A STUDY ON THE CRYSTALLIZATION KINETICS OF NYLON 1010

The kinetic behavior of isohermal and nonisothermal crystallization of nylon-1010has been studied by means of dilatometry and differential scanning calorimetry, respec-tively. The isothermal and nonisothermal process can be descibed by Avrami equationand Ozawa equation, respectively. From the experimental results the kinetic paramters ofcrystallization and crystalline mechanism for isothermal and nonisothermal measurementsare discussed.     

MELTING CRYSTALLIZATION BEHAVIOR OF NYLON 66

Analysis of isothermal and nonisothermal crystallization kinetics of nylon 66 was carried out using differentialscanning calorimetry (DSC). The commonly used Avrami equation and that modified by Jeziorny were used, respectively, tofit the primary stage of isothermal and nonisothermal crystallizations of nylon 66, In the isothermal crystallization process,mechanisms of spherulitic nucleation and growth were discussed. The lateral and folding surface free energies determinedfrom the Lauritzen-Hoffman treatment are σ= 9.77 erg/cm~2 and σ_e= 155.48 erg/cm~2, respectively; and the work of chainfolding is q = 33.14 kJ/mol. The nonisothermal crystallization kinetics of nylon 66 was analyzed by using the Mo methodcombined with the Avrami and Ozawa equations. The average Avrami exponent n was determined to be 3.45, Theactivation energies (ΔE) were determined to be -485.45 kJ/mol and -331.27 kJ/mol, respectively, for the isothermal andnonisothermal crystallization processes by the Arrhenius and the Kissinger methods.     

尼龙1218的等温及非等温结晶动力学研究

采用示差扫描量热计DSC考察了一种新型长烷基链偶偶尼龙 尼龙 12 18 自熔体的结晶过程 ,分别利用Avrami方程和Ozawa方程对等温及非等温结晶动力学进行了描述与研究 ,计算了相关的结晶动力学参数 ,得出相应的结晶机理 .最后计算了等温结晶活化能和非等温结晶活化能 ,依此得到烷基链段长度与尼龙结晶过程有密切关系     

CRYSTALLIZATION KINETICS OF HOMOGENEOUS AND HETEROGENEOUS LLDPE

Based on thermal analysis, the isothermal and nonisothemal crystallization kinetics of Ziegler-Natta catalyzedlinear low density polyethylene (Z-N LLDPE) and metallocene catalyzed LLDPE (m-LLDPE) were studied. Treating theresults with the Avrami equation and the Ozawa equation, the crystallization constant lgk and the Avrami exponent n wereobtained. Some other crystallization parameters were also discussed. According to the different characteristics of the chainstructures of Z-N LLDPE and metallocene LLDPE, their crystallizaton behaviors were analyzed. It is indicated that thehomogeneity and heterogeneity of the two polymers act in different way during the crystallization process of polymers,including the nucleation and the growth of crystals under various conditions.     

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.     

尼龙1010非等温结晶动力学与机理研究

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...     

MULTIPLE MELTING AND CRYSTALLIZATION BEHAVIOR OF NYLON 1212

The wide-angle X-ray diffraction (WAXD) patterns of isothermally crystallized Nylon 1212 show that γ-form crystals form below 90℃ and the α-form crystals can exist above 140℃. In the temperature range of 90-140℃, the α-form and γ-form crystals coexist. Variable-temperature WAXD exhibits that the nylon 1212 γ-form does not show crystal transition on heating, while α-form isothermally crystallized at 160℃ exhibits Brill transition at a little higher than 180℃ on heating. The multiple melting behaviors of Nylon 1212 isothermally crystallized from melt come from a complex mechanism of different crystal structures, dual lamellar population and melting-recrystallization. In polarized optical microscope (POM) observations, Nylon 1212 isothermally crystallized at 175℃ shows the ringed banded spherulites. However, at temperatures below 160℃ the ringed banded image disappears, and cross-extinct spherulites are formed.     

