Intercalated clays from pentaerythritol stearate for use in polymer nanocomposites

Smectite clays treated with quaternary ammonium salts have been utilized for decades in paints, greases, cosmetics, and personal care products as rheological modifiers. They have also been used in industrial wastewater treatment extensively. In more recent times these surface modified clays have demonstrated benefits in polymer/clay nanocomposites. The use of quaternary ammonium modifiers limits the usefulness of these composites in food packaging because they are not approved for direct food contact. It would be advantageous to have surface modifying chemicals acceptable for direct food contact in these composites. This article reports research conducted on a promising surface modifier pentaerythritol stearate (PS), which is approved by the FDA for inclusion in food as a preservative. The surface modification of montmorillonite with PS is reported in detail as well as the production of nanocomposites with selected polymers made with the modified clay. Molecular modeling and purification of commercial PS samples indicate that the mono‐ and diesters are the critical surface modifiers, although the as received commercial material works well in forming intercalated clay complexes. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of organophilic clay and preparation methods on EVA/montmorillonite nanocomposites

Ethylene‐vinyl acetate copolymer (EVA)/montmorillonite MMT nanocomposites have been prepared by using different methods: one is from the organophilic montmorillonite (OMT) and the other is from the pristine MMT and reactive compatibilizer hexadecyl trimethyl ammonium bromide (C16). In this study, different kneaders were used (twin‐screw extruder and twin‐roll mill) to prepare nanocomposites. The nanocomposite structures are evidenced by the X‐ray diffraction (XRD) and high‐resolution electronic microscope (HREM). The thermal properties of the nanocomposites were investigated by thermogravimetric analysis (TGA). Moreover, the tensile tests were carried out with a Universal testing machine DCS‐5000. It is shown that different methods and organophilic montmorillonite have influence on EVA/MMT nanocomposites.© 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 2416–2421, 2004     

Morphology,thermal, and mechanical properties of polyamide 66/clay nanocomposites with epoxy‐modified organoclay

A new kind of organophilic clay, cotreated by methyl tallow bis‐2‐hydroxyethyl quaternary ammonium and epoxy resin into sodium montmorillonite (to form a strong interaction with polyamide 66 matrix), was prepared and used in preparing PA66/clay nanocomposites (PA66CN) via melt‐compounding method. Three different types of organic clays, CL30B–E00, CL30B–E12, and CL30B–E23, were used to study the effect of epoxy resin in PA66CN. The morphological, mechanical, and thermal properties have been studied using X‐ray diffraction, transmission electron microscopy (TEM), mechanical, and thermal analysis, respectively. TEM analysis of the nanocomposites shows that most of the silicate layers were exfoliated to individual layers and to some thin stacks containing a few layers. PA66CX–E00 and PA66CX–E12 had nearly exfoliated structures in agreement with the SAXS results, while PA66CX–E23 shows a coexistence of intercalated and exfoliated structures. The storage modulus of PA66 nanocomposites was higher than that of the neat PA66 in the whole range of tested temperature. On the other hand, the magnitude of the loss tangent peak in α‐ or β‐transition region decreased gradually with the increase in the clay loading. Multiple melting behavior in PA66 was also observed. Thermal stability more or less decreased with an increasing inorganic content. Young's modulus and tensile strength were enhanced by introducing organoclay. Among the three types of nanocomposites prepared, PA66CX–E12 showed the highest improvement in properties, while PA66CX–E23 showed properties inferior to that of PA66CX–E00 without epoxy resin. In conclusion, an optimum amount of epoxy resin is required to form the strong interaction with the amide group of PA66. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1711–1722, 2006     

Melt‐compounded natural rubber nanocomposites with pristine and organophilic layered silicates of natural and synthetic origin

Composites based on natural rubber (NR) and containing organophilic and pristine layered silicates of natural and synthetic origin were produced by melt compounding and sulfur curing. The curing, thermomechanical, and mechanical properties of the mixes, which contained 10 phr (parts per hundred parts of rubber) silicates, were determined. The dispersion of the silicates was studied by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Organophilic clays accelerated the sulfur curing of NR, which was believed to occur because of a complexation reaction in which the amine groups of the clay intercalants participated. The property improvements caused by the fillers were ranked as follows: organophilic clays > pristine synthetic layered silicate (sodium fluorohectorite) > pristine natural clay (purified sodium bentonite) > precipitated nonlayered silica (used as a reference). This was attributed to partial intercalation of the organophilic clay by NR on the basis of XRD and TEM results and to the high aspect ratio of the fluorohectorite. Apart from intercalation, severe confinement (i.e., the collapse of the interlayer distance) of the organoclays was observed. This peculiar feature was traced to the formation of a zinc coordination complex, which extracted the amine intercalant of the organoclays, thus causing the collapse of the layers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 813–819, 2004     

Poly(trimethylene terephthalate) nanocomposite fibers comprising different organoclays: Thermomechanical properties and morphology

