聚乙二醇的等温结晶动力学

用差示扫描量热仪(DSC)研究了聚乙二醇(PEG)的等温结晶动力学。结果表明,在较高温度下处理PEG后,等温结晶过程中,Avrami指数n≈4,表明PEG以均相成核的三维球晶方式生长,同时计算得到结晶活化能为72.013 kJ/mol;而在较低温度处理PEG后,等温结晶过程中,Avrami指数n≈3,表明PEG以异相成核的三维球晶方式生长,结晶活化能为234.791 kJ/mol,比较高温处理后的结晶活化能高,说明PEG的结晶能力随热处理温度的降低而降低。     

纳米银改性聚丙烯的非等温结晶动力学研究

采用共混造粒法制备了含0.5％纳米银的聚丙烯抗菌切片,利用差示扫描量热(DSC)法研究了聚丙烯及纳米银改性聚丙烯的非等温结晶行为及其动力学.结果表明,纳米银的加入使聚丙烯非等温结晶过程的成核自由能降低.Avrami方程能正确地描述聚丙烯及纳米银改性聚丙烯的非等温结晶过程.加入纳米银以后,材料的成核机理和晶体生长几何基本没有变化.聚丙烯和纳米银改性聚丙烯的Avrami指数的平均值分别为4.01和4.28,表明二者在非等温结晶时均以三维球晶方式生长.     

木粉聚丙烯复合材料的等温结晶动力学

应用差示扫描量热法(DSC)研究了有无相容剂(m-TMI-PP)的木粉聚丙烯复合体系的等温结晶行为,采用Avrami方程处理等温结晶过程,计算结晶动力学参数。结果表明,随着结晶温度的升高,各体系的结晶速率下降,结晶速率常数K、n降低,半结晶时间t1/2增大。在同一结晶温度下,木粉起到成核剂的作用,提高了基体的结晶速率;m-TMI-PP的加入,使基体的结晶速率下降。纯PP的等温结晶过程具有异相成核与均相成核的机理,复合材料的等温结晶过程属于异相成核机理。     

PEO/LiClO4复合体系中PEO的等温结晶动力学研究

用差示扫描量热法研究了聚氧化乙烯(PEO)和PEO/LiClO4复合体系中PEO的等温结晶过程.用Avrami方程分析了PEO和复合体系中PEO的等温结晶动力学,得到PEO在不同体系中等温结晶时的动力学参数.PEO的Avrami指数n都趋近2.5,说明PEO晶体以三维方式依热成核生长.动力学参数表明,复合体系中的PEO以异相成核为主.LiClO4对PEO等温结晶过程的影响为:作为PEO结晶的成核剂而加快其结晶过程;增加了复合体系的粘度,缩短了PEO的半结晶时间,使其结晶总速率增大;降低了复合体系中PEO的绝对结晶度.PEO和复合体系中的PEO等温结晶时成核和生长活化能△E分别为59.28kJ/mol、70.85kJ/mol.     

聚氧化乙烯(PEO)及其与高氯酸锂复合体系的等温结晶动力学研究

用示差扫描量热法研究了PEO及其与高氯酸锂复合体系的等温结晶过程。用Avrami方程分析了PEO和复合体系中PEO的等温结晶动力学,得到了PEO在不同体系中等温结晶时的动力学参数。PEO的Avrami指数n都趋近2．5,说明PEO晶体以三维方式依热成核生长。动力学参数表明,复合体系中PEO结晶时以异相成核为主。LiClO4对PEO等温结晶过程的影响如下：作为PEO结晶的成核剂而加快其结晶过程;增加了复合体系的粘度,缩短了PEO的结晶半时间,使其结晶总速率增大;降低了复合体系中PEO的绝对结晶度。     

聚己内酯等温结晶的Avrami动力学研究

利用示差扫描量热仪(DSC)分析了3种不同分子量的聚己内酯(PCL)在30～45℃的等温结晶,并通过Avrami方程对其进行了等温结晶动力学研究。在此温度范围内,PCL的结晶度与等温结晶时间的关系曲线都呈现S型,说明其均采用异相成核的方式。根据Avrami关系式解出的双对数图都存在很好的直线关系部分,推导出Avrami指数(n)的值大都约为整数,在相同的Tc下,PCL生长方式类似,与分子量基本无关。lnK(结晶速率常数)随Tc的升高逐渐减小,说明晶体生长速率逐渐下降。在相同的Tc下,随着分子量的增加,结晶速率逐渐下降。半结晶时间(t1/2)随Tc的升高而降低,说明在此温度范围内晶体的生长速率随着Tc的升高而减慢。通过原子力显微镜(AFM)研究了PCL在30～45℃等温结晶的晶体表面,推导出的n值与Avrami方程拟合出的n值基本一致,说明Avrami动力学分析的结果是比较可靠的。     

