尼龙11/HGB复合材料的非等温结晶动力学

采用熔融共混法制备了尼龙(PA)11/空心玻璃微珠(HGB)(PA11/HGB)复合材料,应用差示扫描量热(DSC)仪研究了不同HGB用量下的PA11/HGB复合材料的非等温结晶过程,采用Jeziorny法和Mo法研究了复合材料的非等温结晶动力学,采用X射线衍射(XRD)仪研究了复合材料的晶型变化情况。DSC结果表明,随着降温速率的增加,复合材料的结晶温度总体上降低,结晶温度区间变宽;HGB在PA11基体中起到了异相成核作用。Jeziorny法不适用于PA11/HGB复合材料的非等温结晶动力学研究,而Mo法较为适合,其研究结果表明适量的HGB具有加速PA11基体结晶的作用,但当HGB用量达到8份后,这种作用趋于稳定。XRD结果表明,HGB可诱导PA11基体生成新的β晶。     

MWNTs/卤-锑阻燃体系对PA6性能的影响

采用熔融共混法制备了聚酰胺6/多壁碳纳米管/十溴二苯乙烷-三氧化二锑(PA6/MWNTs/DBDPE-Sb2O3)阻燃复合材料,通过极限氧指数测试(LOI)、垂直燃烧测试(UL 94)、热重分析(TG)、差示扫描量热分析(DSC)、力学性能测试等方法研究了不同质量比的MWNTs/卤-锑阻燃体系对PA6/MWNTs/DBDPE-Sb2O3复合材料阻燃性能、热稳定性、力学性能以及非等温结晶行为的影响。结果表明:MWNTs的加入起到异相成核剂的作用,提高了复合材料的结晶速率且改变复合材料的晶型,同时使复合材料的热稳定性能得到改善。其中,当MWNTs含量为1%、DBDPE-Sb2O3含量为15%时,PA6/MWNTs/DBDPE-Sb2O3复合材料的LOI可达30.72%,垂直燃烧等级达到FV-0级,同时复合材料具有较好的力学性能。     

SMA用量对PA6/LiCl/SMA复合材料结构与性能的影响

采用熔融挤出的方法制备了聚酰胺6/氯化锂/苯乙烯接枝马来酸酐(PA6/LiCl/SMA)复合材料,研究了SMA用量对PA6/LiCl/SMA复合材料的结晶熔融行为及性能的影响。结果表明:SMA的加入会促进Li+与PA6中酰胺基团的络合作用,破坏PA6分子链间的氢键,另外SMA自身能与PA6分子链发生接枝反应,在双重作用下使复合材料的熔点降低到185.53℃。通过DSC和XRD发现:SMA的加入会促使PA6/LiCl/SMA复合材料的结晶形态由α晶型向γ晶型转变,并能有效提高复合材料的力学性能,当SMA用量为3 phr时,其拉伸强度比未添加SMA时提高了53.02%,冲击强度也有所提高,但复合材料的熔体流动速率会有所下降。     

金属离子配位作用下PA6的受限结晶

采用熔融共混法,制备了聚酰胺6/氯化钙(PA6/CaCl2)复合材料。通过差示扫描量热法(DSC)、X射线衍射法(XRD)研究了PA6基体在受限条件下的非等温结晶及晶型转变行为。结果表明:金属离子Ca2+与酰胺基团的络合配位作用使PA6/CaCl2复合材料中PA6的结晶行为和结晶度受到了限制。随着CaCl2含量的增加,PA6的结晶度、结晶峰温度、熔融峰温度逐渐降低,结晶速率减小,结晶半峰宽增大,当CaCl2的含量大于8%时,PA6变为无定形态;此外,CaCl2的引入有利于PA6中α晶的生成。     

MWNTs/HDPE复合材料的结晶行为研究

采用超声分散溶液混合法制备出多壁碳纳米管(MWNTs)/高密度聚乙烯(HDPE)复合材料.通过场发射电镜观察了MWNTs在HDPE基体中的分散,采用X射线衍射(XRD)分析和差示扫描量热(DSC)分析研究了含碳纳米管的高密度聚乙烯的晶态结构和结晶行为,并利用Avrami方程描述了复合材料的等温结晶动力学.结果表明,MWNTs可以较好地分散在HDPE基体中并且作为一种有效的成核剂,用量较少(1%)和直径较大(60～100 nm)的MWNTs成核效果更明显;它们并没有改变HDPE的品型;随着MWNTs含量的增加和温度的升高,MWNTs/HDPE复合材料中HDPE主要是通过异相成核以球晶生长方式结晶的.     

