共查询到20条相似文献,搜索用时 218 毫秒
1.
2-乙基-4-甲基咪唑固化环氧树脂体系动力学模型 总被引:7,自引:0,他引:7
由2-乙基-4-甲基咪唑(2,4-EMI)固化双酚A二缩水甘油醚型环氧树脂(DGEBA)的等温差示扫描量热(DSC)实验结果发现固化反应分两阶段进行,催化聚合反应有一诱导期.由DSC测试结果求得催化聚合反应的速率常数.从反应机理出发,以诱导期为边界,建立两阶段的微观固化动力学模型.从扩散的角度在模型中引入临界固化度(αc)和扩散因子,进一步建立扩散控制固化动力学模型,对不同2,4-EMI含量和固化温度(Tc)的体系,计算得到αc.研究发现扩散因素对固化动力学影响较大,固化反应前期由化学动力学控制,后期由扩散因素控制;αc主要由体系的玻璃化转变决定,Tc越高,体系玻璃化转变时对应的固化度越大,cα越大. 相似文献
2.
3.
非等温DSC法研究甲壳型液晶PBPCS改性环氧树脂的固化动力学 总被引:1,自引:0,他引:1
采用非等温DSC法对聚乙烯基对苯二甲酸二(对丁氧基苯酚)酯(PBPCS)/环氧树脂/甲基四氢苯酐固化体系的固化反应热行为以及固化动力学进行了研究,分别利用Kissinger和Ozawa动力学模型计算得到各体系固化反应的表观活化能,利用Crane模型计算出固化反应级数,得出了适于该树脂体系固化反应过程的动力学方程.结果表明该体系固化反应按照一级反应进行,PBPCS的加入不改变环氧树脂的固化机理,甲壳型液晶高分子PBPCS可以用于环氧树脂的改性研究.通过固化体系的DSC分析确定了体系固化工艺为90℃/2h→120℃/2h→140℃/1.5h,为聚乙烯基对苯二甲酸二(对丁氧基苯酚)酯/环氧树脂/甲基四氢苯酐体系的固化、性能测试和应用提供了理论依据,也为甲壳型液晶高分子改性环氧树脂的研究提供一定理论基础. 相似文献
4.
5.
6.
热分析量热仪主要包括动态、等温、恒温及绝热四种操作模式。很多学者基于动态及等温模式的测试结果,采用Arrhenius速率常数进行动力学计算,进而发现了所谓的“动力学补偿效应”。为了解绝热模式下是否也存在动力学补偿效应,分别采用绝热加速量热法(ARC)及动态差示扫描量热法(DSC)研究了过氧化二异丙苯(DCP)、40%(质量分数,下同)DCP溶液、葡萄糖、45%葡萄糖溶液的热分解特性,在此基础上基于Arrhenius公式计算了对应的表观活化能E和指前因子A,并对计算结果进行了分析。结果表明:绝热模式下,不同质量的同种样品及其溶液的最佳动力学参数,或者同一组数据采用不同的反应级数获得的lnA和E之间均存在明显的线性关系。此外,尽管由动态DSC数据计算获得的E和lnA普遍小于绝热模式的结果,但两种模式下获得的lnA和E之间仍然存在动力学补偿效应。由此可以推断,具有相同或类似反应机理的反应,虽然实验模式不同,但其E和lnA之间存在明显的动力学补偿效应。 相似文献
7.
8.
高聚物的非等温结晶动力学——从不同速率的升温或降温DSC曲线解析结晶动力学参数 总被引:2,自引:0,他引:2
根据等温DSC法,测定结晶动力学参数在实验上存在着一定的局限性,结晶太快或太慢都难于获得可靠的结果,这就限定了能测定的温度区间。可见,等温DSC法测定结晶动力学参数具有获得的信息量少,结晶起始点难以确定,费时等缺点。这些缺点可通过等速变温DSC法来克服。然而,通过等速变温DSC法测定结晶动力学参数的方法至今还不完善。例如Ozawa曾基于Evans理论把Avrami方程推广于非等温结晶,从Ozawa方程通过等速变温DSC曲线可得到表征结晶机理的函数Avrami $数。和冷却结晶函数。Ozawa方法的不足是从其冷却结晶函数不能解析出表征结晶速率的参数。 相似文献
9.
非等温法研究TGDDM/DDS体系固化反应动力学 总被引:16,自引:0,他引:16
采用DSC对4,4′-四缩水甘油基二氨基二苯基甲烷(TGDDM)和3,3′-二氨基二苯基砜(DDS)体系的固化反应动力学进行了研究.分别通过n级反应法和Malek的最大概然机理函数法确定了固化反应机理函数,求解了固化反应动力学参数,得到了固化反应动力学模型.结果表明,通过Kissinger,Crane方法求解动力学参数所得到的n级反应模型与实验值差别较大;而采用Malek方法判别机理,表明该固化反应按照自催化反应机理进行,实验得到的DSC曲线与模型计算所得到的曲线吻合的较好,所确立的模型在5~20K/min的升温速率下能较好地描述TGDDM/DDS体系的固化反应过程,并为工艺参数的选择和工艺窗口的优化提供了理论依据. 相似文献
10.
11.
12.
Optimization
of roasting process and product quality of peanuts 总被引:2,自引:0,他引:2
Differential scanning calorimetry (DSC) was used
to establish criteria for optimization of raw material selection, roasting
process, eating quality, visual appearance, and shelf-life extension of peanuts
[1-4]. DSC methods were developed as both predictive and analytical
tools to define process operating guidelines and to correlate with traditional
quality attributes of roasted peanuts [1-4]. 相似文献
13.