尼龙6/蒙脱土纳米复合材料的结晶行为

用广角Ｘ 射线衍射（ＷＡＸＤ）、差示扫描量热仪（ＤＳＣ）、小角激光散射（ＳＡＬＳ）等手段研究了尼龙６／蒙脱土纳米复合材料的结晶行为．结果表明分散在尼龙６基体中的蒙脱土纳米粒子起成核剂的作用．蒙脱土的表面改性增加了蒙脱土和尼龙６分子之间的界面粘接，它具有阻碍尼龙６结晶的作用，使结晶活化能增加     

THEORETICAL ANALYSIS OF KINETICS OF NONISOTHERMAL CRYSTALLIZATION OF POLYMERS

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.     

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℃.     

STRESS-INDUCED CRYSTALLIZATION OF POLYURETHANE/MONTMORILLONITE NANOCOMPOSITE

Exfoliated polyurethane/montmorillonite nanocomposites with both high elongation at break and high tensilestrength were studied by dynamic-infrared spectroscopy (dynamic-IR). The results show that crystallization induced byadditional stress is impeded by the nano-layered organo montmorillonite.     

尼龙1212/尼龙6共混体系的非等温结晶行为

用DSC研究了尼龙 12 12 ,尼龙 6及其共混体系的非等温结晶行为 .结果表明 ,加工历史对尼龙的结晶和熔融行为影响很大 .经双螺杆挤出机挤出的尼龙 12 12和尼龙 6 ,由于应力诱导分子链取向 ,其结晶温度都有不同程度的提高 ,且表现出多重熔融现象 .在共混体系中 ,尼龙 12 12分子在共混物的界面上异相成核结晶 ,提高了其结晶温度 ,但酸酐化SEBS的加入抑制了分子链的运动又使其结晶温度降低 .共混体系降低了尼龙12 12的熔融温度 ,并使得其高熔点的熔融峰逐渐消失 ;而尼龙 6的熔融行为基本上没有变化 .     

聚乳酸/矿物填料复合材料的示差扫描量热研究

通过熔融共混法制备了一系列聚乳酸(PLA)/矿物填料复合材料.采用示差扫描量热(DSC)研究了含有碳酸钙(CaCO3)、蒙脱土(MMT)和凹凸棒土(AT)的聚乳酸复合材料在不同热历程中的结晶和熔融行为.研究发现,MMT和AT对PLA的慢速降温结晶无明显影响,而碳酸钙在慢速降温过程中能够有效促进PLA结晶;在2.5 K/min的降温速率下,结晶热焓随碳酸钙含量增加而增加;填料种类和含量会对复合材料升温过程的冷结晶和熔融产生较大影响,低含量矿物填料主要对PLA的冷结晶起成核作用,其中MMT成核效果最好.较高含量下不同填料会对PLA晶体形态产生影响,从而得到多样的DSC曲线变化.     

SYNTHESIS AND CRYSTALLIZATION BEHAVIOR OF POLY(ETHER ETHER KETONE ETHER KETONE)(PEEKEK)*

In this paper, the synthesis and crystallization behavior of poly(ether ether ketone ether ketone) (PEEKEK) arereported. PEEKEK was prepared from 4,4'-bis(p-fluorobenzoyl) diphenyl ether (4,4'-FBDE) and hydroquinone along thenucleophilic substitution route. The thermal properties were investigated by using DSC and TGA. The crystallizationbehavior of PEEKEK under several conditions, i.e., crystallization from the molten state (melt crystallization), crystallizationfrom a quenched sample (cold crystallization) and crystallization induced by exposing glassy sample to methylene chloride(solvent-induced crystallization) has also been investigated. The results show that crystallization of PEEKEK could beinduced by the above methods, and no polymorphism was found. The diflierences in the crystallization of PEEKEK inducedby the above methods are seen in their degree of crystallinity.     

DETERMINATION OF DEGREE OF CRYSTALLINITY OF NYLON 1212 BY WIDE-ANGLE X-RAY DIFFRACTION

Based on the X-ray scattering intensity theory and using the approximate expression for the atomic scattering factor, the correction factors for three crystalline peaks and an amorphous peak of Nylon 1212 were calculated and the formula of degree of crystallinity of Nylon 1212 was derived by a graphic multipeak resolution method. The degree of crystallinity calculated from the WAXD method is compatible with those obtained by density and calorimetry methods.     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.     

