牵伸作用对尼龙6纤维晶型结构及力学性能的影响

利用广角X射线衍射仪(WAXD)、傅里叶变换红外光谱仪(FTIR)、示差扫描量热仪(DSC)、声速取向测量仪、扫描电镜(SEM)以及纱线强伸度仪研究了不同牵伸倍数尼龙6复丝的晶型结构、熔融行为、取向度、表面形貌以及力学性能.结果表明,随着牵伸倍数的增加,伴随着γ晶型片晶的生长以及非晶区链段重排诱导α晶型的生成,尼龙6复丝的结晶度不断的提高,在牵伸倍数达到3倍时,样品中出现了α晶型的特征衍射峰,导致了其熔融温度的提高以及多重熔融峰的出现.同时,牵伸作用也增加了分子链沿纤维轴向的取向程度,消除了纤维表面的残余应力,改善了纤维的表面缺陷.在这些因素的共同作用下,尼龙6复丝的力学性能得到了一定程度的提高,当牵伸倍数为3倍时,拉伸强度与拉伸模量分别达到了5.0 c N/dtex和28.9 c N/dtex,与较低牵伸倍数相比较均有所提高.     

一种含树枝单元的高流动性尼龙6的原位聚合及性能测试

将低代数的树枝状大分子聚酰胺胺(polyamidomine,即PAMAM)分别与对苯二甲酸配制成母盐溶液,再以母盐溶液,己内酰胺,封端剂一起投入高压釜进行原位聚合,通过调节PAMAM在己内酰胺中的比例及改变不同的PAMAM代数得到新型高流动性尼龙6.FTIR显示,与线性尼龙相比较,高流动性尼龙6的γ(N—H)和2δ(N—H)两处对应峰都发生了明显的蓝移.对于树枝单元含量较低(0.3 wt%~0.5 wt%)的新型尼龙6,拉伸性能没有下降,缺口冲击强度增加,而熔体流动却显著得到改善.DSC显示,新型尼龙6的结晶曲线的结晶峰温度有不同程度的降低,晶体生长速率明显减慢.     

尼龙1212/尼龙6共混体系的非等温结晶行为

用DSC研究了尼龙 12 12 ,尼龙 6及其共混体系的非等温结晶行为 .结果表明 ,加工历史对尼龙的结晶和熔融行为影响很大 .经双螺杆挤出机挤出的尼龙 12 12和尼龙 6 ,由于应力诱导分子链取向 ,其结晶温度都有不同程度的提高 ,且表现出多重熔融现象 .在共混体系中 ,尼龙 12 12分子在共混物的界面上异相成核结晶 ,提高了其结晶温度 ,但酸酐化SEBS的加入抑制了分子链的运动又使其结晶温度降低 .共混体系降低了尼龙12 12的熔融温度 ,并使得其高熔点的熔融峰逐渐消失 ;而尼龙 6的熔融行为基本上没有变化 .     

原位缩聚法制备碳纳米管/尼龙11复合材料

用原位缩聚法制备了碳纳米管增强的尼龙11复合材料,用X射线衍射仪、红外(FTIR)、扫描电镜(SEM)、热重(TGA)、机械拉伸测试仪等对其结构、形貌、热性能及机械性能进行了表征测试.扫描电镜结果显示碳纳米管均一地分散在尼龙11/碳纳米管复合材料中.复合材料的拉伸模量比纯尼龙11有较大的提高.当复合材料中碳纳米管含量分别为1%,5%,10%时,材料的拉伸模量分别提高了34.5%,92.9%和113,7%.同时,复合材料的储能模量也有提高.热分析结果显示当复合材料中碳纳米管含量为1%时,其失重5%和10%的温度分别由纯尼龙11的404℃、424℃提高到414℃和437℃.示差扫描量热分析(DSC)显示复合材料的结晶温度随碳纳米管的加入而升高,而结晶度则降低.     

