The Role of Organomodified Different LDHs on Recycled Poly(ethylene terephthalate) Nanocomposites

Recycled poly(ethylene terephthalate)/organomodified‐layered double hydroxide (PET /organo‐LDH ) nanocomposites were successfully synthesized via a melt‐extrusion method. In an attempt to improve the compatibility with PET , LiAl , MgAl , and ZnAl LDH surfaces were modified with sulfanilic acid (SAS ) via electrostatic interaction with LDH cationic layers. In PET nanocomposites containing SAS ‐modified LDH , the (00l ) X‐ray diffraction (XRD ) peaks originating from organo‐LDH were not observed, indicating that the organomodified LDH layers were fully exfoliated and homogeneously dispersed within the PET matrix, which was also confirmed by transmission electron microscopy analysis. However, PET nanocomposites containing SAS ‐modified LiAl , MgAl , and ZnAl LDH showed broad (00l ) XRD peaks, indicating that the organo‐LDH was partially exfoliated. Thermogravimetric analysis confirmed that the thermal stability of PET/SAS‐modified LDH was significantly improved, depending on the type and loading content of SAS‐modified LDH compared to that of pristine PET . PET nanocomposites containing well‐dispersed SAS‐modified LDH showed substantial enhancement of the storage modulus.     

Isothermal crystallization kinetics of poly(3‐hydroxybutyrate)/layered double hydroxide nanocomposites

Poly(3‐hydroxybutyrate) (PHB)/layered double hydroxides (LDHs) nanocomposites were prepared by mixing PHB and poly(ethylene glycol) phosphonates (PEOPAs)‐modified LDH (PMLDH) in chloroform solution. Both X‐ray diffraction data and TEM micrographs of PHB/PMLDH nanocomposites indicate that the PMLDHs are randomly dispersed and exfoliated into the PHB matrix. In this study, the effect of PMLDH on the isothermal crystallization behavior of PHB was investigated using a differential scanning calorimeter (DSC) and polarized optical microscopy. Isothermal crystallization results of PHB/PMLDH nanocomposites show that the addition of 2 wt % PMLDH into PHB induced more heterogeneous nucleation in the crystallization significantly increasing the crystallization rate and reducing their activation energy. By adding more PMLDH into the PHB probably causes more steric hindrance of the diffusion of PHB, reducing the transportation ability of polymer chains during crystallization, thus increasing the activation energy. The correlation among crystallization kinetics, melting behavior and crystalline structure of PHB/PMLDH nanocomposites can also be discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3337–3347, 2006     

Polymorphic behavior in syndiotactic polystyrene/clay nanocomposites

X‐ray diffraction methods were used in an investigation of the structural changes in syndiotactic polystyrene (sPS)/clay nanocomposites. sPS/clay was prepared by the intercalation of sPS polymer into layered montmorillonite. Both X‐ray diffraction data and transmission electron microscopy micrographs of sPS/clay nanocomposites indicated that most of the swellable silicate layers were exfoliated and randomly dispersed in the sPS matrix. The X‐ray diffraction data also showed the presence of polymorphism in the sPS/clay nanocomposites. This polymorphic behavior was strongly dependent on the thermal history of the sPS/clay nanocomposites from the melt and on the content of clay in the sPS/clay nanocomposites. Quenching from the melt induced crystallization into the α‐crystalline form, and the addition of montmorillonite probably increased heterophase nucleation of the α‐crystalline form. The effect of the melt crystallization of sPS and sPS/clay nanocomposites at different temperatures on the crystalline phases was also examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 736–746, 2002     

Poly(L‐lactide)/layered double hydroxides nanocomposites: Preparation and crystallization behavior

