关于纳米蒙脱土影响聚己内酰胺结晶行为及流变行为的研究

通过双螺杆挤出机熔融挤出生产有机改性纳米蒙脱土(MMT)增强聚己内酰胺(PA6)。使用差示扫描量热仪开展自成核试验及非等温结晶行为研究,了解纳米MMT含量对PA6结晶行为的影响,结果表明:少量的纳米MMT可以明显提高成核效率和结晶速率,但继续增加纳米MMT会抑制PA6结晶生长,降低结晶速率和结晶度。使用广角X射线衍射仪研究PA6的结晶行为,结果表明:纯PA6同时存在α及γ晶型,添加纳米MMT的PA6发生α-γ晶型转变,证实纳米MMT与PA6的作用可以改变PA6的结晶行为。使用毛细管流变仪分析纳米MMT含量对PA6熔体受剪切时流变行为的影响,结果表明:纳米MMT含量影响PA6熔体的黏度及非牛顿流体特征,尤其是高纳米MMT含量的PA6在不同剪切速率下表现出明显的黏度变化。     

纳米碳酸钙填充尼龙6体系结晶行为的研究

采用偏光显微镜、差示扫描量热仪和广角X射线衍射仪系统地研究了纳米碳酸钙(n-CaCO3)粒子填充聚酰胺6(PA6)体系的结晶行为。结果表明,n-CaCO3粒子的引入不仅使PA6材料变为两相结构,而且使其结晶行为发生了改变;n-CaCO3粒子对PA6等温结晶行为影响较大,球晶尺寸大小及球晶形态发生了很大变化;n-CaCO3粒子不仅具有异相成核剂的作用,而且能引发PA6产生新的晶型,且这种成核作用具有逾渗行为。     

聚酰胺6/连续碳纤维复合材料的结晶行为

利用自行设计的浸渍装置,通过熔融浸渍法制备了连续碳纤维增强聚酰胺6(PA6/LCF)复合材料。研究了LCF对PA6/LCF复合材料结晶行为的影响。结果表明,LCF的加入对PA6基体具有异相成核作用,增容剂苯乙烯马来酸酐共聚物(SMAH)和聚丙烯接枝马来酸酐(PP-g-MAH)的加入均能促进LCF对PA6基体的异相成核作用。PA6的等温结晶均相成核和异相成核共存,PA6/LCF复合材料则以异相成核结晶为主。非等温结晶研究表明,随着冷却速率的增加,PA6,PA6/LCF复合材料的结晶速率变大,半结晶时间降低。     

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。     

PA6/POE/黏土纳米复合材料的非等温结晶行为

采用差示扫描量热仪(DSC)方法研究尼龙6(PA6)及尼龙6/聚烯烃弹性体(POE)/黏土纳米复合材料的非等温结晶及熔融行为,随着降温速率的增加,PA6和PA6/POE/黏土纳米复合材料的结晶峰变宽,结晶峰向低温移动.在相同降温速率下,PA6/POE/黏土纳米复合材料在更高的温度下结晶;PA6和PA6/POE/黏土纳米复合材料中晶体呈三维生长.降温速率的增加和有机黏土的加入会使体系结晶速率增加;PA6/POE/黏土纳米复合材料的结晶活化能低于PA6.     

铸型PA 6/TiO2纳米复合材料的非等温结晶行为

采用差示扫描量热法(DSC)研究了铸型聚酰胺(PA)6/TiO2纳米复合材料在不同冷却速率下的非等温结晶行为,并用Jeziomy法、Ozawa法和Mo法对DSC测定结果进行了处理。结果表明：纳米TiO2对铸型PA6起到异相成核的作用,提高了铸型PA6的结晶速率和结晶峰温,缩短了半结晶时间。3种方法对比后发现：Ozawa法不适用于铸型PA6及其纳米复合材料非等温结晶动力学的处理,Jeziomy法基本适合,而Mo法最适合。采用Kissinger法计算出铸型PA6及其TiO2纳米复合材料的结晶活化能,发现纳米粒子提高了铸型PA6的结晶活化能．说明纳米TiO2阻碍了铸型PA6的分子链在结晶时的运动。     

