Phosphate Esters Functionalized Dihydroxyl Soybean Oil Tackifier of Pressure-Sensitive Adhesives

Dihydroxyl soybean oil (DSO) has shown potential as a tackifier for pressure-sensitive adhesive (PSA) applications, and perchloric acid was used previously as a catalyst to open the oxirane rings of epoxidized soybean oils (ESO) when we prepared DSO and PSA. Phosphoric acid is a more eco-friendly catalyst than perchloric acid; therefore, the objective of this work was to prepare DSO using phosphoric acid as a catalyst and thereby create DSO-contained phosphate esters, or PDSO. The chemical scaffolds of PDSO were elucidated with H-1, H-1-H-1 COSY, P-31 NMR, FTIR, MALDI-TOF MS, and GPC. ESO PSAs were prepared from a mixture of ESO/PDSO. The ESO PSA prepared with PDSO had peel strength on a plastic carrier comparable to commercial PSA, and while on an aluminum carrier, the ESO PSA had a stronger peel strength. ESO PSA prepared with phosphoric acid was also stronger than the peel strength of the ESO PSA prepared with DSO using perchloric acid.