Unconventional plasticization threshold for a biobased bisphenol-A epoxy substitution candidate displaying improved adhesion and water-resistance

Toxicity concerns over bisphenol A (BPA) based materials like polycarbonates or diglycidyl ether of bisphenol A (BADGE) lead to their progressive substitution in food packaging and can coating applications, even if the eventual release of BPA in food remains debatable. In this paper, we study the adhesive, water resistance and thermo-mechanical properties of a bio-based BADGE substitution candidate issued from Cardanol (CardDE). Different formulations with increasing ratio of BADGE substitution were evaluated, highlighting a real prospect for BPA-based epoxy substitution. During these studies, an unconventional relationship between water uptake by the biobased adhesive and property loss due to plasticization was evidenced. The water resistance of CardDE adhesives was investigated in detail revealing a plasticization threshold at elevated water content, attributed to their hydrophobic structure. While the adhesive properties of conventional BADGE networks are prematurely affected, the deterioration of CardDE adhesives is delayed.