PA66/可反应性纳米SiO_2复合材料的非等温结晶动力学

通过双螺杆挤出机制备出聚酰胺(PA)66/可反应性纳米SiO2(RNS)复合材料,采用Jeziorny法和Mo法对其非等温结晶行为进行了研究。结果表明,RNS具有较强的异相成核能力,能提高PA66的结晶速率,并使PA66的晶体结构和生长机制发生改变;通过对比PA66及其复合材料的结晶活化能发现RNS能够降低PA66的结晶活化能。     

聚酰胺6/可反应性纳米SiO2复合材料的非等温结晶动力学

通过双螺杆挤出机制备出聚酰胺（PA）6/可反应性纳米SiO2（RNS）复合材料,并采用Jeziorny法和Mo法对其非等温结晶行为进行了研究。结果表明,RNS具有较强的异相成核能力,能提高PA6的结晶速率,并使其晶体结构和生长机制发生改变。通过对比纯PA66及其复合材料的结晶活化能还发现,RNS能够降低PA66的结晶活化能。     

制样方法对SiO2/PA6复合材料基体PA6结晶熔融行为的影响

采用差示扫描量热法(DSC)研究了原位聚合法和熔融共混法制样方法对纳米SiO2/PA6纳米复合材料结晶熔融行为的影响,结果表明:通过阴离子原位聚合法制备的纳米复合材料,由于采用超声波分散技术,纳米粒子在基体的分散性好。随着纳米粒子含量的升高,纳米粒子的诱导成核能力增强;熔融共混法制得复合材料中,SiO2在机械力的剪切作用下,很难均匀地分散,多以团聚体的形式存在,在PA6基体结晶时,结晶成核的条件相匹配,有较强的成核效应,纳米粒子的含量影响不大。     

PA6/蒙脱土纳米复合材料力学性能与结晶行为的研究

陈述了纳米MMT直接加入到PA6中对力学性能的效应;阐明了用不同的MMT的处理方法和不同的载体树脂所制成的母料对PA6复合材料力学性能和结晶行为的影响;还研究了母料中纳米分散程度对PA6复合材料力学性能和结晶行为的影响。DSC研究表明:纳米蒙脱土的加入加快了PA6的结晶过程,促使了γ晶的生成,起到了异相成核作用。     

Confined crystallization phenomena in immiscible polymer blends with dispersed micro - and nanometer sized PA6 droplets, part 1: uncompatibilized PS/PA6, (PPE/PS)/PA6 and PPE/PA6 blends

In this paper the crystallization behavior of PA6, dispersed as droplets in various immiscible amorphous polymer matrices, is reported. PA6 was melt-mixed at various compositions with PS, (PPE/PS 50/50 wt/wt) and PPE using twin-screw extrusion. The phase morphologies of the obtained blends were analysed using SEM, etching experiments and image analysis. The crystallization behavior of PA6 was investigated by dynamic and isothermal DSC experiments. In case PA6 is dispersed as droplets, fractionated crystallization behavior occurs, characterized by several crystallization events at different, lowered crystallization temperatures. It is found to depend on the blend morphology (size of the droplets) and the thermal history of the samples (heterogeneous nucleation density). The PA6 droplet size distribution is shown to strongly influence the crystallization behavior of the droplets. Vitrification of the matrix appears to cause nucleation in the droplets at the interface. Decreasing the PA6 droplet size results in slower overall crystallization rates.     

