Abstract
In this work, a series of heptaphenyl siloxane trisilanol/polyhedral oligomeric silsesquioxane (T7-POSS) modified by polyols with different molecular weights were synthesized into liquid-like nanoparticle–organic hybrid materials using the grafted-from method. All grafted POSS nanoparticles changed from solid powders to liquid at room temperature. Polyurethane (PU) nanocomposites with POSS contents ranging from 1.75 to 9.72 wt % were prepared from these liquefied polyols-terminated POSS with polyepichlorohydrin (POSS–PECH). Transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize the morphology of the POSS–PECH/PU nanocomposites. The results showed that the polyol-terminated POSS particles overcame the nanoagglomeration effect and evenly disperse in the polymeric matrix. The damping factor (tan δ) of resultant nanocomposites increased from 0.90 to 1.16, while the glass transition temperature decreased from 15.8 to 9.4 °C when POSS contents increased from 0 to 9.75 wt %. The gel content, tensile strength and Fourier transform infrared (FTIR) analyses demonstrated that the molecular thermal movement ability of the polyurethane (PU) matrix increased with increasing POSS hybrid content. Therefore, the improvement of the damping properties of the composites was mainly due to the friction-related losses occurring in the interface region between the nanoparticles and the matrix.
Highlights
In recent decades, nanocomposites have been intensely investigated by academy and industry researchers in the field of new materials development
The Fourier transform infrared (FTIR) spectrum of POSS–PECH presented in Figure 2 shows a peak at approximately 3442 cm−1 that was assigned to the O–H stretching band
The Tg and the initial temperature of the damping temperature range (T1 ) of the PU–POSS nanocomposites gradually decreased respectively: Tg to 9.4 ◦ C from 15.8 ◦ C and T1 to –6.9 ◦ C from –1.1 ◦ C. These results demonstrate that monodispersed nano-POSS particles effectively improved the damping properties of the composites, importantly demonstrating that the increased POSS content did not restrict the thermal mobility of molecular chains
Summary
Nanocomposites have been intensely investigated by academy and industry researchers in the field of new materials development. Nanocomposites often exhibit excellent strength, modulus of elasticity and toughness due to the reinforcement effects of nanofillers. In these commodity engineering applications, traditional theories of polymer mechanics are usually effective in predicting and guiding the static elastic properties of composites. The value of tan δ is mainly determined by its viscoelastic behavior in the glass temperature (Tg ) transitional region. In this region, macromolecule chain segments tend to vibrate in phase with external vibrations. The higher the internal friction, the higher the tan δ value and the broader the transition region will be; excellent energy dissipation (damping) performance of such composites will be observed [9–14]
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