Although nanocomposites composed of layered clays and polymers have been made with impressive performance enhancements, their full commercial exploitation has been limited by restrictive processing techniques. The key requirement for nanocomposite formation is dispersion of clay particles at nm length scales in polymer matrices, which is not trivial. Such a molecular-level dispersion necessitates complete exfoliation of clay particles, which occurs sporadically with the fabrication procedures currently in use. We propose to use stagnation flow (S-flow) of clay dispersions in an opposed-nozzle device, generating adequate extensional forces to exfoliate smectite clays. We propose to fabricate nanocomposites based on Nylon 6, Nylon 6,6 and polyester resins with montmorillonite as the clay filler using a two-step process: the clay/prepolymer mixture is first subjected to S-flow to cause exfoliation, which is then polymerized to advance the resin molecular weight to desired levels. The primary objective of this proposal is to identify the S-flow process conditions to cause efficient clay exfoliation, which in turn produces nanocomposites with greatly improved modulus, strength and thermal stability. With proof of concept, we propose to extend this work to develop a low-cost, versatile processing technique to produce high modulus, damage-tolerant nanocomposites for missile applications.Anticipated Benefits/Commercial Applications: Polymer-clay nanocomposites possess mechanical properties that set them apart from conventional fiber-reinforced or mineral-filled materials. Property enhancement in nanocomposites occurs at very low clay loadings, < 5 wt%. This means that superior performance can be realized with significant weight savings, which is highly desirable in ballistic missile applications, especially where high stiffness is required in thin-walled sections. Unlike their conventional counterparts, polymer-clay nanocomposites offer superior barrier resistance and flame retardation, both of which are desirable attributes. We have proposed a simple approach to cause efficient clay exfoliation, which is crucial for property enhancement. Our approach calls for a simple, low-cost extension of existing polymerization technologies. We therefore believe that our approach has the potential to revolutionize the polymer composite industry upon successful development and implementation.
