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Effects of cooling rate and crystallization and melt temperatures on the melting curves of predomi-nately β-phase isotactic polypropylene (IPP) were investigated by using DSC instrument. Experimental re-sults indicate that the magnitude of βmelting endctherm increases with decreasing cooling rate and withincreasing crystallization temperature. The temperature of melt has no effect on the β-phase crystallizationof IPP below 300℃, but a further increase of the melt temperature will destroy the β-phase nuclei,then the β-phase crystals will not be produced upon cooling. The linear growth rates of α- and β-phasespherulites were determined as a function of temperature between 123 and 140℃. It was found that thegrowth rate of βspherulites is higher than that of αspherulites below 140℃. Studies of the kinetics ofβ-phase crystallization of IPP were also made using a DSC instrument. The results obtained do not fitthe usual Avrami equation. But it can be described by kinetic theory of imcomplete spher 相似文献
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Three series of polythiophenes containing fluoroalkoxy and fluoroether substituentswere prepared by electrochemical polymerization. The effect of substituents with fluoro-alkoxy or ether functional groups on the electrochemical polymerization of thiophene mono-mers and properties of the obtained polymers were analyzed. The introduction of a flu-oroether functional group at the 3-position of the thiophene ring leads to an increase ofthe oxidation potential of the monomer and to a decrease of the conductivity of the re-sulting polymers, even with the use of a CH_2 group as spacer. Conversely, the presenceof an oxygen atom directly at the 3-position of the thiophene ring, which offsets the nega-tive withdrawing effect of fluoroalkyl groups, facilitates the synthesis of highly conductingpolythiophenes. 相似文献
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聚丙烯β相结晶的研究 总被引:5,自引:0,他引:5
本文研究了冷却速率、结晶温度和熔体温度等因素对聚丙烯β相结晶得到的试样的熔融行为的影响。发现β晶型熔融峰的面积随冷却速率的降低或结晶温度的升高而增加。在低于300℃的温度下,熔体温度对聚丙烯的β相结晶无影响。300℃以上的高温破坏了聚丙烯β相结晶的晶核,冷却结晶时不再生成β相晶体。测定了α相及β相球晶在123—140℃的温度范围内线性增长速率,发现在140℃以下,β球晶的增长速率大于α球晶。研究了β相结晶动力学,发现聚丙烯β相结晶不符合Avrami方程,而要用不完全球晶结晶的动力学理论来描述。 相似文献
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Electrochemical polymerization of 3-fluoroalkoxy and 3-fluoroether thiophenes givespolymers with relatively high molecular weights and good processibility. Investigationof these polymers by means of GPC indicates that an increase in the number of fluorineatoms in the fluorinated group results in a decrease in degree of polymerization of thepolymers in the same polythiophene series. As shown by NMR and FTIR, the polyfluo-rinated group substituted polythiophenes have regular 2, 5-coupling in their main chains.The SEM micrographs of the polymer films exhibit that polymer (1)-poly [3-2, 2, 3, 3-tetrafluoro-propoxy) thiophene] possesses more regular structure than the other polymersdo. Substitution of polythiophenes by fluorinated groups leads to the polymers with highelectric, electrochemical and thermal stability. 相似文献
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