热历史对尼龙1212熔融行为的影响

利用DSC方法研究了不同热历史条件对尼龙1212熔融行为的影响.不同的热历史条件下,在DSC曲线上,观察到尼龙1212产生2个或3个熔融峰,依据聚合物结晶理论,对各峰的来源进行了分析.在160℃下不同温度退火120 min的尼龙1212样品DSC曲线上,低温结晶熔融峰主要由低温结晶形成的一些微晶体或者片晶熔融产生,其晶体完善程度较差,熔融峰值较低,峰面积较小;主熔融峰是由样品在淬火过程中形成的晶体和升温过程中低温结晶形成的晶体的熔融重结晶形成较为完善的晶体熔融所产生,熔融峰值较高,峰面积较大.在不同的升温速率条件下,熔融峰温度有所移动,表明不同升温速率条件下产生的熔融峰的结晶晶型是相同的.在不同结晶时间下结晶,延长结晶时间对较高完善程度晶体的生长有利.在不同温度下依次退火处理的样品,熔融产生两个附加峰,这两个附加峰的峰温都比它们相应的退火温度高,而峰高和峰面积随退火温度降低而减小.根据等温结晶结果,由Hoffman方法确定了尼龙1212的平衡熔融温度为202.8℃.     

卷绕速度对PET纤维固态结晶行为的影响

本文用DSC、X-射线衍射分峰、红外光谱研究高、低速卷线PET纤维的固态结晶行为,探讨在玻璃化温度(Tg)和冷结晶温度(Tc)之间的温度结晶对冷结晶峰的影响。实试结果表明,高速的Tc随结晶时间和结晶温度而增加,低速的Tc随结晶时间和结晶温度而降低。说明在结晶过程中低速的无定形大分子通过滑移重排逐步有序,而高速的无定形大分子的局部取向逐步耗散。若以结晶前、后冷结晶热焓之差表示结晶量,则结晶时间和温度之间存在变换关系,该关系作者已用多元线性回归技术求得。此外,还发现高速的在各个特征温度结晶后的反式指数(Itrans)与冷结晶热焓(△HTc)之间的函数关系,恰好与原纤维的冷结晶峰上各点所表征的结晶速率相对应。从而说明在不同温度下PET结构单元中乙二醇的构象变化是影响结晶速率的因素。     

尼龙1010在加热扫描中结构重组的研究

用DSC观察了经不同热处理的尼龙1010的热历史和结构重组的再现过程。合理地解释了DSC曲线上吸热和放热峰的性质,提出预熔结晶峰表征再结晶集合的观点。确定了对结晶完善敏感的热处理温度范围。为尼龙1010的加工和应用提供了部分理论依据。     

固态缩聚尼龙1010的熔化行为

本工作借助示差扫描量热法和X-射线衍射分析法(WAXD)首次研究了固态缩聚反应所得初生态尼龙1010的结晶特征和熔化行为。实验结果表明:固态缩聚反应的温度和时间以及产物分子量对初生态尼龙1010的熔化行为有着明显的影响。初生态尼龙1010结晶熔融双峰的显隐与其X-射线衍射峰特征没有明显的依赖关系,但随着尼龙大分子结晶的完善化而出现表观体积收缩观象。     

PET纤维的固态转变 Ⅱ.PET纤维玻璃态预转变的研究

本文用DSC法研究了高、低速卷绕pET纤维玻璃态预转变吸热变化的规律,探讨加热速率以及起始冷却温度高于Tg和低于Tg的冷却速率对试样预转变吸热的影响。在对预转变吸热峰有关参数定量处理基础上,阐述预转变吸热峰所表征的玻璃的结构的介稳性质。还通过X-射线衍射分峰的计算数据映证介稳玻璃结构对结晶度的影响。     

尼龙1010在熔融峰温等温结晶生成晶体的热性质和形态结构

用 DSC,TEM,ED 研究了尼龙1010在熔融峰温等温结晶生成晶体的热性质和形态结构。结果表明该晶体在 DSC 扫描的时间尺度范围内是稳定的,能保持原有的熔融特性,不是低熔点晶体转化而成的晶体。对该晶体进行电子衍射,显示对称的清晰的单晶电子衍射斑点,用尼龙1010的晶胞参数标定电子衍射图,证明是单晶的电子衍射图。     

