This thesis discusses the potential large scale production of polymer nanocomposites using polypropylene and high density polyethylene with chitin nanowhiskers (CNW). Fabrication of the nanocomposites with and without compatibilization were prepared over a range of CNW loading through melt compounding. The processing techniques tested included direct melt compounding, and a two step masterbatch dilution process. Three studies were investigated to build an understanding of the composite structure-property relationship based on morphological, thermal, water barrier, mechanical, and rheological properties. The addition of CNW and compatibilizer provided mechanical reinforcement and improvements in water barrier. However, the CNW significantly affected the crystallinities of the composites, which impacted its overall properties. Finally, the masterbatch diluted composites maintained good mechanical and water barrier compared to the neat polymer, but the directly compounded composites were still better. Therefore, further optimization of this process is required to maximize CNW dispersion, which also greatly affected the composite properties.