M. Paczuski R. Pulawski F. Tomaszewska 《Journal of Thermal Analysis and Calorimetry》1995,43(1):143-147
The processes of oxidation of microcrystalline petroleum (residual) wax were investigated. DSC was applied to estimate the thermal conditions and the influence of selected catalysts on the process. Laboratory tests of oxidation fully confirmed the results of the DSC investigations. 相似文献
14.
Beata Mossety-Leszczak Magdalena Włodarska Henryk Galina G.W. Bąk Tadeusz Pakula 《Macromolecular Symposia》2005,227(1):149-160
In the present paper we describe the curing process of a new liquid crystalline epoxy monomer with 4,4′-diaminodiphenylenemethane (DDM). The characteristic of cured product is presented. Both the monomer and cured product have been characterized by IR and NMR spectroscopy, differential scanning calorimetry (DSC), polarized optical microscopy (POM), wide-angle X-ray scattering (WAXS) and dielectric relaxation spectroscopy (DRS).The curing process was analysed with the use of DSC and real-time DRS. 相似文献
15.
16.
不同实验条件对DSC峰形的影响以及相变温度的确定 总被引:2,自引:0,他引:2
本文通过深入分析实际的DSC过程,阐述了DSC曲线上各个特征点以及这些点所对应的物理意义。在理论上分析各种不同的实验条件对DSC曲线形状的影响,指出目前在DSC分析中所用的确定试样熔点的方法以及用高纯金属DSC变曲线上熔融峰峰前沿的斜率修正试样相变温度所存在的问题,指出DSC相变曲线刚开始偏离基线的那点所相应试样盒的温度即为试样的熔点,本文还提出了通过提高试样,试样盒以及试样支座之间的热导率,来提 相似文献
17.
Identification of collagen-based materials that are supports of cultural and historical objects 总被引:1,自引:0,他引:1
Budrugeac P. Miu L. Popescu C. Wortmann F.-J. 《Journal of Thermal Analysis and Calorimetry》2004,77(3):975-985
The TG, DTG, DTA methods were used for investigation of the thermal degradation in static air atmosphere of some collagen-based
materials (some sorts of collagen, recent manufactured parchments and tanned leathers, patrimonial (historical) leathers).
At the progressive heating, all investigated materials exhibit two main successive processes, associated with the dehydration
and thermo-oxidative degradation. The patrimonial leathers were divided in two groups, namely: a group containing the majority
of the analyzed materials, for which the rates of the thermo-oxidation process are substantially lower than those corresponding
to the recent manufactured leathers, and a group for which the rates of thermo-oxidation process are closed to those corresponding
to the recent manufactured leathers. Consequently, if by the thermal analysis in air atmosphere of a leather sample, a value
of the rate of the thermo-oxidation process smaller than that corresponding to the recent manufactured leathers is obtained,
then the analyzed leather is a patrimonial one. The reciprocal statement of this qualitative criterion for distinction between
recent manufactured leather and patrimonial leather is not valid. The DSC analyses of collagen-based materials were performed
in air (DSC(air)) and in water (DSC(water)). The denaturation process takes place at lower temperatures in water than in air.
Unlike recent manufactured leathers and parchments, each patrimonial leather exhibits on DSC(water) plot 2-4 peaks. Consequently,
the number of peaks from DSC(water) curve could be another qualitative criterion for distinction between a recently manufactured
leather and a patrimonial leather.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
单轴取向聚对苯二甲酸乙二酯非等温结晶动力学研究 总被引:2,自引:0,他引:2
采用等速升温DSC方法对单轴取向聚对苯二甲酸乙二酯 (PET)的结晶过程进行了研究 ,发现单轴取向PET的冷结晶峰表现为多重结晶峰 .等温DSC方法的研究结果进一步证实结晶重峰的存在 .为此 ,本文提出了一种依据非等温DSC曲线解析高聚物结晶动力学参数的新方法 .对单轴取向PET的研究结果表明 ,与其他方法相比较 ,由新方法计算出的理论曲线与实验数据能更好地吻合 .单轴取向PET的总的结晶过程由三个子结晶过程组成 .根据不同拉伸比 ,各个子过程的Avrami指数和质量分数的变化 ,对结晶机理进行了解释 .与各向同性PET样品相比 ,单轴取向PET在低温部分的结晶速率明显增快 相似文献
19.
微管系统在细胞中执行许多重要功能山.微管在细胞中呈现高度的时间和空间有序性,并与构成它的结构单元—一微管蛋白(土。l})lllil。)保持动态平衡,而且这种平衡是局域的和暂时的,Mit(Jlisou和Krscllner根据他们的微管体外实验及体内微管聚合特性称之为微管生长的动态不稳定性*1.微管的生理功能正是与它的这种根本特性有关.另有研究发现微管是许多药物包括许多抗癌药物作用的靶子问.如紫杉醇(TaX01)*等.因此国际上研究微管蛋白的聚合过程以及药物分子的作用是微管研究中的热点问题之一.生理状态下微管蛋白以。月异二聚体… 相似文献
20.
Studying the Glass Transition by DSC and TMDSC 总被引:5,自引:0,他引:5
First, the principal features of the glass transformation process in polymers are reviewed, and then it is shown how they
are manifest in conventional DSC, and the quantitative analysis of typical DSC data is discussed in terms of the Tool-Narayanaswamy-Moynihan
(TNM) model. Subsequently, the way in which the glass transition is manifest in Temperature Modulated DSC is presented, and
the effects of both experimental and material parameters are discussed. In conclusion, the two techniques are compared in
terms of the information they provide about the glass transformation process.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献