尼龙1010的多重熔化

本文用差示扫描量热法(DSC)研究了尼龙1010的多重熔化行为。研究了部分扫描,部分扫描再退火,加热速率,冷却速率,依次降温退火对熔化曲线的影响。实验结果表明,在DSC扫描过程中试样经历了连续熔化与再结晶的过程。尼龙1010含有强烈地依赖于其热历史的晶体完全程度的分布,从结构再组合观点解释了熔化曲线上双重和多重熔化峰的原因。     

尼龙1010经逐步降温退火形成的晶体的热稳定性

本文用DSC研究了尼龙1010在低于其熔点下进行逐步降温热处理后的熔化行为及其由热处理所形成的晶体的热稳定性。实验结果表明,尼龙1010经逐步降温热处理后可产生与之相应步数的熔化峰,直观地反映了试样的热历史记忆,从而说明逐步降温热处理能够产生各自独立熔化的晶体。这些晶体在低于其热处理温度下是稳定的。     

尼龙610的多重熔融行为及其平衡热力学参数

用DSC,WAXD等方法研究了尼龙610的多重熔融行为。在DSC热谱图上,观察到三个熔融峰并按照部分熔融及分级熔融的观点对各峰的来源作了讨论。根据程序升温及等温结晶和比容测定的结果,求得尼龙610的T°_m及ΔH_m的值分别为517.6K及211.7j/g。     

半晶PBT在室温存放时的聚态结构变化

用DSC观察了不同冷却条件半晶PBT样品在室温存放时所发生的聚态结构变化。实验表明,在310～325K出现的热焓松弛峰的峰高和峰温随存放时间的变化与冷却条件有关。该峰表征试样中“硬无定形部分”的松弛。本文定量地描述了它的峰高与峰温对存放时间的依赖关系。发现水对松弛过程和随之发生的冷结晶有一定程度的抑制。室温存放过程中,晶态结构缺陷有,所减少并少量新的亚稳态晶体形成。     

Solid-state crystallization and thermal relaxation in nylon 1010

Quenched nylon 1010 was taken as a sample. Through demonstration that the exothermic peak in the DSC curve is a cold-crystallization peak, the effects of isothermal-crystallization periods and isochronal-crystallization temperatures on the cold-crystallization peak were studied. The effects of annealing temperatures and periods on the thermal relaxation peak were studied. It turned out that the rate of solid-state crystallization is higher in a short period of isothermal crystallization than that in a long period, which possibly results from new hydrogen-bond formation. The solid-state crystallization proceeds easily at higher temperature; the optimum crystallization temperature is 315 K. The temperature range between 277 K and 284 K is a sensitive one as concerns thermal relaxation, the most sensitive point being 281 K.

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Zusammenfassung Als Proben wurden abgeschrecktes Nylon 1010 verwendet. Anhand der Demonstrierung, daß es sich bei dem endothermen Peak der DSC Kurve um den Peak einer kalten Kristallisation handelt, wurde der Einfluß von isothermen Kristallisationsperioden und isochroner Kristallisationstemperaturen auf den Peak der kalten Kristallisation untersucht. Der Einfluß des oberen Kühlpunktes und der Kühlperioden auf den Peak der thermischen Relaxation wurde untersucht. Es stellte sich heraus, daß die Geschwindigkeit der Feststoffkristallisation bei einer kürzeren isothermen Kristallisationsperiode höher liegt, als bei einer längeren Periode, was möglicherweise von der Bildung neuen Wasserstoffbrückenbindungen herrührt. Bei höheren Temperaturen verläuft die Feststoffkristallisation einfacher, die optimale Kristallisationstemperatur beträgt 315 K. Der Temperaturbereich 277 – 284 K ist wegen der thermischen Relaxation empfindlicher, der empfindlichste Punkt liegt bei 281 K.

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Thanks are due to Fu Zhaohui for her beneficial work on the paper.     

