High performance long chain polyamide/calcium silicate whisker nanocomposites and the effective reinforcement mechanism

PA1012/calcium silicate whisker nanocomposites with contents of whisker ranging from 10 wt% to 40 wt%, are prepared by twin screw extruder without any additions of coupling agent. The effect of whisker on the matrix is analyzed by the studies of morphology, the mechanical properties, water absorption and thermal stabilities. SEM micrographs obviously demonstrate, even under the high filler content of 40 wt% and without surface treatment, calcium silicate whisker can be homogeneously dispersed in polyamide, directly leading to the enhanced mechanical properties. The mechanism of higher efficiency of reinforcement is needle-like shape whisker, having access to be intercalated, and mutual affinity caused by hydrogen bonding interaction between carbonyl group in polyamide chain and hydroxyl group in whisker surface. Both aspects attach matrix with excellent stress-transfer properties. In addition, with the assistance of whisker, the nanocomposite favors an improved water absorption as well as thermal stability, which is intimately associated with physical performance.     

Polyamide‐6/natural clay mineral nanocomposites prepared by solid‐state shear milling using pan‐mill equipment

The polyamide‐6 (PA6)/natural clay mineral nanocomposites were successfully prepared by solid‐state shear milling method without any treatment of clay mineral and additives. PA6/clay mixture was pan‐milled to produce PA6/clay compounding powder, using pan‐mill equipment. The obtained powder as master batch was diluted with neat PA6 to prepare composites by a twin‐screw extruder. The clay silicate layers were found to be partially exfoliated and dispersed homogeneously at nanometer level in PA6 matrix. The rheological measurements and mechanical properties of nanocomposites were characterized. The shear viscosities of nanocomposites were higher than that of pure PA6, and tensile strength and tensile modulus increased, but Izod impact strength decreased, with increasing concentration of clay. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 249–255, 2006     

Inclusion of aramid chains into the layered silicates through solution intercalation route

Aramid–organoclay nanocomposites were fabricated through solution intercalation technique. Montmorillonite was modified with p-amino benzoic acid in order to have compatibility with the matrix. The effect of clay dispersion and the interaction between clay and polyamide chains on the properties of nanocomposites were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), tensile testing of thin films, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and water uptake measurements. Excessive clay dispersion was achieved even on the addition of high proportions of clay. The structural investigations confirmed the formation of delaminated nanostructures at low clay contents and disordered intercalated morphology at higher clay loadings. The tensile behavior and thermal stability significantly amplified while permeability reduced with increasing dispersibility of organoclay in the polyamide matrix.     

Thermal and mechanical properties of syndiotactic polystyrene/organoclay nanocomposites with different microstructures

The fabrication of syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process with poly(styrene‐co‐vinyloxazolin) (OPS), that is, melt intercalation of OPS into organoclay followed by blending with sPS. The microstructure of nanocomposite mainly depended on the arrangement type of the organic modifier in clay gallery. When organoclays that have a lateral bilayer arrangement were used, an exfoliated structure was obtained, whereas an intercalated structure was obtained when organoclay with a paraffinic monolayer arrangement were used. The thermal and mechanical properties of sPS nanocomposites were investigated in relation to their microstructures. From the thermograms of nonisothermal crystallization and melting, nanocomposites exhibited an enhanced overall crystallization rate but had less reduced crystallinity than a matrix polymer. Clay layers dispersed in a matrix polymer may serve as a nucleating agent and hinder the crystal growth of polymer chains. As a comparison of the two nanocomposites with different microstructures, because of the high degree of dispersion of its clay layer the exfoliated nanocomposite exhibited a faster crystallization rate and a lower degree of crystallinity than the intercalated one. Nanocomposites exhibited higher mechanical properties, such as strength and stiffness, than the matrix polymer as observed in the dynamic mechanical analysis and tensile tests. Exfoliated nanocomposites showed more enhanced mechanical properties than intercalated ones because of the uniformly dispersed clay layers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1685–1693, 2004     

Characterization of HDPE /Polyamide 6/ Nanocomposites Using Scanning-and Transmission Electron Microscopy

