Well dispersed graphite-polymer nanocomposites with enhanced physical properties are readily produced with the continuous solid state shear pulverization (S3P) process. Abstract ADVANTAGES Graphite-polymer nanocomposites with superior properties versus identical melt extruded compositions are manufactured with the S3P process. A significantly higher degree of filler dispersion is created than previously reported for these systems. SUMMARY Polymer nanocomposites are of scientific and commercial interest because of their potential for enhanced properties compared to the neat polymer. Currently there are few reports of graphite-based polymer nanocomposites, principally due to poor graphite dispersion or exfoliation in the polymer matrix with melt processing. The present invention overcomes this limitation by employing the continuous, scaleable solid state shear pulverization (S3P) process to intimately disperse graphite into polypropylene (PP). Graphite particles (2.5 wt%) upon S3P copulverization yielded a powder, which was compression molded at 483°K. Properties versus 2.8 wt% graphite melt extruded PP and neat PP were evaluated. Photograph and SEM images of S3P and melt extruded composite PP samples reveal the significantly greater uniformity and graphite dispersion in the S3P prepared material (Figure 1). XRD analysis indicates the absence of inter-graphene sheet spacing supporting extensive graphite exfoliation in the S3P nanocomposite (Figure 2). Physical properties are enhanced in the S3P processed polymer composites. The S3P generated graphite-nanocomposite exhibits a 100% greater Young's modulus (1870 MPa) than neat PP (910 MPa) versus a 40% increase with the melt extruded composite PP (1300 MPa). Greater retention (560 %) of the neat PP elongation (810 %) is observed in the S3P nanocomposite than observed in the melt extruded composite PP (8 %). The S3P nanocomposite exhibits an unusual 33 fold reduction in isothermal crystallization half-time (3.6 min) with a 21°K increase in crystallization onset temperature (411°K) while retaining the same degree of crystallinity as neat PP. These enhancements in graphite-polypropylene nanocomposite properties promise significant improvement in other graphite-polymer systems employing S3P. STATUS The process has been operated on pilot scale equipment and a patent has been filed.
|State||Published - Nov 6 2012|