Rectorite/thermoplastic polyurethane nanocomposites. II. Improvement of thermal and oil‐resistant properties

Organ‐rectorite/thermoplastic polyurethane (OREC/TPUR) nanocomposites were synthesized via melt intercalation. The dynamic mechanical properties by dynamic mechanical analysis (DMA), thermal and oil‐resistant properties were investigated. The results show that the storage modulus (E′), loss modulus (E″), and glass‐transition temperature (T_g) of the nanocomposites have an increase to some extent than those of pure TPUR. The thermal stability of nanocomposites was also studied in detail by thermal gravity analysis (TGA), which was higher than that of pristine TPUR matrix when the content of organic REC is at 2 wt %, and the decomposition temperature at 10% weight loss of OREC/TPUR is greatly increased up to 330°C from 315°C. Oil uptake of the composites is also significantly reduced in comparison with TPUR matrix, which is ascribed to the good barrier effect of nanosheets of OREC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1165–1169, 2005     

有机累托石的合成及其复合材料的性能

以具有层状硅酸盐结构的粘土累托石（REC）为主体，以不同碳链长度的烷基季铵盐（QAS1，QAS2）及联苯二胺（BZD）为改性剂合成了有机累托石（OREC），采用红外光谱表征了REC及不同OREC的化学结构，采用X－射线衍射方法研究了REC处理产后层间距的变化，结果表明，BZD可以使REC层间距增加到最大，脂肪族季铵亍中，碳链越长，得到的OREC的层间距越大，采用熔融共混法制备了粘土／聚合物复合材料，初步研究了复合材料的力学性能及热性能。结果表明，有机粘土改性后的聚合物力学性能有大幅度提高，OREC及其复合材料的热分解温度较高。     

Novel intercalated nanocomposites of polypropylene,organic rectorite,and poly(ethylene octene) elastomer: Morphology and mechanical properties

The melt‐blending method was applied to prepare ternary composites of polypropylene (PP), organic rectorite (OREC), and poly(ethylene octene) elastomer (POE) with a constant content of 2 phr (parts per hundred parts of PP) OREC and 5 or 15 phr POE (PRE25 and PRE215, respectively). At the same time, OREC/PP binary composites with a 2 phr loading of OREC (PR2) and POE/PP systems with 5 or 15 phr POE (E5 and E15, respectively) were prepared to investigate synergistic effects of OREC and POE. Scanning electron microscopy was used to study the distribution of OREC and POE in the matrix, X‐ray diffraction (XRD) and transmission electron microscopy were used to investigate the intercalation performance of OREC in the composites, and polarized light microscopy (PLM) was used to observe the crystallization form and crystallite size. The mechanical properties and dynamic mechanical analysis were also measured. The PRE composites exhibited a multiphase structure, that is, a spherical texture of POE, a plate of clay, and a continuous phase of PP; a larger content of POE produced a larger size, a broader distribution of the spherical phase, and a better intercalation performance of the clay. The E systems were binary phases, that is, a spherical texture of POE and a continuous phase of PP. The crystallite size of the PRE composites was finer than that of pure PP according to XRD data, and this was confirmed by PLM. The impact strength and tensile elongation at break of the PRE composites increased dramatically in comparison with those of the PP, PR2, and corresponding E systems, and this indicated that POE and OREC had synergistic toughening and strengthening effects on PP. The storage modulus of PRE was higher than that of pure PP and lower than that of PR2. There were two glass‐transition temperatures in the PRE systems according to the curve of tan δ; they represented those of pure PP and POE, respectively, and indicated that the PRE systems were physical mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1907–1914, 2005     

Preparation and properties of styrene–butadiene rubber based nanocomposites: The influence of the structural and processing parameters

Rubber‐based nanocomposites were prepared with octadecyl amine modified sodium montmorillonite clay and styrene–butadiene rubber with different styrene contents (15, 23, and 40%). The solvent used to prepare the nanocomposites, the cure conditions, and the cure system were also varied to determine their effect on the properties of the nanocomposites. All the composites were characterized with X‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The XRD studies revealed exfoliation for the modified clay–rubber composites. The TEM photomicrographs showed a uniform distribution of the modified clay in the rubber matrix. The thickness of the particles in the exfoliated composites was around 10–15 nm. Although the FTIR study of the unmodified and modified clays showed extra peaks due to the intercalation of the amine chains into the gallery, the spectra for the rubber–clay nanocomposites were almost the same because of the presence of a very small amount of clay in the rubber matrix. All the modified clay–rubber nanocomposites displayed improved mechanical strength. The styrene content of the rubber had a pronounced effect on the properties of the nanocomposites. With increasing styrene content, the improvement in the properties was greater. Dicumyl peroxide and sulfur cure systems displayed similar strength, but higher elongation and slightly lower modulus values were obtained with the sulfur cure system. The curing of the samples at four different durations at 160°C showed that the cure time affected the properties. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 698–709, 2004     