原位聚合制备尼龙-6/多壁碳纳米管复合材料及其结晶行为

采用酰氯化处理的多壁碳纳米管(MWNT)同氨基封端的尼龙-6(PA6)原位聚合的方法制备了PA6/MWNT复合材料.红外光谱说明了MWNT与PA6化学的键合作用.DSC测试表明MWNT对PA6的分子链段运动有较大的阻碍作用.动力学分析表明MWNT具有成核作用,提高了PA6的结晶温度;共价键连接使MWNT对PA6的分子链段运动有强烈的阻碍作用,造成复合材料(含MWNT质量分数2%)的总结晶速率降低.     

聚酰胺6/丙烯酸酯橡胶共混物热性能和结晶行为研究

采用熔融共混法制备了聚酰胺6/环氧型丙烯酸酯橡胶(PA6/ACM)共混物,并通过差示扫描量热仪(DSC)、X射线衍射仪(XRD)和偏光显微镜(PLM)对PA6/ACM共混物的热性能和结晶行为及晶体形貌进行了研究。结果表明,随着ACM含量的增加,共混物的融熔温度(Tm)和结晶温度(Tc)均略有下降;由于环氧型ACM的加入,PA6的晶型也由γ晶型转化为 α晶型,且随着橡胶加入量的增加,结晶度逐渐降低,晶粒逐渐变小,结晶也越来越不完善;共混物的缺口冲击强度明显提高。     

PA6/CaCl_2/玻璃纤维复合材料非等温结晶动力学研究

采用挤出方式分别制备尼龙6/氯化钙(PA6/Ca Cl_2)、尼龙6/氯化钙/玻璃纤维(PA6/Ca Cl_2/GF)复合材料。利用差示扫描量热仪(DSC)研究了氯化钙和玻璃纤维对两种复合材料非等温结晶行为的影响,并用Jeziorny法、Mo法对复合材料结晶动力学进行研究。结果表明,Ca Cl_2的络合作用使PA6/Ca Cl_2复合材料起始结晶温度、结晶速率降低;而GF提高了PA6/Ca Cl_2结晶的起始温度,减小其总结晶时间,对于PA6/Ca Cl_2/GF复合材料,GF起到了成核作用。X射线衍射仪(XRD)研究表明,与金属离子诱导PA6生成α晶型不同,GF诱导其生成γ晶型。     

聚对苯二甲酸丁二醇酯/多壁碳纳米管复合材料的流变及结晶行为

采用熔融共混的方法制备了对聚对苯二甲酸丁二醇酯(PBT)/多壁碳纳米管(MWNT)复合材料,研究了复合体系的流变及结晶行为.结果表明MWNT具有显著的增强作用,使得复合体系低频区的模量出现类固态黏弹响应,这源于MWNT逾渗网络结构的形成.MWNT的加入并未改变PBT的α晶型结构,但其异相成核作用却能有效地促进复合体系PBT基体的结晶.     

尼龙6/石墨复合材料非等温结晶动力学研究

采用差示扫描量热法(DSC)研究了不同石墨含量的尼龙6(PA6)/石墨(Gr)复合材料的非等温结晶行为,运用Avrami方程确定其非等温结晶动力学参数,发现Avrami方程可以很好地描述PA6/Gr复合材料的非等温结晶过程。当石墨含量增加时,PA6/Gr复合材料的结晶放热曲线出现双峰,结晶速率略有提高,但均低于纯PA6树脂的结晶速率。同时,石墨的加入导致复合材料的结晶度减小,而且随着石墨含量的增加,其结晶度逐渐降低。     

Effects of acid- and diamine-modified MWNTs on the mechanical properties and crystallization behavior of polyamide 6

The acid- and diamine-modified multi-walled carbon nanotubes were characterized by XPS, apparent density test and SEM. Their effects on the mechanical properties and crystallization behavior of polyamide 6 (PA6) were comparatively investigated via SEM, DMA, tensile test and DSC. It was revealed that acid treatment could effectively induce polar oxygen-containing groups on the surface of MWNTs, which was beneficial for MWNTs to combine with polar PA6 matrix. However, the interactions such as the hydrogen bonds among the acid-modified MWNTs caused a compact stacking morphology, resulting in a worse dispersion in PA6 matrix. Further diamine modification on the acid-modified MWNTs could graft diamine molecules onto the surface of MWNTs, which weakened the interactions among the MWNTs and thus resulted in a less compact stacking morphology compared with acid-modified MWNTs. Therefore, a better dispersion and a stronger interfacial adhesion of MWNTs in PA6 matrix could be obtained with diamine-modified MWNTs. The storage modulus, glass transition temperature, yield strength, Young's modulus and crystallization temperature of PA6 were found to be improved significantly by the incorporation of diamine-modified MWNTs.     

