Enhanced Mechanical Properties of Epoxy Resin Modified With Monomer Production From Depolymerization of Waste Polyethylene Terephthalate

The recycling of waste polyethylene terephthalate (PET) can be facilitated by processing and utilizing the small molecules depolymerized from waste PET. To address the poor post-curing performance of high internal cross-linking in impact resistance, it is necessary for epoxy resin (EP) to undergo toughening modification and broaden its applicability. In the present study, a method used to prepare monomer production from depolymerization was proposed to depolymerize waste PET through the alcohol-alkali combination. The process parameters were further optimized with pretreatment. As the monomer production from depolymerization, recycled terephthalic acid (rTPA) was treated as a chain extender to obtain high-performance modified epoxy resins. Compared with epoxy resin E51, the mechanical properties of rTPA-modified epoxy resin were significantly enhanced. For instance, when rTPA was introduced in small amounts, the tensile strength increased by 46.7% from 50.5 to 74.1 MPa, the flexural strength improved by 49.9% from 78.9 to 118.3 MPa, and the bond strength increased by 32% to 4.38 MPa. As the rTPA content rose sharply, however, the impact strength soared by 384.3% from 7.1 to 34.5 KJ/m 2 , and the flexural modulus rose by 196.4% from 1039 to 3080 MPa. Meanwhile, the water absorption rate remained at an extremely low level.