Structure—Functional property relationship of aliphatic polyurethane-silica hybrid films

Abstract

The novel aliphatic polyurethane-silica hybrid films were prepared using prepolymerization method in the presence of spherical, submicron amorphous SiO2 Sidistar T120 particles (0, 1, 2, 5 and 10 wt%). The study of the influence of silica distribution on the structure–functional property relationship of polyurethane (PU) composites was performed using FT-IR, SEM, AFM, TGA, DSC, DMTA, tensile testing and immersion test. It was found that the presence of low SiO2 content is acting as dispersing agent between soft- and hard-segments. Achieved uniform distribution of 1 and 2 wt% of silica caused the formation of additional hydrogen bonds between organic matrix and inorganic filler, and remarkably improved thermal stability, thermal and mechanical properties of obtained polyurethane composites. The agglomerates, formed at higher SiO2 loading (5 and 10 wt%), caused the change of thermal degradation mechanism as well as the change of physical crosslinking disruption mechanism. Despite significantly deteriorated mechanical properties of polyurethanes with heterogeneously incorporated silica particles, the onset temperature of elastomers and the starting of melting of hard domains were registered at higher temperature compared to pure PU. Optimal thermal characteristics (onset, decomposition and melting temperatures) and remarkable tensile properties (especially high elongation-at-break and tensile strength, and extraordinary energy-to-break) compared to pure polyurethane have been determined for the polycarbonate-based polyurethanes containing 1 wt% and especially 2 wt% of SiO2. It allows them to be utilized as mechanically strong and durable coatings or films in biomedical applications or as packaging materials. The solvent-resistance data are well described using novel proposed model covering two swelling and dissolution phenomena. The presence of silica decreased the rate and the amount of swelling in water, acetone, toluene and hexane. The rate and mass reduction of swollen sample in acetone, toluene and hexane also decreased by the addition of SiO2 particles.