Melting behavior and nonisothermal crystallization kinetics of polyamide 6/polyamide 66 molecular composites via in situ polymerization

The melting behavior and nonisothermal crystallization kinetics of pure polyamide 6 (PA 6) and its molecular composites with polyamide 66 (PA 66) were investigated with differential scanning calorimetry. The PA 6/PA 66 composites had one melting peak, whereas the coextruded PA 6/PA 66 blends had two melting peaks. With the addition of PA 66 to PA 6 via in situ anionic polymerization, the melting temperature, crystallization temperature, and crystallinity of PA 6 in the composites decreased. The half‐time of nonisothermal crystallization increased for a PA 6/PA 66 molecular composite containing 12 wt % PA 66, in comparison with that of pure PA 6. The commonly used Ozawa equation was used to fit the nonisothermal crystallization of pure PA 6 and its composites. The Ozawa exponent values in the primary stage were equal to 1.28–3.03 and 1.28–2.97 for PA 6 and its composite with 12 wt % PA 66, respectively, and this revealed that the mechanism of primary crystallization of PA 6 and PA 6/PA 66 was mainly heterogeneous nucleation and growth. All the results indicated that the incorporation of PA 66 into PA 6 at the molecular level retarded the crystallization of PA 6. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 2172–2177, 2005     

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     

Thermal behavior and morphology of polyamide 6 based multicomponent blends

The thermal behavior and morphology of multicomponent blends based on PA6, polyamide 6 (PA6)/styrene–acrylonitirle copolymer (SAN), PA6/acrylonitrile–butadiene–styrene terpolymer (ABS), and their compatibilized blends with styrene–acrylonitrile–maleic anhydride copolymer (SANMA) were studied using DSC and SEM. The blends were prepared in a twin‐screw extruder under similar processing conditions, keeping the PA6 content fixed at 50 wt %. It was found that, in all the blends, the second component had a nucleating effect and improved the overall degree and rate of crystallization of PA6, whereas addition of a compatibilizer slightly diminished these effects and resulted in significant changes in the blend morphology. The nucleating effect and consequent changes in the crystallization behavior was attributed to the presence of SAN, which is a common component in all the blends. The T_g of PA6 in the blends with a cocontinuous morphology, due to the connectivity between the phases, is higher than in the blends with a disperse‐type morphology. The compatibilized blends have a lower crystallization rate and nucleation ability with a cocontinuous morphology, whereas the uncompatibilized blends have a higher crystallization rate with a higher nucleation ability and a disperse and/or a coarse cocontinuous morphology. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2753–2759, 2002     

纳米SiO_2/MC尼龙6原位复合材料等温结晶行为的研究

将纳米SiO2均匀分散在己内酰胺单体熔体中,采用阴离子开环聚合法制备了纳米SiO2/单体浇铸(MC)尼龙6原位复合材料。通过差示扫描量热仪(DSC)、Avrami方程、Lauritizen-Hoffmann方程对复合材料的等温结晶行为进行了研究。结果表明:纳米SiO2的引入改变了基体MC尼龙6的成核机理和生长方式;低含量的纳米SiO2阻碍了MC尼龙6的结晶行为,高含量的纳米SiO2降低了MC尼龙6的结晶活化能,提高了其球晶生长速率,并促进了其结晶行为。     

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     

Effect of ultrafine,fully vulcanized acrylate powdered rubber on the mechanical properties and crystallization behavior of nylon 6

Nylon 6 (PA6) is a widely used engineering plastic. However, its poor toughness limits its applications. Therefore, toughening PA6 has been a point of interest in the field of PA6 modification. Generally, toughening a plastic with an elastomer reduces the stiffness and heat distortion temperature of the matrix. It has been an important goal of polymer researchers to find a way of toughening PA6 without reductions in its stiffness and heat distortion temperature. In this study, a new kind of material—an ultrafine, fully vulcanized acrylate powdered rubber (UFAPR)—was used to toughen PA6 through melt blending. The influence of UFAPR on the isothermal crystallization kinetics and nonisothermal crystallization behavior of PA was studied with differential scanning calorimetry. The results showed that, with the addition of a little UFAPR, the crystallization rate of PA could be increased, the crystallization temperature could be augmented, and the crystal size distribution of the crystal grain could be narrowed. The changes in the free energy perpendicular to the crystal nucleus were consistent with the results of an Avrami equation according to the theory of Hoffman. The unit surface free energy of the radially developing crystal spherulites decreased with an increasing amount of UFAPR. The results for the mechanical properties, crystalline structure, and crystallization kinetics of PA6/UFAPR composites showed that UFAPR was not only a good toughening agent for PA6 but also an excellent nucleation agent for PA6. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3503–3511, 2003     

