Isothermal crystallization kinetics and melting behavior of nylon/saponite and nylon/montmorillonite nanocomposites

DSC thermal analysis and X‐ray diffraction have been used to investigate the isothermal crystallization behavior and crystalline structure of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of ε‐caprolactam and then exfoliating the layered silicates by subsequent polymerization. The DSC isothermal results reveal that introducing saponite into the nylon structure causes strongly heterogeneous nucleation induced change of the crystal growth process from a two‐dimensional crystal growth to a three dimensional spherulitic growth. But the crystal growth mechanism of nylon/montmorillonite nanocomposites is a mixed two‐dimensional and three‐dimensional spherulitic growth. The activation energy drastically decreases with the presence of 2.5 wt % clay in nylon/clay nanocomposites and then slightly increases with increasing clay content. The result indicates that the addition of clay into nylon induces the heterogeneous nucleation (a lower ΔE) at lower clay content and then reduces the transportation ability of polymer chains during crystallization processes at higher clay content (a higher ΔE). The correlation among crystallization kinetics, melting behavior, and crystalline structure of nylon/clay nanocomposites is also discussed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2196–2204, 2004     

Structure and thermal behaviour of nylon 6 nanocomposites

In this article, nylon 6/clay nanocomposites with 5 wt % clay (NCN5) were prepared by a twin screw extruder. The effects of annealing including solid‐state annealing (170 and 190°C) and melt‐state annealing (240°C) on the polymorphic behavior and thermal property of NCN5 and nylon 6 have been comparatively studied as a function of annealing time using modified differential scanning calorimetry (MDSC) and wide‐angle X‐ray diffraction. It was demonstrated that NCN5 and nylon 6 exhibit a similar polymorphic behavior when they were annealed at 190°C for different time durations. As the annealing temperature was elevated to 240°C, significant differences in thermal behavior and polymorphism between NCN5 and nylon 6 could be found. For example, the α crystal became the absolutely dominating crystalline phase for NCN5 sample independent on the annealing durations, whereas the formation of γ crystal is greatly enhanced in neat nylon 6 with increasing annealing time. Moreover, a small endothermic peak is observed around 180°C in both nylon 6 and NCN5 samples annealed at 170 and 190°C, which might be related to the melting of microcrystals formed in the amorphous regions during annealing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3116–3122, 2006     

Polymorphic behavior of nylon 6/saponite and nylon 6/montmorillonite nanocomposites

X‐ray diffraction methods and DSC thermal analysis have been used to investigate the structural change of nylon 6/clay nanocomposites. Nylon 6/clay has prepared by the intercalation of ε‐caprolactam and then exfoliaton of the layered saponite or montmorillonite by subsequent polymerization. Both X‐ray diffraction data and DSC results indicate the presence of polymorphism in nylon 6 and in nylon 6/clay nanocomposites. This polymorphic behavior is dependent on the cooling rate of nylon 6/clay nanocomposites from melt and the content of saponite or montmorillonite in nylon 6/clay nanocomposites. The quenching from the melt induces the crystallization into the γ crystalline form. The addition of clay increases the crystallization rate of the α crystalline form at lower saponite content and promotes the heterophase nucleation of γ crystalline form at higher saponite or montmorillonite content. The effect of thermal treatment on the crystalline structure of nylon 6/clay nanocomposites in the range between Tg and Tm is also discussed.     

Modifying montmorillonite clay via silane grafting and interfacial polycondensation for melt compounding of nylon‐66 nanocomposite

A trifunctional organo alkoxysilane (3‐aminopropyl)triethoxysilane (γ‐APS) has been used as reagent for the chemical modification of montmorillonite clay. Silane grafting was taken place in dry and hydrolyzing conditions. Silane grafted and pristine clay took part in interfacial polycondensation process to deposit a layer of nylon‐66 onto the clay lamellae and therefore, enhance their affinity with nylon‐66 matrix. Evidence of presence of grafted silane molecules and deposition of nylon‐66 on clay particles were provided by Fourier transform‐infrared, thermogravimetric analysis (TGA), and X‐ray diffraction (XRD). Such modified clays and pristine clays were melt compounded with nylon‐66. The structures of the resulting nylon composites were characterized using XRD and transmission electron microscopy and the results showed presence of both intercalation and exfoliation. TGA thermograms of nanocomposites indicated improved thermal stability upon the incorporation of silane grafted montmorillonite. Furthermore, differential scanning calorimetry scans showed that silane modified clays promoted crystallization in nanocomposites. Increase of storage modulus and depression of tan δ peak in nanocomposites in dynamical mechanical thermal analysis were observed. The rheological properties of nylon‐66 and nanocomposites were also evaluated and differences in values of complex viscosity of samples were noticed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Abrasion studies of nylon 6/montmorillonite nanocomposites using scanning electron microscopy,fourier transform infrared spectroscopy,and X‐ray photoelectron spectroscopy

