共查询到19条相似文献,搜索用时 640 毫秒
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尼龙1010非等温结晶动力学与机理研究 总被引:3,自引:0,他引:3
尼龙1010非等温结晶动力学与机理研究朱诚身,王经武,李卓美(郑州大学材料工程系郑州450052)(中山大学高分子研究所广州510275)关键词尼龙1010,非等温结晶动力学,结晶机理,动力学结晶能力尼龙1010的结晶动力学,无论是等温还是非等温,研... 相似文献
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本文用DSC首先论证淬火尼龙1010试样在DSC曲线上出现的放热峰是冷结晶峰,然后研究淬火尼龙1010在不同热处理条件下,冷结晶峰和玻璃态热松驰峰的变化规律。实验结果表明,等温结晶时间较短,试样的固态结晶速率较快;等温结晶时间较长,固态结晶速率较慢,这可能与在Tg区域等温所形成的新氢键有关。当升高等温温度时,固态结晶速率加快。在低于Tg的不同温度退火,玻璃态热松弛峰的峰高及热焓在281K达最大值,进而确定对玻璃态热松驰影响最敏感的温度区间是277~284K。 相似文献
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用DSC法研究了苯乙烯-丙烯等规立构嵌段共聚物的非等温结晶动力学。结果表明:冷却速率在5~20℃/min范围内,共聚物的非等温结晶动力学参数能很好地符合Avrami动力学方程,非等温结晶速率常数与冷却速率有关,动力学结晶能力则同时受到冷却速率和共聚物组成比的影响。文中还讨论了在非等温结晶条件下共聚物的结晶成核和生长方式与共聚物组成和结构的关系。联合Avrami方程和Ozawa方程推导的非等温结晶动力学方程较好地描述了iPS-b-iPP嵌段共聚物的非等温结晶动力学过程。 相似文献
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根据Ъорохоъский提出的相似于Avrami方程的近似公式 X =1 -exp[-Z(at) n],采用加权最小二乘法 ,对尼龙 1 0 1 0非等温结晶动力学过程进行了模拟 ,编制了模拟非等温结晶动力学过程的软件。该软件可用于精确处理结晶动力学参数 ,也可用于计算机辅助教学。 相似文献
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采用差示扫描量热(DSC)法对反式-/顺式-1,4-聚异戊二烯共混体系的等温及非等温结晶动力学进行了研究,分别采用Avrami方程和莫志深法对其动力学参数进行了解析.研究结果表明,在反式-/顺式-1,4-聚异戊二烯共混体系的等温及非等温结晶过程中,顺式-1,4-聚异戊二烯(CPI)组分的存在会降低反式-1,4-聚异戊二烯(TPI)组分的结晶速率;在等温结晶过程中,CPI组分会提高TPI组分自身的结晶度;而非等温结晶过程中,CPI则提高了共混物中β晶型的相对含量. 相似文献
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尼龙66/蒙脱土复合材料结晶行为的研究 总被引:8,自引:0,他引:8
在密炼机中采用熔融共混法制备蒙脱土重量分数为 2 5 %、4 5 %的尼龙 6 6 /蒙脱土复合材料 .通过DSC法对非等温结晶行为及在 2 2 8~ 2 4 0℃范围内的等温结晶行为进行研究 ,并与纯尼龙 6 6进行比较 .从其等温和非等温结晶行为的研究表明 ,蒙脱土起成核剂的作用 ,它的填入使尼龙 6 6结晶速率提高 ,但填料与基体间的相互作用使其链段运动困难 ,结晶活化能提高 ;在研究的填料含量变化范围内 ,结晶行为变化不大 ,并且找到该复合材料在 2 2 8~ 2 34℃范围结晶对温度的不敏感区 ;对非等温结晶过程分析 ,刘结平 莫志深方程是适用的 ,而Ozawa方程则是不适用的 . 相似文献
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PMMA—b—PTHF/PTHF共混体系中共聚物结晶能力的增强 总被引:3,自引:0,他引:3
结晶嵌段共聚物具有一般均聚物所没有的许多特殊结晶行为。虽然,人们很早就已开始对聚氧化乙烯/聚苯乙烯诸类嵌段共聚物的结晶行为进行研究,但对这类体系相分离规律及结晶行为的认识仍很不够。这主要是因为已研究的体系非常有限,此外,大都为对体系非平衡态结构的研究。所以,尽管Whitmore和Noolandi最近提出了结晶嵌段共聚物及其共混物的平衡形态理论,但缺乏实验数据与之比较。 相似文献
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The classical crystallization theories proposed by Avrami, Evans, and Mandelkern wereextended to the nonisothermal situation. The expressions derived from the classical equations canbe expressed in either the differential form or the integral form. A method was provided so as toobtain the parameters characterizing the crystallization rate and mechanism from DSC curves withseveral constant heating or cooling rates. The rate constants of crystallization obtained from bothisothermal and nonisothermal curves of poly(ethylene terephthalate)were compared. 相似文献
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应用X射线衍射、偏光显微镜及电子显微镜研究了胆甾液晶与甲基丙烯酸甲酯(MMA)─甲基丙烯酸丁酯(BMA)无规共聚物共混体系的形态结构。研究了体系的结晶态及液晶态的行为和共聚物含量及组成对光学织构的影响。 相似文献
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《Soft Materials》2013,11(1):47-56
