Conversion of Protein-Rich Waste Biomass into Value-Added Polymers

• Author / Creator

  El-Thaher, Nayef

• Conversion of protein-rich biomass waste into value-added industrial products via chemical cross-linking reactions was explored. Two types of cross-linking reagents were investigated: dialdehydes and epoxy resins. Reaction chemistry was the main focus of this investigation and the main reaction parameters selected for study were electrolytes and protein molecular weight since raw material modification usually involves these two parameters. First, the reaction chemistry of glutaraldehyde was investigated. Glutaraldehyde is a cheap and highly reactive cross-linking reagent. Its reaction chemistry, however, is poorly understood. At low reaction temperatures, protein amine groups form Schiff bases with carbonyl groups of glutaraldehyde. The resulting C═N bond is weak and can be easily broken by heat or dissolution in water. As the reaction temperature is increased, the more stable C—N bond is formed. A network with low water solubility and significantly improved thermal stability is produced. The presence of water has a dual effect. Water acts as a medium to disperse hydrolyzed proteins into glutaraldehyde and is also a hydrogen source to drive the reaction forward. However, water is a byproduct. Its presence suppresses the reaction from the standpoint of thermodynamic equilibrium, and it must therefore be driven off. Epoxy-protein reaction chemistry was also investigated. The effects of salt, molecular weight and viscosity, and mass ratio on the apparent activation energy of the cross-linking reaction of epoxy resins and protein hydrolysate were studied by nonisothermal differential scanning calorimetry. The presence of salts contributed to an increase in the apparent activation energy. The curing of epoxy resins with lower molecular weight protein hydrolysates was found to have lower activation energy and order of reaction. An increase in the concentration of curing groups resulted in a small increase in the order of reaction. The activation energy of curing bisphenol A diglycidyl ether, with viscosity 500–700 cP, was found to be significantly higher than the curing activation energy of polypropylene glycol diglycidyl ether (viscosity ~50 cP). Denaturant addition was also investigated and was found to be an energetically efficient alternative to higher degrees of protein hydrolysis for subsequent reactions.

• Subjects / Keywords

  • Glutaraldehyde
  • Sustainable Chemistry
  • Activation Energy
  • Differential Scanning Calorimetry
  • Protein-rich Biomass
  • Polymers
  • Reaction Kinetics

• Graduation date

  Spring 2014

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R36T0H46W

• 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.