Poly(trimethylene terephthalate) (PTT) nano composites were synthesized by in situ polymerization at high temperature with two thermally stable organoclays: 1,2‐dimethylhexadecylimidazolium‐montmorillonite (IMD‐MMT) and dodecyltriphenyl phosphonium‐MMT (C₁₂PPh‐MMT). PTT hybrid fibers with various organoclay contents were melt‐spun at various draw ratios (DRs) to produce monofilaments. The thermomechanical properties and morphologies of the PTT hybrid fibers were characterized using differential scanning calorimetry, thermogravimetric analysis, wide‐angle X‐ray diffraction, electron microscopy, and mechanical tensile properties analysis. The nanostructure of the hybrid fibers was observed by both scanning and transmission electron microscopy, which showed that the clay layers were well dispersed into the matrix polymer, although some clusters or agglomerated particles were also detected. Unlike the hybrids containing IMD‐MMT, the clay layers of the C₁₂PPh‐MMT hybrid fiber were more dispersed into the matrix polymer. The thermal stability and tensile properties of the hybrid fibers increased with increasing clay content for DR = 1. However, as DR increased from 1 to 9 the ultimate strength and initial modulus of the hybrid fibers with IMD‐MMT increased slightly whereas those of C₁₂PPh‐MMT hybrid fibers decreased slightly. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4535–4545, 2006     

Metallocene‐based functionalized polyolefins as compatibilizers in polyolefin nanocomposites

This article reports a study of some functionalized polyolefins evaluated as compatibilizers in polyethylene nanocomposites. The functionalized polymers were prepared by direct metallocene‐mediated copolymerizations of ethylene and a functional comonomer. The prepared nanocomposites were evaluated for mechanical and barrier property enhancement. A good combination of mechanical and barrier properties was obtained with the metallocene‐based functionalized polyethylene. The toughness–stiffness balance was better than or comparable to that achieved with conventional functionalized polymers such as maleic anhydride grafted polyethylene. The results also indicated that these metallocene‐based functionalized polyolefins, when used as compatibilizers, could have relatively higher molar masses and lower functionality than those of conventional post‐reactor‐modified compatibilizers, and so the drawbacks associated with the latter could be avoided. Their inherent properties could also further improve the final nanocomposite properties. This was attributed to the more homogeneous nature of metallocene‐catalyzed polymers in comparison with post‐reactor‐modified products. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1094–1100, 2004     

Structure and properties of nanocomposites based on poly(butylene succinate) and organically modified montmorillonite

Poly(butylene succinate) and organically modified montmorillonite nanocomposites with there different compositions were prepared via melt blending in a twin‐screw extruder. The structure of the nanocomposites was studied with X‐ray diffraction and transmission electron microscopy, which revealed the formation of intercalated nanocomposites, regardless of the silicate loading. Dynamic mechanical analysis revealed a substantial increase in the storage modulus of the nanocomposites over the entire temperature range investigated. The tensile property measurements showed a relative increase in the stiffness with a simultaneous decrease in the yield strength in comparison with that of neat poly(butylene succinate). The oxygen gas barrier property of neat poly(butylene succinate) improved after nanocomposite preparation with organically modified montmorillonite. The effect of the layered‐silicate loading on the melt‐state linear viscoelastic behavior of the intercalated nanocomposites was also investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 777–785, 2006     

The role of clay network on macromolecular chain mobility and relaxation in isotactic polypropylene/organoclay nanocomposites

It is well known that a so-called “three-dimensional filler network structure” will be constructed in the polymer/layered silicate nanocomposites when the content of layered clay reaches a threshold value, at which the silicate sheets are incapable of freely rotating, due to physical jamming and connecting of the nanodispersed layered silicate. In this article, the effect of such clay network on the mobility and relaxation of macromolecular chains in isotactic polypropylene(iPP)/organoclay nanocomposites was investigated in detail with a combination of DMTA, DSC, TGA, TEM, rheometry and melt flow index measurements. The main aim is to establish a relationship between the mesoscopic filler network structure and the macroscopic properties of the polymer nanocomposites, particularly to explore the role of the clay network on the mobility and relaxation of macromolecular chains. It was found that the nanodispersed clay tactoids and layers play less important or dominant roles on the mobility of iPP chains depending on the formation of percolating filler network. The turning point of macroscopic properties appeared at 1 wt% organoclay content. Before this point, the effect of organoclay can be negligible, and the increase of chain mobility was ascribed to the decrease of molecular weight of polymer chains, as commonly occurs during dynamic melt processing; after this point, however, a reduced mobility of chains and a retarded chain relaxation were observed and attributed to the formation of a mesoscopic filler network. The essential features of such a mesoscopic organoclay network were estimated and discussed on the basis of stress relaxation and structural reversion measurements. A schematic model was proposed to describe the different relaxation and motion behaviors of macromolecular chains in the unfilled polymer and the filled hybrids with partial and percolated organoclay networks, respectively.     

新型尿素产品的开发

介绍了国内外新型尿素产品（大颗粒尿素、涂层尿素、包膜尿素、长效尿素）的生产工艺和产品特点。