Facile exfoliation of rectorite nanoplatelets in soy protein matrix and reinforced bionanocomposites thereof

The rectorite (REC), a form of layered silicate, was facilely intercalated and even exfoliated in soy protein isolate (SPI) matrix. Furthermore, the reinforced biodegradable nanocomposite sheets were produced, in which the exfoliated REC lamellae plays a key role. After solution‐mixing, XRD patterns showed that the REC lamellae were intercalated and even completely exfoliated for 4 wt % REC added, but the expanded gallery gradually became narrower with increasing REC content. FT‐IR also verified the molecular‐level associations between SPI molecules and REC lamellae by vibration variances of hydrogen bonding. The compression‐molding further promoted intercalation and exfoliation, namely the 8 wt % REC can also be almost dispersed as exfoliated lamellae, while the interlayer of RECs also further separated for nanocomposites with higher REC content. TEM images visualized the transfer from exfoliation to intercalation and the decrease of interlayer distance with increasing REC content. The thicker and longer exfoliated REC lamellae resulted in high load and easy‐to‐yield of material. The maximum strength of nanocomposite sheets occurred at the addition of 12 wt % REC. Thereafter, the SPI chain can move more easily because of weak interaction between free negative‐charge rich domain of SPI and REC surface in gallery, which did not favor enhancing mechanical performance. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Synthesis and characterization of resol‐layered silicate nanocomposites

Resol‐layered silicate nanocomposites were synthesized by intercalative polymerization of phenol and formaldehyde using layered clays such as an aminoacid‐modified montmorillonite (MMT) and a commercial modified MMT (Cloisite 30B). The composites were prepared by a sequential process in which one of the reactives of the phenolic resin was reacted with the organosilicate and subsequently cured with triethylamine. The nanocomposites were studied by means of X‐ray diffraction, atomic force microscopy, and thermogravimetric analysis. Results show a strong clay composition dependence on the intercalation state. The composite of resol with 2 wt % aminoacid‐modified MMT content has the best dispersion of clay layers. Thermal stability of nanocomposites was slightly increased in comparison with the neat resol. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Analysis of interfacial action of rectorite/thermoplastic polyurethane nanocomposites by inverse gas chromatography and molecular simulation

The compatibility of surface properties and the degree of interfacial action between filler and base directly affect the structure of their composites and make great contribution to a series of properties of composite materials. Interactions among rectorite (REC), quaternary ammonium salt and polymer are investigated via molecular simulation. Inverse gas chromatography (IGC) has been used to investigate the surface properties of REC, organic-modified rectorite with dodecyl benzyl dimethyl ammonium bromide (12-OREC) and hexadecyl trimethyl ammonium bromide (16-OREC), and thermoplastic polyurethane (TPUR). The correlation of the surface properties and the interfacial action between REC and TPUR and the structure of composite were analyzed. The results indicate that the modification of REC lowers its surface energy, and changes the surface from being acidic to being predominantly basic and increased the binding energy hence improving the dispersibility of 12-OREC and 16-OREC in TPUR; 12-OREC was found to be the best dispersibility in TPUR because the dispersive energy is approached to TPUR, the acid-base property is most comparable with TPUR and the binding energy between 12-OREC and TPUR is larger, which can yield higher interfacial strength.     

