高含量碳纤维对尼龙6非等温结晶与熔融行为的影响

利用差示扫描量热仪（DSC）研究了高含量碳纤维（CF）对尼龙6（PA6）非等温结晶与熔融行为的影响。结晶行为研究结果表明，高含量CF的引入对PA6的结晶起到异相成核作用，提高了PA6的总结晶速率。熔融行为研究结果表明在低的降温速率下。CF诱导基体尼龙6形成亚稳态的γ^＊结晶，其熔融峰为一个明显的不对称单峰；高降温速率下为熔融双峰，低温峰为亚稳态的γ^＊结晶的熔融。而高温峰为亚稳态的结晶在升温过程中发生再结晶和再组合形成更稳定的γ结晶的熔融。     

MC尼龙6/TiO2原位纳米复合材料等温结晶动力学的研究

采用差示扫描量热法(DSC)研究了阴离子原位聚合法制备的铸型尼龙6(MC尼龙6)/TiO2纳米复合材料的等温结晶行为,并应用Avrami方程分析了MC尼龙6的等温结晶动力学过程.结果表明纳米TiO2对MC尼龙6基体具有异相成核作用,使其原位纳米复合材料结晶速率常数变大,半结晶时间变小.Hoffman成核结晶理论计算结果表明,原位纳米复合材料的Kg(与结晶温度无关而与成核方式有关的参数)大于MC尼龙6且随着纳米含量的增加而增加,说明纳米TiO2阻碍了MC尼龙6分子链的运动,同时尼龙6由晶核生长占主导地位逐渐向成核机制占主导地位转变.     

纳米二氧化硅/MC尼龙6原位复合材料非等温结晶动力学的研究

通过阴离子开环聚合法制备了纳米二氧化硅(SiO2)／MC尼龙6原位复合材料。采用差示扫描量热法研究了MC尼龙6及其原位纳米复合材料的非等温结晶行为；并利用修正Avrami方程的Jeziomy和Liu法进一步处理原位纳米复合材料的非等温结晶动力学。结果表明，在纳米SiO2／MC尼龙6原位复合材料中，纳米SiO2对基体MC尼龙6的结晶有一定的成核作用，并提高了其结晶速率。     

碳纤维增强聚酰胺6复合材料的结晶行为研究

通过偏光显微镜和差示扫描量热仪(DSC)研究了碳纤维(CF)和滑石粉对聚酰胺6(PA6)结晶行为的影响。结果表明,CF的加入在PA6和CF的界面诱发横晶,CF和滑石粉在PA6基体中起到了异相成核作用,改变PA6的成核机理和晶体生长方式,提高了起始结晶温度和结晶速率。结晶速率随普等温结晶温度的升高而下降。当冷却速率增大时,起始结晶温度下降,结晶度增大。     

PA11/白炭黑纳米复合材料等温结晶动力学的研究

采用差示扫描量热法(DSC)研究了原位聚合尼龙11/白炭黑纳米复合材料的等温结晶行为,并应用Avrami方程分析了其等温结晶动力学过程。结果表明,纳米白炭黑对尼龙11基体起到异相成核作用,使其原位纳米复合材料动力学常数变大。Hoffman成核结晶理论计算结果表明,原位纳米复合材料的Kg大于尼龙11且随着纳米含量的增加而增加,说明纳米白炭黑阻碍了尼龙11分子链的运动,同时尼龙11有晶核生长占主导地位逐渐向成核机制占主导地位转变。     

尼龙6/高岭土复合材料的非等温结晶行为研究

用差示扫描量热法研究了尼龙6/高岭土复合材料的熔融结晶行为,并用Jeziorny法、Ozawa法、Mo法对复合材料的非等温结晶动力学进行研究。结果表明,3种高岭土的加入均使复合体系的熔融峰变窄,熔点增加;结晶峰温和结晶起始温度提高,结晶速率增大;高岭土填料起到异相成核作用;Jeziorny法、Mo法均适合分析尼龙6及复合体系的非等温结晶动力学过程,而Ozawa法不适合。     

氧化钕填充尼龙6的结晶行为

利用示差扫描量热仪（ＤＳＣ）研究了氧化钕（Ｎｄ２Ｏ３）对尼龙６（ＰＡ６）等温结晶行为的影响。结果表明，Ｎｄ２Ｏ３在ＰＡ６体系中起到了异相成核作用，提高了ＰＡ６的晶体增长速率。     

原位复合阻燃尼龙6的非等温动力学研究

采用差示扫描量热法研究了原位聚合反应制备阻燃尼龙6的非等温结晶行为,用Jeziorny法和莫志深法对其动力学过程进行了分析。结果表明:由于阻燃剂起到异相成核作用,使晶核的生长变快,提高了阻燃尼龙6的结晶温度和成核速率。随降温速率的增加,其结晶峰从高温向低温方向移动,峰形变宽,结晶时间缩短。同时阻燃剂在尼龙6分子链中存在相互作用力,阻碍了尼龙6分子链在结晶过程中的运动,导致结晶活化能提高,晶体生长速度下降,结晶度降低。     