热处理对尼龙6及其与聚酰胺嵌段共聚物共混体系晶体熔融行为和结晶结构的影响

采用溶液共混-共沉淀的办法获得尼龙6及聚酰胺嵌段共聚物/尼龙6共混体系粉末,样品在260℃下熔融之后经程序降温的方法得到非淬火样品,然后分别在190℃下高温退火不同时间(0~48 h),采用示差扫描量热仪(DSC)、广角X射线衍射仪(WAXD)、偏光显微镜(POM)等表征手段研究热处理对体系晶体熔融行为和结晶结构的影响.结果表明,(1)在相同的热历史条件下,嵌段共聚物的存在影响了尼龙6的结晶行为及结晶结构;(2)退火处理对两种样品有着不同的影响,对于尼龙6体系,退火处理促进了非晶相向晶相的转变,大大提高样品的结晶完善程度和结晶度;对于共混体系,退火处理同样促进了非晶相向晶相的转变,同时形成新的α型和γ型结晶,体系的结晶完善程度明显提高,退火48 h后,结晶度比原始样品提高约84%.     

纳米SiO_2粒子表面官能团对尼龙6原位聚合的影响

研究了无机纳米粒子表面反应性官能团对尼龙 6 纳米SiO2 原位聚合的影响 .红外光谱和热重分析结果证实了无论对SiO2 进行表面处理与否 ,在原位聚合过程中其表面均能形成一定量的接枝聚合物 .随表面反应性官能团数目的增加 ,SiO2 的表面接枝率呈上升趋势 .与纯的尼龙 6相比 ,带有不同反应性官能团的纳米SiO2 的加入使复合产物的分子量呈下降的趋势 .对应于复合体系中可能发生的反应 ,提出了几种可能的表面接枝的键接方式 .力学性能测试结果显示经表面处理的SiO2 的加入能同时提高复合物的强度和韧性 ,而加入未处理的SiO2 时 ,材料强度可得到提高 ,但韧性明显降低 ,表明由偶联剂处理引入的柔性界面层的存在对于复合材料的力学性能有重要的影响     

尼龙6/SiO_2纳米复合材料的制备及其力学性能和热稳定性

以表面含有氨基的可反应性纳米SiO2(RNS-A)和表面含有烷基碳链的可分散性纳米SiO2(DNS-3)作为填料,利用原位聚合法制备了尼龙6/SiO2纳米复合材料(相应的复合材料分别简记为RPA和DP3);采用透射电子显微镜观察了复合材料中纳米SiO2的表面形貌,并利用热失重分析仪测定了复合材料的热稳定性,进而考察了纳米SiO2表面功能基团对尼龙6力学性能和热稳定性的影响.结果显示,纳米SiO2能够很好地分散在尼龙6基体中,并使尼龙6的热分解温度提高10℃左右.与此同时,RPA的最大拉伸强度和冲击强度较纯尼龙6的分别提高34.5%和12.5%,DP3的最大拉伸强度和冲击强度分别提高18.2%和45.7%.这表明两种纳米SiO2均可以有效地提高尼龙6的力学性能和热稳定性;可以推测,纳米SiO2的增强效应与其在尼龙6基体材料中的分散和界面作用有关.     

聚合法制备无卤阻燃尼龙的研究进展

在全球阻燃材料无卤化的推进过程中,氮系、磷系、硅系等阻燃剂以及其复配物受到各国研究人员的广泛关注。利用聚合法(原位聚合法和共聚法)制备阻燃尼龙,可有效解决共混法中常存在的阻燃剂在基体中分散不均匀而导致的材料性能下降的问题。原位聚合法和共聚法是根据阻燃成分在基体中的存在方式而区分的,通常前者以物理均匀分散为主,后者多以化学键结合。本文在不同制备方法的背景下,根据阻燃剂类别进一步细分,综述了用原位聚合法和共聚法制备无卤阻燃尼龙的相关研究,并探讨了该领域中亟待解决的问题及未来发展方向。     

