苯乙烯-丙烯等规立构嵌段共聚物(iPS-b-iPP)的非等温结晶动力学的研究

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。     

氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物及其马来酸酐接枝共聚物增韧聚对苯二甲酸乙醇酯共混材料的辐射效应

采用双螺杆熔融共混的方法制备了含三羟甲基丙烷三丙烯酸酯(TMPTA)的聚对苯二甲酸乙二酯/氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物（PET/SEBS）和聚对苯二甲酸乙二酯/马来酸酐接枝氢化苯乙烯-丁二烯-苯乙烯嵌段共聚物（PET/SEBS-g-MAH）共混材料,并在Co-60源中对其进行辐照。 通过对共混材料的力学性能、相态结构测和凝胶含量分析,对比研究了辐射对以上2种共混材料结构及性能的影响。 扫描电子显镜观察和凝胶含量分析结果表明,在适量TMPTA存在时,辐射有效地改善了PET/SEBS体系的相容性。 冲击强度的变化证实了这种增容效应,当SEBS的质量分数为20%、TMPTA质量分数为1%,经50 kGy辐照后,冲击强度达到17.3 kJ/m2。 当在SEBS分子链上引入马来酸酐官能团,辐照后,体系的相态结构变化并不明显,冲击强度最大值仅为11.5 kJ/m2,明显低于不含马来酸酐官能团的体系。     

苯乙烯-丙烯嵌段共聚物等温结晶动力学的研究

用DSC法研究苯乙烯-丙烯嵌段共聚物(iPS-b-iPP)的等温结晶动力学。结果表明,在所选择的结晶温度(127～132℃)范围内,共聚物很好地符合Avrami动力学方程;共聚物结晶温度、结晶速率、结晶成核和生长方式都与共聚物结构和组成比有关,随着嵌段共聚物中iPS段含量的增加,结晶速率和Avranu指数(n)明显降低。     

反式-/顺式-1,4-聚异戊二烯共混体系的结晶动力学

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.     

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     

低密度聚乙烯/乙丙烯三元共聚(LDPE/EPO)共混体系的结晶动力学

用DSC方法研究了LDPE/EPO共混体系的等温及非等温结晶动力学,对LDPE/EPO共混体系的等温结晶动力学研究表明,共混物是三维生长的异相成核,共混物在各个结晶温度下的结晶过程都是以方式K_g(Ⅱ)进行的.采用联系Avrami方程和Ozawa方程导出的新非等温结晶动力学方程,处理了LDPE/EPO共混体系,得到了非等温结晶过程的一些基本参数,新方程很好地描述了此共混体系的非等温结晶动力学过程.     

乙烯-辛烯共聚物/淀粉共混体系的非等温结晶动力学(英文)

通过差示扫描量热仪(DSC)研究了乙烯-辛烯共聚物/淀粉共混体系的非等温结晶动力学,用Jeziorny和Ozawa方程描述了结晶动力学过程.共混物的结晶温度和结晶焓强烈依赖于淀粉含量和冷却速率.结果表明,随着冷却速率的增加,每个试样的结晶放热曲线均变宽,并向低温区移动.当温度一定高时,所有试样均具有较快的结晶速率. Jeniorzy方程可以较好地描述POE/淀粉共混物的非等温结晶模式,而Ozawa方程对于POE/淀粉共混体系不太适合.     

电子束辐照法制备交联共混物聚(ε-己内酯)/苯乙烯-丙烯腈共聚物的结晶动力学研究

将线形聚(ε-己内酯)(PCL)、苯乙烯-丙烯腈共聚物(SAN)和三烯丙基异三聚氰酸酯(TAIC)熔融共混,通过电子束辐照法制备了3组凝胶含量不同的交联PCL和PCL/SAN共混物样品.采用相差显微镜(PCOM)观察发现PCL与SAN具有良好的相容性.利用示差扫描量热法(DSC)和偏光显微镜(POM)研究了交联PCL和PCL/SAN共混物的等温结晶动力学和非等温结晶行为.结果表明,当体系交联程度相近时,交联聚己内酯的结晶动力学随SAN含量的增加而明显减慢.在SAN含量相同时,交联聚己内酯的结晶速率随交联程度增大而减小.对分离提取的线形和交联组分进行结晶动力学的研究则表明SAN引入对PCL的结晶速率起到了关键性的抑制作用.     

GMA/苯乙烯多组分单体接枝聚丙烯结晶行为研究

使用差示扫描量热计 (DSC)研究了甲基丙烯酸缩水甘油酯 苯乙烯 (GMA St)多单体熔融接枝聚丙烯[PP g (GMA co St) ]的等温和非等温结晶行为 ,用偏光显微镜观察了结晶的形态 ,并利用Avrami方程对其结晶动力学进行了分析 .研究发现接枝聚丙烯的结晶模式与PP相似 ,属于异相成核控制的球晶三维生长 ;但接枝聚丙烯的结晶温度 (Tc)显著提高 ,幅度高达 16～ 19℃ ,总结晶速率与纯PP相比明显加快 .接枝聚丙烯上GMA co St支链的存在 ,降低了成核界面自由能 ,促进了聚丙烯结晶的异相成核 .在接枝率不太高的情况下 ,随着接枝率的提高 ,接枝聚丙烯的结晶温度升高 ,总结晶速率加快 .在高接枝率范围内 ,随着接枝率的提高 ,接枝PP的Tc 不再升高 ,且由于接枝链的增长严重阻碍了球晶生长 ,导致接枝PP的总结晶速率反而随接枝率的升高而下降     

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.     

