Polyamide-12 layered silicate nanocomposites by melt blending

Polyamide-12/tetrasilisic fluoromica (PA12-ME100) and polyamide-12/quaternary tallow ammonium chloride modified fluoromica nanocomposites (PA12-MAE) were prepared by melt compounding. The nanocomposite morphology and clay dispersion were investigated using wide angle X-ray diffraction (XRD), scanning electron microscopy (SEM), SEM-energy dispersive X-ray analysis (SEM-EDX), transmission electron miscroscopy (TEM), high resolution transmission electron microscopy (HRTEM) and atomic force microscopy (AFM). A predominantly intercalated morphology was observed for PA12-ME100, and a very high degree of exfoliation for PA12-MAE. HRTEM showed that the polymer crystallites lie perpendicular to the clay surface. The tensile and flexural properties of the PA12-MAE nanocomposite were significantly enhanced compared to neat polyamide-12, even with the addition of only 4 wt% nanoclay. Furthermore, the elongation at break (%) increased from 180% for polyamide-12 up to >500% for the PA12-MAE nanocomposite. In situ measurement of the heat generated in the test specimens during uniaxial tensile deformation using infra-red thermal imaging showed that the temperature of the dumbbell samples increased from room temperature (23 °C) to as high as 70 °C regardless of the strain rate used. This is considerably above the glass transition temperature (T_g) of PA12-MAE (30 °C), as measured by dynamic mechanical thermal analysis (DMTA). The mechanism of deformation is partially explained in terms of microvoid formation. The shear viscosity of the PA12-MAE nanocomposite determined by dual capillary rheometry was lower than both neat polyamide-12 and PA12-ME100. The reduction in shear viscosity of the nanocomposites was shown, from gel permeation chromatography (GPC) studies, not to originate from polymer degradation during melt blending. The coefficient of thermal expansion, decomposition temperature, and melting and crystallisation temperatures and relative crystalline content of the nanocomposite materials were measured by thermo-mechanical analysis (TMA), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) respectively—properties which can be related to polymer nanoclay interactions.     

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.     

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     

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     

阻隔性尼龙611／有机蒙脱土纳米复合材料的研究

以11-氨基十一酸对蒙脱土(MMT)进行有机化改性,采用原位聚合法制备了尼龙611/有机蒙脱土(OM-MT)纳米复合材料.通过傅立叶变换红外光谱仪研究了OMMT及尼龙611/OMMT纳米复合材料的化学结构,使用扫描电子显微镜观察了纳米复合材料的形貌.详细考察了OMMT含量对尼龙611/OMMT纳米复合材料阻隔性能和力学性能的影响,探讨了OMMT的阻隔机理.结果表明,MMT经有机化改性后,其片层在尼龙基体中分散均匀,并与尼龙基体发生键合作用,使尼龙611分子的内聚力增强,分子链堆积程度提高,极大地提高了阻隔性能;OMMT质量分数为3%时,材料的拉伸强度达到最大值,但在常温、低温下冲击强度略有下降.     

Epoxy/acrylonitrile-butadiene-styrene copolymer/clay ternary nanocomposite as impact toughened epoxy

Epoxy resins have low impact strength and poor resistance to crack propagation, which limit their many end use applications. The main objective of this work is to incorporate both acrylonitrile-butadiene-styrene copolymer (ABS) and organically modified clay (Cloisite 30B) into epoxy matrix with the aim of obtaining improved material with the impact strength higher than neat epoxy, epoxy/clay and epoxy/ABS hybrids without compromising the other desired mechanical properties such as tensile strength and modulus. Impact and tensile properties of binary and ternary systems were investigated. Tensile strength, elongation at break and impact strength were increased significantly with incorporation of only 4 phr ABS to epoxy matrix. For epoxy/clay nanocomposite with 2.5% clay content, tensile modulus and strength, and impact strength were improved compared to neat epoxy. With incorporation of 2.5% clay and 4 phr ABS into epoxy matrix, 133% increase was observed for impact strength. Ternary nanocomposite had impact and tensile strengths greater than values of the binary systems. Morphological properties of epoxy/ABS, epoxy/clay and epoxy/ABS/clay ternary nanocomposite were studied using atomic force microscopy (AFM) phase imaging, scanning electron microscopy (SEM) and wide angle X-ray diffraction (WAXD). New morphologies were achieved for epoxy/ABS and epoxy/ABS/clay hybrid materials. Exfoliated clay structure was obtained for epoxy/clay and epoxy/ABS/clay nanocomposite.     