Novel nanocomposites from poly(L ‐lactide) (PLLA) and an organically modified layered double hydroxide (LDH) were prepared using the melt‐mixing technique. The structure and crystallization behavior of these nanocomposites were investigated by means of wide‐angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), and polarized optical microscopy (POM). WAXD results indicate that the layer distance of dodecyl sulfate‐modified LDH (LDH‐DS) is increased in the PLLA/LDH composites, compared with the organically modified LDH. TEM analysis suggests that the most LDH‐DS layers disperse homogenously in the PLLA matrix in the nanometer scale with the intercalated or exfoliated structures. It was found that the incorporation of LDH‐DS has little or no discernable effect on the crystalline structure as well as the melting behavior of PLLA. However, the crystallization rate of PLLA increases with the addition of LDH‐DS. With the incorporation of 2.5 wt % LDH‐DS, the PLLA crystallization can be finished during the cooling process at 5 °C/min. With the addition of 5 wt % LDH‐DS, the half‐times of isothermal melt‐crystallization of PLLA at 100 and 120 °C reduce to 44.4% and 57.0% of those of the neat PLLA, respectively. POM observation shows that the nucleation density increases and the spherulite size of PLLA reduces distinctly with the presence of LDH‐DS. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2222–2233, 2008     

Fully exfoliated layered silicate epoxy nanocomposites

Fully exfoliated layered silicate epoxy nanocomposites are reported in this article. The processing route that resulted in these fully exfoliated layered silicate epoxies is based on a combination of high‐shear mixing in the presence of acetone and ultrasonication. Homomogeneous and random dispersion of the individual silicate nanolayers in the epoxy is confirmed through transmission electron microscopy images spanning low to high magnification as well as by X‐ray diffraction. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3981–3986, 2004     

Structure,thermal stability,and photocrosslinking characterization of HDPE/LDH nanocomposites synthesized by melt‐intercalation

Structure, thermal properties, and influence of layered double hydroxide (LDH) fillers on photocrosslinking behavior of high‐density polyethylene (HDPE)/LDH nanocomposites have been studied in the present article. The X‐ray diffraction and transmission electron microscopy analysis demonstrate that the completely exfoliated HDPE/LDH nanocomposites can be obtained by controlling the organomodified LDH loading via melt‐intercalation. The data from the thermogravimetric analysis show that the HDPE/LDH nanocomposites have much higher thermal stability than HDPE sample. When the 50% weight loss was selected as a comparison point, the decomposition temperature of HDPE/LDH sample with 5 wt % LDH loading is ～40 °C higher than that of HDPE sample. The effects of UV‐irradiation on the HDPE/LDH nanocomposites show that the photoinitiated crosslinking can destroy the completely exfoliated structure to form the partially exfoliated structure, which decreased the thermal stability of the nanocomposites. However, the thermal stability of photocrosslinked samples can increase with increasing the UV‐irradiation time. The effect of LDH loading on the gel content of UV‐irradiated nanocomposites shows that the LDH materials can greatly absorb the UV irradiation and thus decrease the crosslinking efficiency. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 3165–3172, 2006     

乳液聚合法制备聚苯乙烯/Mg-Al层状双氢氧化物纳米复合材料

采用乳液聚合法制备阻燃性聚苯乙烯MgAl层状双氢氧化物(LDHs)纳米复合材料.通过对不同合成条件下复合材料的XRD谱,讨论了纳米复合材料的形成过程;经SEM图证实了LDHs是以剥离的纳米级层片分散在基体中的;TG和DSC谱图揭示了LDHs纳米层板可有效提高PS的热稳定性,并可使PS的玻璃化转化温度明显提高;当层状双氢氧化物在插层复合材料中含量为14.92%时,纳米复合材料的氧指数可达23.5%,其用量比在PS中直接添加纳米LDHs时要少约一倍.文中还分析了纳米复合材料的形成过程.     

Preparation and nonisothermal crystallization behavior of polyamide 6/montmorillonite nanocomposites

Polyamide 6 (PA6)/montmorillonite (MMT) nanocomposites were prepared via melt intercalation. The structure, mechanical properties, and nonisothermal crystallization kinetics of PA6/MMT nanocomposites were investigated by X‐ray diffraction (XRD), tensile and impact tests, and differential scanning calorimetry (DSC). Before melt compounding, MMT was treated with an organic surfactant agent. XRD traces showed that PA6 crystallizes exclusively in γ‐crystalline structure within the nanocomposites. Tensile measurements showed that the MMT additions are beneficial in improving the strength and the stiffness of PA6, at the expense of tensile ductility. Impact tests revealed that the impact strength of PA6/MMT nanocomposites tended to decrease with increasing MMT content. The nonisothermal crystallization DSC data were analyzed by Avrami, Ozawa, modified Avrami‐Ozawa, and Nedkov methods. The validity of these empirical equations on the nonisothermal crystallization process of PA6/MMT nanocomposites is discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2878–2891, 2004     