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     

Improving dispersion of multiwalled carbon nanotubes in polyamide 6 composites through amino‐functionalization

The focus of this study is to investigate the state of dispersion of different treated multiwalled carbon nanotubes (MWNTs) in polyamide 6 (PA6). The MWNTs used in composites were grafted by 1,6‐hexamethylenediamine (HMD) via acid‐thionyl chloride to improve their compatibility with PA6 matrix. A microstructure transformation of MWNTs is found during the treatment process. Acidification makes the MWNTs compact and grafting HMD promotes the compact structure loose again. The MWNTs after different treatment were used to fabricate MWNTs/PA6 composites through melt blending. The dispersion of different MWNTs in PA6 was observed by a combination of scanning electron microscopy, optical microscopy, and transmission electron microscopy. The results show that the amino‐functionalized MWNTs are dispersed more homogeneously in PA6 than the purified MWNTs, and the poorest dispersion is achieved for acid treated MWNTs. It is indicated that the loose structure and functionalized surface of MWNTs benefit the dispersion of MWNTs in PA6. In addition, the amino‐functionalization of MWNTs improves the compatibility between the MWNTs and PA6, resulting in stronger interfacial adhesion. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Dispersion,migration, and ‘network‐like’ structure formation of multiwall carbon nanotubes in co‐continuous,binary immiscible blends of polyamide 6 and acrylonitrile–butadiene–styrene copolymer during simultaneous melt‐mixing

Multiwall carbon nanotubes (MWNTs) were melt‐mixed in polyamide 6 (PA6) and acrylonitrile–butadiene–styrene (ABS) copolymer blends using a simultaneous mixing protocol in order to investigate the state of dispersion of MWNTs in PA6/ABS blends. The blend composition was varied from 40/60 (wt/wt) to 60/40 (wt/wt) in PA6/ABS blends, which showed ‘co‐continuous’ morphology in the presence of MWNTs. State of dispersion of MWNTs in these blends was assessed through bulk electrical conductivity measurements, morphological analysis, solution experiments, and UV‐vis spectroscopic analysis. MWNTs were subsequently modified with a novel organic modifier, sodium salt of 6‐aminohexanoic acid (Na‐AHA), to improve the state of dispersion of MWNTs. Blends with unmodified MWNTs exhibited the DC electrical conductivity in the range ～10^?11 to ～10^?5 S/cm, whereas blends with Na‐AHA‐modified MWNTs exhibited DC electrical conductivity in the range ～10^?7 to ～10^?5 S/cm. The reduction in MWNTs ‘agglomerate’ size (～73.7 μm for 40/60 blend with unmodified MWNTs to ～59.9 μm in the corresponding blend with Na‐AHA‐modified MWNTs) was observed through morphological analysis. The rheological studies showed increased complex viscosity and storage moduli in lower frequency region in case of blends with Na‐AHA‐modified MWNTs confirming a refined ‘network‐like’ structure of MWNTs. POLYM. ENG. SCI., 55:443–456, 2015. © 2014 Society of Plastics Engineers     

Crystallization and melting behavior of multi‐walled carbon nanotube‐reinforced nylon‐6 composites

The crystallization and melting behavior of neat nylon‐6 (PA6) and multi‐walled carbon nanotubes (MWNTs)/PA6 composites prepared by simple melt‐compounding was comparatively studied. Differential scanning calorimetry (DSC) results show two crystallization exotherms (T_{CC, 1} and T_{CC, 2}) for PA6/MWNTs composites instead of a single exotherm (T_{CC, 1}) for the neat matrix. The formation of the higher‐temperature exotherm T_{CC, 2} is closely related to the addition of MWNTs. X‐ray diffraction (XRD) results indicate that only the α‐phase crystalline structure is formed upon incorporating MWNTs into PA6 matrix, independently of the cooling rate and annealing conditions. These observations are significantly different from those for PA6 matrix, where the increase in cooling rate or decrease in annealing temperature results in the crystal transformation from α‐phase to γ‐phase. The crystallization behavior of PA6/MWNTs composites is also significantly different from those reported in PA6/nanoclay systems, probably due to the difference in nanofiller geometry between one‐dimensional MWNTs and two‐dimensional nanoclay platelets. The nucleation sites provided by carbon nanotubes seem to be favorable to the formation of thermodynamically stable α‐phase crystals of PA6. The dominant α‐phase crystals in PA6/MWNTs composites may play an important role in the remarkable enhancement of mechanical properties. Copyright © 2005 Society of Chemical Industry     

碳纳米管/尼龙6复合材料的非等温结晶动力学研究

碳纳米管经过了酸化处理,用FTIR对处理后的碳纳米管进行了结构表征.采用哈克转矩流变仪制备了碳纳米管/尼龙6纳米复合材料.利用SEM对碳纳米管与尼龙6复合材料的结构进行了研究.通过DSC对复合材料的非等温结晶动力学进行了研究,采用Jeziorny修正的Avrami方程对非等温结晶动力学进行了处理.结果表明,Jeziorny 可以很好地描述碳纳米管/尼龙6复合材料的非等温结晶过程.随着降温速率的升高,结晶温度降低,结晶温度范围变大,结晶所需要的时间缩短.     

