Method of Producing an Exfoliated Polymer-Clay Nanocomposite Through Solid-State Shear Pulverization (22089)
Well dispersed polymer-clay nanocomposites are readily produced with continuous solid state shear pulverization (S3P). Process affords polymer hybrid nanocomposites with enhanced properties in the absence of compatabilizing agents.
ADVANTAGES: A general process affording highly dispersed polymer-clay nanocomposites in a wide variety of polymer systems.
SUMMARY: Polymer-clay nanocomposites provide enhanced mechanical and thermal properties compared to conventional materials. Increased tensile strength, modulus, and resistance to heat distortion are realized versus the pure polymer matrix. Reduced gas permeability, moisture sensitivity and flammability have also been observed in these materials. A major barrier to producing well dispersed polymer-clay nanocomposites is the tightly bound stacks of clay platelets that resist dispersion or exfoliation in the polymer matrix. Use of pretreated organophilic clays and insitu polymerization have been employed to make polymer-clay nanocomposites in selected systems.
This invention employs the established S3P technology, in a general method, to produce highly dispersed polymer-clay nanocomposites with a variety of polymers. In fully exfoliated nanocomposite the layers or platelets comprising the clay stacks are completely separated and uniformly distributed throughout the polymer matrix. Thus, a mixture of 90/10% polypropylene – organoclay (Nanocor™, ~50% clay / 50% organic) upon S3P treatment produced completely exfoliated clay material in the polymer matrix as determined by X-ray scattering analysis (Figure 1). Maximum exfoliation is achieved employing an initial melt-extrusion step followed by solid state shear pulverization (sample E), whereas the intermediary treatments (A, B, C) alone retain significant layered clay structure.
The process can be employed with a range of polymers including polyolefins, copolymers, condensation polymers and blends thereof. A variety of organoclays can also be incorporated with these polymers at 5-12% loadings. Thus a general process utilizing a broad spectrum of components is available to afford new polymer-clay nanocomposite materials with improved performance properties.
STATUS: The process has been operated on pilot scale equipment and a patent issued (US 7,223,359)
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