细旦尼龙6纤维加工过程中的晶型转化行为

通过引入富镧稀土化合物等添加剂,成功实现了细旦尼龙6纤维的熔融纺丝．考察了在纺丝卷绕成型以及牵伸过程中尼龙6纤维的晶型变化．借助XRD和FT－IR等研究手段,发现尼龙6在纺丝过程中可以生成亚稳态的B晶型晶体．这种β晶型经过沸水处理后很容易转化为α晶型,而γ晶型尼龙6经沸水处理后不发生相转变．因此可以通过沸水热处理的方法区分尼龙6的β和γ晶型．在纤维的卷绕过程中,当熔体拉伸倍数较高时,尼龙6可能产生β晶型;当熔体拉伸倍数较低时,则以γ晶型为主．在纤维的牵伸过程中,γ晶型经过β晶型中间态向α晶型相转变．上述结果对于指导改进细旦尼龙6纤维的加工工艺以及提高产品性能有指导意义．     

kevlar纤维增强尼龙6复合材料的力学性能

对Kevlar纤维进行了改性,使其成为己内酰胺阴离子开环聚合的活性中心,采用阴离子接枝法在Kevlar纤维(KF)表面接枝尼龙6低聚物,并与基体尼龙6混合,用挤出和注塑方式制备了尼龙6/改性Kevlar纤维(PA6/KF1)复合材料。ESEM和XPS分析表明,Kevlar纤维表面接枝上了尼龙6低聚物。比较了尼龙6/未改性Kevlar纤维(PA6/KF0)和PA6/KF1复合材料的力学性能及破坏形态,同时探讨了其破坏机理。结果表明,接枝尼龙6的KF1增强了KF与尼龙6复合材料界面的相互作用,拉伸强度、弯曲强度和弯曲模量分别提高了20.69%、12.26%和14.23%,但冲击强度降低了8.2%;当复合材料被破坏时,未改性纤维表面只粘附有少量的树脂尼龙6,而改性纤维的表面有较多的树脂包覆层,呈部分非界面脱粘破坏,具有良好的界面结合能力。     

Crystalline Morphology and Crystallization Characteristics of In-situ Blends of Anionic Polyamide 6 with Noncrystallizable Semiaromatic Polyamide Copolymer

A noncrystallizable semiaromatic polyamide copolymer(NSAP) was dissolved in molten caprolactam, and PA6/NSAP blends were produced in-situ via the anionic ring-opening polymerization of caprolactam. The presence of a single loss tangent(tanδ) peak measured by means of dynamic mechanical analysis(DMA) proves the miscibility between PA6 and NSAP in the blends. It was found that there existed drastic changes in the crystallographic form and crystallization kinetics for the in-situ blends, e.g., when 20% NSAP was added, nearly all crystallites existed in the γ form and the crystallization could hardly occur upon cooling even at a rate of 2.5 ℃/min. Moreover, cold crystallization appears during the subsequent heating, and its melting point is 40 ℃ lower than that of the virgin system. On the other hand, the size of the spherulites only decreases modestly. It is suggested that the introduction of irregular stiff segments originated from NSAP into PA6 macromolecule chain, which resulted from transamidation during the polymerization play a dominant role in the drastic change of crystallization kinetics and the resultant morphology of the in-situ blends.     

