Thermoplastic layered silicate nanocomposites for technical applications
I. Increase in performances by optimizing the thermal behavior of the dispersed phase at the temperature of processing


Marius Murariu, Jeffrey Gilman, Serge Bourbigot, Rick Davis

Materials and Products Research Group

Building and Fire Research Laboratory

Nowadays the subjects "nanoscale, nanoscience, nanotechnology, nanocomposite" are very important for many applications and are attracting the attention of government, academic and industrial researchers due to the unprecedented new opportunities to create revolutionary material combinations.

As surely as polymer composites changed the face of industry forty years ago, we think that the polymer nanocomposites will open a new area in material development.

Numerous benefits of polymer layered silicates have been studied. The property improvements can generally be divided into following areas: mechanical properties, heat resistance, dimensional stability, barrier and flame retardation.

It is important to recognize that the nanoparticles confers significant property improvements at very low loading levels, while traditional microparticle additives require much higher loading levels to achieve similar performance. This in return results in significant weight reductions, greater strength for similar structural dimensions and increased barrier performance for similar material thickness. All these are crucial for improving the performance of various commercial, military and aerospace components.

To achieve the potential property improvements usually requires some degree of delamination, which is shown to be dependent upon a combination of proper chemical treatment and optimized processing. Material variables which can be controlled have a strong influence on the nature and properties of the final nanocomposite. This includes the type of clay, the choice of organomodifier, the selection of polymer component and the way in which the polymer is incorporated into the nanocomposite.

The synthesis, processing and recycling of clay polymer nanocomposites often requires long residence times and high temperatures (e.g. about 280 ºC for polyethylene terephtalate). If the processing temperature is greater than thermal stability of organic treatment of the clay, decomposition will occur, altering the interface between the filler and polymer.

Unfortunately, minimal studies connecting the chemical reactivity of the alluminosilicates to the thermal stability of the organoclays, under processing conditions are available.

The results for three types of clays (Na montmorillonite, two clays with different percents of organic modifiers) will be presented. In this poster session, we will illustrate the advantage of using of thermogravimetric analysis as a technique to provide new information about the behavior of dispersed phase at high temperatures for the synthesis, injection molding, recycling cycle.