Pressure-Sensitive Adhesives Based on Epoxidized Soybean Oil and Dicarboxylic Acids

Existing pressure sensitive adhesives (PSAs) are mainly derived from petrochemicals. This study describes a novel approach for development of biobased PSAs. Epoxidized soybean oil was polymerized and cross-linked with a dicarboxylic acid to generate superior PSAs. The dicarboxylic acids used in this study included dimer acid (DA), sebacic acid, adipic acid, and a difunctional polymeric carboxylic acid that was prepared from polymerization of bisphenol A diglycidyl ether (BPAGE) and an excess of DA. AMC-2, a chromium-(III)-based organometallic compound, was found to be the most effective catalyst for the polymerization/cross-linking. The PSAs had a peel strength of 1.4-5.0 N/cm, a loop tack of 7.1-12.6 N, a shear strength of 34 min to more than 168 h, and a good aging resistance. The adhesive properties of the PSAs can be tailored for specific applications such as PSA tapes and labels through the selection of the dicarboxylic acid and its usage. Incorporation of a small amount of phenylene-containing monomer BPAGE into the PSAs significantly increases the peel and shear strengths of the resulting PSAs. This new class of PSAs can be fully based on renewable materials. The preparation of the PSAs does not use any organic solvent or toxic chemicals, thus being environmentally friendly.