聚2-吡咯烷酮的非等温结晶动力学

用差示量热扫描热分析仪(DSC)测试了不同降温速率下聚2-吡咯烷酮(PPD)样品的温度-热焓曲线,样品黏均分子量为2.2×10~4,熔点为272℃。采用Jeziorny法、Ozawa法和莫志深法分析了PPD的非等温结晶动力学。结果表明,在给定降温速率范围内,Ozawa法不适用于描述PPD的非等温结晶动力学过程,Jeziorny法只适用于描述PPD的主结晶阶段,而莫志深法能很好地描述整个结晶过程。Jeziorny法处理结果表明,PPD主结晶阶段的Avrami指数(n)为1.68~1.78,晶体生长为准二维生长。莫志深法处理结果表明,在单位结晶时间里达到某一相对结晶度所需的降温速率随相对结晶度的增加而增大。用Kissinger方程求得PPD的非等温结晶活化能为-31.9kJ/mol。     

聚乙交酯非等温结晶行为研究

利用差示量热扫描热分析仪(DSC)测得了不同降温速率下聚乙交酯(PGA)的非等温结晶的温度-热焓曲线。分别通过Ozawa法、Jeziorny法和莫志深法对PGA的非等温结晶机理进行了分析。Ozawa法结果表明:在给定的温度范围内,Ozawa法并不适用于描述PGA的非等温结晶行为;Jeziorny法结果表明:不同降温速率下,PGA结晶过程的Avrami指数(n)接近4,PGA非等温结晶为均相成核、晶粒三维增长的过程;莫志深法结果表明:Avrami指数与Ozawa指数的比值(a)基本无变化,动力学参数f(T)随降温速率增加逐渐增大,即在更快的降温速率下,PGA结晶更充分,可获得更高的结晶度。通过Kissinger方程计算得到的PGA结晶扩散活化能为-66.9kJ/mol。     

聚丙烯-g-聚氨酯共聚物的非等温结晶动力学研究

用DSC法研究了聚丙烯 (PP)和聚丙烯接枝聚氨酯的共聚物 (PP g PU)在不同冷却速率下的非等温结晶动力学 .用Avrami方程和莫志深改进法对DSC测定结果进行了处理 ,结果表明 ,PP g PU的动力学参数能很好的符合Avrami方程和莫志深改进方程 .PP接枝了聚氨酯支链后 ,结晶速率增大 ,球晶的生长和成核机制也相应发生改变 ,而其变化规律与接枝物的组成和结构密切相关     

聚丙烯/累托石纳米复合材料的非等温结晶动力学研究

在双螺杆挤出机上熔融共混制备了聚丙烯 (PP) 有机累托石 (OREC)纳米复合材料 ,采用广角X 射线衍射 (WAXD)定性地分析了PP OREC纳米复合材料及纯PP的结晶形态 ,由半峰宽定性地判断了对应晶面法向的晶粒的大小 .结果表明有机累托石没有改变聚丙烯的结晶晶型 (纳米复合材料主要还是α晶型 ) ,但是细化了晶粒的尺寸 .采用差示扫描量热法 (DSC)定量地研究了复合材料的非等温熔融结晶动力学 ,对所得数据分别用Jeziorny法的Mo法进行了处理 ,表明非等温结晶动力学参数Zc 及Avrami指数n随冷却速率的增加而增加 ,复合材料的Avrami指数n大于纯PP的n ;对相同配比的纳米复合材料 ,随着结晶度的增加 ,单位结晶时间里达到一定结晶度所需要的降温速率F(T)增大 ,对同一个设定的结晶度 ,纳米复合材料的F(T)比纯PP的小 ,说明需要的降温速率减小 .所有这些均说明有机累托石可作为聚丙烯的结晶成核剂 .     

改性高岭土对PP/高岭土纳米复合材料结晶性能的影响

通过将不同改性的高岭土与聚丙烯共混, 制备了聚丙烯插层的PP/高岭土纳米复合材料. 并通过X射线衍射分析(XRD)、透射电子显微镜(TEM)研究了复合材料的微观结构, 同时通过差示扫描(DSC)非等温结晶方法和偏光显微镜(PLM)照片, 研究了改性高岭土母粒对聚丙烯的结晶性能的影响. 采用Avrami方程式及Jeziorny修正过的Avrami的方程式对PP/高岭土的非等温结晶动力学进行了研究. 结果表明, 有机改性过的高岭土可被聚丙烯完全剥离, 在XRD谱图中, 高岭土的001峰不可见, 在TEM中可见剥离的片层. 同时随着改性高岭土的加入, 使得聚丙烯异相成核结晶增长, 且填充聚丙烯的最快结晶温度在395K. 结果也表明, 有机改性的高岭土能有效促进PP的异相成核, 提高PP的结晶速率和结晶温度, 但对结晶速率常数影响不是很大.     