Effects of corona treatment on composite formation. Adhesion between incompatible polymers

Polypropylene–nylon 6 10 composites were prepared by the in situ polymerization of the nylon monomers on polypropylene films. The adhesion between the nylon and the polypropylene was markedly improved by a brief corona discharge treatment of the films in nitrogen prior to coating. This improvement was demonstrated by an increase in the peel strength of the nylon coating and a decrease in brittleness of photo-oxidized compesites when corona treatment was used. Adhesive bonding between the nylon and substrate was sufficiently strong to cause cohesive failure in the corona-treated polypropylene. Only interfacial failure was observed at untreated surfaces. These effects were demonstrated by electron microscopy of the surfaces produced in peel tests. The effects of corona treatment on adhesive bonding characteristics of surfaces are discussed in terms of the chemical and physical changes observed in treated surfaces.     

Effect of drawing on the molecular orientation,polymorphism, and properties of melt‐spun nanocomposite fibers based on nylon 6 with polyhedral oligomeric silsesquioxane,montmorillonite, and their combination

In this work, binary and ternary nanocomposite systems based on nylon 6 with montmorillonite (MMT), polyhedral oligomeric silsesquioxane (POSS), and their combination were prepared using a melt‐compounding process. In the transmission electron microscope (TEM) images, the MMT was found to be generally well dispersed in all materials resulting in its good chemical compatibility with nylon 6, affording intercalated disordered microstructures. On the other hand, the TEM images showed that POSS formed micron‐size crystalline agglomerates possibly resulting from a lack in chemical compatibility with nylon 6. These nanocomposite systems were melt‐spun into fibers, and the relevant structure–property relationships that occur during the cold drawing process was established by correlating the tensile properties to the changes in crystallinity, polymorphic crystal forms, and molecular orientation. The properties of the resulting fibers were found to be rather skewed and significantly affected by the polymer/nanoparticles interface. The agglomeration of POSS and POSS–MMT particles coupled with the weak nylon 6/POSS interface, reflected on the tensile properties of the nylon 6/POSS and nylon 6/MMT‐POSS fibers which underperformed. Some nanocomposite fiber systems offered significant improvements in modulus without excessively compromising the extensibility of the fibers. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

The effect of trimethylol propane tetraacrylate (TMPTA) and organoclay loading on the properties of electron beam irradiated ethylene vinyl acetate (EVA)/natural rubber (SMR L)/organoclay nanocomposites

Ethylene vinyl acetate (EVA)/natural rubber (SMR L)/organoclay nanocomposites were prepared by melt blending technique with 0–10 phr organoclay loading and 3 phr TMPTA. Electron beam initiated crosslinking on these samples was carried out using a 3.0 MeV electron beam machine with doses ranging from 50 to 200 kGy. XRD results proved that dispersion of organoclay in the nanocomposites was slightly improved by irradiation with TMPTA. This was further supported by transmission electron microscopy images, where the nanoscale dispersion of organoclay was more homogenous throughout the irradiated polymer matrix compared to nonirradiated samples. TMPTA also increased the gel fraction yield, tensile properties and thermal stability of the irradiated neat EVA/SMR L and its nanocomposites. TMPTA was found to act as a crosslink initiator, which promotes crosslink bridges via free radical mechanism in EVA/SMR L matrix. SEM observation shows that the fracture behavior of the irradiated neat EVA/SMR L and its nanocomposites with TMPTA is significantly different compared to the fracture behavior of the nonirradiated neat EVA/SMR L. The distinct failure surface structure formed in the irradiated samples with TMPTA explains the overall higher value of tensile properties. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Flame retardancy and char microstructure of nylon‐6/layered silicate nanocomposites

