Preparation and Characterization of Carbon Nanotubes Enhanced Canola Protein Isolate (CNT/CPI) Bio-Adhesive for Wood Application

Abstract

The current wood adhesives technologies rely mainly on formaldehyde-based adhesives produced from petrochemicals. Moreover, these adhesives are derived from non-renewable sources is known to be carcinogenic together with other serious health effects. Therefore, there is an increasing interest in the use of renewable and biodegradable sources for the evolution of an environmentally friendly adhesives for interior wood applications.The canola meal (the remnant after oil extraction from the canola seed) contains about 36 – 39% (8.5% moisture basis) can be used as a low value feed for the animals. Moreover, its protein content is currently exploring other applications such as in the adhesive technology and it can be used as an alternative to the widely used formaldehyde-based adhesives. Canola proteins (CP) as adhesives have many unique properties such as ease of handling, low cost, low pressing temperatures, and the ability to bind wood with relatively high moisture content. On the other hand, it has relatively low adhesion strength and low water resistance which are the major drawbacks. This study will address these issues by modifying CP adhesive with carbon nanotubes (CNT). CNT are one of the most encouraging strengthening nanofillers with the extraordinary tensile modulus and strength, it has been proved to significantly improve the physical and mechanical properties of the nanocomposites. Generally, this study will intend to improve the water resistance and adhesive strength of the CP adhesive by incorporating different concentrations of the CNT into the protein matrix.This study is made up of two parts: incorporation of CNT and functionalized CNT (FCNT) into the CP matrix. Incorporation of CNT at 1% (w/w) enhanced the adhesive strength from 5.98, 1.80, and 5.42 to 9.20, 5.64, and 7.44 at percentage increment of 53.85, 213.33, and 37.27% for dry, wet, and soaked strength respectively. The presence of carbonyl group in the CNT after purification as well as the polyvinylpyrrolidone (PVP) helped to attain this improvement in the water resistance and adhesion.In the second part, functionalization of the CNT greatly improved the shear strength at 1% FCNT concentration to 10.62, 8.10, and 8.13 at 77.59, 350, and 50% increase for dry, wet, and soaked strength respectively. The introduction of the carboxylic group by functionalization significantly improved the mechanical and thermal properties of the CP due to a proper dispersion giving rise for a better hydrophobic and cohesive interactions between the wood and adhesive.These results proved an enhanced water resistance and adhesion of the CP contributed by the CNT and its functionalization.