Bio-nanocomposites for enhancing water vapor barrier of cellulose-based packaging materials
University of New Brunswick
The use of renewable materials within the packaging industry has gained increasing interest in recent years. Cellulose fiber is the most abundant biopolymer on planet earth due to it is sustainable, biodegradable and environmental friendly nature, it is widely utilized in many fields. However, the barrier properties of porous and hydrophilic cellulose fiber network products are inadequate for most barrier applications. In order to improve its barrier properties and widen its applications, extensive studies have been carried out in the current thesis work. In the first section, two biopolymers, poly lactic acid (PLA), poly (3-hydroxybutyrate-co-4-hydroxybutyrate), (PHBV) and their nanocomposites with different nanoclays and with various clay contents were coated on paper. Moreover, various coating methods were also used to control the hydrophilic surface and cover the porous structure of paper in an attempt to improve the water vapor resistance of paper products. It was found that the coating method and clay exfoliation were the most important factors affecting water vapor permeability. The papers coated with exfoliated PHBV nanocomposites drastically improved the water vapor barrier of the paper by lowering the water vapor transmission rate (WVTR) to a level that is similar to those of polypropylene (PP) and low density polyethylene (LDPE). In the second section, a simple route was used to produce regenerated cellulose and regenerated cellulose nanocomposites with sodium-montmorillonite (Na-MMT). A series of novel modified montmorillonites were prepared via solution blending in aqueous alkaline/urea solvent at low temperatures, followed by regeneration of films. The effect of nanoclays loading on the mechanical, crystallinity and water vapor transmission properties of the nanocomposites was investigated. Generally, nanoclays loading improved the mechanical and water vapor barrier properties of the cellulose films. Although, the WVTR values of the resulted nanoclay-cellulose films was much lower than regular paper, but the WVTR values remain much higher than most of the fossil-based polymers.