Molecular Simulation Study of the Adsorption Mechanism and Mechanical Properties at the Interface between Epoxy Resin and Phosphogypsum

Phosphogypsum (PG) exhibits poor plasticity and low strength. Enhancing its properties by curing PG with epoxy resin could prove beneficial for applications in road construction, which can address the shortage of natural sand and gravel materials. Understanding the atomic-scale mechanism of PG cured by epoxy resin is crucial to exploring its improved properties. In this study, three interface models involving diglycidyl ether of bisphenol A epoxy resin (DGEBA), diglycidyl ether 4,4'-dihydroxy diphenyl sulfone (DGEDDS), and aliphatic epoxidation of olefin resin (AEOR) with PG were constructed by using the molecular dynamics method. The study investigated the adsorption behavior and mechanical properties of these three interface models between epoxy resins and PG. The results indicated that (1) DGEBA exhibited the highest number of interface hydrogen bonds on the PG surface and AEOR demonstrated the highest adsorption energy with PG due to the strong coordination of the epoxy groups with Ca²⁺ on the PG surface. (2) In terms of the overall mechanical properties of the modeled systems, the DGEBA-PG system performed the best, while DGEDDS-PG performed poorly due to its relatively flexible molecular chain. (3) In terms of the radius of gyration of the systems, the AEOR-PG system exhibited a more rigid structure than the DGEBA-PG system and the DGEDDS-PG system.