PET/SiO2纳米复合材料的非等温结晶动力学

为了研究溶胶-凝胶原位聚合法合成的PET/SiO2纳米复合材料的结晶性能,用Avrami法和莫志深法对该复合材料进行了非等温结晶动力学研究。通过研究,得出以下结论:SiO2纳米粒子对基体PET具有异相成核作用,使PET的结晶温度明显升高,SiO2纳米粒子的加入使PET的结晶速率提高;SiO2粒子改变了PET基体的成核机理和生长方式;PET/SiO2纳米复合材料非等温结晶行为适合莫志深法。     

原位交联改性PP/POE共混物的等温结晶行为

采用热塑性聚烯烃弹性体(POE)作为增韧材料,以过氧化二异丙苯(DCP)为交联剂制备了PP/POE共混物。利用差示扫描量热仪(DSC)和偏光显微镜(PLM)研究了PP/POE共混物等温结晶行为,并用Avrami方程分析了PP/POE共混物结晶动力学。结果表明,POE的加入能起到异相成核的作用,加快了PP的结晶成核速率。Avrami指数在1.93～3.09,DCP的引入对聚丙烯(PP)的成核与生长机理影响不大,但其原位交联作用阻碍了PP分子链的运动,使得PP结晶速率降低,结晶时间延长。     

间规聚苯乙烯的非等温结晶动力学

用DSC法研究了间规聚苯乙烯(s-PS)的非等温结晶过程,并以Бopoxobckuu方程进行非等温结晶动力学数据处理,根据Ziabicki理论,确定了动力学结晶能力(Gc)。结果表明,冷却速率在1．25(-K／min)～20(-K／min)范围内,s-PS非等温结晶过程中t0.5和tmax均随冷却速率(a)增加呈指数下降,二者关系为t0.5=1．007tmax.非等温结晶过程中存在二次结晶现象,结晶前、后期成核机理有明显差异,前期成核受a影响较大;后期基本上均为异相成核,三维生长。非等温结晶活化能为382kJ／mol。     

蒙脱土填充聚丙烯的等温结晶动力学

用示差扫描量热法(DSC)研究蒙脱土对聚丙烯的等温结晶的影响，结果表明，蒙脱土对聚丙烯的结晶起到了异相成核的作用，提高了聚丙烯的结晶速率，结晶一半时的时间tl／2明显缩短，熔点升高，结晶度增大。用Avrami方程进行等温结晶动力学研究，参数n对结晶温度有依赖性，PP／Mont复合材料的k值随温度的升高而减小。     

Effect of low multi-walled carbon nanotubes loading on the crystallization behavior of biodegradable poly(butylene adipate)

The effect of low carboxyl-functionalized multi-walled carbon nanotubes (f-MWCNTs) loading on the crystallization behavior of biodegradable poly(butylene adipate) (PBA) was studied with various techniques in this work. For the nonisothermal melt crystallization, f-MWCNTs accelerate the crystallization process of PBA apparently due to the heterogeneous nucleation effect. The Ozawa method fails to describe the nonisothermal crystallization process of neat PBA and its nanocomposite. Isothermal melt crystallization kinetics of neat PBA and its nanocomposite was analyzed by the Avrami equation. The overall isothermal crystallization rate of neat PBA and its nanocomposite increases with increasing crystallization temperature. The addition of f-MWCNTs accelerates the isothermal crystallization of PBA as compared with that of neat PBA at a given crystallization temperature, indicative of the nucleating agent effect of f-MWCNTs; however, the crystallization mechanism does not change. The crystal structure of PBA remains unchanged in the PBA/f-MWCNTs nanocomposite despite the presence of f-MWCNTs.     

聚酯／热致液晶聚合物体系的非等温结晶动力学研究

热致性液晶共聚酯ＰＥＴ／６０ＰＨＢ组分对ＰＥＴ及ＰＢＴ在两种共混体系中的非等温结晶行为的影响用ＤＳＣ方法进行了研究，并用Ｏｚａｗａ方法处理了动力学数据。随共混体系ＬＣＰ含量的增加，ＰＥＴ的Ａｖｒａｍｉ指数ｎ趋于降低而ＰＢＴ的ｎ值趋于增加，表明在非等温结晶条件下，对不同组成的共混物体系有着不同的成核和晶体生长的机理。     

Crystallization kinetics of Zr-33 at % Ni amorphous alloy

The amorphous to crystalline transition in Zr-33 at% Ni amorphous alloy has been found to occur by polymorphic crystallization. The product of the cyrstallization process has been identified as the equilibrium Zr₂Ni intermetallic phase. The kinetics of crystallization have been studied independently using differential scanning calorimetry (DSC) and transmission electron microscopy. The activation energy of crystallization has been evaluated by isothermal and continuous heating in DSC. The isothermal anneals have revealed that the crystallization follows the Johnson-Mehl-Avrami kinetics with an Avrami exponent close to 4. The microstructural changes accompanying crystallization have been studied for an interpretation of the Avrami exponent. The nucleation and growth rates of crystals have been estimated at different temperatures in order to determine the activation energies of the two processes. It has been found that nucleation is thermally activated and growth is interface controlled.     