In this article, abrasion performance of commercial nylon 6 and nylon 6/montmorillonite (MMT) nanocomposites was studied. The polymer nanocomposites showed poor abrasion resistance compared to the neat polymer. The wear loss increased linearly with clay concentration. Changes in surface morphology, composition, and structure were investigated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR)‐attenuated total reflection spectroscopy, and X‐ray photoelectron spectroscopy (XPS). SEM images showed that all the abraded surfaces contained fractured particles. However, the abraded nanocomposite surfaces had much deeper grooves compared to the homopolymer. FTIR results showed an increase in the amount of α crystals and a decrease in the amount of γ crystals on all the surfaces after abrasion. This was attributed to the strain‐induced γ to α crystal transformation. The largest amount of α crystals was formed in the abraded surface of pure nylon 6, and the amount of α crystals formed decreased with increasing MMT content. XPS results showed an increase in the [Si]/[N] elemental ratio for all nanocomposites after abrasion, indicating an increase in the clay content of the surface. Abrasive wear mechanism is as follows: (1) tensile tearing is the dominant wear mechanism for all the samples; (2) the cutting mechanism becomes more important when MMT content increases; (3) the polymer matrix is easier to be removed than clay during the abrasion process; (4) in nylon 6/MMT systems, the poor abrasion resistance is attributed to defects at the clay‐polymer interface, resulting in greater wear of the polymer matrix. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of nylon 6/clay nanocomposites prepared by ultrasonication and in situ polymerization

Nylon 6 nanocomposites were prepared by the in situ polymerization of ε‐caprolactam with ultrasonically dispersed organically modified montmorillonite clay (Cloisite 30B®). Dispersions of the clay platelets with concentrations in the range 1–5 wt % in the monomer were characterized using rheological measurements. All mixtures exhibited shear‐thinning, signifying that the clay particles were dispersed as platelets and forming a “house of cards” structure. Samples with Cloisite concentrations above 2 wt % showed a drop in viscosity between the initial shearing and repeated shearing, indicative of shearing breaking down the initial “house of cards” structures formed on sonication. DMTA measurements of the samples showed an increase in the β‐relaxation temperature with increasing clay concentration. The bending modulus, at temperatures below T_g, showed an increase with increasing clay concentration up to 4 wt %. X‐ray diffraction measurements showed that all nylon 6/Cloisite 30B samples were exfoliated apart from the 5 wt %, which showed that some intercalated material was present. The nylon crystallized into the α‐crystalline phase, which is the most thermodynamically stable form. Preference for this form may be a consequence of the long time associated with the postcondensation step in the synthesis or the influence of the platelets on the nucleation step of the crystal growth. DSC measurements showed a retardation of the crystallization rate of nanocomposite samples when compared with that of pure nylon 6, due to the exfoliated clay platelets hindering chain movement. This behavior is different from that observed for the melt‐mixed nylon 6/clay nanocomposites, which show an enhancement in the crystallization rate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Morphology and crystallization behavior of nylon 6‐clay/neat nylon 6 bicomponent nanocomposite fibers

