Preparation and Performance Study of Silicone-Oligomer Composite-Modified Polyurethane Sealant

To address the shortcomings of traditional polyurethane (PU) sealants, including inadequate weather resistance, low curing efficiency, and limited environmental performance, this study synthesized a functional silicone oligomer (DQPSi) featuring both dynamic crosslinking and hydrophobic properties via the sol-gel method, which was subsequently incorporated into the polyurethane matrix. The effects of DQPSi content (0-20 wt%) on the properties of silane-modified polyurethane (SPU) sealants were systematically investigated. Results demonstrate that DQPSi significantly enhances the comprehensive performance of the material. At 15% loading, the sealant achieves optimal performance balance: surface-drying time shortens to 110 min (45% reduction), curing rate increases to 1.7 mm/d (112.5% improvement), tensile modulus rises by 14% to 0.88 MPa, elongation at break substantially increases to 420%, and contact angle improves to 78° with markedly enhanced hydrophobicity. Microscopic analyses (SEM, nanoindentation) confirm that these improvements stem from DQPSi forming a uniform interpenetrating network (IPN) structure with the PU matrix, where dynamic Si-O-Si bonds provide rigidity and stress dissipation while hydrophobic groups (methylpropyl) migrate to the surface to form a barrier. However, excessive addition (20%) induces silicone phase separation and over-crosslinking, causing mechanical degradation (tensile strength decreases to 0.70 MPa, elongation at break drops to 331%) and microcrack formation. This research elucidates DQPSi's reinforcement mechanism and critical loading threshold, establishing theoretical and technical foundations for developing high-performance eco-friendly silane-modified polyurethane sealants.