PA6/类水滑石纳米复合材料的制备与性能研究

将自制的双甲氧基苯甲酸根离子插层的类水滑石(MgAl-PMOBA-LDHs)分散到己内酰胺（CL）水溶液中,利用CL原位水解开环聚合制备了聚酰胺6（PA6）/MgAl-PMOBA-LDHs纳米复合材料,并通过透射电子显微镜、X射线衍射仪、紫外吸收光谱仪、热分析等对其性能进行了表征。结果表明,MgAl-PMOBA-LDHs 在复合材料中呈纳米级均匀分散,少量均匀分散的MgAl-PMOBA-LDHs 使复合材料对波长为320~380 nm的紫外线吸收效果明显;少量均匀分散的MgAl-PMOBA-LDHs 起到了很好的异相成核剂的作用,不仅提高了PA6的结晶温度,而且也提高了其结晶度;部分板层剥离的MgAl-PMOBA-LDHs 明显有助于PA6 的γ 晶型的产生。     

Properties of anionic polymerized ε‐caprolactam in the presence of carbon nanotubes

The results of the investigations of the relations between structure, physical and usage properties of polyamide 6 (PA6) reinforced with multiwall carbon nanotubes (MWNTs) are presented. A method of in situ anionic bulk polymerization of ε‐caprolactam in the presence of MWNTs was used for the preparation of reinforced PA6. The polymerization product was crushed, and the pellets of PA6 and PA6/MWNTs composites were injection molded to produce the standard test specimens for various measurements. The surface morphology (SEM), thermal (DSC, TGA, DMTA), and mechanical properties (tensile strength, Charpy's notched impact strength) of these materials were examined. Some differences between our specimens and those obtained by hydrolytic polymerization of ε‐caprolactam (CL) were found. It was found that a small amount of carbon nanotube decreases the crystallinity degree of PA6 matrix in the composites. The thermal stability was higher than that for neat PA6. DMTA results showed that the magnitudes of the storage modulus are higher for the PA6/MWNTs composites than for the unmodified PA6 in the temperature range between ?90 and 200°C. The tensile strength and tensile modulus are higher compared with the neat PA6. The elongation at break showed no noticeable change in the range of MWNTs loading considered, while the Charpy's notched impact strength slightly decreased. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

In situ polymerization approach to multiwalled carbon nanotubes-reinforced nylon 1010 composites: Mechanical properties and crystallization behavior

A series of polyamide 1010 (PA1010 or nylon 1010) and multiwalled carbon nanotubes (MWNTs) composites were prepared by in situ polymerization of carboxylic acid-functionalized MWNTs (MWNT-COOH) and nylon monomer salts. Mechanical tensile tests and dynamic mechanical analysis (DMA) show that the Young modulus increases as the content of the nanotubes increases. Compared with pure PA1010, the Young's modulus and the storage modulus of MWNTs/PA1010 in situ composites are significantly improved by ca. 87.3% and 197% (at 0 °C), respectively, when the content of MWNTs is 30.0 wt%. The elongation at break of MWNTs/PA1010 composites decreases with increasing proportion of MWNTs. For the composites containing 1.0 wt% MWNTs, the Young modulus increases by ca. 27.4%, while the elongation at break only decreases by ca. 5.4% as compared with pure PA1010 prepared under the same experimental conditions. Compared with mechanical blending of MWNTs with pure PA1010, the in situ-prepared composites exhibit a much higher Young's modulus, indicating that the in situ polycondensation method improves mechanical strength of nanocomposites. Scanning electron microscopy (SEM) imaging showed that MWNTs on the fractured surfaces of the composites are uniformly dispersed and exhibit strong interfacial adhesion with the polymer matrix. Moreover, unique crystallization and melting behaviors for MWNTs/PA1010 in situ composites are observed using a combination of differential scanning calorimetry (DSC) and X-ray diffraction methods. It was shown that only the α-form crystals are observed in our MWNTs/PA1010 in situ composites. This result is quite different from PA1010/montmorillonite and PA6-clay composites, where both of α- and γ-form crystals were found.