Effect of nature and extent of functional group modification on properties of thermosets from methacrylated epoxidized sucrose soyate

A study was carried out to evaluate the impact of modification of epoxidized sucrose soyate using a combination of methacrylate and inert esters (acetate propionate, butyrate) on the properties of the resins as well as the thermosets. Previous studies have shown that methacrylated epoxidized sucrose soyate (MESS) can yield thermosets having high glass transition temperature (Tg) and good mechanical properties, but had high resin viscosity due to hydrogen bonding of the hydroxyl groups. Further functionalization to yield dimethacrylated epoxidized sucrose soyate (DMESS) resulted in reduced resin viscosity, but some of the thermosets were brittle. In this study, to maintain low resin viscosity and improve thermoset ductility, replacement of some methacrylate groups with various ester groups was explored. The synthesis of these resins was carried out in a one-pot process involving the sequential slow addition of anhydrides of the acids mixed prior to addition. The synthesized resins were characterized for their viscosity with and without styrene diluent. Formulations were made using varying amounts of styrene and free-radically cured using peroxyesters as initiators. The bio-based resins with 30% styrene gave much lower viscosities compared to commercial resins containing higher amounts of styrene (33% and 45%). The thermosets produced had improved flexibility and toughness with only a slight reduction in the glass transition temperature. The inclusion of the non-functional esters in the resin structure acted as internal plasticizers for the polymer system. The new sets of thermomechanical properties demonstrated the tunability of the bio-based resin system and opens up different avenues for end-use applications.