Nylon 6‐clay hybrid/neat nylon 6, sheath/core bicomponent nanocomposite fibers containing 4 wt % of clay in sheath section, were melt spun at different take‐up speeds. Their molecular orientation and crystalline structure were compared to those of neat nylon 6 fibers. Moreover, the morphology of the bicomponent fibers and dispersion of clay within the fibers were analyzed using scanning electron microscopy and transmission electron microscopy (TEM), respectively. Birefringence measurements showed that the orientation development in sheath part was reasonably high while core part showed negligibly low birefringence. Results of differential scanning calorimetry showed that crystallinity of bicomponent fibers was lower than that of neat nylon 6 fibers. The peaks of γ‐crystalline form were observed in the wide‐angle X‐ray diffraction of bicomponent and neat nylon 6 fibers in the whole take‐up speed, while α‐crystalline form started to appear at high speeds in bicomponent fibers. TEM micrographs revealed that the clay platelets were individually and evenly dispersed in the nylon 6 matrix. The neat nylon 6 fibers had a smooth surface while striped pattern was observed on the surface of bicomponent fibers containing clay. This was speculated to be due to thermal shrinkage of the core part after solidification of the sheath part in the spin‐line. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39996.     

Facile preparation of nylon 6 nanocomposites based on clay reinforcement and core‐shell latex toughening: Morphology,properties, and impact fracture behavior

This work is focused on a facile route to prepare a new type of nylon 6‐based nanocomposites with both high fracture toughness and high strength. A series of nylon 6‐matrix blends were prepared via melting extrusion by compounding with poly (methyl methacrylate‐co‐butadiene‐co‐styrene) (MBS) or poly(methyl methacrylate‐co‐methylphenyl siloxane‐co‐styrene) (MSIS) latices as impact modifier and diglycidyl ether of bisphenol‐A (DGEBA) as compatibilizer. Layered organic clay was also incorporated into above nylon 6 blends for the reinforcement of materials. Morphology study suggests that the MBS or MSIS latex particles could achieve a mono‐dispersion in nylon 6 matrix with the aid of DGEBA, which improves the compatibilization and an interfacial adhesion between the matrix and the shell of MBS or MSIS. High impact toughness was also obtained but with a corresponding reduction in tensile strength and stiffness. A moderate amount of organic clay as reinforcing agent could gain a desirable balance between the strength, stiffness and toughness of the materials, and tensile strength and stiffness could achieve an improvement. This suggests that the combination of organic clay and core‐shell latex particles is a useful strategy to optimize and enhance the properties of nylon 6. Morphology observation indicates that the layered organic clay was completely exfoliated within nylon 6 matrix. It is found that the core‐shell latex particles and the clay platelets were dispersed individually in nylon 6 matrix, and no clay platelets were present in MBS or MSIS latex particles. So the presence of the clay in nylon 6 matrix does not disturb the latex particles to promote high fracture toughness via particle cavitation and subsequent matrix shear yielding, and therefore, provides maximum reinforcement to the polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Direct Melt Extrusion Processing of Nylon 6/Clay Nanocomposites Based on Pristine Montmorillonite

Summary: An original direct melt extrusion processing of nylon 6/clay nanocomposites was reported based on pristine (Na⁺‐based) montmorillonite as well as a simple approach using a typical two‐screw extruder. By the application of intercalation agents as the thermodynamic assistants, this method is as an appropriate procedure for industrialized manufacture together with much lowered production cost. Interestingly enough, the synergistic effects of montmorillonite with other inorganic particulates was observed for the first time here.

X‐ray diffraction patterns of pristine MMT and nylon 6/MMT composites with grouped intercalation agents.     

PA6/蒙脱土纳米复合材料的力学性能研究

利用未改性蒙脱土和两种季胺盐改性蒙脱土与尼龙(PA)6混合,成功制备得到了不同结构的PA6/蒙脱土纳米复合材料.X射线衍射图谱和力学性能分析表明,季胺盐改性剂可以插入蒙脱土片层之间,使蒙脱土片层扩张,层间距增大.与PA6相比,制备得到的三种纳米复合材料的力学性能都有不同程度的提高.改性蒙脱土与PA6表现出良好的相容性,...     