端氨基聚氨酯接枝聚丙烯和聚丙烯共混物的结晶动力学研究

通过反应挤出的方法将端氨基聚氨酯接枝到聚丙烯上,提纯后产物的红外光谱上出现氨基甲酸酯的C=O和N-H的特征吸收峰.使用光学解偏振仪、DSC对改性聚丙烯进行结晶动力学的研究.结果表明等温结晶过程基本上符合Avrami方程,功能化基团的加入起到类似成核剂的作用,能够加快聚丙烯的结晶速率;用Mandelkern理论处理DSC非等温结晶数据,研究表明纯聚丙烯的结晶能力小于功能化聚丙烯,而且非等温结晶过程也较好地符合Mandelkern理论.     

等规聚丙烯自成核的等温结晶动力学

近年来 ,有关等规聚丙烯 (i PP)的自成核研究已引起了人们的关注 [1 ] ,但有关其结晶动力学的报道并不多见 .Carfagna等 [2 ]用膨胀计法研究了 i PP在未完全熔融重结晶情况下的等温结晶动力学 ,得到的 Avrami指数远远小于 3 .张新远等[3 ] 研究了 i PP未完全熔融情况下的非等温结晶动力学 .到目前为止 ,i PP自成核的熔体降温等温结晶动力学尚未见报道 .本文在 i PP自成核研究的基础上 [4] ,用 DSC方法研究了 i PP自成核在较高温度下的等温结晶动力学 ,讨论了结晶机理 .结果表明 ,在本实验的自成核条件下 ,i PP依然是三维球晶生长 ,…     

PET/PEN/DBS共混物非等温结晶动力学研究

采用DSC方法, 用修正的Avrami, Ozawa, Ziabicki宏观动力学模型描述PET/PEN/DBS[PET: 聚对苯二甲酸乙二醇酯; PEN: 聚2,6-萘二甲酸乙二醇酯; DBS: 1,3∶2,4-二(亚苄基)-D山梨醇]共混物的非等温熔融结晶过程, 研究结果表明, 修正的Avrami模型能很好地描述此共混物非等温结晶过程. 冷却速率在5-20 ℃/min范围内, Ozawa方程能很好地描述初期结晶过程, 但结晶后期由于忽略次级结晶而不适宜. 由Ziabicki结晶动力学参数可知, 该共混物的结晶随着成核剂DBS含量的增加而降低, 结晶速率随着成核剂DBS含量的增加而提高. 在非等温结晶条件下, 共混物结晶同时受到冷却速率和共混物组成的影响, 与共混物非等温结晶过程的有效能垒分析结果基本一致.     

聚苯硫醚/纳米二氧化硅复合材料的非等温结晶动力学及动态力学性能

用DSC法研究了聚苯硫醚（PPS）及其纳米SiO2复合材料的非等温结晶动力学,分析了结晶峰值温度Tp以及结晶起始温度T0等参数,并采用莫志深方程研究了复合材料的非等温结晶动力学。结果表明,莫志深方程能够较好地描述复合材料的非等温结晶动力学,纳米SiO2在PPS基体中起异相成核作用,而使得纳米复合材料的结晶速率明显快于纯聚合物的结晶速率。动态力学分析研究结果表明,纳米SiO2的加入提高了PPS的储能模量,Tg向高温方向移动,说明纳米SiO2与PPS之间存在着较强的相互作用。     

SEBS-g-MAH对LLDPE结晶行为的影响

利用差示扫描量热法结合Avrami方程研究了线性低密度聚乙烯(LLDPE)、LLDPE与苯乙烯-乙烯-丁烯-苯乙烯嵌段共聚物(SEBS)共混体系及LLDPE与不同接枝率的SEBS共聚物接枝马来酸酐(SEBS-g-MAH)共混体系的非等温结晶动力学,探讨了SEBS-g-MAH对LLDPE结晶行为的影响.通过偏光显微镜(POM)观察了各体系的结晶形态.通过Gupta法、Jeziorny法和莫志深法分别对非等温结晶过程进行表征,结果显示:热塑性弹性体SEBS及其接枝物SEBS-g-MAH的加入阻碍了LLDPE分子链的规则排列,影响了链段在结晶扩散迁移过程中的规整排列速率,使得结晶速率变慢,对LLDPE晶体生长起了抑制作用.样品的Avrami指数均为1.1～1.5,说明LLDPE的结晶成核机理和生长方式没有改变.     