Abstract The phase behavior of syndiotactic polystyrene (sPS)/1,2‐dichloroethane (DCE) gels has been investigated by differential scanning calorimetry (DSC) and wide angle x‐ray diffraction (WAXD) for different gel formation conditions. DSC data show that the gel melting temperatures are independent of the cooling conditions leading to gel formation, whereas the melting enthalpies of the gels depend on the cooling history. WAXD measurements show that for low concentration gels the sPS/DCE clathrate structure is obtained, whereas for high concentration gels both the clathrate structure and the solvent‐free β phase can be obtained. Furthermore, the onset of formation of the β phase is dependent on the cooling rate. In light of combined DSC and WAXD data, the reliability of the DSC in evaluating the absolute stoichiometry of polymer‐solvent compounds formed in sPS/DCE gels is discussed. 相似文献
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通过自主设计的动态保压注塑成型装置研究剪切应力场下聚丙烯(PP)熔体在近熔点处冷却结晶的晶体结构.用扫描电子显微镜(SEM)、示差扫描量热法(DSC)和广角X射线衍射(WAXD)分析了PP试样在近熔点处冷却后从表层到剪切层的结晶结构的变化.SEM研究表明,与传统注塑成型样品(SL)和剪切力场中高熔体温度下冷却得到的试样(DH)相比,近熔点附近冷却得到的PP试样(DL)从表层到剪切层的结晶结构和形态有明显变化.DL从表层到剪切层均生成了尺寸较大的取向结晶结构,无明显的串晶产生.DSC研究表明,与SL和DH相比,DL剪切层无脊纤维晶熔融峰且晶片熔融温度较高,证明其样品内部晶片尺寸较大.WAXD进一步研究显示,DL内部主要晶面(110,040和130)的结晶尺寸与SL和DH相比并没有发生明显改变. 相似文献
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J. M. Ginés M. J. Arias A. M. Rabasco C. Novák A. Ruiz-Conde P. J. Sánchez-Soto 《Journal of Thermal Analysis and Calorimetry》1996,46(1):291-304
In the present study, the effect of the molecular weight and thermal treatments on commercial polyethylene glycols (PEG) samples used in the pharmaceutical processing technology, has been analyzed using DSC and HSM. The molecular weight of these polymers range from 1500 to 200000. Thermal investigations on the melting behavior of original PEG samples (as received from the manufacturer) showed only one single melting DSC endotherm effect before 373 K. This fact was associated to the presence of only one type of polymeric chain. Using standard conditions, PEG samples were solidified from the melt at 373 K, either by flash cooling (using liquid nitrogen and an ice bath) and by slow cooling, soaked and by slow cooling at room temperature. They were further studied by DSC. It was found that after cooling, PEG with molecular weight 1500 and 15000 showed DSC thermograms with a single endothermic peak. However, thermograms for PEG 4000 and 6000 produced a splitted melting endotherm. This fact was attributed to the presence of two types of chains, that are the folded and extended chains.Ageing time influences also the shape of the DSC endothermal effects. It was concluded that the endotherms obtained after heating these PEG indicate that the thermal history determine the structure (extended or folded chain type forms) and the degree of crystallinity, as evidenced by changes in heat of fusion values, melting points and structures after crystallization. The relationships between melting enthalpies and melting points, as deduced from DSC diagrams, with molecular weight of the polymers are also presented. 相似文献
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对Fevotte提出的由DSC曲线构建玻璃化温度谱图的方法进行了改进,将橡胶态含量为0.5时的温度定义为聚合物的Tghr.采用改进Fevotte方法重新研究了PS的玻璃-橡胶态转变,PS的Tghr值比半比热外推法结果Tghc高约4K,当考察热处理时间和降温速率对聚合物玻璃-橡胶态转变的影响规律时,改进方法得到的结果与理论分析更为一致.聚合物的Tghr受热历史影响,随热处理条件改变,通过对不同降温速率冷却后样品滞后焓数据的拟合,推测PS样品的Tghr在377.5~390.9K范围内变化. 相似文献