ABSTRACT
This chapter reports the development and evaluation of a novel environmentally friendly adhesive proposed as a replacem ent for the existing formaldehyde and petrochemical adhesive. The proposed adhesive was prepared from soy protein isolate (SPI) by incorporating CNTs as the nanofiller in the SPI. The multifunctional properties of carbon nanotubes (CNTs) as the nanofiller in a polymer matrix were explored in the development o f the soy-
based adhesive with improved bond strength and water resistance. Scanning electron m icroscopic images of the prepared samples show a homogeneous distribution of CNTs in the nanocomposite adhesive samples. Fourier transform infrared (FTIR ) spectroscopy reveals expected surface functionalities. The presence of hydroxyl and carboxyl groups on the surface of the nanocomposite adhesive was observed, which enhanced the dispersion of the functionalized carbon nanotubes (FCNTs) and contributed to the high shear strength of the adhesive. Thermogravimetric analysis of the samples shows that the soy/CNT nanocomposite adhesive was more thermally stable compared to the pure adhesive (without CNTs). The shear strength was investigated according to the European standard (EN -204) for interior wood application on a tensile testing machine. The results showed that incorporating FCNTs into the alkalinemodified SPI increased the shear strength by over 100% both in w et and dry states. A 0.3 w t% loading fraction of FCNTs displayed the highest tensile shear strength of 8.4 MPa, and the shear strength decreased as the percentage loading increased beyond 0.3 wt%. The shear strength of the SPI/FCNT adhesive was about 25% higher than that of the SPI/CNT adhesive. According to European standard (EN -204) for interior wood application, the minimum value for the shear strength is > 10 MPa. Results from the literature show that the incorporation of other fillers into soy-based adhesives improves the shear strength, although at a higher percentage loading. However, CNTs, an example of a nanofiller used in this study, improved the shear strength of the adhesive at a reduced percentage loading (0 .3% ) compared to other modifiers. The results of this study have shown the benefit of the functionalization of CNTs in enhancing the adhesive performance of SPI/CNT nanocomposite adhesive developed and reported in this chapter.