Effect of silver nanoparticles on the morphology,crystallization, and melting behavior of polypropylene: A study on non-isothermal crystallization kinetics

The nanocomposites were prepared using melt intercalation method and the effects of the processing conditions on silver nanoparticles dispersion were investigated by transmission electron microscopy. Non-isothermal crystallization kinetics of virgin polypropylene (PP) and its nanocomposites have been evaluated using differential scanning calorimetric technique. The non-isothermal crystallization melt data were analyzed using macro kinetics equation with the help of Avrami, Malkin, and Mo’s models. The crystallization rate increased with the increasing of cooling rates for virgin PP and nanocomposite, but the crystallization of nanocomposite was faster than that of PP at a given cooling rate. The activation energy for non-isothermal crystallization of virgin polymer and nanocomposites based on Kissinger method has been determined to be 186 and 211 kJ/mol, respectively. Transmission electron microscopy analysis reveals balanced dispersion and presence of some silver nanoparticles aggregates, which act as a heterogeneous nucleating agent during the crystallization of the nanocomposite.     

聚丙烯/蒙脱土纳米复合材料非等温结晶动力学的研究

用熔融插层法制备聚丙烯 蒙脱土纳米复合材料 ,用DSC手段研究了其非等温结晶行为 ,并与聚丙烯进行了对比 .对所得数据分别用修正Avrami方程的Jeziorny法、Ozawa法和Mo法进行处理 .结果表明 ,用Jeziorny法和Mo法处理非等温结晶过程比较理想 ,而用Ozawa法处理则不太适用 .用Jeziorny法求出的参数Zc和n随冷却速率的增加而增加 ,但复合材料的Zc 和n略大于聚丙烯的Zc 和n ,用Mo法求出的参数F(T)随结晶度的增加而略有增加 ,a几乎未变 ,复合材料的F(T)略小于聚丙烯的F(T) ,复合材料的a约为 1.40略大于聚丙烯的a(其值约为 1.0 4) .按Kissinger方法计算出聚丙烯及聚丙烯 蒙脱土纳米复合材料的结晶活化能分别为 189.37kJ mol,15 5 .6 9kJ mol,说明有机蒙脱土的加入 ,降低了聚丙烯的结晶活化能 ,起到了异相成核的作用     

Different influences of nucleating agents on crystallization behavior of polyethylene and polypropylene

The crystallization behavior of polyethylene (PE) and polypropylene (PP), including the neat ones and the ones nucleated with the same nucleating agent (NA), was studied by DSC. It was found that the nucleating agent decelerated the PE nonisothermal crystallization process. NA did enhance the nucleating rates for both PE and PP, but the linear growth rate dominated the volumetric growth rate for PE, and the volumetric growth rate dominated the overall crystallization rate. That is why PE nucleated with NA had a slower overall crystallization rate than the neat one.     

Non-isothermal crystallization behavior of polypropylene with nucleating agents and nano-calcium carbonate

The non-isothermal crystallization kinetics of isotactic polypropylene (iPP) and nucleated iPP was investigated by DSC. The crystalline morphology of iPP was observed by polarized light microscopy. It was found that the crystallization rate increased with the addition of nanometer-scale calcium carbonate (nm-CaCO₃) particles. The addition of dibenzylidene sorbitol (DBS) could greatly reduce the spherulite size of iPP. The crystallization temperature for the iPP with DBS was higher than for non-nucleated iPP. DBS was an effective nucleating agent for iPP. The results of measurements suggested that there was a coordinated action to the crystallization of iPP when the organic nucleating agents (DBS) and nm-CaCO₃ were added to iPP together. Comparison to the modified Avrami equation and Ozawa equation, another method—Mo’s method can describe the non-isothermal crystallization behavior of iPP and nucleated iPP more satisfactorily.     

