Hemicellulose is the second most abundant component of plant cell walls after cellulose. It has received increasing interest as an alternative to petroleum based polymers for packaging applications because of its abundance, renewability and biodegradability. However, there are some challenges in the utilization of hemicellulose as a packaging material. Hemicelluloses are complex heteropolysaccharides with varied compositions and structures depending on the hemicellulose source (e.g., plant species, location and growth stage); they can also be influenced by the chemical, physical and biological isolation processes used to isolate them, and by any pretreatment used before isolation. It is critical to understand the influence of these factors (hemicellulose source, isolation approach, and pretreatment) on the final hemicellulose properties, such as mechanical and barrier properties, which are important for packaging applications. In addition, pure hemicellulose obtained from plants is water sensitive, brittle and weak, making it unsuitable for most packaging applications even though it is a good barrier for oxygen. Modification of hemicellulose is needed to meet the requirements of packaging materials such as protection against chemical, mechanical, physical and biological damage, and good barrier against water, oxygen, odors, etc.This research focuses on the fabrication and characterization of hemicellulose based films with adequate properties to enable their potential application as packaging materials. Three types of raw materials, aspen ChemiThermoMechanical Pulp (CTMP), spruce CTMP and hybrid poplar powder, with different pretreatments (bleaching and no bleaching) were employed to obtain hemicelluloses by an alkaline extraction method. The extracted hemicellulose was further formed into film by solvent casting in water with the addition of sorbitol and glutaraldehyde. These two chemicals were used as a plasticizer and a cross-linking agent, respectively, to improve the properties of hemicellulose films.Mechanical and barrier properties of the hemicellulose based films were determined. Hemicellulose sources and pretreatments played an important role in the properties of hemicellulose based films. Hemicellulose based films from less treatment (powder samples, no bleaching) displayed better properties than the films from more treatment (pulp samples, bleaching) in general. Hemicellulose based films prepared from hybrid poplar powder without bleaching exhibited the highest tensile strength (76.5 ± 7.0 MPa) and elongation at break (5.4 ± 0.9%), which were higher than the values obtained from other studies of similar hemicellulose based films. Glutaraldehyde was suggested to be responsible for this improvement. The modulus of elasticity (MOE) (3.5 ± 0.4 GPa) was comparable with those obtained for similar hemicellulose based films in other studies. The differences in molecular weight, lignin content and crystallinity for the hemicellulose film obtained from different approaches were believed to result in the differences in tensile properties. No significant improvement in the barrier properties (water vapor and oxygen barrier properties) of the hemicellulose based films was observed in this study, which is similar to the results obtained in other studies. Hemicellulose based films prepared from both unbleached spruce CTMP and hybrid poplar powder had better barrier properties than the other films as indicated by the lower water vapor transmission rate (WVTR) values obtained at 23 °C and 100% RH, but not as good as most current commercial packaging films whose WVTR values were several orders of magnitude lower.
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