纳米二氧化硅／MC尼龙6原位复合材料非等温结晶动力学

通过阴离子开环聚合法制各纳米二氧化硅／MC尼龙6原位复合材料,采用差示扫描量热法研究MC尼龙6及其原位纳米复合材料非等温结品行为,并利用修正Avrami方程的Jeziomy和Liu的方法进一步处理原位纳米复合材料的非等温结晶动力学,结果表明在纳米二氧化硅／MC尼龙6原位复合材料中,纳米二氧化硅对基体MC尼龙6的结晶有一定的成核作用,并提高了其结品速率。     

原位增容PA6/PE-HD共混物的非等温结晶动力学研究

利用差示扫描量热仪研究了原位增容的聚酰胺6/高密度聚乙烯（PA6/PE-HD）共混物的非等温结晶过程,用经Jeziorny 修正的Avrami方程和Mo法对其非等温结晶动力学进行了研究,计算并得到非等温结晶动力学参数。结果表明,该方程和方法适合于处理纯PA和PA6/PE-HD共混物的非等温结晶过程;在PA6/PE-HD共混物非等温结晶过程中, 在其初期结晶阶段可能同时包含了均相成核和异相成核, 在二次结晶阶段结晶生长可能是一维生长,并且PE-HD的加入,起到异相成核的作用,促进了晶核的生长。此外, 还利用Vyazovkin的方法求出PA6/PE-HD共混物结晶活化能与温度之间的关系。     

玻璃纤维增强PA66复合材料非等温结晶动力学的研究

采用差示扫描量热仪对玻璃纤维（GF）增强聚酰胺66（PA66）复合材料进行了非等温结晶研究;用莫志深法和Kissinger法计算并得到了非等温结晶动力学参数。结果表明,GF对PA66基体具有异相成核作用,可提高其结晶速率;当GF含量为30 %（质量分数,下同）时,复合材料的结晶速率最大;在相同时间内,复合材料的结晶度越大,其所需的降温速率越大;PA66、PA66/15 %GF、PA66/30 %GF、PA66/45 %GF的结晶活化能分别为-297.22、-356.32、-481.00、-365.59 kJ/mol。     

Crystallization behavior of polyamide 11/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC) was used to investigate the isothermal and nonisothermal crystallization kinetics of polyamide11 (PA11)/multiwalled carbon nanotube (MWNTs) composites. The Avrami equation was used for describing the isothermal crystallization behavior of neat PA11 and its nanocomposites. For nonisothermal studies, the Avrami model, the Ozawa model, and the method combining the Avrami and Ozawa theories were employed. It was found that the Avrami exponent n decreased with the addition of MWNTs during the isothermal crystallization, indicating that the MWNTs accelerated the crystallization process as nucleating agent. The kinetic analysis of nonisothermal crystallization process showed that the presence of carbon nanotubes hindered the mobility of polymer chain segments and dominated the nonisothermal crystallization process. The MWNTs played two competing roles on the crystallization of PA11 nanocomposites: on the one hand, the MWNTs serve as heterogeneous nucleating agent promoting the crystallization process of PA11; on the other hand, the MWNTs hinder the mobility of the polymer chains thus retarding the crystal growth process of PA11. The activation energies of PA11/MWNTs composites for the isothermal and nonisothermal crystallization are lower than neat PA11. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

原位增容PA6/PE-HD共混物的等温结晶动力学研究

采用差示扫描量热仪研究了原位增容聚酰胺6/高密度聚乙烯（PA6/PE-HD）共混物的等温结晶行为,采用Avrami方程分析了纯PA6和PA6/PE-HD共混物的等温结晶动力学,并通过Hoffman-Weeks方法计算出了共混物的平衡熔点。结果表明,二者的Avrami指数介于2.19~3.70之间,表明PA6晶体的生长方式为二维盘状生长和三维球晶生长并存,PE-HD的加入并没有影响PA6晶体的生长方式。偏光显微镜分析表明,纯PA6能够生成球晶,但加入PE-HD后,球晶尺寸明显变小,说明PE-HD的加入起到了异相成核的作用,加快了PA6的结晶过程。     

Isothermal crystallization kinetics and melting behavior of multiwalled carbon nanotubes/polyamide‐6 composites

Pristine and functionalized multiwalled carbon nanotubes (MWNTs) were used to fabricate polyamide 6 (PA6) composites through melt blending. The functionalized MWNTs were obtained by grafting 1,6‐hexamethylenediamine (HMD) onto the pristine MWNTs to improve their compatibility with PA6 matrix. The effect of MWNTs on the isothermal crystallization and melting behavior of PA6 was investigated by differential scanning calorimetry (DSC) and X‐ray diffraction (XRD). The Avrami and Lauritzen–Hoffmann equations are used to describe the isothermal crystallization kinetics. The values of the Avrami exponent found for neat PA6, the pristine MWNTs/PA6 and functionalized MWNTs/PA6 composite samples are about 4.0, 1.7, and 2.3, respectively. The activation energies are determined by the Arrhenius method, which is lower for the composites, ?320.52 KJ/mol for pristine MWNTs/PA6 and ?293.83 KJ/mol for functionalized MWNTs/PA6, than that for the neat PA6 (?284.71 KJ/mol). The following melting behavior reveals that all the isothermally crystallized samples exhibit triple melting endotherms at lower crystallization temperature and double melting endotherms at higher crystallization temperature. The multiple melting endotherms are mainly caused by the recrystallization of PA6 during heating. The resulting equilibrium melting temperature is lower for the composites than for neat PA6. In addition, polarizing microscopy (PLM) and small angle light scanning (SALS) were used to study the spherulite morphology. The results show that the MWNTs reduce the spherulite radius of PA6. This reduction is more significant for pristine MWNTs. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