Summary: Preparation and morphology of high density polyethylene (HDPE)/ polyamide 6 (PA 6)/modified clay nanocomposites were studied. The ability of PA 6 in dispersing clays was used to prepare modified delaminated clays, which were then mixed with HDPE. Mixing was performed using melt processing in a torque rheometer equipped with roller rotors. After etching the materials with boiling toluene and formic acid at room temperature, the morphology was examined by SEM analyses, showing that the PA 6 formed the continuous phase and HDPE the dispersed phase. X-ray diffraction patterns show that the (001) peak of the clay is dramatically decreased and shifted to lower angles, indicating that intercalated/exfoliated nanocomposites are obtained. TEM analyses confirmed the typical structure of exfoliated nanocomposites. A scheme for the mechanism of exfoliation and/or intercalation of these HDPE /PA 6/ /organoclay nanocomposites is proposed.     

激光烧结制备尼龙12/累托石纳米复合材料

将有机累托石与尼龙12粉末混合,采用激光烧结(SLS)技术制备了尼龙12累托石纳米复合材料,这是一种使纳米复合材料的制备与材料的成型同时进行的方法.利用X射线衍射(XRD)、红外光谱(FTIR)、扫描电镜(SEM)等手段对复合材料的结构进行了表征,并对其力学性能及热性能进行了研究.结果表明,尼龙12分子在激光烧结过程中插入到累托石层间,形成的复合材料在拉伸强度、弯曲强度、冲击强度等力学性能及热稳定性能方面均优于尼龙12烧结试样.     

Towards scalable production of polyamide 12/halloysite nanocomposites via water‐assisted extrusion: mechanical modeling,thermal and fire properties

In this study, polyamide 12 (PA12)/untreated halloysite nanotubes (HNTs) nanocomposites are prepared in a semi‐industrial scale extruder using a non‐traditional “one step” water‐assisted extrusion process. A morphological study is carried out using a combination of scanning electron microscopy and transmission electron microscopy analyses to evaluate the influence of water injection and filler content on the quality of clay dispersion. The use of water injection slightly improves the nanoscale dispersion at low HNTs content (<8 wt.%), while this effect is more pronounced at higher filler loading (16 wt.%). A mechanism explaining the physico‐chemical action of water during extrusion is proposed. The materials are characterized with respect to their mechanical, thermo‐mechanical, thermal and fire properties. A strong correlation is found between nanostructure and physical properties; the more uniform dispersion of the clay nanotubes, the higher mechanical reinforcement, thermal stability and fire retardancy of PA12 nanocomposites. Tensile tests results are interpreted in terms of three mechanical models: the Halpin–Tsai's model for stiffness and the interfacial strength model and the Pukanszky's equation for yield strength. Linear fits of the experimental data confirm that the superior reinforcement of nanocomposites prepared using water injection results from improved clay dispersion and better interfacial adhesion between PA12 and HNTs. In view of these promising results, the proposed direct melt compounding method could be easily scaled‐up towards the production of PA12–HNTs nanocomposites at an industrial scale. Copyright © 2013 John Wiley & Sons, Ltd.     

One-step water-assisted melt-compounding of polyamide 6/pristine clay nanocomposites: An efficient way to prevent matrix degradation

Polyamide 6 (PA6)/clay nanocomposites, based on organo-modified and pristine (i.e. purified but non-modified) montmorillonite, were prepared using a water-assisted extrusion process based on the injection of water during extrusion. The formation of a single PA6/water phase during extrusion (shown by High Pressure Differential Scanning Calorimetry (HPDSC)) improves the clay dispersion, decreases the PA6 melting temperature by 66 °C (so-called cryoscopic effect), and thus prevents the polymer matrix degradation during processing. This process enables the compounding of pristine clay-based nanocomposites whose dispersion state, thermal and mechanical performances are close to what is generally reported for organo-modified montmorillonite-based nanocomposites. Advantage was taken of water-assisted extrusion to optimize the clay dispersion by increasing shear rate and of the cryoscopic effect to limit the degradation by decreasing the processing temperature. Using these conditions PA6/pristine clay nanocomposites properties are similar to those of more conventional PA6/organomodified clay nanocomposites.     

