Structural Stability and Hydration-Induced Failure Mechanisms of Borax-Modified PVA-Coated PAA-SAP Beads for Mine Pipeline Transport

Poly(acrylic acid)-based superabsorbent polymer (PAA-SAP) rapidly absorbs water and swells during pipeline transport in mine water-based inhibitor fluids, increasing flow resistance and potentially causing blockage. To improve aqueous structural stability, PAA-SAP beads were coated with poly(vinyl alcohol) (PVA) by rotary spraying and hot-air curing, with borax introduced to regulate the coating structure. The effects of PVA concentration, coating thickness, temperature, and hydrodynamic disturbance were evaluated using stability tests, scanning electron microscope (SEM), energy-dispersive X-ray spectrometer (EDS), fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), dry-film swelling, and mass-loss analyses. A 10% PVA formulation showed favorable film-forming and processing performance. Increasing coating thickness prolonged structural retention, whereas higher temperature and stronger disturbance accelerated hydration and failure. At 0.30 mm coating thickness and 2.5 m·s−1 laboratory hydrodynamic disturbance parameter, the borax-modified PVA coating failed after approximately 16 min, compared with 10 and 12 min for PVA and PVA/poly(vinylpyrrolidone) (PVP) coatings, respectively. Boron incorporation and possible boron–oxygen interactions restricted chain mobility and improved coating compactness and stability. A power-law model based on 46 datasets showed good interpolation performance (Coefficient of determination (R2) = 0.9421; Mean Absolute Percentage Error (MAPE) = 5.44%). Failure involved swelling, gelation, network weakening, cracking, and chain dissolution, with core swelling potentially promoting crack propagation. These findings support coating-parameter selection and subsequent mine-scale pipeline validation.