纳米聚酰胺6结晶行为影响研究

纳米聚酰胺6作为一种新型的材料,影响其结晶行为的因素有很多种。主要通过差式扫描量热仪(DSC)、万能材料试验机和冲击仪研究不同的生产工艺和降温速率对纳米聚酰胺6结晶温度的影响及结晶度对力学性能的影响。生产工艺的不同会导致其结晶温度和材料的结晶度有很大的差异;降温速率对纳米聚酰胺6的结晶温度影响也较大,降温速率越大,结晶温度也就越低,结晶度越高,且不是成正比变化;结晶度越高,纳米聚酰胺6的拉伸强度、弯曲强度、冲击强度就越低,且对其影响程度不成正比关系,反之结晶度越低,纳米聚酰胺6的拉伸强度、弯曲强度、冲击强度越低。     

聚乳酸/纤维素纳米晶纳米复合物的结晶性能

通过溶液混合,将纤维素纳米晶(CNC)与聚乙二醇(PEG)复合得到了改性的CNC-PEG纳米粒子,然后将其与PLA熔融共混得到PLA/CNC-PEG纳米复合物.采用扫描电子显微镜(SEM)表征了纳米复合物的形貌,结果表明,PLA/CNC-PEG复合物中纳米粒子的分散效果更均匀.采用示差扫描量热仪(DSC)研究了PLA、...     

聚酰胺6纳米复合材料的新进展

介绍了聚酰胺 6纳米复合材料的研究进展 ,并给出了其 5种制备方法。对纳米粒子增强增韧机理与PA6单体插入聚合制纳米复合材料的反应模式作了简介。     

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共聚物的制备与表征

采用两种不同的二元酸(己二酸和间苯二甲酸)与二元胺(4,4′-二氨基二环己基甲烷)以摩尔比1∶1混合作共聚单体,制备系列聚酰胺(PA)6共聚物,并通过傅里叶变换红外光谱仪和差示扫描量热仪对PA 6共聚物的结构与性能进行表征。结果表明:随着共聚单体含量的增加,PA 6共聚物的结晶温度、熔点与结晶度均降低;此外对于添加同样含量的二元酸,己二酸与4,4′-二氨基二环己基甲烷体系、间苯二甲酸与4,4′-二氨基二环己基甲烷体系对PA 6结晶性能均有调控作用,但己二酸与4,4′-二氨基二环己基甲烷体系对PA 6结晶性能调控更加显著。     

聚酰胺6／聚酰胺610共混物的结晶与熔融行为

用DSC和DSC-FTIR同时测定的方法研究了不同组成(φ)的聚酰胺(PA)6／(PA)610共混物的结晶与熔融行为。DSC结果表明:φN610=0．1共混物的结晶温度比纯PA6的高,其余共混物的结晶温度比PA6的稍低,并不随组成变化;φN610≤0．3共混物的熔融温度及DSC曲线形状与PA6的相似,随着φN610的增加,共混物低温熔融峰逐渐变小,DSC曲线形状趋于PA610的。DSC-FTIR同时测定的结果表明:在降温冷却时,φN610≤0．3共混物中PA6优先与PA610结晶,其余组成共混物中PA6和PA610同时进行结晶。     

聚酰胺6／凹凸棒土纳米复合材料的制备与性能

采用双螺杆挤出机将凹凸棒土与聚酰胺6共混，制备聚酰胺6／凹凸棒土纳米复合材料，考察了凹凸棒土活化前后对聚酰胺6力学性能、微观形态、结晶行为的影响，结果表明：凹凸棒土以纳米尺寸分散于复合材料中；凹凸棒土的加入，可以促进聚酰胺6结晶；与未经硅烷偶联剂活化的凹凸棒土相比，活化后凹凸棒土的加入，可以提高复合材料的拉伸强度、冲击强度，经过硅烷偶联剂处理的凹凸棒土可以用于改性聚酰胺6。     

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。     

纳米晶纤维素改性及其功能性材料的研究进展

纳米晶纤维素(CNC)是一种具有优异性能的纳米粒子,对CNC的改性和其功能性材料的应用一直是研究的热点。本文综述了CNC改性的方法,包括小分子改性、偶联剂改性,自由基开环接枝和ATRP接枝、RAFT接枝改性,吸附改性和一些特殊的化学改性,并分析了CNC功能性纳米材料在生物药物、聚合物电解质、生物激发力学适应性纳米材料方面的研究进展。     

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。     

Microstructural,Thermal, Crystallization,and Water Absorption Properties of Films Prepared from Never-Dried and Freeze-Dried Cellulose Nanocrystals

In this paper, the microstructural, optical, thermal, crystallization, and water absorption properties of films prepared from never-dried (ND) and freeze-dried (FD) cellulose nanocrystals (CNCs) are reported. Morphology of the ND CNCs reveals a needle-like structure, while after freeze-drying, they show a flake-like morphology. Microstructural analysis of ND and FD CNCs are further studied via small angle X-ray scattering to probe interactions. ND CNCs yield a transparent film with a low surface roughness (14 ± 4 nm), while the FD CNC film evidence a significant reduction of their transparency due to their higher surface roughness (134 ± 20 nm). Although Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy analyses reveal no chemical change occurs during the freeze-drying process, yet a more intense thermal degradation profile is observed for FD CNC film, probably due to the higher oxygen ingress within the gaps created between the stacked flakes. This, in turn, results in a greater loss of crystallinity at a higher temperature (300 °C) compared to the ND CNC film. A rapid decrease in water contact angle of the FD CNC film proves that the morphology of flakes and their orientation within the film has a strong influence in increasing water absorption capacity.     

