Zongneng Qi

Studies on nylon 6/clay nanocomposites by melt‐intercalation process

The preparation of nylon 6/clay nanocomposites by a melt-intercalation process is proposed. X-ray diffraction and DSC results show that the crystal structure and crystallization behaviors of the nanocomposites are different from those of nylon 6. Mechanical and thermal testing shows that the properties of the nanocomposites are superior to nylon 6 in terms of the heat-distortion temperature, strength, and modulus without sacrificing their impact strength. This is due to the nanoscale effects and the strong interaction between the nylon 6 matrix and the clay interface, as revealed by X-ray diffraction, transmission electron microscopy, and Molau testing.

Crystallization, properties, and crystal and nanoscale morphology of PET-clay nanocomposites

The crystallization process and crystal morphology of poly(ethylene terephathalate) (PET)–clay nanoscale composites prepared by intercalation, followed by in-situ polymerization, have been investigated by scanning electronic microscopy (SEM), transmission electronic microscopy (TEM), dynamic scanning calorimetry (DSC), and X-ray techniques, together with mechanical methods. Results of the nonisothermal crystallization dynamics show that the nanocomposites of PET (Nano-PET) have 3 times greater crystallization rate than that of pure PET. The thermal properties of Nano-PET showed heat distortion temperature (HDT) 20–50°C higher than the pure PET, while with a clay content of 5%, the modulus of Nano-PET is as much as 3 times that of pure PET. Statistical results of particle distribution show that the average nanoscale size ranges from 10 to 100 nm. The particles are homogenously distributed with their size percentages in normal distribution. The agglomerated particles are 4% or so with some particles size in the micrometer scale. The morphology of exfoliated clay particles are in a diordered state, in which the morphology of the PET spherulitics are not easy to detect in most of microdomains compared with the pure PET. The molecular chains intercalated in the interlamellae of clay are confined to some extent, which will explain the narrow distribution of the Nano-PET molecular weight. The stripe-belt morphology of the intercalated clay show that polymer PET molecular chains are intercalated into the enlarged interlamellar space.

Synthesis and properties of silicone rubber/organomontmorillonite hybrid nanocomposites

In this article, silicone rubber/organomontmorillonite hybrid nanocomposites were prepared via a melt-intercalation process. The resulting hybrid nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The results proved that the organomontmorillonite could be exfoliated into ca. 50-nm thickness and uniformly dispersed in the silicone rubber matrix during the melt-intercalation process. Furthermore, the mechanical properties and thermal stability of the hybrids were very close to those of aerosilica-filled silicone rubber.

FTIR Spectra, Thermal Properties, and Dispersibility of a Polystyrene/Montmorillonite Nanocomposite

This article presents FTIR spectra, thermal properties, and dispersibility of an exfoliated polystyrene/montmorillonite (PS/montmorillonite) nanocomposite. First, the infrared bands of CTAB-montmorillonite and the PS/montmorillonite nanocomposite are assigned tentatively. FTIR results indicate that the montmorillonite is transformed into small particles and dispersed homogeneously in the PS matrix. The PS/montmorillonite nanocomposite exhibits a higher decomposition onset temperature and glass transition temperature, which may be due to the nanoscale dispersion of the montmorillonite particles. The powder sample can be perfectly dispersed in toluene and chloroform, partly dispersed in benzene, and is not dispersible in acetone.

Preparation and properties of organosoluble polyimide/silica hybrid materials by sol–gel process

Organosoluble polyimide/silica hybrid materials were prepared using the sol–gel process. The organosoluble polyimide was based on pyromellitic anhydride (PMDA) and 4,4′-diamino-3,3′-dimethyldiphenylmethane (MMDA). The silica particle size in the hybrid is increased from 100–200 nm for the hybrid containing 5 wt % silica to 1–2 µm for the hybrid containing 20 wt % silica. The strength and the toughness of the hybrids are improved simultaneously when the silica content is below 10 wt %. As the silica content is increased, the glass transition temperature (Tg) of the hybrids is increased slightly. The thermal stability of the hybrids is improved obviously and their coefficients of thermal expansion are reduced. The hybrids are soluble in strong polar aprotic organic solvents when the silica content is below 5 wt %.

The effects of promoter and curing process on exfoliation behavior of epoxy/clay nanocomposites

The effects of a catalyst and coupling agent as well as a curing process on exfoliation behavior of CH3(CH2)15NH3+–montmorillonite clay in an anhydride-cured epoxy–clay system have been investigated by XRD, DSC, and TEM. The results have shown that the organoclay is easily intercalated by the epoxy precursor during the mixing process, and the clay galleries continue to expand during the curing process, but the Na+–montmorillonite clay is not intercalated during either the mixing or the curing process. The results also suggest that in the cured system without any promoter although partial exfoliated clay layers have already formed, an amount of the intercalation structure still remains. Although addition of a promoter or coupling agent into the cured system significantly lowers the maximum reaction temperature, and during the curing process the layered organoclay can be gradually broken into nanoscale structures, in which no d001 diffraction peaks are observed, the complete exfoliation is achieved at gel time or before. The possible mechanism for the complete exfoliation is discussed on the thermodynamic and kinetic point of view.

Polyamide 6-clay nanocomposites/polypropylene-grafted-maleic anhydride alloys

Polyamide 6-clay nanocomposites (PA6CN) based on montmorillonite typically show some brittleness with clay addition. In order to address this problem, PA6CN/PP-g-MAH alloys were prepared through blending PA6CN with polypropylene-grafted-maleic anhydride (PP-g-MAH). The mechanical properties, dynamic mechanical temperature spectra, morphology and water absorption of the alloys were studied. Compared with PA6CN, the notched impact strength of the alloys increased greatly while the alloys still maintained higher stiffness and strength than that of PA 6. The morphological studies via scanning electron microscopy (SEM) showed a PP-g-MAH toughen phase dispersed in PA6CN matrix. As the PP-g-MAH content was increased, reduced water absorption was observed.

Investigation on unusual crystallization behavior in polyamide 6/montmorillonite nanocomposites

The crystallization behavior and crystal structure of polyamide 6/montmorillonite (PA6/MMT) nanocomposites were investigated by differential scanning calorimetry and X-ray diffraction, and an inter ...

Preparation and properties of organosoluble montmorillonite/polyimide hybrid materials

Organosoluble montmorillonite/polyimide hybrids were prepared using a monomer solution intercalation polymerization method. Montmorillonite was organo-treated with p-aminobenzoic acid and the organosoluble polyimide was based on pyromellitic dianhydride and 4,4′-diamino-3,3′-dimethyldiphenylmethane. The particle size of montmorillonite in the hybrid containing 1 wt % of montmorillonite is about 400 nm. The strength and the toughness of montmorillonite/polyimide hybrids are improved simultaneously when the montmorillonite content is below 5 wt %. The thermal stabilities of montmorillonite/polyimide hybrids are obviously improved and their thermal expansion coefficients are reduced. When the montmorillonite content is below 5 wt %, the montmorillonite/polyimide hybrids are soluble in strong aprotonic polar organic solvents.

Self-assembly in a polystyrene/montmorillonite nanocomposite

A self-assembly phenomenon in an extruded polystyrene/clay nanocomposite sample in observed during a temperature increase process. Wide-angle X-ray diffraction (WAXD), transmission electron microscopy (TEM), and infrared dichroism techniques have been employed to investigate the self-assembly phenomenon. The results show that in the self-assembly structure the montmorillonite primary particles orient parallel, and the phenyl rings of the polystyrene align perpendicular to the primary particles, whereas no obvious orientation of the aliphatic chain was observed.