PA6/PSAM/MMT纳米复合材料制备与性能研究

将聚(苯乙烯-丙烯酰胺)季铵盐(PSAM)修饰蒙脱土(MMT)与尼龙(PA)6熔融共混,制备了PA6/PSAM/MMT纳米复合材料。考察了在MMT含量相同的情况下不同丙烯酰胺含量的PSAM修饰MMT对纳米复合材料力学性能的影响,并通过热重分析、X射线衍射等方法对此种纳米复合材料进行了表征。结果表明,当PSAM中丙烯酰胺的质量分数为10%时,PA6/PSAM/MMT纳米复合材料的综合性能较好。     

Crystallization behavior of nylon 11/montmorillonite nanocomposites under annealing

Exfoliated nylon 11/montmorillonite (MMT) nanocomposites were prepared via in situ polymerization by the dispersion of organically modified MMT in 11‐aminoundecanoic acid monomer. The polymorphic behavior of the nylon 11/MMT nanocomposites was investigated with X‐ray diffraction, transmission electron microscopy, and Fourier transform infrared with attenuated total reflectance. MMT induced and stabilized the δ‐crystalline form of nylon 11. The crystal structure of nylon 11 was transformed from a hexagonal δ‐form structure to a triclinic α‐form structure during the annealing process. Meanwhile, the hydrogen bonds in the nanocomposites also exhibited some differences from neat nylon 11 after annealing. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5483–5489, 2006     

Morphology and properties of nylon6 and high density polyethylene blends in absence and presence of nanoclay

The morphology and properties of nylon6/HDPE blends without and with nanoclay has been reported. Scanning electron microscopy study of the (70/30 w/w) nylon6/HDPE blends with small amount (0.1 phr) of nanoclay indicated a reduction in the average domain sizes (D) of dispersed HDPE phase and hence better extent of mixing compared to the blend without any nanoclay. X‐ray diffraction study and transmission electron microscopy revealed that nanoclay layers were mostly located in nylon6 matrix of the (70/30 w/w) nylon6/HDPE blend. However, the same effect of nanoclay on the morphology was not observed in (30/70 w/w) nylon6/HDPE blend where HDPE became the matrix. In (30/70 w/w) nylon6/HDPE blend, addition of nanoclay increased the D of dispersed nylon6 domains by preferential location of the clays in side the nylon6 domains. Thus, the clay platelets in the matrix phase acted as barrier that restricted the coalescence of dispersed domains during melt‐mixing. Addition of PE‐g‐MA in both the compositions of nylon6/HDPE blend effectively reduced the D of dispersed phases. Storage modulus and thermal stability of the blend were improved in presence of small amount of clay, whereas addition of PE‐g‐MA lowered the mechanical and thermal properties of the blends. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of nylon 1012/clay nanocomposite

A nylon 1012/clay nanocomposite was prepared by melt polycondensation polymerization of diamine and diacid in the presence of organoclay. The nylon 1012 and nanocomposite were characterized by Fourier transform IR spectroscopy with attenuated total reflection, and a shift of the Si? O? Si band toward a lower wavenumber was found as the result of the strong interaction of nylon 1012 with the organoclay. The X‐ray diffraction analysis and transmission electron microscopy observation showed that the clay minerals were exfoliated. Clay platelets increased the crystallization rate but decreased the crystallinity. Differential scanning calorimetry and dynamic mechanical thermal analysis measurements showed that the glass‐transition temperature of the nylon 1012/clay nanocomposite decreased to some degree as compared to nylon 1012 because of the combined effect of confinement and the reduction of the physical crosslink density. The mechanical properties of the nanocomposite such as the tensile strength and tensile modulus are higher than those of nylon 1012, and the water absorption is reduced because of the improvement in the barrier property of the nanocomposite. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2403–2410, 2002     

Effect of the silane modification of clay on the tensile properties of nylon 6/clay nanocomposites

A commercially available organomodified clay, Cloisite 25A, was modified with 3‐aminopropyltriethoxysilane, 3‐(glycidoxypropyl)trimethoxysilane, and 3‐isocyanate propyltriethoxysilane to enhance its interaction with the nylon 6 matrix. Composites made of nylon 6 and clays modified with the different silane compounds were prepared by melt mixing with a twin‐screw extruder. The dispersion and degree of exfoliation of the organomodified clays were evaluated from X‐ray diffraction patterns and transmission electron microscopy images of the corresponding composites. The tensile properties of the composites were measured, and their enhancement was attributed to the work of adhesion and interfacial tension of the composites. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and characterization of nanocomposites based on thermoplastic elastomers from rubber–plastic blends