Optimization of organo‐layered double hydroxide dispersion in LDPE‐based nanocomposites

Low‐density polyethylene/layered double hydroxide (LDPE/LDH) nanocomposites were prepared via melt extrusion using organo‐LDH particles and maleic anhydride functionalized polyethylene as compatibilizer. Processing parameters, preparation method, and feed composition were properly modulated until obtaining nanocomposites with intercalated/exfoliated morphologies, and an uniform distribution of nanolayers, as evidenced by X‐ray diffraction and transmission electron microscopy analysis. These materials showed a significant improvement of the thermal‐oxidative stability, which increased of about 50°C during the first step of the degradation process. Moreover, a remarkable reduction of the oxygen permeability, proportional to the aspect ratio of LDH stacks dispersed in the polyolefin matrix was evidenced, indicating the possible application of nanocomposite films as food packaging materials. As highlighted by dynamic mechanical thermal analysis, interactions at the interface between LDH layers and polymer chains caused a shift of the LDPE β‐relaxation toward higher temperatures and a reduction of the peak intensity with respect to the matrix. It was also found that the storage modulus of the nanocomposites was lower in all the temperature range with respect to the reference samples. Finally, on‐line capillary rheometer measurements evidenced that the shear thinning behavior of the nanocomposites was dominated by the matrix so that the melt processability was not compromised by the presence of the filler. Copyright © 2010 John Wiley & Sons, Ltd.     

Biodegradable poly(p‐dioxanone) reinforced and toughened by organo‐modified vermiculite

Poly(p‐dioxanone) (PPDO)/vermiculite (VMT) nanocomposites with exfoliated structure were prepared successfully by in situ intercalative polymerization of p‐dioxanone (PDO) in the presence of organo‐modified vermiculite (OVMT) with the aid of ultrasonic action. The nano‐structure of the nanocomposites was established using X‐ray diffraction (XRD) analysis and transmission electron microscopy (TEM) observations. The investigation of crystallization behavior by differential scanning calorimetry (DSC) and polarized optical microscopy (POM) proved that exfoliated OVMT platelets acted as a template for spherulite growth. The thermal stability of nanocomposites was enhanced than that of pure PPDO. Dynamic mechanical analysis (DMA) indicated nanoscale OVMT platelets restricted the motion of PPDO segments, which benefitted the increase of storage and loss modulus. The tensile properties showed that nanocomposites were reinforced and toughened significantly by the addition of nanoscale OVMT platelets. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and Characterization of Poly(ethylene terephthalate)/Modified Lithium‐Aluminum‐Layered Double Hydroxide Nanocomposites Prepared Using In‐situ Polymerization

Layered double hydroxides are a type of layered stacked compound, which can be intercalated with organic‐molecule modifiers. An ion‐exchange process for layered double hydroxide (LDH) was used to intercalate water‐soluble sulfanilic acid salt (SAS) and dimethyl 5‐sulfoisopthalate (DMSI) into lithium aluminum layered double hydroxides (LiAl LDHs). In this work, a hydrothermal process was used to modify LiAl LDHs, and the modified LiAl LDHs were treated with either SAS or DMSI through an ion‐exchange process and were then intercalated using bis‐hydroxyethylene terephthalate (BHET). The results indicate that the modified LiAl LDHs improved the interlayer compatibility between the PET and LiAl LDH layers; thus, enabling the oligomer molecules to more easily enter the gallery of the LiAl LDH layers so that polymer chains could be included between the LDH layers during polymerization of the matrix. The better barrier, mechanical properties, and thermal stability of these new types of PET nanocomposites are discussed.     

