Enhancement of lignocellulosic feedstocks and biorefinery byproducts for composite and polymer applications

• Author / Creator

  George, Michael

• The volatility of the petroleum-based markets, increasing ecological concerns, and the accumulation of waste from the plastic industry have motivated a paradigm shift in research. Researchers are searching for sustainable, renewable, and competitive platforms ideally suited for replacement of conventional petroleum-based chemicals and fuels. The purpose of this research is to study the macrostructure of biomass and byproducts from the different bio-based industries for preparation and characterization of bio-based composite and polymer materials. Lignocellulosics have been identified as a key resource for this space. Natural fibres are composed primarily of cellulose, hemicellulose, lignin, and other minor components including pectic material and waxes. As determined by their native composition, they are characterized with limited thermal stability, poor water resistance, and incompatibility with most commercial resin systems. Researchers in the past have studied the effect of chemical, physical, and to some extent, biological treatment of natural fibres. Unfortunately, chemical methods in most cases are associated with large volume of organic waste and high energy requirement. Likewise, physical methods have been shown to be limited because of high capital requirements and less than desired improvement in properties. If these uncertainties can be addressed with new chemistries that are green, and technologies that are easily scalable, that would be an achievement in this area. In the first approach investigated in this thesis, hemicellulases, pectinases and an oxidoreductase were used to enhance hemp and flax fibres. Treatment with xylanase and pectinase (polygalacturonase and pectinmethylesterase) improved the thermal properties for both fibre types. X-ray photoelectron spectroscopy (XPS) measurements confirmed reduction of the hemicellulosic content of both fibres for xylanase and pectinases. Removal of amorphous hemicellulosic material from the fibre surface and consequent exposure of the crystalline cellulose network resulted in a lower contact angle for all the treated samples. After initial property determination, enzymatically enhanced fibres were then tested for their ability to reinforce polypropylene. The removal of hemicellulose and pectic components resulted in improved thermal properties and greater water resistance whereas the mechanical properties were unaffected in most cases. In the second approach investigated, hemp fibres were enhanced using two sulfonic acid derivative systems. An aqueous reaction medium was used with little or no organic solvent at relatively low temperatures (below 50 °C). Successful modification was subsequently confirmed through the use of FTIR. The degree of substitution for the treated fibres peaked at 30 °C and XPS data of the treated fibres were characterized by reduction of the O/C ratio and an increase in abundance of the C-C-O, attributed to the ester linkages. The “green index” of the sulfonic systems was then evaluated and confirmed using Life Cycle Analysis (LCA). The studied methods had measurable benefits in regards to impact on the environment and society when compared to mercerization, alkylation, and the production of glass fibre. Subsequently, a novel polymer system was developed using epoxy resin and a renewable, waste stream – tall oil rosin acids, which were derived from the pulp and paper industry. Replacement up to 15 % (w/w) with TORAs resulted in no change in mechanical properties of the plastics. This study demonstrated the successful integration of waste streams from the pulp and paper industry validate a multi-product bio refinery concept. In summary, this thesis has demonstrated that a better understanding of the structural and compositional properties of natural fibres can result in technologies tailored for specific applications. Additionally, it has been demonstrated that chemical methods and/or enzymes can be used to enhance natural fibres for composite applications. The thesis also demonstrates that there is potential to use waste streams, such as TORAs to produce plastics with a renewable and sustainable index. Finally, this work demonstrates that these technology platforms are more environmentally sustainable than the conventional petroleum-based platforms and established methods in the literature.

• Subjects / Keywords

  • Life-cycle assessment
  • Enzymes
  • Surface and thermal characterization
  • Natural fibres

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3KH0F46C

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.