Polymer/layered silicate nanocomposites: a review from preparation to processing

Crystallization behavior of nylon 6 nanocomposites

Multiwalled carbon nanotubes (MWNTs)/nylon-6 (PA6) nanocomposites with different MWNTs loadings have been prepared by the simple melt-compounding approach. A fine and homogeneous dispersion of MWNT...

Morphology and Mechanical Properties of Multiwalled Carbon Nanotubes Reinforced Nylon-6 Composites

Polymer nanocomposite foams

Processing-property relationships of polycarbonate/graphene composites

We present an experimental investigation on the creep behavior of molten polypropylene organically modified clay nanocomposites. The nanocomposite hybrids were prepared by melt intercalation in an extruder in the presence or absence of a compatibilizer. They were subsequently annealed and simultaneously characterized using high-temperature wide-angle X-ray diffraction and controlled stress rheometry. The creep resistance of compatibilized hybrids was significantly higher than that of uncompatibilized hybrids and also increased with annealing time. The microstructure of the nanocomposites as investigated by TEM and high-temperature WAXD showed the presence of clay crystallites dispersed within the polymer matrix. The creep data together with the microstructural investigation are probably indicative of a small amount of exfoliation from the edges of the clay crystallites during extrusion and annealing. The zero shear viscosity of the compatibilized nanocomposites containing greater than 3 wt % clay was at l...

A rheological study on the kinetics of hybrid formation in polypropylene nanocomposites

The crystallization of nylon-6 from the melt was monitored in situ by X-ray diffraction. The nylon-6 was found to crystallize into a high-temperature α‘-phase as indicated by the two-peak nature of the diffractogram. On cooling from the crystallization temperature to room temperature, nylon-6 retained the two-peak nature. However, data analysis indicates a change from high-temperature (HT) α‘-phase to low-temperature α-phase at ∼180 °C. On heating, the α-phase transformed into the α‘-phase at about 190 °C and melted in the α‘-phase. The transition took place over a temperature range where both phases coexisted. However, samples crystallized from the melt at temperatures 140 and 180 °C showed the α-phase at room temperature, but on heating the α-phase first transformed into a pseudohexagonal phase and before melting the pseudohexagonal phase further transformed into the α‘-phase. The α-phase was transformed into the γ-phase, by potassium iodide−iodine treatment, and the behavior of the γ-phase with tempera...

High-Temperature X-ray Diffraction Studies on the Crystalline Transitions in the α- and γ-Forms of Nylon-6

This article describes experimental results for both the rheology and flow-induced orientation of a series of intercalated syndiotactic polypropylene nanocomposites which were prepared by melt intercalation in the presence or absence of an i-PP/maleic anhydride copolymer. The nanocomposites showed typical rheological signatures of well-dispersed interacalated nanocomposites such as a low frequency plateau in dynamic moduli and an apparent yield transition from very high viscosity at low shear stresses to low viscosity above a yield stress. In situ x-ray diffraction (XRD) measurements during shear provided direct evidence of rheology-microstructure links in these materials. It was found that the clay tactoids could be easily oriented by shear and that a high degree of orientation can be achieved after the yield transition. Further, the rheo-XRD apparatus allowed measurements of the relaxation of orientation upon the cessation of flow. The orientation relaxation time matched the characteristic relaxation times estimated from independent rheological measurements well.

In situ rheo-x-ray investigation of flow-induced orientation in layered silicate–syndiotactic polypropylene nanocomposite melt

The structural changes occurring during heating in a syndiotactic polystyrene (sPS)−solvent complex were monitored in situ by X-ray diffraction. The room temperature δ form transformed into the γ form on heating above the glass transition temperature of the sPS. The transition temperature showed a linear dependency on the amount of solvent absorbed; the higher the solvent molecules absorbed, the higher the transition temperature. However, the transition temperature does not depend on the nature of the solvent. The emptied clathrate form transformed into the γ form at the glass transition temperature. The γ form transformed into the α‘ ‘ form at ∼200 °C on heating and is independent of the δ to γ form transition. Calorimetric studies showed an endotherm followed by an exotherm during these transitions and indicated that the transitions are first order in nature.The studies provided information on the stability of various crystalline forms of sPS.

Crystalline Transitions of the Clathrate (δ) Form of Syndiotactic Polystyrene during Heating: Studies Using High-Temperature X-ray Diffraction

Amorphous syndiotactic polystyrene (sPS) was crystallized at room temperature in dichloromethane, chloroform, toluene, o-dichlorobenzene, and decalin (cis−trans) to form the clathrate structure (δ ...

C. Ramesh

Papers

A rheological study on the kinetics of hybrid formation in polypropylene nanocomposites

High-Temperature X-ray Diffraction Studies on the Crystalline Transitions in the α- and γ-Forms of Nylon-6

In situ rheo-x-ray investigation of flow-induced orientation in layered silicate–syndiotactic polypropylene nanocomposite melt

Crystalline Transitions of the Clathrate (δ) Form of Syndiotactic Polystyrene during Heating: Studies Using High-Temperature X-ray Diffraction

Studies on the Clathrate (δ) Form of Syndiotactic Polystyrene Crystallized by Different Solvents Using Fourier Transform Infrared Spectroscopy