聚苯硫醚/尼龙6共混物界面对结晶行为的影响

高分子作为材料时 ,其力学性能受其结晶形态的影响 ,而其结晶形态与其结晶行为有关 .结晶性聚合物共混物中结晶组分由于第二组分存在 ,改变了结晶组分在熔体时的化学与物理环境 .因此 ,其结晶组分的结晶行为不仅取决于两组分在熔体时的相容性 ,而且与第二组分是否起到异相晶核作用和 /或两组分间界面是否诱导成核作用有关 ,从而影响共混物中结晶组分的结晶行为 ,导致共混物力学性能的改变[1～ 4] .在ＰＰＳ/ＰＡ6共混物中 ,由于ＰＰＳ的熔点和熔体结晶温度都比ＰＡ6的高 ,共混物熔体降温结晶ＰＰＳ是在ＰＡ6熔体存在下发生结晶 ,而ＰＡ6是在…     

熔体插层制备尼龙6/蒙脱土纳米复合材料的性能表征

通过熔体插层成功地制备了尼龙６／蒙脱土纳米复合材料，测试了力学性能、耐热性能和耐溶剂性．通过ＴＥＭ、ＷＡＸＤ、ＤＳＣ等手段，研究了结构与结晶行为，并与插层聚合的尼龙６／蒙脱土纳米复合材料进行了对比．实验表明通过熔体插层可使尼龙６基体插层于蒙脱土中，所得到的复合物的性能较尼龙６有很大提高，且与插层聚合的尼龙６／蒙脱土纳米复合材料的性能相当．     

THE ORIENTATION AND CRYSTALLIZATION OF POLYETHYLENE TEREPHTHALATE

The drawing behavior of three types of PET spherulites and PET amorphous samples have beenstudied. Two different sample preparation techniques were used in this study: (1) The films withnormal positive, normal negative or abnormal spherulites were prepared by solution casting tech-niques, then the films were deformed by uniaxial drawing. The uniaxial drawing behavior of PETspherulites appears to be dependent on the angles between the c-axis and the radius direction of thespherulites and that the deformation of spherulites becomes more difficult the larger the angles. (2)Amorphous films of PET were prepared first, then the films were deformed under uniaxial drawingto achieve c-axis orientation at a temperature near the glass transition temperature. The orientedfilms were subsequently annealed with fixed length at 215℃The films prepared in this way ex-hibit excellent c-axis orientation along the stretching direction. The degree of perfection of thecrystalline structure is much greater than that of the spherulites.     

SYNTHESIS AND CHARACTERIZATION OF ORGANOMONTMORILLONITE AND POLYAMIDE 66/MONTMORILLONITE NANOCOMPOSITES

The montmorillonites (MMTs), layered, smectite-type silicates, were premodified by two different methods priorto the polymer melt intercalation. In one case MMTs were modified with cetyltrimethylammonium bromide (CTAB), andtermed as organomontmorillonites (OMMTs); in the other case MMTs were modified by nylon, and the products were calledmodified montmorillonites (MMMTs). The effects of CTAB and nylon on the MMTs were investigated by using TG andWAXD. The results show that interlayer spacings of CTAN and nylon modified MMTs are larger than that of sodium MMTs.Then, polyamide 66 (PA 66)/MMT nanocomposites were obtained through the method of melt intercalation of polymers. Thenanocomposites were characterized by WAXD, TEM and Molau experiments. The results indicate that the MMTs dispersehomogeneously in the PA 66 matrix. The mechanical properties of nanocomposites, such as tensile properties and flexuralproperties, were also measured and show a tendency to increase with increase of MMT content and reach the maximumvalues at 5phr MMT content. The heat distortion temperature (HDT) of the nanocomposites (7 phr) is about 32 K higher thanthat of pure PA 66.