In the present work, thermoplastic elastomer (TPE)–clay nanocomposites (TPN) based on different rubber–plastic blends from ethylene–octene copolymer [Engage]–Polypropylene and brominated poly(isobutylene‐co‐paramethyl styrene)–nylon 6 were prepared by melt blending. Hexadecyltrimethylammonium bromide and octadecyl amine‐modified sodium montmorillonite were used as organoclays. The nanocomposites were prepared by adding the nanoclay separately into the rubber and plastic phases. The TPNs were characterized with the help of transmission electron microscopy (TEM) and X‐ray diffraction. The X‐ray diffraction peaks observed in the range of 3–10° for the modified clays disappeared in the thermoplastic elastomeric nanocomposites. TEM photographs showed exfoliation and intercalation of the clays in the range of 20–30 nm in the particular phase where the clay was added. Excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus was observed on incorporation of the nanoclays in the rubber phase of TPN. When the nanoclay was added to the plastic phase, the mechanical reinforcement is comparatively poorer due to partial destruction of the crystallinity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1645–1656, 2006     

Influence of grafting on structural and optical properties of nylon‐6 fibers

This study throws light on the change of the optical properties and some structural properties due to graft copolymerization of polydiallyldimethyl ammonium chloride (PDADMAC) and polyacrylamide (PAA) of nylon‐6 fibers. Multiple‐beam interferometric technique in transmission was used to study the change of the diameter, refractive indices, and birefringence of nylon‐6 fibers at different graft yields. The results were utilized to investigate the isotropic refractive index, the mean polarizabilities per unit volume, dielectric constant, dielectric susceptibility, and surface reflectivity for nylon‐6 and grafted nylon‐6 fiber. The effect of grafted PAA onto modified nylon‐6 fibers containing PDADMAC on the crystallinity was studied by X‐ray diffraction. These results reflect good effect of grafting on the optical and structural properties of nylon‐6 fibers. The opto‐thermal properties of grafted PAA with different graft yields have been studied. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Preparation and properties of silver‐containing nylon 6 nanofibers formed by electrospinning

Nylon 6 nanofibers containing silver nanoparticles (nylon 6/silver) were successfully prepared by electrospinning. The structure and properties of the electrospun fibers were studied with the aid of scanning electron microscopy, transmission electron microscopy, energy‐dispersive spectroscopy, and X‐ray diffraction. The structural analysis indicated that the fibers electrospun at maximum conditions were straight and that silver nanoparticles were distributed in the fibers. Finally, the antibacterial activities of the nylon 6/silver nanofiber mats were investigated in a broth dilution test against Staphylococcus aureus (Gram‐positive) and Klebsiella pneumoniae (Gram‐negative) bacteria. It was revealed that nylon 6/silver possessed excellent antibacterial properties and an inhibitory effect on the growth of S. aureus and K. pneumoniae. On the contrary, nylon 6 fibers without silver nanoparticles did not show any such antibacterial activity. Therefore, electrospun nylon 6/silver nanocomposites could be used in water filters, wound dressings, or antiadhesion membranes. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Polymer‐Clay Nanocomposites Based on Blends of Polyamide‐6 and Polyethylene

The preparation of polyamide‐6/clay, high‐density polyethylene/clay, and high‐density polyethylene/ polyamide‐6/clay nanocomposites is considered. X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier Transform Infrared (FTIR) measurements show that the clay enhances the crystallization of the γ‐form of polyamide‐6. The clay also acts as a nucleation agent and causes a reduction of spherulitte size. Scanning electron microscopy (SEM) analysis of fracture surfaces shows that the clay reduces the PA‐6 particle size in the HDPE/PA‐6/clay nanocomposites and changes the morphology. Mechanical properties and the effect of maleated polyethylene are also reported.     

Crystalline forms in melt‐crystallized syndiotactic polystyrene/clay nanocomposites

X‐ray diffraction methods and polarized optical microscopy have been used to investigate the structural change of syndiotactic polystyrene/clay nanocomposites. The nanocomposite has prepared by mixing an sPS polymer solution with organically modified montmorillonite. Both X‐ray diffraction and transmission electron microscopy results indicate that most of the swellable silicate layers are exfoliated and randomly dispersed into the sPS matrix. The X‐ray diffraction data also show the presence of polymorphism in sPS/clay nanocomposites, which is strongly dependent on the thermal history of the nanocomposites from the melt and on the content of clay. In this study, the effect of premelting temperatures and crystallization temperatures of sPS and sPS/clay nanocomposites on their crystalline phases is discussed.