We investigated the effect of organically modified clay alone and in combination with zinc borate on the thermal/flammability behavior of nylon‐6 nanocomposites. Differential thermogravimetric analysis indicated that the peak decomposition temperature was not affected by the addition of clay, but the rate of weight loss decreased with increase in clay concentration. Nanocomposite films of approximately 0.5 mm thickness with 2.5 and 5 wt % clay burned for almost the same duration as neat nylon‐6 but with reduced dripping in horizontal flame test. The 10 wt % clay nanocomposite sample burned without any dripping and the flame spread rate was reduced by 25–30%. Zinc borate/clay containing nanocomposite developed into a very good intumescent system in cone calorimeter test, swelling about 10–13 mm height prior to ignition forming a cellular char structure. This was found to be an effective composition in reducing the heat release and mass loss rate of nylon‐6 by about 65% and at par with 10 wt % clay nanocomposite. Flame retardant behavior could be attributed to distinct char morphologies observed through scanning electron microscopy. Fourier transform infrared spectroscopy of the 10 wt % clay nanocomposite char showed the presence of amides, indicating possible residual polymer within the shielded char. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1540–1550, 2007     

Amino functionalization of multiwalled carbon nanotubes by gamma ray irradiation and its epoxy composites

In this paper, γ‐ray radiation technique was utilized to simply functionalize multi‐walled carbon nanotube (MWCNT) with amino groups. The successful amino functionalization of MWCNTs (MWCNTs‐Am) was proven and the physicochemical properties of MWCNTs before and after radiation grafting modifications were characterized using FT‐IR, X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The results indicated that the γ‐ray radiation had the visible effects on the surface properties of MWCNTs. The effects of various functionalized MWCNTs on morphological, thermal, and mechanical properties of an epoxy‐based nanocomposite system were investigated. Utilizing in situ polymerization, 1 wt% loading of MWCNT was used to prepare epoxy‐based nanocomposites. Compared to the neat epoxy system, nanocomposites prepared with MWCNT‐Am showed 13.0% increase in tensile strength, 20.0% increase in tensile modulus, and 24.1% increase in thermal decomposition temperature. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Effect of organoclay structure on nylon 6 nanocomposite morphology and properties

A carefully selected series of organic amine salts were ion exchanged with sodium montmorillonite to form organoclays varying in amine structure or exchange level relative to the clay. Each organoclay was melt-mixed with a high molecular grade of nylon 6 (HMW) using a twin screw extruder; some organoclays were also mixed with a low molecular grade of nylon 6 (LMW). Wide angle X-ray scattering, transmission electron microscopy, and stress-strain behavior were used to evaluate the effect of amine structure on nanocomposite morphology and physical properties. Three surfactant structural issues were found to significantly affect nanocomposite morphology and properties in the case of the HMW nylon 6: decreasing the number of long alkyl tails from two to one tallows, use of methyl rather than hydroxy-ethyl groups, and use of an equivalent amount of surfactant with the montmorillonite, as opposed to adding excess, lead to greater extents of silicate platelet exfoliation, increased moduli, higher yield strengths, and lower elongation at break. LMW nanocomposites exhibited similar surfactant structure-nanocomposite behavior. Overall, nanocomposites based on HMW nylon 6 exhibited higher extents of platelet exfoliation and better mechanical properties than nanocomposites formed from the LMW polyamide, regardless of the organoclay used. This trend is attributed to the higher melt viscosity and consequently the higher shear stresses generated during melt processing.     

尼龙11/蒙脱土纳米复合材料的研究

采用熔体插层法制备了尼龙11／蒙脱土纳米复合材料。研究了纳米蒙脱土对尼龙11力学性能的影响。结果表明,在蒙脱土含量为5％时,尼龙11／蒙脱土纳米复合材料的冲击强度达到最大值,是纯尼龙11冲击强度的2．5倍;随着蒙脱土含量的增加,复合材料的拉伸强度先降低后升高,但变化幅度不大。通过电镜观察冲击断面形态发现,蒙脱土以片状形式均匀分散在尼龙11基体中,受冲击时基体产生了屈服。     

Friction and wear studies on nylon‐6/SiO2 nanocomposites

Composites of nanometer‐sized silica (SiO₂) filler incorporated in nylon‐6 polymer were prepared by compression molding. Their friction and wear properties were investigated on a pin on disk tribometer by running a flat pin of steel against a composite disc. The morphologies of the composites as well as of the wear track were observed by scanning electron microscopy (SEM). The addition of 2 wt % SiO₂ resulted in a friction reduction (μ) from 0.5 to 0.18 when compared with neat nylon‐6. This low silica loading led to a reduction in wear rate by a factor of 140, whereas the influence of higher silica loadings was less pronounced. The smooth morphology obtained after the wear test indicated the negligible contribution to friction of the pin to the nanocomposite. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1855–1862, 2004     

