Preparation and development of a chemically modified bio-adhesive derived from soybean flour protein

Published Date
December 2016, Vol.71:48–54, doi:10.1016/j.ijadhadh.2016.08.011

Author 

• Farnaz Eslah ^a,
 
• Mehdi Jonoobi ^a,,
 
• Mehdi Faezipour ^a,
 
• Maryam Afsharpour ^b,
 
• Ali Akbar Enayati ^a,

• aDepartment of Wood and Paper Science and Technology, Faculty of Natural Resources, University of Tehran, Karaj, Iran
• bChemistry & Chemical Engineering Research Center of Iran, 14335-186 Tehran, Iran

Accepted 22 August 2016. Available online 28 August 2016.

Abstract

In this study, the potential of chemically modified soybean flour (SF) to be used as a strong and water resistant adhesive for bonding plywood composites was investigated. SF, sodium hydroxide (NaOH), acetic anhydride (AA), and polyethylenimine (PEI) were used to prepare adhesive formulations. Solid content and viscosity of adhesives were measured. Formulations were characterized using FTIR and UV absorption spectra to evaluate chemical changes of adhesives during modification. Water resistance and shear strength of plywood samples were measured, as well. FTIR analysis indicated that NaOH denatures SF; therefore amino groups buried inside the compact protein structure become available. In an SF/acetic anhydride adhesive (ASF), reaction with AA converted amine and hydroxyl groups to less polar components i.e. amides and esters, respectively. Using PEI for adhesives resulted in improved bond strength and water resistance. In this case, FTIR analysis showed that primary and secondary amines in ASF/PEI/NaOH formulations had disappeared. This could be due to a reduction in amine concentration and the formation of amides resulting in the occurrence of cross linking reactions. Absorption spectra of PEI, SF/PEI, and acetylated formulations with PEI showed a shift of λ _max to a shorter wavelength due to the modifications. Comparing the water resistance and the shear strength of plywood samples containing the above mentioned formulations, with ones based on phenol formaldehyde (PF), revealed that SF with NaOH, AA, and PEI had the best adhesion performance.

Keywords

Soybean flour protein adhesive

Plywood

Water resistance

Shear strength

FTIR

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