Multiscale Investigation of Resorcinol Bis(diphenyl phosphate) as an Efficient Thermal Stabilizer for Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)

In this work, resorcinol bis(diphenyl phosphate) (RDP) was investigated as an efficient thermal stabilizer for poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB). Its influence on the thermal stability of P34HB was first evaluated by simultaneous thermal analysis (TG-DSC) in N₂ and air atmospheres. The TGA results showed that the addition of 20% RDP significantly increased the initial and maximum degradation temperatures (i.e., 60.8 °C for T_1% in N₂ and 19.5 °C for T_5% in air) compared to the neat P34HB. The mechanism of its improved thermal stability was further explored through TG-FTIR analysis. This result indicated that RDP did not change the pyrolysis mechanism of P34HB, but postponed its thermal degradation process by restraining the intramolecular ester exchange and cis-scission reactions. This was achieved through the end capping, chain extension, and steric hindrance effects. Additionally, RDP improved the toughness and melt flowability of P34HB due to its plasticizing effects. This research provides innovative routes to solve the processing of PHAs for their wider applications.