The effect of chain extension method on the properties of polyurethane/SiO2 composites

The polyurethane (PU)/SiO2 composites with diverse microstructure were obtained with different chain extension methods by pre-polymerization method. The composites with multitudinous crosslink density micro-domains were denoted as PUm/SiO2 composites, the other were denoted as PUh/SiO2 composites. The microstructure and the properties of PUm/SiO2 and PUh/SiO2 composites were investigated. The results showed that the particles of SiO2 were well-dispersed in PU matrix. It was demonstrated that the mechanical properties of PUm/SiO2 composites had optimal tear strength and maintained similar tensile strength in comparison with PUh/SiO2 composites. Scanning electron microscope (SEM) photographs indicated that the tensile sectional morphology of PUm/SiO2 composites was presented complex without rules, which verified that the PUm/SiO2 composites had better fracture toughness and strength. Differential scanning calorimetry (DSC) studies suggested a better micro-phase separation of soft and hard segments in PUm/SiO2 composites. Besides, the PUm/SiO2 composites had excellent solvent resistance performance.