Preparation and characterisation of hydroxyl-terminated polybutadiene-based polyurethane/graphene nanocomposites

Polyurethane nanocomposites based on hydroxyl-terminated polybutadiene and graphene with different formulations were cured using toluene diisocyanates. The rheological, physical, mechanical, thermal and morphological properties of the nanocomposites were investigated. The viscosity of the samples increased rapidly with graphene content. However, the kinetic rate of the curing process was lower for the nanocomposites in comparison to the neat matrix. The mechanical properties showed a successive increase in the tensile strength and reduction in elongation at break with an increase in graphene content. The highest value of the modulus, density and degradation temperature was obtained for the nanocomposite with 1?wt-% graphene. The hardness properties of the nanocomposites enhanced with curing time. The morphological properties of the nanocomposites are also investigated with the field emission scanning electron microscopy which confirmed the agglomeration occurrence at the high graphene contents.     

高黏度尼龙6膜拉伸性能研究

以采用阴离子淤浆聚合法制备的高黏度尼龙6为原料,分别加入增塑剂DBP和低摩尔质量尼龙6树脂,以甲酸为溶剂制备溶液,用流延法制膜,研究了增塑剂和小分子尼龙6对膜力学性能的影响.结果表明,增塑剂和小分子尼龙6的加入有助于提高膜的拉伸性能.加入无水氯化钙制备尼龙6络合膜,膜的拉伸性能可提高3倍以上;在水中解络合后,膜的力学性能有较大的恢复.     

Nylon 10 10–montmorillonite nanocomposite made by intercalating polymerization

Nylon 10 10–montmorillonite nanocomposite has been prepared successfully using intercalating polymerization. The nanocomposite was investigated by X‐ray diffraction (XRD), Fourier transform infrared (FTIR), Atom force microscopy (AFM), Scanning electron microscopy (SEM), Thermogravimetric analysis (TGA), Differential scanning calorimeter (DSC), and Dynamic mechanical analysis (DMA). The results show that there are uniformly dispersed silicate layers in the nylon 10 10 matrix. The resulting nanocomposites have higher onset decomposition temperature and dynamic storage moduli than those of pure nylon 10 10. In addition, it was found that montmorillonite plays an important role in heterophase nucleation of the crystallization of nylon 10 10 in composites. Mechanical testing shows that the tensile modulus of nanocomposites is superior to that of nylon 10 10, and the ultimate strain values of the nanocomposites remain at a level similar to nylon 10 10 if the content of montmorillonite is not more than 6 wt%.     

Mechanism of enhanced tenacity in a polymer nanocomposite studied by small-angle X-ray scattering and electron microscopy

A poly[(butylene succinate)-co-adipate] (PBSA) nanocomposite containing 3 wt% organically modified montmorillonite exhibited an improvement in tenacity (elongation at break) as compared to the neat PBSA. The nanocomposite also showed moderate improvement in tensile modulus and strength. The small-angle X-ray scattering and transmission electron microscopy were used to investigate the exact tenacity improvement mechanism in the nanocomposite.     

The effect of nanosilica on mechanical,thermal and morphological properties of epoxy coating

In this study, nanosilica of very high specific surface area is used as reinforcing filler for preparing an epoxy-based nanocomposite coating. For appropriate dispersion of nanoparticles in the polymer matrix, ultrasound waves were applied after mechanical mixing. The resulting perfect dispersion of nanosilica particles in epoxy coating revealed by transmission electron microscopy ensured the transparency of the nanocomposite. Nanoindentation was used to determine some mechanical properties such as hardness and elastic modulus. The obtained results show 26 and 21% increases in hardness and elastic modulus, respectively for resin filled with 5% nanosilica compared to neat epoxy. DMA results show that the glass transition temperature of samples is increased with increasing silica nanoparticles. The result of TGA shows significant improvement of the thermal decomposition temperature of epoxy coating containing 5% nanosilica compared to neat epoxy. Scanning electron microscopy (SEM) micrographs of fractured surfaces show increased roughness with nanosilica addition.