TRANSAMIDATION IN THE in situ BLENDING OF POLYAMIDE 1212 WITH POLYAMIDE 6 THROUGH ANIONIC POLYMERIZATION OF CAPROLACTAM

20 wt% polyamide 12(PA1212)pellets were dissolved in molten caprolactam.The caprolactam was then catalyzed at 180℃and polymerized by means of anionic ring-opening polymerization to produce in situ blends of the resultant polyamide 6(PA6)and PA1212.Mechanical blends with same ingredient were prepared through melt blending on a twin-screw extruder.Scanning electron microscopy(SEM)observation revealed that contrary to the mechanical blends with small spherulites embedded in the matrix,no phase-separation existed in the in situ blends.The results of thermal analysis by differential scanning calorimetry(DSC)showed that single melting peak and crystallization peak existed for the in situ blends,while two melting and crystallization peaks appeared for the mechanical blends.The in situ blend film and the mixed blend film,both cast from a dilute formic acid solution with a concentration of 0.5 g/L,remained similar crystallization and melting behavior as above.It is proved by solution ~(13)C-NMR analysis that transamidation took place during the in situ blending,and it is suggested that the combination of temperature increasing and the basic surrounding derived from NaOH during polymerization resulted in the occurrence of transamidation.Furthermore,it is proposed that the interchange reaction between PA1212 and PA6 also resulted from the degradative reaction during the anionic polymerization.     

MODIFICATION OF POLYAMIDE 6 WITH POLYAMINOAMIDE-g-POLY(ETHYLENE GLYCOL) VIA HYDROLYTIC POLYMERIZATION

To enhance the impact strength of polyamide 6,hydrolytic polymerization modification by the polyaminoamide-gpoly (ethylene glycol)(PAAEG)derivatives with poly(ethylene glycol)(PEG)molecular weight of 400-10000 was studied. Amide groups of polyaminoamide segments were postulated to form hydrogen bonding with polyamide 6,and hydroxy groups of PAAEG units were expected to react with carboxylic acid groups of polyamide 6 forming copolymers during the polymerization.The improved compatibility in amorphous reg...     

显微镜图像分析研究聚丙烯/尼龙1010共混物相结构及其性能

用扫描电子显微镜图像分析研究了聚丙烯/聚酰胺1010共混物及其部分相容体系的相形态结构,计算了表征相结构和尺寸的结构参数,如分散相的平均直径、平均弦长和分散相的质心相关距等.并分别讨论了聚丙烯/聚酰胺1010共混物及其部分相容体系的相形态以及其结构参数与共混物组成的关系.测定了聚合物及其共混物体系的力学性能,讨论了共混物组成与力学性能的关系.聚丙烯/聚酰胺1010共混物的拉伸模量与组成的关系较为复杂,但其部分相容体系的拉伸模量与组成呈线性关系.聚丙烯/聚酰胺1010及其共混物体系的屈服强度与共混物组成均呈线性关系.表征相结构的两相平均弦长比(l-1/-l2)与组成以及共混物体系力学性能与组成的关系,二者相似.同时讨论了体系力学性能随相尺寸等的变化规律.     

INTERFACIAL MOLECULAR DESIGN OF A RIGID- PARTICLE TOUGHENED POLYAMIDE 6 COMPOSITE

The effects of interfacial modifier on the mechanical properties of kaolin-filled polyamide 6 (PA6) have been studied. The interracial interaction between polyamide 6 and kaolin has been character ized by means of infrared spectroscopy (IR) and scanning electron microscopy (SEM). The results show that the role of the interracial modifier lies in forming an elastic interlayer with good adhesion between kaolin and PA 6. A composite with high impact strength, high tensile strength and high elastic modulus can be obtained by inserting the elastic interfacial modifier into the rigid-particle-filled polymer system.     

