Soybean-Based Bio-Adhesives: Role of Diamine on the Adhesive Properties.

One possible approach to achieving sustainable development in the materials sector is to produce polymers from plant oils (POs), which are renewable and environmentally beneficial. Polymers with a high concentration of functional groups can be used as cross-linking agents to enhance the properties of epoxidized POs (epoxidation of plant oil)-based polymers. In this work, a unique resin with novel properties and potential uses was produced by cross-linking epoxidized soybean oil (ESO) with branched and flexible polyamines by ring-opening and amidation polymerizations. This approach is straightforward and ecologically benign. After curing, melamine pentane diamine (MPD) polymer maintained its position as the strongest structural adhesive among the synthesized resins, with a bonding strength of almost 2000 kPa for stainless steel; irrespective of the temperature, stainless steel consistently outperforms melamine ethylene diamine-ESO resin in strength comparisons. At 100 °C, stainless steel has a lap shear strength of about 300 kPa, which is far higher than copper and aluminum; at 180 °C, this value increases by another 750 kPa. While MPD-ESO resin has a shear strength of 1996 kPa at 180 °C, melamine butane diamine-ESO resin has a shear strength of only 1220 kPa.