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研究了晶种存在下,丙烯酸/乙酸乙烯酯无规共聚物对二水合硫酸钙从过饱和水溶液中结晶动力学的影响。发现该共取物存在下CaSO4·2H2O的结晶过程存在诱导期。诱导期随共聚物浓度或共聚物中乙酸乙烯酯含量的增加而增加,随温度、晶种含量或初始钙离子浓度的降低而增加。诱导期后的结晶生长速度与共聚物浓度、共聚物组成和晶种用量几乎无关。 相似文献
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水溶性聚合物和两亲聚合物:21.丙烷酸/乙酸乙烯酯共聚物对… 总被引:1,自引:0,他引:1
研究了晶种存在下丙烯酸/乙酸乙烯酯无人聚物对碳酸钙从过饱和水溶液中结晶的影响。发现我们的实验条件下碳酸钙结晶包括溶液本体成核结晶和晶种上晶体生长两种不同过程,丙烯酸/乙酸乙烯酯共聚物同时具有明显抑制溶液成核结晶和抑制晶种上体的双重作用, 相似文献
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水溶液中丙烯酸/乙酸乙烯酯无规共聚物的存在不仅降低了Na2SO4和CaCl2生成CaSO4的沉淀量和结晶速度,而且可显减小CaSO4粒子的大小,改变其形状和晶形,降低结晶的完善程度。 相似文献
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在亚乙基双( 茚基) 二胺化茂铪(rac C2H4(Ind)2Hf(NMe2)2 ,简称1 ,Ind = 茚基,Me= 甲基) 催化作用下,对乙烯(E) 与1 辛烯(O) 无规共聚合进行了研究.作为比较,利用异亚丙基( 环戊二烯基)(1 芴基) 二甲基锆茂催化体系((CH3)2C(Fluo)(Cp)ZrMe2 ,简称2 ,Fluo = 芴基,Cp = 环戊二烯基) 对乙烯/1 辛烯在相同共聚合条件下进行了共聚合.结果表明,在单体浓度比[O]/[E] 较小时共聚合速率随单体浓度比增加而增加,进一步增加单体浓度比则导致共聚合速率降低.催化体系1/Al(iBu)2H/[Ph3C][B(C6F5)4](3) 催化共聚活性比2/ MAO高得多.共聚物中辛烯含量随反应单体1 辛烯含量的增加而增加,两单体竞聚率乘积( rE×ro) 小于1 ,表明聚合物为无规共聚物.相同共聚单体浓度比下1/Al(iBu)2H/3 催化共聚物中辛烯含量比2/ MAO 共聚物中辛烯含量高,表明前者具有更强的共聚合能力.所得无规共聚物熔点温度、结晶度、本体粘度及密度随共聚物中辛烯含量的增加而显著降低.辛烯含量较高时共聚物呈现明显无结晶行为.差示扫描量热分析显示,同乙烯均聚? 相似文献
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用DSC方法对乙烯基甲醚/马来酸酐交替共聚物多缩乙二醇酯(CBP) 聚氧化乙烯(PEO)共混体系的非等温结晶动力学进行了研究,用Mandelkern、Z J(Ziabiki Jeziorny)、Ozawa和对Ozawa方法的一种修正方法对该体系进行了处理.结果表明:得到了一种既没有结晶又有较多EO单元含量的共混物,CBP对PEO的结晶有抑制作用.Avrami指数随冷却速率的加快在38~57之间波动.Mandelkern方法求得的结晶动力学参数Zc随冷却速率的增加而增加,共混物的Gc值不随冷却速率的变化而变化,随PEO含量增加而减少,处理结果表明而Z J理论能较好地解释本体系的非等温结晶过程和机理. 相似文献
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对剪切场作用下的全同聚丙烯/弹性体乙烯-辛烯共聚物(iPP/PEcO)的共混物结晶行为进行研究, 结果表明, 剪切使得iPP球晶密度增加, 微晶和片晶均发生取向, 且片晶取向明显; 片晶取向度随共混物中PEcO含量的增加而增大, 而微晶取向度随PEcO含量的增加而减小; 强剪切诱导出现纤维状结晶形态. 利用同步辐射(SAXS)技术对共混物在剪切场下的等温结晶行为进行研究, 结果表明, 随结晶的进行长周期呈现先减少而后固定的趋势; 高剪切速率缩短了结晶诱导时间, 加快了共混物中结晶部分的结晶动力学过程. 相似文献
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研究了聚苯乙烯大单体与乙酸乙烯酯的溶液聚合,结果表明,接枝效率随引发剂用量、聚合温度及小单体与大单体的投料比的增加而增加,随大单体的分子量增加而减少,而随单体浓度的变化呈现一最大值。共聚过程中大单体的转化率开始较小单体的增加快,后期变慢。用萃取法纯化的接枝共聚物经GPC、IR、~1H-NMR及PGC等表征,并算得平均接枝数为4—7。透射电镜表明接枝共聚物中存在微观相分离。 相似文献
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The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted
indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator
model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was
established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing
analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997. 相似文献
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Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position. 相似文献
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The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations
were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples
were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of
hematite Fe2O3. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the
best fitting experimental data.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6. 相似文献
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微量钙的测定方法研究进展 总被引:5,自引:0,他引:5
介绍了1995-2006年期间测定微量和痕量钙的方法,如电感耦合等离子体-原子发射光谱法、原子吸收光谱法以及离子色谱法等的工作原理和特点,并说明了其测定微量钙的应用领域。并对微量钙的测定技术进行了展望(引用文献55篇)。 相似文献
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Thermal behaviour of sodium oxo-salts of sulphur: Na2SO4, Na2S2O7, Na2S2O6, Na2SO3, Na2S2O5, Na2S2O4, Na2S2O3, Na2S3O6 and of sulphides Na2S and Na2S2 was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products
by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been
proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition
mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition
processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase
analysis. 相似文献
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Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared. 相似文献