Influence of silica nanofiller on the isothermal crystallization and melting of polyurethane elastomer

Abstract

In this article, isothermal crystallization kinetic of the linear hydroxyl polyester urethane (PUR), as well as influence of amorphous silica nanofiller, was investigated. With the aim to investigate the influence of filler surface modification on the crystallization process of polyurethane matrix, nonmodified silica, as well as silica modified with methacrylsilane and octylsilane, were used as fillers for PUR composite preparation. The crystallization kinetics depending on temperature of the isothermal crystallization and volume fraction of filler by using differential scanning calorimetry (DSC) were investigated. The measurements at temperatures 7, 12, and 17°C for PUR and composites with 0.5, 1, 2, and 4 vol % of filler were done. Kinetic parameters of the isothermal crystallization n and K were determined according to Avrami model. Melting of the isothermally crystallized samples was also investigated. Results of the research indicate that by increasing the isothermal crystallization temperature, the crystallization rate of the PUR soft phase decreases and that the perfection of the crystallites is improved. By addition of all fillers up to ≈1 vol %, the crystallization rate increases; however, addition of a higher amount of the filler significantly decreases the crystallization rate. It was found that surface modification can significantly affect crystallization rate and that the nucleation efficiency of silica increases in the following order: methacrylsilane‐modified silica < nonmodified silica < octylsilane‐modified silica. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Multiscale Study of Shape-Memory Behavior of Semicrystalline Polyurethane Nanocomposites Doped with Silica Nanoparticles Based on Coarse-Grained Molecular Dynamics Simulation

“…However, when the crystallinity of the polymer chains was observed near the silica surface, the soft segment in the interphase region did not form a crystalline arrangement because of the strong adsorption on the silica surface. These findings are in line with experimental results indicating that the presence of silica nanoparticulate fillers can hinder the crystallization of thermoplastic polyurethane by reducing the chain mobility. − …”

Inhibition of Recrystallization of Amorphous Lactose in Nanocomposites Formed by Spray-Drying

“…In addition, if the compartments size are reduced to a few nanometers, that is, nanoconfinement, the recrystallization can be completely suppressed as the volume of the crystallizing material is smaller than the critical volume needed for nucleation to occur . In polymer nanocomposites, nanoparticles such as fumed silica, montmorillonite, ZnO, and carbon nanotubes are reported to induce the nucleation of polymers, but lowering the recrystallization rate at high fractions in nanocomposites due to physical hindrance or confinement of the polymer. Despite a few reports on utilizing composites of amorphous low molecular compounds as a formulation strategy to inhibit the recrystallizing tendency, a better understanding of the stabilization mechanism is necessary, especially how the molecular mobility of the amorphous component is affected and how the structure on a nano‐ to micrometer length scale influences the recrystallization tendency.…”

Análise térmica e propriedades mecânicas de resíduos de polietileno de alta densidade (PEAD)

“…Consequentemente, a cristalização é nucleada em temperaturas maiores quando as amostras de polímero são resfriadas em velocidades mais baixas. Ao contrário, em velocidades de resfriamento mais altas a ativação dos núcleos ocorre em temperaturas mais baixas [8,9] . Isso explica as tendências observadas, ou seja, a redução dos valores de T c , ΔH c , ΔH m e %χ c .…”