Synthesis and structural characterizations of [chromophore]+‐saponite/polyurethane nanocomposites

In this study, three chromophores—p‐nitroaniline, 4‐(4‐nitrophenylazo)aniline, and 4‐[(E)‐2‐{4‐[(E)‐2‐(4‐nitrophenyl)‐1‐diazenyl]phenyl}‐1‐diazenyl]aniline—were intercalated into layered aluminosilicate saponite and then dispersed into the polyurethanes matrix. The intercalated chromophore/saponite complexes were examined by inductively coupled plasma emission and element analysis technologies. The molecular orbital package computation simulation and X‐ray diffraction (XRD) analysis showed that possible configurations of chromophore ions on the gallery surfaces of saponite suggest that the chromophore molecules lie parallel to the basal planes of silicate as an inclined paraffin structure or as pseudo‐multilayers. The XRD and transmission electron microscopy analysis indicated that the delamination of organoclay in the polyurethanes matrix exhibited nanolayers, exfoliated structure, or both. In particular, even at high doping levels up to 15 wt % of organoclay, the [chromophore]⁺‐saponite/polyurethanes film did not display a macroscopic aggregation of layered silicates and showed high transparency. The thermal stability of chromophore was significantly enhanced as intercalated into the layered aluminosilicate saponite, and the glass‐transition temperature of [chromophore]⁺‐saponite/polyurethanes nanocomposites proportionally increased with increased clay content. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1690–1703, 2002     

Polypropylene/montmorillonite nanocomposites toughened with SEBS‐g‐MA: Structure–property relationship

Polypropylene (PP)/organo‐montmorillonite (Org‐MMT) nanocomposites toughened with maleated styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MA) were prepared via melt compounding. The structure, mechanical properties, and dynamic mechanical properties of PP/SEBS‐g‐MA blends and their nanocomposites were investigated by X‐ray diffraction (XRD), polarizing optical microscopy (POM), tensile, and impact tests. XRD traces showed that Org‐MMT promoted the formation of β‐phase PP. The degree of crystallinity of PP/SEBS‐g‐MA blends and their nanocomposites were determined from the wide angle X‐ray diffraction via profile fitting method. POM experiments revealed that Org‐MMT particles served as nucleating sites, resulting in a decrease of the spherulite size. The essential work of fracture approach was used to evaluate the tensile fracture toughness of the nanocomposites toughened with elastomer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3112–3126, 2005     

Multiple melting and crystallization of nylon‐66/montmorillonite nanocomposites

Nylon‐66 nanocomposites were prepared by melt‐compounding nylon‐66 with organically modified montmorillonite (MMT). The organic MMT layers were exfoliated in a nylon‐66 matrix as confirmed by wide‐angle X‐ray diffraction (WAXD) and transmission electron microscopy. The presence of MMT layers increased the crystallization temperature of nylon‐66 because of the heterogeneous nucleation of MMT. Multiple melting behavior was observed in the nylon‐66/MMT nanocomposites, and the MMT layers induced the formation of form II spherulites of nylon‐66. The crystallite sizes L₁₀₀ and L₀₁₀ of nylon‐66, determined by WAXD, decreased with an increasing MMT content. High‐temperature WAXD was performed to determine the Brill transition in the nylon‐66/MMT nanocomposites. Polarized optical microscopy demonstrated that the dimension of nylon‐66 spherulites decreased because of the effect of the MMT layers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2861–2869, 2003     

Isothermal crystallization behavior of exfoliated‐PP/IMMT nanocomposites via in situ polymerization

Highly exfoliated isotactic‐polypropylene/alkyl‐imidazolium modified montmorillonite (PP/IMMT) nanocomposites have been prepared via in situ intercalative polymerization. TEM and XRD results indicated that the obtained composites were highly exfoliated PP/IMMT nanocomposites and the average thickness of IMMT in PP matrix was less than 10 nm, and the distance between adjacent IMMT particles was in the range of 20–200 nm. The isothermal crystallization kinetics of highly exfoliated PP/IMMT nanocomposites were investigated by using differential scanning calorimeter(DSC) and polarized optical microscope (POM). The crystallization half‐time t_1/2, crystallization peak time t_max, and the Avrami crystallization rate constant K_n showed that the nanosilicate layers accelerate the overall crystallization rate greatly due to the nucleation effect, and the crystallization rate was increased with the increase in MMT content. Meanwhile, the crystallinity of PP in nanocomposites decreased with the increase in clay content which indicated the PP chains were confined by the nanosilicate layers during the crystallization process. Although the well‐dispersed silicate layers did not have much influence on spherulites growth rate, the nucleation rate and the nuclei density increased significantly. Accordingly, the spherulite size decreased with the increase in MMT content. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2215–2225, 2009     

