的活度积。 相似文献
97.
98.
M.C. García-Gutiérrez A. Nogales C. Domingo G. Broza K. Schulte T.A. Ezquerra 《Polymer》2006,47(1):341-345
We report the appearance of a novel self-assembling of a fraction of single-wall carbon nanotubes (SWCNT) within a SWCNT-polymer nanocomposite subjected to flow fields upon injection molding processing. By combining X-ray diffraction and Raman spectroscopy techniques, both working on a microfocus fashion, we probe that a fraction of the thinnest SWCNT self-assembles into a rectangular lattice in the sample regions where the shear stress induces the highest levels of nanotube aggregation. Additionally, we demonstrate that a modest amount in weight of nanotubes is enough to template the morphology of crystallization during flow providing a method to obtain a highly desirable fiber-like morphology. 相似文献
99.
100.
通过在结晶器保护渣中添加Li2O和B2O3作助熔剂,在实验室内模拟渣膜的形成条件,结合岩相和扫描电镜能谱分析,研究了Li2O3和B2O3对含稀土氧化物保护渣结晶矿物组成的影响.结果表明:稀土氧化物可以促进保护渣中枪晶石析出,抑制玻璃相形成,提高保护渣结晶率;当稀土氧化物含量达到一定数值,保护渣结晶矿物中可以形成稀土硅酸钙相,稀土氧化物继续增加,会有未溶稀土氧化物固态质点出现;保护渣中加入少量B2O3和Li2O作助熔剂,不仅可以促进硅灰石生成,而且能够有效抑制高熔点的枪晶石和稀土硅酸钙形成,防止渣膜形成过程中过早析出高熔点相. 相似文献