Vol. 26 No. 2
March-April 2004

Structure and Properties of Polymer/Clay Nano-Composite Materials

Recent developments in the technology of inserting (intercalating) polymer chains in nano-scale layers of clay have produced new types of high-performance polymer composites. However, the effects of the higher order structure on mechanical properties are not yet well understood. For example, little is known about the crystallization of polymer chains confined in the nano-scale layers and subsequently occurring morphology formation. Since mechanical properties of the composites are strongly affected by the higher order structure, the control of the higher order structure becomes a key technology to design nano-composites with excellent performance and/or functions.

Polymer/Clay Nano-composites could be used in food packaging applications such as beer cans.

Barrier properties of the composite to various gas molecules are greatly improved by the exfoliated structure that occurs when the clay layers are completely separated by the polymer chain and the clay sheets in the nano-scale are dispersed throughout the polymer matrix. Only a small amount of clay is needed to reduce drastically the permeability of the nano-composite to oxygen and carbon dioxide. The composite could be used in food packaging applications, such as beer containers.

The purpose of this study is to clarify the relationship between the higher order structure and properties of commercially available nano-composites composed of polyamide, PMMA, and clay. The topics cover a wide range of research from characterization of the components through physical properties in the solid state. Rheological properties of the melts are also an important topic related to the processability of the composites. In this project, several commercial grade nano-composites comprising polyamide/clay, PMMA/clay will be evaluated. The following topics will be covered in the study:

1. Morphology and Crystallization Behavior: Morphology and crystallization behavior will be analyzed by wide angle x-ray diffraction, small angle x-ray scattering, differential scanning calorimetry, polarized optical microscopy, transmission electron microscopy, and atomic force microscopy measurements.
   
2. Rheological Properties of the Melts: Dynamic visoco-elasticity, stress relaxation, shear and elongational flow properties will be measured.
   
3. Mechanical Properties in the Solid State: Stress-strain behavior, stress relaxation, creep, dynamic mechanical properties, impact strength, fatigue behavior, and micromechanics/fracture analysis will be conducted.
   
4. Gas Permeability: Oxygen and carbon dioxide permeability will be correlated to the high order structure of the composite evaluated through the morphology analysis.

The polymer/clay nano-composites with high modulus, high strength and gas barrier properties have a wide range of applications. With the dispersion of nano-scale plates of clay with high aspect ratio, enhanced mechanical properties as well as the barrier properties can be obtained with only a small amount of clay. Critical evaluation of the structure and properties will allow industry to expand the application of these new types of materials.

Three to five publications in Pure and Applied Chemistry are expected as a result of this project.

Any person who has information to contribute to the project, please contact the Task Group Chairmen Sung Chul Kim <[email protected]> or K. Nitta <[email protected]>.

www.iupac.org/projects/2003/2003-051-1-400.html