Influence of Fe‐MMT on crosslinking and thermal degradation in silicone rubber/clay nanocomposites

In this article, silicone rubber (SR)/clay nanocomposites were synthesized by a melt‐intercalation process using synthetic Fe‐montmorillonite (Fe‐MMT) and natural Na‐MMT which were modified by cetyltrimethyl ammonium bromide (CTAB). This study has been designed to determine if the presence of structural iron in the matrix can result in radical trapping and then enhance thermal stability, affect the crosslinking degree and elongation. The SR/clay nanocomposites were characterized by X‐ray diffraction (XRD) patterns and transmission electron microscopy (TEM). Exfoliated and intercalated nanocomposites were obtained. Thermo gravimetric analysis (TGA) and mechanical performance were applied to test the properties of the SR/clay nanocomposites. The presence of iron significantly increased the onset temperature of thermal degradation in SR/Fe‐MMT nanocomposites. The thermal stability, gel fraction and mechanical property of SR/Fe‐MMT were different from the SR/Na‐MMT nanocomposites. So the iron not only in thermal degradation but in the vulcanization process acted as an antioxidant and radicals trap. Copyright © 2006 John Wiley & Sons, Ltd.     

COMPARISON OF POLYAMIDE 66/MONTMORILLONITE NANOCOMPOSITES PREPARED FROM POLYAMIDE 6 AND POLYAMIDE 66 BASED MASTER-BATCHES

Two master-batches,polyamide 66 (PA66)/organo-montmorillonite (OMMT) and polyamide 6 (PA6)/OMMT, prepared by melt compounding with methyl methacrylate (MMA) as co-intercalation agent,have been used to prepare nearly exfoliated PA661montmorillonite (MMT) nanocomposites.The resulting nanocomposites are compared in view of their morphology and properties.Nano-scale dispersion of OMMT is realized in both types of nanocomposites,as revealed by XRD,TEM and Molau tests.PA66/MMT nanocomposites having superior me...     

聚酰胺6/粘土纳米复合材料结晶行为研究进展

由于粘土的异相成核作用以及硅酸盐片层间形成的纳米受限空间,使聚酰胺6,粘土纳米复合材料（PA6CN）的结晶行为与纯聚酰胺6（PA6）相比,有着很大的差别,其结晶行为和影响因素倍受关注。本文着重从PA6CN结晶行为的基本特征、热处理、成型加工和结晶动力学等四个方面对PA6CN的结晶行为进行了综述。     

Structure and properties of polyamide‐6/vermiculite nanocomposites prepared by direct melt compounding

Polyamide‐6 (PA6)/vermiculite nanocomposites were fabricated through the direct melt compounding of maleic anhydride‐modified vermiculite (MAV) with PA6 in a twin‐screw extruder followed by injection molding. The structure and morphology of the nanocomposites were determined by X‐ray diffraction and scanning and transmission electron microscopy techniques. The results revealed the formation of intercalated and exfoliated vermiculite platelets in the PA6 matrix. Tensile measurement showed that the tensile modulus and strength of the nanocomposites tended to increase with increasing vermiculite content. The thermal properties of the nanocomposites were determined by dynamic mechanical analysis, differential scanning calorimetry, and thermogravimetry measurements. The storage modulus of the PA6–MAV nanocomposites increased to almost twice that of the neat PA6. The thermal stability of the nanocomposites increased dramatically, and this was associated with the addition of vermiculite. The effect of the addition of maleic anhydride on the formation of the PA6–vermiculite nanocomposites was examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2860–2870, 2002     

Preparation and Characterization of Copper Nanowire/Polyamide 6 Nanocomposites and Its Properties

Copper nanowire/polyamide 6 (denoted as nano-Cu/PA6) nanocomposites were readily prepared via in situ polymerization in reducing atmosphere. The microstructure, phase composition, and chemical state of typical elements of as-prepared nano-Cu/PA6 nanocomposites were analyzed by transmission electron microscopy, and X-ray diffraction, while their thermal stability and crystallization behaviors were evaluated by thermogravimetric analysis and differential scanning calorimetry. Moreover, the mechanical strength of as-prepared nano-Cu/PA6 nanocomposites was determined with a universal testing machine, and their friction and wear behaviors were evaluated with an MRH-3 high speed block-on-ring test rig. Findings indicate that copper nanowire is coated by surrounding molecular chains of PA6 and well disperses in the polymeric matrix. Besides, copper nanowire consists of metallic copper, which indicates that copper nanowire coated by PA6 matrix has good chemical stability and is not oxidized during the preparation of the title nanocomposites under high-temperature reactions. Furthermore, copper nanowire filler is able to remarkably improve the mechanical strength and wear resistance of polyamide 6. Particularly, nano-Cu/PA6 composite containing 0.5% (mass fraction) copper nanowire possesses the maximum tensile strength (its tensile strength is higher than that of pure PA6 by 77.41%); and its friction coefficient and wear scar diameter are also much smaller than those of PA6.     