Sodium alginate/Na+‐rectorite composite films: Preparation,characterization, and properties

Rectorite (REC), one kind of layered silicates, has been applied to polymers to improve their properties. The sodium alginate (SA) layered silicate is a new option to modify the properties of polysaccharides. In this article, SA was modified by Na⁺‐rectorite (Na⁺REC). The chemical structures and microstructures of Na⁺REC and Na⁺REC modified SA (SA/Na⁺REC) were analyzed by using Fourier transform infrared spectrometer and X‐ray diffraction. The morphologies of SA/Na⁺REC composites were observed by using scanning electron microscopy and transmission electron microscopy. The mechanical and anti‐ultraviolet properties as well as thermal properties of SA/Na⁺REC composites were investigated. The results show that the properties of pure SA film can be improved by the addition of Na⁺REC, and SA/Na⁺REC composite containing 2 wt % Na⁺REC has the best intercalation effect and optimum comprehensive properties among the prepared composites in this article. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of layered silicate structure on the mechanical properties and structures of protein‐based bionanocomposites

In this work, a nonconventional protein source of pea protein isolate (PPI) was filled with montmorillonite (MMT) and rectorite (REC) by solution intercalation respectively, and then the reinforced PPI‐based nanocomposites were produced by hot press. The structure and interaction in the nanocomposites were investigated by FTIR, XRD, DSC, DMA, and pH and Zeta‐potential tests whereas the reinforcing effect was verified by tensile test. Furthermore, the origin of enhancing mechanical performances and the effects of layered silicate structure were explored. Although the MMT with lower negative‐charge surface and smaller apparent size of crude particles was easier to be exfoliated completely, the exfoliated REC nanoplatelets with more negative‐charge could form stronger electrostatic interaction with positive‐charge‐rich domains of PPI molecules, and hence produced the highest strength in two series of nanocomposites. In this case, the newly formed hydrogen bonds and electrostatic interaction on the surface of silicate lamellas guaranteed the transferring of the stress to rigid layered silicates. The cooperative effect of newly formed physical interaction between layered silicates and PPI molecules as well as the spatial occupancy of intercalated agglomerates of layered silicates destroyed the original microphase structure of PPI matrix and cleaved the entanglements among PPI molecules. It was not in favor of enhancing the elongation and strength. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Morphology,thermal, and mechanical properties of vinylester resin nanocomposites with various organo‐modified montmorillonites

New nanocomposites based on a vinylester resin (VER) and the organo‐montmorillonites (ODA‐M, BHL‐M, DEM‐M, BHLV‐M) modified with octadecylammonium, bis(2‐hydroxyethyl)lauryl ammonium, diethyl[2‐(methacryloyloxyl)ethyl]ammonium, and bis(2‐hydroxyethyl)lauryl(vinylbenzyl)‐ammonium chlorides, respectively, were prepared by dispersing the organoclays in VER, and subsequent crosslinking at finally 120°C. X‐ray diffraction studies and morphological studies using transmission electron microscopy revealed that exfoliation occurs for the VER/ODA‐M and BHL‐M composites, intercalation occurs for the VER/BHLV‐M composite, and neither intercalation nor exfoliation occur for the VER/DEM‐M and unmodified montmorillonite composites. On the whole, although the enhancement in flexural modulus was observed for the exfoliated ODA‐M and BHL‐M composites, the flexural strength was rather lowered. Dynamic viscoelastic measurement revealed that the ODA‐M, BHL‐M, and BHLV‐M nanocomposites have significantly higher storage modulus at the rubbery state than the other composites. Polym. Eng. Sci. 44:2041–2046, 2004. © 2004 Society of Plastics Engineers.     

Nanocomposites based on poly(butylene adipate‐co‐terephthalate) and montmorillonite

Nanocomposites based on biodegradable poly(butylene adipate‐co‐terephthalate) (PBAT) and layered silicates were prepared by the melt intercalation method. Nonmodified montmorillonite (MMT) and organo‐modified MMTs (DA‐M, ODA‐M, and LEA‐M) by the protonated ammonium cations of dodecylamine, octadecylamine, and N‐lauryldiethanolamine, respectively, were used as the layered silicates. The comparison of interlayer spacing between clay and PBAT composites with inorganic content 3 wt % measured by X‐ray diffraction (XRD) revealed the formation of intercalated nanocomposites in DA‐M and LEA‐M. In case of PBAT/ODA‐M (3 wt %), no clear peak related to interlayer spacing was observed. From morphological studies using transmission electron microscopy, the ODA‐M was found to be finely and homogeneously dispersed in the matrix polymer, indicating the formation of exfoliated nanocomposite. When ODA‐M content was increased, the XRD peak related to intercalated clay increased. Although the exfoliated ODA‐M (3 wt %) nanocomposite showed a lower tensile modulus than the intercalated DA‐M and LEA‐M (3 wt %) composites, the PBAT/ODA‐M composite with inorganic content 5 wt % showed the highest tensile modulus, strength, and elongation at break among the PBAT composites with inorganic content 5 wt %. Their tensile properties are discussed in relation to the degree of crystallinity of the injection molded samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 386–392, 2005     