超临界聚合法等规聚丙烯的结晶行为

采用差示扫描量热法及带热台在线偏光显微镜直接观察法,研究了超临界聚合与常规淤浆聚合这两种不同聚合工艺所制备等规聚丙烯的等温结晶行为.结果表明,超临界法聚丙烯（sc-iPP）由于其较低的分子量及较窄的分布,使得等温结晶速率比常规淤浆法聚丙烯（c-iPP）快,结晶度高,且sc-iPP的晶体呈负光性,倾向于异相成核.而c-iPP的晶体则呈混光性,倾向于均相成核,但两者均为典型的球晶,均体现热成核机理.     

Two-stage crystallization kinetics equation and nonisothermal crystallization analyses for PTEG and filled PTEG

A novel modified Avrami model considering both primary and secondary crystallization has been presented to extract the kinetic behavior of these two crystallization stages in nonisothermal crystallization process of polymers. Nonisothermal crystallization kinetics of poly(trimethylene terephthalate)–poly(ethylene glycol) segmented copolyesters (PTEG) has been investigated by differential scanning calorimetry. The crystallization rate constants and Avrami exponents at various cooling rates were obtained from the analyses for neat PTEG and multiwalled carbon nanotube (MWNT) filled PTEG. Secondary crystallization displays a lower-dimensional crystal growth compared with primary crystallization and the results of kinetics analyses are consistent with morphology study. The MWNTs introduced into PTEG matrix take the role of effective nucleating agents during composites crystallization and can expedite the process of crystallization of the matrix by providing more nucleation sites to the crystallizing phase.     

Crystal morphology,mechanical property and non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) copolymer binary blends

The crystal morphology, impact strength and nonisothermal crystallization kinetics of poly(trimethylene terephthalate)/maleinized poly(ethylene-octene) (PTT/PEO-MA) copolymer blends were studied by using the polarized optical microscopy, impact tester and differential scanning calorimetry (DSC). Avrami theory modified by Jeziorny, Ozawa and Mo theories were used to study the non-isothermal crystallization kinetics of the blends, respectively. The results suggest that these methods are suitable for analyzing the crystallization kinetics of the PTT/PEO-MA blends. The PEO-MA component, serving as a nucleation agent in blends, can increase the start crystallization temperatures and accelerate the crystallization rate of the blends. The crystal dimensions are predominantly three-dimensional growths, judged from the Avrami exponent n and the Ozawa exponent m, but the spherulites in blends are much smaller than those in pure PTT. The crystallization active energy suggests that the PEO-MA component can make the PTT component easy to crystallize in blends. The blend has the highest Izod impact strength as PEO-MA content is 3wt.%. Considering both the crystallization kinetic analyses results and the crystal morphology of the blends, the modified Avrami method is believed to be the most useful in reflecting the crystallization of the blends.     

熔融聚合耐高温聚酰胺的等温结晶动力学研究

通过差示扫描量热仪(DSC)研究了熔融聚合耐高温聚酰胺10T以及10T/11树脂的等温结晶行为。通过Avrami方程分析了PA10T和PA10T/11的等温结晶动力学,其Avrami指数n值介于1.79~2.31之间,表明了PA10T和PA10T/11晶体以一维针状生长和二维片状生长并存,然后计算了相关的结晶动力学参数。通过Arrhenius方程计算了PA10T和PA10T/11的等温结晶活化能,同时通过Hoffman-Weeks外推法得到了PA10T和PA10T/11的平衡熔点。并且,利用Turnbull-Fisher方程和Lauritzen-Hoffman方程研究了PA10T和PA10T/11的结晶生长方式。偏光显微镜和X射线衍射分析表明,在实验条件下PA10T和PA10T/11以一维针状生长和二维片状生长并存,并且加入11-氨基十一酸后PA10T/11的晶粒尺寸显著细化。     

纳米CaCO3填充聚丙烯的非等温结晶动力学

利用差示扫描量热仪(DSC)研究了未处理纳米CaCO3和经偶联剂处理的纳米CaCO3对聚丙烯非等温结晶行为的影响。结果表明，处理的与未处理的纳米CaCO3粒子在聚丙烯基体中都能起到异相成核作用。但是，与未处理的纳米CaCO3相比，经表面改性的纳米CaCO3粒子能更加有效的提高聚丙烯的结晶温度。研究还发现，当偶联剂用量为纳米复合材料中CaCO3含量的1％～2％(质量)，同时降温速率大于5K／min小于40K／min，相对结晶度要求大于30％时，处理的纳米CaCO3粒子可使聚丙烯的结晶动力学参数Zc有小幅度的增加，F(T)值则显著减小，此结果具有非常重要的实际应用价值。