Exfoliated high-impact polystyrene/MMT nanocomposites prepared using anchored cationic radical initiator-MMT hybrid

High-impact polystyrene (HIPS)/montmorillonite (MMT) nanocomposites were prepared via in-situ polymerization of styrene in the presence of polybutadiene, using intercalated cationic radical initiator-MMT hybrid. Incomplete exfoliation of the silicate layers in the HIPS nanocomposites was observed when a bulk polymerization was employed. On the other hand, the silicate layers were efficiently exfoliated in the PS matrix during a solution polymerization, due to the low extra-gallery viscosity, which can facilitate the diffusion of styrene monomers into the clay layers. The resulting exfoliated HIPS/MMT nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, thermogravimetric analysis, particle size analysis, gel permeation chromatography, and dynamic mechanical analysis. The nanocomposites exhibited significant improvement in thermal and mechanical properties. For example, about 50% improvement in Young’s modulus was achieved with 5 wt% of clay, compared to the unmodified polymer counterpart.     

Study of nylon 66–clay nanocomposites via condensation polymerization

Nylon 66–clay (polyamide 66 (PA66)–organophilic montmorillonite (OMT)) exfoliated nanocomposites were synthesized based on nylon 66 salt and organoclay (OMT) modified by hydro-aminocaproic acid via condensation polymerization. And the nanocomposites were characterized by X-ray diffraction and transmission electronic microscopy. Exfoliated morphology with different clay content was obtained. The effects of cation exchange capacity and organic modified agent of OMT on the formation of exfoliated nanocomposites were investigated. It was shown that only suitable cation exchange capacity and organic modified agent could result in the formation of exfoliated morphology under the condition of condensation polymerization. The thermal and flammability properties of the nanocomposites were investigated through thermogravimetry and cone calorimetry experiments. Results indicate that the exfoliated nanocomposites have enhanced thermal stability and flame retardant properties compared with pure PA66.     

Nanocomposite Fibers for Cosmetotextile Applications

In this work, a series of nylon 6 nanocomposites with different nanoclay/jojoba oil contents have been prepared by direct melt compounding. Nanocomposite morphologies were characterized by means of WAXS analysis. Thermal and mechanical fibers properties were studied as well. The kinetic desorption of the cosmetic oil through the polymer matrix was evaluated by FT-IR microscopy. It was found that the state of the clay particles affected the thermal behaviour and the tensile mechanical properties of each polymer/clay hybrid. On the other hand, the release of the cosmetic oil, tested by FT-IR microscopy, is a good perspective for the application of polyamide 6 nanocomposite fibers as textiles in cosmetic field.     

Vibrational energy-harvesting performance of bio-sourced flexible polyamide 11/layered silicate nanocomposite films

The energy-harvesting efficiency of melt processed polyamide 11 (PA11) films and its nanocomposites have been investigated as a function of filler type and content. In the present work, nanoclays have been used as structural modifiers in a PA11 matrix. The nanocomposites were prepared using layered clays, Cloisite 20A, 10A, and Na⁺, by extrusion process through varying the filler content, 1, 2, 4, and 5?wt.%. The crystalline structure of these nanocomposites has been studied by X-ray diffractometer. It has been demonstrated that layered silicates are not significant for the structural quality of the obtained nanocomposites. Regarding the interlayer peak of different clays, it has also been revealed that Cloisite 20A is partially exfoliated, whereas 10A and Na⁺ are totally exfoliated in the PA11 matrix. From mechanical and dynamic mechanical analyses, it was found that the addition of layered silicates results in an increase in mechanical properties. The piezoelectric strain coefficient d₃₃ and dielectric constant ε_R have been measured on polarized films at ambient temperature. Among all the prepared nanocomposites only Cloisite Na⁺-loaded PA11 nanocomposites showed the best piezoelectric constant. This observation showed that piezoelectric constant not only depends on the crystalline phases but also on the nature of the filler. Cloisite Na⁺ is more polar than other modified clays and high polarity leads to a better polarization response. A specific method for the quantification of energy vibration recovery has been developed for these nanocomposites. The capabilities of vibrational energy recovery were studied on PA11 loaded with Cloisite Na⁺.     

