Preparation and Thermodynamic Analysis of Easily Degradable Capsule Wall Materials

Graphical This study explores thermally degradable polyurethane acrylate (PUA) capsule wall materials tailored for deep oilfield environments. The hydrothermal degradation properties of PUA at 150 °C are improved by molecular structure adjustment and incorporation of α-MeSt. The thermal degradation kinetics of PUA is systematically investigated using the Kissinger method and Flynn–Wall–Ozawa method. To meet the practical needs of oilfield capsule acids, series thermos-degradable polyurethane acrylate (PUA) capsule wall materials are prepared. The PUA consist of light-curing co-polymerization of isophorone diisocyanate, polybutylene glycol adipate, hydroxyethyl methacrylate, α-methylstyrene (α-MeSt), and other acrylate monomers. The successful synthesis of the polymer is confirmed by IR and the successful preparation of capsule acid is demonstrated by SEM. The mechanical properties of PUA are tested using an electronic tensile strength tester. The polymer residual content under hydrothermal conditions at 150 °C proves the hot water degradation ability of polyester-type PUA is better than that of polyether-type PUA and the degradation ability can be improved with the increase of α-MeSt content. For elucidating the thermal degradation phenomenon of PUA, the initial decomposition of the copolymers at relative low temperatures is monitored by differential scanning calorimetry (DSC). The results show that the PUA with the addition of the α-MeSt monomer have a thermal effect at about 140 °C and begin to undergo thermal degradation. The thermal degradation kinetics are systematically investigated by Kissinger method and Flynn-Wall-Ozawa (FWO) method, which explain that the degradation activation energy value of PUA decreased with the increase of the content of α-MeSt units.