Synthesis and characterization of UV-curing epoxy acrylate coatings modified with organically modified rectorite

Epoxy acrylate (EA) coatings modified with organically modified rectorite (OREC) were synthesized employing the ultraviolet-curing technique. Two kinds of alkyl ammonium ions, octadecyltrimethylammonium chloride (OTAC) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (MAOTMA), were used to modify rectorite (REC). The methacrylate functionalities of MAOTMA were capable of reacting with the acrylate groups of EA. The structure of OREC was characterized by FTIR and XRD and the results indicated that the surfactants were successfully intercalated into the REC interlayers via cation exchange process. The morphology of nanocomposites was investigated by SEM and TEM. OREC showed better dispersion in EA matrix compared with unmodified REC. The T _g of neat EA obtained by DMA was 75.6°C, while for 5 wt% EA/MAOTMA-REC and EA/OTAC-REC nanocomposites it increased to 76.5 and 80.8°C, respectively. The nanocomposite with 3 wt% loading of OTAC-REC had the highest T _g (89.7°C). TGA revealed that the thermal stability of nanocomposites was enhanced by OTAC-REC and MAOTMA-REC and the thermal stability of EA/MAOTMA-REC nanocomposites was better than that of EA/OTAC-REC nanocomposites. The mechanical properties of nanocomposites containing OTAC-REC and MAOTMA-REC were better than those of nanocomposites containing unmodified REC. With increasing OREC content, the adhesive force of nanocomposites decreased slightly and the flexibility increased significantly.     

Preparation and characterization of modified‐clay‐reinforced and toughened epoxy‐resin nanocomposites

Epoxy–clay nanocomposites were prepared by the dispersion of an organically modified layered clay in an epoxy resin (diglycidyl ether of bisphenol A) and curing in the presence of methyl tetrahydro acid anhydride at 80–160°C. The nanometer‐scale dispersion of layered clay within the crosslinked epoxy‐resin matrix was confirmed by X‐ray diffraction and transmission electron microscopy, and the basal spacing of the silicate layer was greater than 100–150 Å. Experiments indicated that the hydroxyethyl groups of the alkyl ammonium ions, which were located in the galleries of organically modified clay, participated in the curing reaction and were directly linked to the epoxy‐resin matrix network. Experimental results showed that the properties of epoxy were improved, evidently because of the loading of organically modified clay. The impact strength and tensile strength of the nanocomposites increased by 87.8 and 20.9%, respectively, when 3 wt % organic clay was loaded, and this demonstrated that the composites were toughened and strengthened. The thermal‐decomposition and heat‐distortion temperatures were heightened in comparison with those of pure epoxy resin, and so were the dynamic mechanical properties, including the storage modulus and glass‐transition temperature. Moreover, experiments showed that most properties of the composites were ameliorated with low clay contents. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2649–2652, 2004     

Morphology and thermal/mechanical properties of alkyl‐imidazolium‐treated rectorite/epoxy nanocomposites

A novel organic rectorite (OREC) was prepared by treating the natural sodium‐rectorite (Na‐REC) with ionic liquid 1‐hexadecyl‐3‐methylimidazolium bromide ([C₁₆mim]Br). X‐ray diffraction (XRD) analysis showed that the interlayer spacing of the OREC was expanded from 2.23nm to 3.14nm. Furthermore, two types of OREC/epoxy nanocomposites were prepared by using epoxy resin (EP) as matrix, 2‐ethyl‐4‐methylimidazole (2‐E‐4‐MI) and tung oil anhydride (TOA) as curing agents, respectively. XRD and transmission electron microscope (TEM) analysis showed that the intercalated nanocomposite was obtained with addition of the curing agent 2‐E‐4‐MI, and the exfoliated nanocomposite was obtained with addition of the curing agent TOA when the OREC content was less than 2 wt %. For the exfoliated nanocomposite, the mechanical and thermal property tests indicated that it had the highest improvement when OREC content was 2 wt% in EP. Compared to pure EP, 60.3% improvement in tensile strength, 26.7% improvement in bending strength, 34% improvement in bending modulus, 14°C improvement in thermal decomposition temperature (T_d) and 5.7°C improvement in glass transition temperature (T_g) were achieved. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Technological and processing properties of natural rubber layered silicate‐nanocomposites by melt intercalation process