Effects of clay‐modifying agents on the morphology and properties of poly(methyl methacrylate)/clay nanocomposites synthesized via γ‐ray irradiation polymerization

Via γ‐ray irradiation polymerization, poly(methyl methacrylate) (PMMA)/clay nanocomposites were successfully prepared with reactive modified clay and nonreactive clay. With reactive modified clay, exfoliated PMMA/clay nanocomposites were obtained, and with nonreactive clay, intercalated PMMA/clay nanocomposites were obtained. Both results were confirmed by X‐ray diffraction and high‐resolution transmission electron microscopy. PMMA extracted from PMMA/clay nanocomposites synthesized by γ‐ray irradiation had higher molecular weights and narrow molecular weight distributions. The enhanced thermal properties of the PMMA/clay nanocomposites were characterized by thermogravimetric analysis and differential scanning calorimetry. The improved mechanical properties of PMMA/clay were characterized by dynamic mechanical analysis. In particular, the enhancement of the thermal properties of the PMMA/clay nanocomposites with reactive modified clay was much more obvious than that of the PMMA/clay nanocomposites with nonreactive clay. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3218–3226, 2003     

Studies of ABS-graft-maleic anhydride/clay nanocomposites: Morphologies, thermal stability and flammability properties

ABS-g-MAH (maleic anhydride) with different grafting degree, ABS/OMT (organo montmorillonite) and ABS-g-MAH/OMT nanocomposites were prepared via melt blending. The grafting reaction, phase morphology, clay dispersion, thermal properties, dynamic mechanical properties and flammability properties were investigated. FTIR spectra results indicate that maleic anhydride was successfully grafted onto butadiene chains of the ABS backbone in the molten state using dicumyl peroxide as the initiator and styrene as the comonomer and the relative grafting degree increased with increasing loading of MAH. TEM images show the size of the dispersed rubber domains of ABS-g-MAH increased and the dispersion is more uniform than that of neat ABS resin. XRD and TEM results show that intercalated/exfoliated structure formed in ABS-g-MAH/OMT nanocomposites and the rubber phase intercalated into clay layers distributed in both SAN phase and rubber phase. TGA results reveal the intercalated/exfoliated structure of ABS-g-MAH/OMT nanocomposites has better barrier properties and thermal stability than intercalated ones of ABS/OMT nanocomposites. The T_g of ABS-g-MAH/OMT nanocomposites was also higher than that of neat ABS/OMT nanocomposites. The results of cone measurements show that ABS-g-MAH/OMT nanocomposites exhibit significantly reduced flammability when compared to ABS/OMT nanocomposites even at the same clay content. The chars of ABS-g-MAH/OMT nanocomposites were tighter, denser, more integrated and fewer surface microcracks than ABS/OMT residues.     

Chlorinated polyethylene/layered silicate nanocomposites: Poly(ε-caprolactone)-based “masterbatch” approach

Chlorinated polyethylene (CPE)/organophilic-montmorillonite (Cloisite^®30B (CL30B)) nanocomposites have been prepared by melt intercalation using (poly(ε-caprolactone), (PCL)) as CPE/clay compatibilizer. Actually, a high clay content masterbatch-based on PCL was first produced and then dispersed by melt blending within CPE. CPE/CL30B nanocomposites was also prepared by direct blending of CPE with CL30B for sake of comparison. All the composites were characterized by wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM). The thermal stability of the nanocomposites was analyzed by thermogravimetric analysis (TGA) while the mechanical properties were assessed by tensile testing. When using low molecular mass PCL chains as compatibilizer, the nanocomposites displayed a rather intercalated structure but their ultimate properties remained unchanged whereas with high molecular weight PCL chains, clay delamination was favoured and led to an increase of both thermal and mechanical properties of the resulting nanocomposites.