Crystallization and melting behavior of isotactic polypropylene nucleated with individual and compound nucleating agents

In this study, α-phase nucleating agent (NA) 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS), β-phase rare earth NA (WBG), and their compound NAs were introduced into isotactic polypropylene (iPP) matrix, respectively. Crystallization kinetics and subsequent melting behavior of the nucleated iPPs were comparatively studied by differential scanning calorimetry (DSC) under both isothermal and nonisothermal conditions. For the isothermal crystallization process, it is found that the Avrami model successfully described the crystallization kinetics. The active energy of nonisothermal crystallization of iPP was determined by the Kissinger method and showed that the addition of nucleating agents increased the activation energy. Melting behavior and crystalline structure of the nucleated iPPs are dependent on the nature of NAs and crystallization conditions. Higher proportion of β-phase can be obtained at higher content of β-nucleating agent and lower crystallization temperature or lower cooling rate.     

Crystallization kinetics of isotactic polypropylene nucleated with octamethylenedicarboxylic dibenzoylhydrazide under isothermal and non-isothermal conditions

Octamethylenedicarboxylic dibenzoylhydrazide (TMC-300) was used as a nucleating agent for isotactic polypropylene (iPP) for the first time. The Avrami method and the Caze method were used to analyze the isothermal and non-isothermal crystallization kinetics of iPP incorporated with TMC-300, respectively. During isothermal crystallization, the half crystallization time at 130 °C reduces from 130 s of virgin iPP to 44 s after addition of TMC-300, which reflects that TMC-300 increased the crystallization rate of iPP obviously. The crystallization activation energy decreases from 382.5 kJ mol^?1 of virgin iPP to 275.3 kJ mol^?1 of iPP/TMC-300. During non-isothermal crystallization, the crystallization peak temperature of iPP nucleated with TMC-300 was increased by 5.1 °C when compared to that of virgin iPP at the cooling rate of 20 °C min^?1, and both the reduction of half crystallization time and the increase in peak crystallization temperature also justified that the addition of TMC-300 accelerated the crystallization of iPP.

     

聚丙烯/聚(丙烯-g-马来酸酐)/蒙脱土纳米复合材料结晶动力学研究

非等温结晶动力学;聚丙烯/聚(丙烯-g-马来酸酐)/蒙脱土纳米复合材料结晶动力学研究     

The influences of α/β compound nucleating agents based on octamethylenedicarboxylic dibenzoylhydrazide on crystallization and melting behavior of isotactic polypropylene

The influences of α/β compound nucleating agents based on octamethylenedicarboxylic dibenzoylhydrazide on crystallization and melting behavior of isotactic polypropylene (iPP) were analyzed. It is found that the crystallization temperatures of nucleated iPP were increased by above 11.0°C and the relative contents of β‐crystals (K_β ) in iPP reached above 0.40 after addition of compound nucleating agents. The K_β values depend on cooling rate, crystallization temperature in isothermal crystallization, and the difference between the crystallization temperatures of iPP nucleated by two individual nucleating agents. The nonisothermal crystallization kinetics were studied by Caze method and Mo method, respectively. The effective activation energy was calculated by the Friedman's method. The results illustrate that the half crystallization time was shortened and the crystallization rate was increased obviously after addition of nucleating agents, and the effective activation energy was increased with the relative crystallinity.     

Isothermal crystallization behaviors of isotactic polypropylene nucleated with α/β compounding nucleating agents

Sodium 2,2′‐methylene‐bis(4,6‐di‐tert‐butylphenyl) phosphate (NA40) and N,N‐dicyclohexylterephthalamide (NABW) are high effective nucleating agents for inducing the formation of α‐isotactic polypropylene (α‐iPP) and β‐iPP, respectively. The isothermal crystallization kinetics of iPP nucleated with nucleating agents NABW, NA40/NABW (weight ratio of NA40 to NABW is 1:1) and NA40 were investigated by differential scanning calorimetry (DSC) and Avrami equation was adopted to analyze the experimental data. The results show that the addition of NABW, NA40/NABW and NA40 can shorten crystallization half‐time (t_1/2) and increase crystallization rate of iPP greatly. In these three nucleating agents, the α nucleating agent NA40 can shorten t_1/2 of iPP by the largest extent, which indicates that it has the best nucleation effect. While iPP nucleated with NA40/NABW compounding nucleating agents has shorter t_1/2 than iPP nucleated with NABW. The Avrami exponents of iPP and nucleated iPP are close to 3.0, which indicates that the addition of nucleating agents doesn't change the crystallization growth patterns of iPP under isothermal conditions and the crystal growth is heterogeneous three‐dimensional spherulitic growth. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 590–596, 2007