Mitigating Shrinkage Stress in UV-Curable Resin: Shape Memory Microcapsules Enable Shrinkage Stress Reduction via Photopolymerization-Induced Shape Recovery

UV-curable resins find applications across various industries, but their performance and service life often suffer due to the significant shrinkage stress generated during rapid curing. This study focuses on the preparation of ellipsoidal-shape memory polyurethane microcapsules and investigates their impact on shrinkage stress and the fundamental properties of UV-cured resin, considering different particle sizes and aspect ratios. Our findings reveal that incorporating a mere 3.0 wt % of shape memory ellipsoidal microcapsules, measuring 21.4 μm with an aspect ratio of 1.82, results in a remarkable reduction of approximately 36.4% in shrinkage stress. During the resin curing process, the generated shrinkage stress triggers a shape-recovery mechanism in the ellipsoidal microcapsules, which transitions them into a spherical shape. This transformation effectively dissipates the shrinkage stress, and the reduction in volume is dynamically compensated for during the shape recovery process. This innovative approach offers an efficient means to mitigate the shrinkage stress of UV-cured resin with minimal additive content, thus avoiding adverse effects on the coating’s fundamental performance. It introduces a new paradigm for addressing shrinkage stress concerns in UV-cured resin applications.