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 PET/LDH or Clay Nanocomposites through the Microcompounding Process

Thermally stable modifier were used to modify clay or lithium aluminum layered double hydroxides (LiAl LDH) nanoparticles for preparation of poly (ethylene terephthalate)/clay or LiAl LDH nanocomposites. The effect of modify agent, studied by microcompouding process. The PET nanocomposites which were made by twin‐screw microcompounder dispersion morphology of inorganic layered materials in nanocomposites could be explained by wide‐angle X‐ray diffraction (WXRD), and transmission electron microscopy (TEM). Nanocomposite also formed the better mechanical, UV resistance, and gas barrier properties. Optical properties and crystallization behaviour of these new types of nanocomposites are investigated in this paper.     

Shear‐induced change of exfoliation and orientation in polypropylene/montmorillonite nanocomposites

For the improved dispersion of montmorillonite (MMT) in a polypropylene (PP) matrix, PP/MMT nanocomposites prepared via direct melt intercalation were further subjected to oscillating stress achieved by dynamic packing injection molding. The shear‐induced morphological changes were investigated with an Instron machine, wide‐angle X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The original nanocomposites possessed a partly intercalated and partly exfoliated morphology. A transformation of the intercalated structure into an exfoliated structure occurred after shearing, and a more homogeneous dispersion of MMT in the PP matrix was obtained. However, the increase of the exfoliated structure was accompanied by the scarifying of the orientation of MMT layers along the shear direction. Some bended or curved MMT layers were found for the first time by TEM after shearing. However, the orientation of PP chains in the PP/MMT nanocomposites became very difficult under an external shear force; this indicated that the molecular motion of PP chains intercalated between MMT layers was highly confined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1–10, 2003     

Preparation and characterization of PP/clay nanocomposites based on modified polypropylene and clay

X‐ray diffraction and differential scanning calorimeter (DSC) methods have been used to investigate the crystallization behavior and crystalline structure of hexamethylenediamine (HMDA)‐modified maleic‐anhydride‐grafted polypropylene/clay (PP‐g‐MA/clay) nanocomposites. These nanocomposites have been prepared by using HMDA to graft the PP‐g‐MA (designated as PP‐g‐HMA) and then mixing the PP‐g‐HMA polymer in hot xylene solution, with the organically modified montmorillonite. Both X‐ray diffraction data and transmission electron microscopy images of PP‐g‐HMA/clay nanocomposites indicate that most of the swellable silicate layers are exfoliated and randomly dispersed into PP‐g‐HMA matrix. DSC isothermal results revealed that introducing 5 wt % of clay into the PP‐g‐HMA structure causes strongly heterogeneous nucleation, which induced a change of the crystal growth process from a three‐dimensional crystal growth to a two‐dimensional spherulitic growth. Mechanical properties of PP‐g‐HMA/clay nanocomposites performed by dynamic mechanical analysis show significant improvements in the storage modulus when compared to neat PP‐g‐HMA. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3242–3254, 2005     

Preparation and characterization of rigid poly(vinyl chloride)/MMT nanocomposites. II. XRD,morphological and mechanical characteristics

A Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on X‐ray diffraction (XRD), morphology, and mechanical characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. Results of XRD and transmission electron microscopy (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to that of pristine PVC. However, the addition of Na⁺‐MMT or O‐MMT should be kept as not more than 3 wt % to optimize the mechanical properties and the processing stability of the rigid PVC/MMT nanocomposites. SEM micrographs of the fractured surfaces of the rigid PVC/Na⁺‐MMT and PVC/O‐MMT nanocomposites both before and after tensile tests were also illustrated and compared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2145–2154, 2006