热历史对已固化环氧树脂松弛行为的影响

<正> 环氧树脂是一种性能优良且应用广泛的高分子材料,近年来,人们对已固化环氧试样在玻璃化温度(T_g)以下贮存时,物理性能随时间而变化的物理老化现象进行了广泛的研究.Ophir等发现已固化环氧试样经淬火处理后,其T_g随贮存时间升高,认为是由于自由体积随贮存时间减小所致.Mijovic用不同的方法进行过类似的研究,发现淬火环氧试样的T_g随贮存时间降低,认为是由于试样中的内应力松弛所致.本文试图进一步搞     

尼龙-1010非等温结晶动力学

<正> 尼龙-1010是我国独创的工程塑料品种,已被较广泛地应用于精密机械零件、仪表制造、家用电器、航空等方面。有关尼龙-1010的基础研究大多在我国学者中间进行,由于在实际加工生产过程中,如通常的融熔纺丝、注射、模压等工艺均是在非等温条件下进行,有关它的非等温结晶动力学尚未见报道,本文用几种理论方法对尼龙-1010的非等温结晶动力学过程进行研究。     

Molecular Dynamics of PGA Bioabsorbable Polymer During Isothermal Cold Crystallization

An investigation was carried out on the molecular dynamics of poly(glycolide) (PGA) in its completely amorphous state and during isothermal cold crystallization. Experimental results were generated over a wide range of frequency and temperature by broad-band dielectric spectroscopy (DRS). The variation of the average relaxation time (defined as τ= ½πf_max where f_max is the frequency at maximum loss for the main α relaxation) has been studied during cold crystallization and the temperature dependence of this average relaxation time for completely amorphous and crystallized samples has been analyzed. This behaviour has been modelled by Havriliak-Negami and Vogel-Fulcher equations. The sensitiveness of the segmental dynamics to the degree of crystallinity has been analyzed, taking into account the relaxing segments and the amorphous layers between lamellae. Supporting evidence about the thermal behaviour of the polymers has been obtained with DSC. Complementarily, the evolution of the morphologies obtained during crystallization processes has been followed by optical microscopy.     

Miscibility Behaviour of Poly(ether Sulphone)/nylon-6 Blends

Binary blends of poly (ether sulphone) (PES) and Nylon-6 were prepared in a whole range of composition by melt extrusion. Miscibility behaviour of the blends were studied using thermal analytical techniques like differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Due to the rapid crystallization of Nylon-6 as it is cooled from the melt state, its glass transition behaviour could not be detected even in the quenched samples by DSC. Furthermore, the crystallization and melting behaviour of the blends have been studied by DSC. DMA results show that the dynamic storage modulus of the blends were in-between those of the constituent polymers. Also the glass transition of Nylon-6 phase as determined by the peak in loss tangent remains constant which shows that the two polymers are immiscible. Thermal expansion coefficient of the blends as determined by TMA is greater than that of Nylon-6 signifying the increased dimensional stability of the blends at higher temperatures. Morphological studies done by scanning electron microscopy (SEM) show the biphasic nature of the blends, with clear cut boundaries between the phases because of poor interfacial adhesion. Dispersed particle size is small when Nylon-6 is the dispersed phase because of its lower melt viscosity as compared to PES. Thermal stability of the blends was measured using thermogravimetric analysis (TG). Two-step decomposition behaviour was observed because of macro-phase separated morphology. This revised version was published online in July 2006 with corrections to the Cover Date.     

尼龙1010结晶与熔融行为的研究

用DSC研究了降温速率R对尼龙10 10结晶与熔融的影响,以及室温(RT)和液氮(LN)骤冷退火样品的熔融.降温时结晶温度随R增大线性降低;T_g以上可完成结晶时结晶度相同;结晶起始温度>181℃生成的晶体有三个熔融峰,对应于环状和放射状球晶的转化与熔融;在181℃和T_g间结晶,无放射球晶转化峰;T_g下有结晶放热峰样品加热时有冷结晶发生.RT未退火样品三个熔融峰,退火温度T_α≥180℃样品两个峰,结晶度C∝T_a;LN未退火样品单一熔融峰,T_a>160℃双峰,T_a≤160℃三峰,低温峰温与C均∝T.     

Primary and secondary crystallization of poly(ethylene adipate)

Secondary crystallization of PEA, occurring during DSC scan and performed after isothermal primary crystallization has been investigated. The high temperature exotherm peak has been attributed to the crystallization of amorphous fraction included between crystallites formed at the primary crystallization. The temperature position of the highest rate of the secondary crystallization depended on the temperature of the isothermal primary crystallization.     

尼龙1010盐固态缩聚反应的研究

采用测定转化率和分子量、红外光谱、X-射线衍射分析、元素分析、偏光显微镜和扫描电镜等方法研究了结晶尼龙1010盐的特性、尼龙1010盐固态缩聚反应的动力学及其相应的晶体结构形态,用DSC法探讨了其反应机理。