Preparation of Cu nanoparticles-modified PA6 composites using CuO as filler

This work focuses on the preparation of copper nanoparticles-modified polyamide 6 composites (denoted as nano-Cu/PA6) by in situ polymerization, with which cupric oxide as metallic copper source is directly reduced to metallic copper in the process of the opening-ring polymerization of ε-caprolactam only using the reducing atmosphere of reaction system. The obtained composites are characterized by means of transmission electron microscopy, X-ray diffraction, laser granulometry instrument, and ultraviolet–visible absorption spectroscopy. Moreover, the friction and wear resistance, mechanical strength, and antistatic performance of as-prepared composites are also readily evaluated. The results show that cupric oxide as filler is reduced to metallic copper and the as-reduced copper nanoparticles with 4–5-nm-size clusters separately disperse in polyamide 6 (PA6) matrix. Additionally, the addition content (mass fraction) of cupric oxide has significant effect on the crystalline form of PA6, and γ crystalline form of PA6 is predominant when higher dosage of CuO is introduced to fabricating nano-Cu/PA6 composites. Moreover, introducing a proper amount of CuO filler favors to generate nano-Cu/PA6 composites with improved mechanical properties and wear resistance. Particularly, nano-Cu/PA6 composite prepared at a CuO content of 0.5 % possesses the best tensile strength and wear resistance, showing promising application as a functional polymer–matrix composite.     

PREPARATION AND CHARACTERIZATION OF POLYAMIDE 11/CLAY NANOCOMPOSITES

INTRODUCTIONIn recent years, polymer/clay nanocomposites have attracted great interest from researchers since they frequentlyexhibit unexpected hybrid properties synergistically derived from the two components. Compared to their microcounterparts and the pristine polymer matrix, polymer/clay nanocomposites exhibit improved tensile strength andmodulus, decreased thermal expansion coefficient, decreased gas permeability, increased swelling resistance,enhanced ion conductivity, and reduced fl…     

Influence of preparation methods on the structures and properties for the blends between polyamide 6co6T and polyamide 6: Melt‐mixing and in‐situ blending

Two blends between polyamide 6 (PA6) and Polyamide 6co6T (PA6co6T, a random copolymer between polyamide 6 and polyamide 6T) were fabricated by melt‐mixing on a twin‐screw extruder and the subsequent injection molding, or through the in‐situ polymerization of ε‐caprolactam in the presence of PA6co6T. As far as the former method is concerned, there exist an obvious decline of toughness and a slight increase in strength and modulus; however, for the latter, there appear a remarkable improvement in toughness and a simultaneous moderate increase in strength and modulus. A series of characterizations were carried out including scanning electron microscopy, wide‐angle X‐ray diffraction, polarized optical microscopy, differential scanning calorimetry, dynamic mechanical analysis, and Fourier transform infrared spectrometry. It is found that both blends exhibit single glass transition on DMA tan δ curves. However, contrary to that of the melt‐mixed blends, the glass transition temperature (T_g) of the in‐situ ones decreases with increasing PA6co6T content. It is suggested that different mixing levels are the main reasons. Moreover, the addition of PA6co6T containing linear rigid segments conducts remarkable refinement of spherulites for the blends. Significantly different changes in the crystallographic form, spherulite size, crystalline content and perfection due to the introduction of PA6co6T for the two blends are ascribed to their varied thermomechanical histories and the presence of interchange reaction only for the in‐situ blends. On the basis of the characterizations of the microstructures, the different trends of changes in the mechanical properties with the addition of PA6co6T for the two fabrication methods are discussed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 201–211, 2008     

聚苯硫醚/尼龙6共混物界面对结晶行为的影响

高分子作为材料时 ,其力学性能受其结晶形态的影响 ,而其结晶形态与其结晶行为有关 .结晶性聚合物共混物中结晶组分由于第二组分存在 ,改变了结晶组分在熔体时的化学与物理环境 .因此 ,其结晶组分的结晶行为不仅取决于两组分在熔体时的相容性 ,而且与第二组分是否起到异相晶核作用和 /或两组分间界面是否诱导成核作用有关 ,从而影响共混物中结晶组分的结晶行为 ,导致共混物力学性能的改变[1～ 4] .在ＰＰＳ/ＰＡ6共混物中 ,由于ＰＰＳ的熔点和熔体结晶温度都比ＰＡ6的高 ,共混物熔体降温结晶ＰＰＳ是在ＰＡ6熔体存在下发生结晶 ,而ＰＡ6是在…