稀土荧光PA6等温结晶动力学的研究

采用差示扫描量热法研究了稀土荧光PA6的等温结晶过程。结果表明,PA6的结晶速率随着荧光粉含量的增加而增加,稀土荧光PA6的Avrami指数随着结晶温度的增加而增加。稀土荧光PA6结晶时的表观活化能随着荧光粉含量的增加而增加,荧光粉的加入对PA6链段的运动起阻碍作用。     

Crystallization behavior of carbon nanotubes‐filled polyamide 1010

The nanocomposites of polyamide1010 (PA1010) filled with carbon nanotubes (CNTs) were prepared by melt mixing techniques. The isothermal melt‐crystallization kinetics and nonisothermal crystallization behavior of CNTs/PA1010 nanocomposites were investigated by differential scanning calorimetry. The peak temperature, melting point, half‐time of crystallization, enthalpy of crystallization, etc. were measured. Two stages of crystallization are observed, including primary crystallization and secondary crystallization. The isothermal crystallization was also described according to Avrami's approach. It has been shown that the addition of CNTs causes a remarkable increase in the overall crystallization rate of PA1010 and affects the mechanism of nucleation and growth of PA1010 crystals. The analysis of kinetic data according to nucleation theories shows that the increment in crystallization rate of CNTs/PA1010 composites results from the decrease in lateral surface free energy. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3794–3800, 2006     

Isothermal crystallization behavior of polyamide 6,6/multiwalled carbon nanotube nanocomposites

The good dispersion of functionalized multiwalled carbon nanotube (f‐MWCNT) in polyamide 6,6 (PA 6,6) matrix was prepared by solution mixing techniques. The crystalline structure and crystallization behaviors of PA 6,6 and PA 6,6/f‐MWCNT nanocomposites were studied by X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and polarized optical microscopy (POM) analysis. DSC isothermal results revealed that the overall isothermal crystallization rates of PA 6,6 increased as well as the activation energy of PA 6,6 extensively decreased by adding f‐MWCNT into PA 6,6, suggesting that the addition of f‐MWCNT probably induces the heterogeneous nucleation. The effect of f‐MWCNT on the chain arrangement for the crystallization of PA 6,6/f‐MWCNT nanocomposites was also discussed. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Isothermal and nonisothermal crystallization kinetics of MC nylon and polyazomethine/MC nylon composites

Crystallization kinetics of MC nylon (PA6) and polyazomethine (PAM)/MC nylon (PAM/PA6) both have been isothermally and nonisothermally investigated by different scanning calorimetry (DSC). Two stages of crystallization are observed, including primary crystallization and secondary crystallization. The Avrami equation and Mo's modified method can describe the primary stage of isothermal and nonisothermal crystallization of PA6 and PAM/PA6 composite, respectively. In the isothermal crystallization process, the values of the Avrami exponent are obtained, which range from 1.70 to 3.28, indicating an average contribution of simultaneous occurrence of various types of nucleation and growth of crystallization. The equilibrium melting point of PA6 is enhanced with the addition of a small amount of rigid rod polymer chains (PAM). In the nonisothermal crystallization process, we obtain a convenient method to analyze the nonisothermal crystallization kinetics of PA6 and PAM/PA6 composites by using Mo's method combined with the Avrami and Ozawa equations. In the meanwhile, the activation energies are determined to be ?306.62 and ?414.81 KJ/mol for PA6 and PAM/PA6 (5 wt %) composite in nonisothermal crystallization process from the Kissinger method. Analyzing the crystallization half‐time of isothermal and nonisothermal conditions, the over rate of crystallization is increased significantly in samples with a small content of PAM, which seems to result from the increased nucleation density due to the presence of PAM rigid rod chain polymer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2844–2855, 2004     

锦纶6/聚偏二氟乙烯共混纤维的非等温结晶行为

采用差示扫描量热法(DSC)研究了熔融纺丝法制备的锦纶6(PA6)/聚偏二氟乙烯(PVDF)共混纤维的非等温结晶行为,并利用修正Avrami方程的Jeziorny法和R-t法对其结晶动力学进行分析。结果表明,由于PVDF的黏度大,且PVDF中的氟原子能与PA6的酰胺键形成氢键,阻碍了PA6分子链在结晶过程中的运动,导致共混纤维的结晶温度和结晶速率比纯PA6纤维低,半结晶时间比PA6大,且随着PVDF含量的增加,其变化更为明显。