Well-Dispersed Polymer/Carbon Nanotube Nacomposites with Major Property Improvements: Fabrication by Two-Step Solid-State Shear Pulverization and Melt Processing (28065)
A continuous, solventless, scalable process (S3P) in concert with melt mixing producing well-dispersed polymer/multiwall CNT nanocomposites.
ADVANTAGES: A scalable process to produce well dispersed polymer / carbon nanotube nanocomposites with enhanced thermal and mechanical properties
SUMMARY: Carbon nanotubes (CNTs) have been widely examined as nanofillers in materials due their excellent mechanical, electrical and thermal properties. However, a major challenge for their use in polymer/CNT nanocomposites is to achieve uniform CNT dispersion in an industrial scalable and environmentally effective process. Melt mixing can provide limited CNT dispersion in polymers. Blending polymers and CNTs in solvents or in situ polymerization can also improve dispersion. However these processes are not well suited for scaleable industrial use.
This invention utilizes solid state shear pulverization (S3P) in combination with melt mixing (MM) to produce well dispersed polymer/CNT nanocomposites. S3P ability to overcome mixing limitations with immiscible blends and exfoliation of nanoparticles in composites has been well established. Coupling S3P with MM affords a simple two step process providing well dispersed unmodified multiwalled carbon nanotubes (MWCNTs) in a polypropylene (PP) matrix.
Thus dry blends of PP/CNT (1 wt%) first processed under optimized S3P conditions were melt mixed at 473°K for 15 minutes then cooled. Field-emission scanning electron microscopy (FE-SEM, Figure 1) displays the transformation of 30-50 nm feed CNT agglomerates, after S3P treatment with PP, and final S3P / MM processing into a finally dispersed, interpenetrated matrix. The S3P / MM treated PP/CNT exhibits faster recrystallization kinetics at 411°K and improved thermal stability than neat PP. Most notably the process significantly increased blend mechanical properties (Table 1). Young’s modulus (50-57%), yield strength (27-30%) and strain properties increased. The property improvements are only observed with the combined S3P/MM process. The process offers wide application to a variety of other polymer / nanofiller systems.
REFERENCE: Macromolecules (2008), 41(16), 5974
John Torkelson, Jun’ichi Masuda
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