改性高岭土/聚丙烯复合材料的热性能及非等温结晶行为研究

以自制的剥离高岭(MK)、原高岭土(K)以及聚丙烯(PP)和马来酸酐接枝聚丙烯(PP-g-MA)等作为基本原料,通过熔融挤出、注塑成型,制备PP复合材料。采用XRD、DSC、TG研究复合材料的非等温结晶行为、结晶动力学以及热降解性能。结果表明:高岭土的加入,使结晶温度、结晶度、热稳定性都有所提高,且结晶速率加快,具有异相成核作用。与原高岭土相比,改性高岭土更能促进PP复合材料的PP异相成核,促进PP稳态晶型(α晶型)的转变,结晶速率较快。与纯PP和PP/PP-g-MA复合材料相比,PP/改性高岭土复合材料的结晶峰温度、最大热降解温度分别提高了16.7、7.8、9.7、12.6℃。     

Nonisothermal crystallization kinetics of polyamide 6 and ethylene‐co‐butyl acrylate blends

The nonisothermal melt‐crystallization behavior of PA6 and EBA blends at varying EBA content was investigated using differential scanning calorimetry at different scanning rates. Several macrokinetic models such as Avrami, Jeziorny, Ozawa, Liu, Ziabicki, and Tobin were applied to analyze the crystallization behavior thoroughly under nonisothermal conditions. The Avrami and Tobin model predicted that, for pure PA6 and PA6/EBA blends, simultaneous growth of all forms of crystal structures such as fibrillar, disc‐like, and spherulitic proceeds at an increasing nucleation rate. However, when applied to blends for isothermal crystallization, the Avrami model predicted that the crystallization process is diffusion‐controlled for pure PA6 and PA6/EBA blend containing higher content of EBA (50 phr), where the nylon‐6 chains were able to diffuse freely to crystallize under isothermal conditions. Liu model predicted that, at unit crystallization time, a higher cooling rate should be used to obtain a higher degree of crystallinity for both PA6 and PA6/EBA blends. The kinetic crystallizability of PA6 in the blends calculated using Ziabicki's approach varies depending upon the nucleation density and PA6‐rich regions present in the blend compositions. Nucleation activity of the blends estimated by Dobreva and Gutzowa method reveals that the EBA particles are inert at lower concentrations of EBA and do not act as nucleating agent for PA6 molecules in the blends. The activation energy of nonisothermal crystallization, calculated using Augis–Bennett, Kissinger, and Takhor methods indicated that the activation energy is slightly lower for the blends when compared to the neat PA6. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effects of swelling agents on the crystallization behavior and mechanical properties of polyamide 6/clay nanocomposites

Montomorillonite was organically modified with three different swelling agents: n‐dodecylamine, 12‐aminolauric acid, and 1,12‐diaminodecane. These organoclays and polyamide 6 (PA6) were blended in a formic acid solution. X‐ray diffraction analysis showed that the clay still retained its layer structure in the PA6/clay nanocomposite. Consequently, these materials were intercalated nanocomposites. The effects of the swelling agent and organoclay content on the crystallization behavior of the PA6/clay nanocomposites were studied with differential scanning calorimetry. The results showed that the position and width of the exothermic peak of the PA6/clay nanocomposites were changed during the nonisothermal crystallization process. The clay behaved as a nucleating agent and enhanced the crystallization rate of PA6.The crystallinity of PA6 decreased with an increasing clay content. Different swelling agents also affected the crystallization behavior of PA6. The effects of the type and content of the swelling agent on the tensile and flexural properties of PA6/clay nanocomposites were also investigated. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1686–1693, 2003