Polymers offer a light-weighting alternative to many applications, especially in the automotive industry, but their properties are not always satisfactory. Combining a polymer with a nanofiller can allow for a composite with tunable properties, creating a multifunctional material. Current automotive fuel tanks are made from a layered structure, with the bulk being high density polyethylene (HDPE) sandwiched around a barrier polymer such as polyamide 610. The HDPE provides mechanical stability, while the barrier polymer prevents fuel from evaporating out of the system. Replacing this structure with a nanocomposite could offer a way to improve the efficiency of the system. Graphene nanoplatelets (GnP) are a few layered stack of graphene produced in a cost effective process They have excellent mechanical, thermal and electrical properties, and their platelet structure offers potential improvements to the barrier properties of a polymer This dissertation explores the addition of GnP to both HDPE and a barrier polymer.GnP and HDPE were compounded through melt mixing and the properties of the composites were characterized over a large concentration range, 0-40 wt. percent GnP. It was found that the flexural modulus and strength of the materials increased with increasing GnP content. However, the impact resistance fell sharply. The thermal stability of the composites was improved, and the barrier properties to both oxygen and fuel were improved up to 20 wt. percent GnP, after which a plateau occurred. This was attributed to misalignment and dispersion issues of the GnPAlternative processing techniques were explored to overcome the limits of melt mixing. Microlayer co-extrusion yielded highly aligned platelet, but the absolute value was not improved over melt mixing. Solution mixing yielded a better dispersion of the platelets, but that advantage was lost when re-processed through a melt mixing process. Cryo-milling the HDPE resulted in a small improvement to the dispersion of the GnP, resulting in improved barrier properties, but the mechanical properties were weakened. Coating the platelets with a low modulus, HDPE compatible material resulted in recovery of some lost impact resistance, but weakened the flexural improvements, and did not yield large improvements in barrier properties.An alternative approach was to lay thin layers of GnP onto the surface of polymer using layer by layer deposition to control the completely control the alignment and dispersion of the GnP. This was done by both alternating the GnP with a cationic polymer, and by depositing monolayers of GnP successively onto the surface. Both methods resulted in 60% reductions in oxygen permeability with less than 1 wt. percent GnPThe final method explored was the melt mixing of GnP and a biobased polyamide. As with the HDPE composites, the flexural properties of the composite increased while the impact resistance was lessened. The thermal stability of the polymer was greatly improved. The barrier properties were also improved, and it was also found that increasing the mixing time in the melt extrusion process resulted in further enhancements. The electrical conductivity of the samples was unsatisfactory. To improve this, carbon nanotubes (CNT) and carbon nanofibers (CNF), one dimensional nanofillers, were added to the composites in small quantities. It was found that through the addition of these, the electrical conductivity was greatly improved by over an order of magnitude.
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