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。     

超声辅助挤出对尼龙6性能的影响

在尼龙(PA)6的熔融挤出过程中引入超声振动外场,通过X射线衍射、高压毛细管流变性能、熔体流动速率测定、特性黏度测定和力学性能测试等手段研究超声振动对PA6性能的影响。结果表明,引入超声外场后,PA6的结晶度提高,热力学稳定的α晶型所占比例提高;特性黏度和粘均分子量降低,熔体黏度降低;力学性能基本保持不变。     

Investigation on Unusual Crystallization Behavior in Polyamide 6/Montmorillonite Nanocomposites

The crystallization behavior and crystal structure of polyamide 6/montmorillonite (PA6/MMT) nanocomposites were investigated by differential scanning calorimetry and X‐ray diffraction, and an interesting behavior was observed. The material was prepared via melt compounding using an organophilic clay obtained by co‐intercalation of epoxy resin and quaternary ammonium into Na‐montmorillonite. A maximum in degree of crystallinity was obtained at 5 wt.‐% MMT and the reasons for this, based on the MMT layer distribution, were discussed. The degree of crystallinity showed a strong dependence on the cooling rates. In contrast with typical behavior, a higher cooling rate resulted in a higher degree of crystallinity. In nanocomposites, the γ‐crystalline phase was dominant.     

纤维素纳米晶改性光固化水性聚氨酯丙烯酸酯及其性能研究

以纤维素纳米晶（ CNC）作为添加物,对紫外光固化水性聚氨酯丙烯酸酯（ UV-WPUA）进行共混改性。通过实时红外、转矩流变仪、紫外 -可见光分光光度计、扫描电子显微镜（ SEM）、电子万能试验机等表征手段探究了 CNC的添加量对复合树脂及其光固化涂层的性能影响。结果表明：当 CNC的添加量为 2%时, CNC颗粒在复合树脂中分散性良好,复合涂层的可见光透过率大于 85%,铅笔硬度 3H,附着力 0级,拉伸强度 9. 8 MPa,复合涂层的综合性能最好。     

MC聚酰胺6／Kevlar纤维复合材料的非等温结晶行为研究

采用改性的Kevlar纤维（KF）增强MC聚酰胺6，用差示扫描量热仪考察了纤维改性前后及纤维含量对复合材料非等温结晶行为的影响，并用修正Avrami方程的Jeziorny法研究了材料的非等温结晶动力学。结果表明：改性KF对基体聚酰胺6具有异相成核作用，提高了其起始结晶温度，结晶速率常数z。可由纯聚酰胺6的0．432增大至0．627，缩短了复合材料的半结晶时间，当KF含量为1％（质量分数，下同）时半结晶时间最短。Avrami指数n均相对于纯MC聚酰胺6的3．10有所降低，其中含6％KF的复合体系的n值下降最多，而1％未改性KF对其影响不如改性的KF显著。     

Preparation of Spherical Cellulose Nanocrystals from Microcrystalline Cellulose by Mixed Acid Hydrolysis with Different Pretreatment Routes

Spherical cellulose nanocrystal (CNC), as a high value cellulose derivative, shows an excellent application potential in biomedicine, food packaging, energy storage, and many other fields due to its special structure. CNC is usually prepared by the mixed acid hydrolysis method from numerous cellulose raw materials. However, the pretreatment route in preparing spherical CNC from cellulose fiber is still used when choosing microcrystalline cellulose (MCC) as the raw material, which is not rigorous and economical. In this work, pretreatment effects on the properties of spherical CNC produced from MCC by mixed acid hydrolysis were systematically studied. Firstly, the necessity of the swelling process in pretreatment was examined. Secondly, the form effects of pretreated MCC (slurry or powder form) before acid hydrolysis in the preparation of spherical CNC were carefully investigated. The results show that the swelling process is not indispensable. Furthermore, the form of pretreated MCC also has a certain influence on the morphology, crystallinity, and thermal stability of spherical CNC. Thus, spherical CNC with different properties can be economically prepared from MCC by selecting different pretreatment routes through mixed acid hydrolysis.     

纤维素纳米晶的乙酰化修饰研究

通过乙酸酐对纤维素纳米晶进行表面化学修饰,得到乙酰化的纤维素纳米晶(ACN)。用XRD、FTIR以及溶解性探讨乙酰化的纤维素纳米晶的结晶性、表面官能团以及在水及有机溶剂中的溶解性。     

聚苯硫醚/尼龙6非等温结晶动力学的研究

用差示扫描量热仪(DSC)研究了聚苯硫醚(PPS)／尼龙6(PA6)的非等温结晶动力学。结果表明,PPS的结晶温度随降温速率提高而降低,但是纯PPS的结晶温度受降温速率改变的影响要大于PPS／PA6中的PPS的。PPS／PA6中PPS结晶的Ozawa指数(m)比纯PPS的小,结晶速度常数lgKr与结晶温度高低的规律相一致,即结晶温度越高,lgKr值越大。     

Miscibility and Crystallization Behaviors of Polyamide 6/Polytetrafluoroethylene Blends

Summary: The miscibility and crystallization behaviors of polyamide 6 (PA 6)/polytetrafluoroethylene (PTFE) blends, prepared via reactive extrusion, are systematically investigated by means of wide‐angle X‐ray diffraction (WAXD), differential scanning calorimetry (DSC), and dynamic mechanical thermal analysis (DMTA). WAXD measurements show that no co‐crystallization occurred between two components, while DSC and DMTA measurements suggest that a certain degree of miscibility between them might exist due to the formation of some copolymers during the reactive extrusion.

DMTA curves for the pure PA 6 sample and PA 6/PTFE blends with various compositions.