Effect of Electron Beam Irradiation on the Kinetics of Non-isothermal Crystallization of Nylon 66

The non-isothermal crystallization kinetics was studied by differential scanning calorimetric analysis on nylon 66 and e-beam irradiated nylon 66 at different cooling rates. The Modified Avrami equation, the Ozawa equation and the Combined Avrami-Ozawa equation were applied to study the kinetics of non-isothermal crystallization of nylon 66. The crystallization behavior of pristine nylon 66 polymer was compared with that of e-beam irradiated nylon 66 and observed that the kinetics of non-isothermal crystallization of nylon66 was affected largely upon e-beam irradiation. E-beam irradiation not only decreased the crystallization temperature of nylon 66, but influenced the mechanism of nucleation and crystal growth and reduced the overall crystallization rate of nylon 66 also. The crystallization activation energy calculated by the Kissinger method for irradiated nylon 66 was lower than that of pristine nylon 66.     

PA13N的合成和非等温结晶动力学研究

采用DSC方法研究了PA13N在不同降温速率下的结晶过程,并利用Avrami方程研究了其非等温结晶动力学。在非等温结晶过程中,随着降温速率的增大,结晶温度向低温偏移。综合利用Avrami方程得到Avrami指数为1.35~1.88和结晶速率常数Zc≈1;并求得其结晶活化能为-58.42kJ/mol。结果表明,PA13N的结晶能力小于其他脂肪族尼龙。     

Non-isothermal crystallization kinetics of continuous glass fiber-reinforced poly(ether ether ketone) composites

Current studies on crystallization kinetics for glass fiber-reinforced poly(ether ether ketone) mainly focused on short glass fiber-reinforced composites and their isothermal crystallization. It is worth noting that continuous glass fiber-reinforced poly(ether ether ketone) composite (CGF/PEEK) possesses relatively higher mechanical performance than short fiber-reinforced PEEK under high temperature. Here, for the first time, we investigate the non-isothermal crystallization kinetics and melting behavior of CGF/PEEK by differential scanning calorimetry at four different cooling rates. By evaluating the crystallite size of CGF/PEEK using X-ray diffraction, it is found that with the decreasing cooling rate, the crystallite size distribution evolves more uniform, and the size of crystallites enlarges. Besides, by systematical analysis, we find the modified Avrami equation can well describe crystallization behavior of the CGF/PEEK. The higher Avrami value of CGF/PEEK than pure PEEK indicates that CGF could introduce a more complex geometry effect on the crystallization. The addition of CGF greatly reduces the absolute value of crystallization activation energy of PEEK, suggesting that CGF can reduce the nucleation energy barrier. The obtained results illustrate that CGF can accelerate the nucleation rate due to heterogeneous nucleation while reduce the growth rate due to retarded polymer chain mobility. And the cooling conditions can influence crystal growth and morphology.

     

Crystallization of irradiated polyethylene

This study compares the effects of radiation dose on the isothermal and non-isothermal crystallization of LLDPE, LDPE and HDPE by differential scanning calorimetry (DSC). It includes qualitative comparison of the non-isothermal data and quantitative calculations of Avrami parameters for crystallization rate and nucleation mode. The isothermal crystallization allowed the observation of the changes in the crystallization rate, related to the decrease in the crystallization temperature caused by the crosslinking of the polymer. It was also observed by the non-isothermal crystallization, the development of crystallites of very different sizes in the polymer.     

一种研究聚合物非等温结晶动力学的方法

作者基于多年对聚合物结晶动力学方面研究的工作积累,联合Avrami方程和Ozawa方程,提出了一种研究聚合物非等温结晶动力学的新方法.该方法既克服了使用Ozawa方程所获得的数据点过少,常常出现非线性,不能获得可靠的动力学参数的缺点,又克服了使用经Jeziorny修正的Avrami方程所获得的表观Avrami指数无法准确预测非等温过程成核生长机理的缺点.该方法已成功用于多种聚合物体系,被国内外学者引用数百次,已成为研究聚合物非等温结晶动力学一种有效方法.     

Crystallization behavior of biodegradable poly(ethylene adipate) modulated by a benign nucleating agent: Zinc phenylphosphonate

Zinc phenylphosphonate (PPZn), a benign and biocompatible nucleating agent, was prepared and incorporated into the biodegradable poly(ethylene adipate) (PEA) to investigate its effect on the crystallization behavior, crystallization kinetics and spherulite morphology of PEA. Upon addition of PPZn, the crystallization temperature and crystallinity of PEA in the non-isothermal crystallization process increased significantly. Analysis of crystallization kinetics by Avrami equation suggests that the crystallization time shortened greatly and crystallization rate increased markedly after addition of PPZn. In the presence of PPZn, the spherulite size decreased and spherulite density increased significantly. It suggests that PPZn is an efficient nucleating agent for the crystallization of PEA. The accelerated crystallization in the presence of PPZn is mainly attributed to the epitaxial nucleation of PEA crystals on the surface of PPZn crystals, that is, a perfect lattice matching between PEA crystal and PPZn crystal occurs.