- Author
-
Vaia, R. A.
- Title
- Mesoscopic Structure of Polymer-Inorganic Nanocomposites: Impact on Chain Behavior and Physical Properties. BFRL Fire Research Seminar. VHS Video.
- Coporate
- Air Force Research Lab., Wright-Patterson AFB, OH
- Report
-
Video
April 18, 2000
- Keywords
-
nanocomposites
|
physical properties
|
additives
|
thermal properties
- Abstract
- Over the last decade, the utility of inorganic nanoparticles as additives to enhance polymer performance has been established. Not withstanding these accomplishments, an understanding of the fundamental correlation between nano (1-100 nm) and mesoscale (100-1000 nm) structure and ultimate physical, mechanical and thermal properties have only been tentatively examined for a few specific systems, without the possibility for any broad predictive guidelines being discernible. As with other multiphase systems exhibiting nano (1-100 nm) and meso (100-500 nm) order (such as biopolymers, block-copolymers, colloidal suspensions, liquid crystals), physical properties ranging from toughness to optical clarity are determined by morphology on various lengthscales which in turn is dependent on everything from process history to specific polymer-inorganic interactions. Additionally, because of the morphological length scales, the exceedingly large interfacial area between constituents results in the volume fraction of interfacial regions approaching one! Thus physical properties are dominated by the properties of these interfacial regions and understanding chain behavior (conformation, relaxation, crystallization) in these regions is paramount to understanding these nanocomposites. This presentation will discuss two current efforts to understand the impact of nanoscale and mesoscale distribution of inorganic on the ultimate physical properties of nanocomposites. First, in contrast to conventional wisdom that addition of the inorganic phase is for reinforcement, the nanoscale dispersion affords the opportunity to utilize the ultrafine particles as precursors to form passivation coatings on the materials surface in response to aggressive environments. Optimization of the size and spatial distribution of the inorganic constituent significantly increases the char's resistance to oxidation and mechanical erosion in an ablative environment resulting in a new class of ablatives with performance rivaling current state-of-the-art options. Second, the impact of phase distribution and polymer-silicate interactions on crystallization of poly(caprolactam) (nylon 6) will be discussed. In addition to a change in crystal form, the presence of the layers substantially alters nucleation rate and growth kinetics. These observations are attributed to the layers disrupting the crystal lamellae organization. Control of these processes is critical to process optimization of the properties of these semi-crystalline polymer nanocomposites. These studies are portions of our general program to establish a fundamental understanding of the influence of nanoscopic constituents and there hierarchical morphology on bulk mechanical, electrical and optical properties.