Natural rubber nanocomposites were produced by melt‐mixing of natural rubber with organically modified silicates. For comparison, a pristine‐layered silicate and a nonlayered version [English Indian clay (EIC)] were also included in the study. The layered silicate used was sodium bentonite (BNT) and organoclays used were octadecylamine‐ modified montmorillonite (MMT‐ODA) and methyltallow bis‐2‐hydroxyethyl ammonium‐modified montmorillonite (MMT‐ TMDA). Accelerated sulfur system was used for the vulcanization of the nanocomposites. The dispersion of these silicates was studied by X‐ray diffraction and transmission electron microscopy. The organoclay‐incorporated composites exhibited faster curing and improved mechanical properties. The improvement in the mechanical properties of the composites followed the order MMT‐ODA > MMT‐TMDA > EIC > BNT. The property improvement was attributed to the intercalation/exfoliation of the organically modified silicates because of their high initial interlayer distance. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2537–2543, 2006     

有机累托石/环氧树脂(OREC/EP)复合材料的制备和性能研究

用单体原位插层技术制备了有机累托石/环氧树脂(OREC/EP)复合材料,考察了OREC的加入及其含量对复合材料OREC/EP体系的力学性能、耐介质性能和耐紫外线性能的影响。研究发现:OREC是一种良好的环氧树脂增韧改性剂,OREC的加入可改善复合材料的综合性能。当OREC质量分数为3%时,冲击强度和弯曲强度提高幅度最大,分别为6.25%和8.39%,耐海水性能效果最好;在添加质量分数为1%~7%时,复合材料体系的耐酸(碱)和耐紫外线性能均随OREC含量的增加而上升。     

Processing of transmission electron microscope images for quantification of the layer dispersion degree in polymer‐clay nanocomposites

Quantification of the layered silicates dispersion level is necessary to more accurately evaluate the performance in polymer/clay nanocomposites. In this article, a new approach is developed to quantify the degree of exfoliation, intercalation, and immiscibility of layered silicates in polymer matrix, based on bright‐dark pixel measurement (BDPM) in transmission electron microscope (TEM) images. Several examples of exfoliated, intercalated, and immiscible composites with different polymer and clay systems were examined. The method is capable of estimating the percent contribution of all morphologies present in the image. Comparing with X‐ray diffraction (XRD) evidences, it is indicated that as a rule of thumb, the exfoliated structure is dominant whenever the exfoliation percent calculated by BDPM methodology is over 65%, no matter what kind of clay or polymer matrix is used. The intercalated structure can be ascribed to the images with exfoliation level less than 65%, but with the intercalation degree over 28%. Application of this method can facilitate the modeling or correlation of various nanocomposite properties with respect to exfoliation degree. A quantified relation is also possible between XRD and TEM using this approach. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

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     

Synthesis and material properties of syndiotactic polystyrene/organophilic clay nanocomposites

Syndiotactic polystyrene (sPS)/organophilic clay nanocomposites were fabricated by direct‐melt intercalation method. To overcome the thermal instability of organophilic clay at high‐melt processing temperatures of sPS, an organophilic clay modified by alkyl phosphonium was adopted, which is known to be thermally stable. By using the newly synthesized clay, we could fabricate sPS intercalated nanocomposites. The microstructures of nanocomposites were confirmed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallization rate of nanocomposites investigated by differential scanning calorimetry (DSC) does not increase despite the presence of clay, which may be due to the physical hindrance of organic modifiers in the clay dispersion. Nanocomposites exhibited enhanced mechanical properties such as strength and stiffness relative to the virgin polymer. In addition, thermal stability was confirmed to be improved by thermogravimetric analysis (TGA). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2144–2150, 2004     

黏土及界面剂对乳液插层法天然橡胶纳米复合材料结构与性能的影响

采用乳液插层法制备了黏土/天然橡胶(NR)纳米复合材料,考察了蒙脱土(MMT)、累托石(REC)2种黏土和用界面剂等量替代NR的方式对复合材料微观结构及性能的影响.结果表明,在2种纳米复合材料中,大部分MMT和REC均以纳米片层结构分散在橡胶基体中,与REC片层相比,MMT片层边界模糊且稍微有些弯曲,且层间距变化较大,...