Summary
This work presents the preparation of modified titanates nanotubes with tetraethyl orthosilicate (TNT‐TEOS) and their use in the synthesis of TNT‐TEOS/polyurethane nanocomposite by in situ polymerization. The filler was added in a proportion of 1% (w/w) relative to the polyol weight. The TNT‐TEOS presented a specific surface area of 127 m2/g lower than that obtained for TNT (177 m2/g). The addition of TNT‐TEOS in a polyurethane matrix promoted an increase in thermal stability of the polymer when compared to the pure PU and in crystallinity as observed by increase in melting and crystallization enthalpies. This effect can be attributed to good filler dispersion into polymer matrix and the interaction between the filler and the soft segments of the polyurethane.
Aliphatic polyurethane (PU) nanocomposites were prepared using modified titanate nanotubes (TNTs) as filler in order to improve the mechanical and thermal properties of the initial polymer. With a view to achieving greater interaction between the polymer chains and TNTs, the latter was functionalized with hexamethylene diisocyanate (H) and/or aminopropyl trimethoxysilane groups (A), producing the modified nanotubes TNTH, TNTA, or TNTHA. The thermogravimetric analyses used to quantify the amount of anchored diisocyanate or/and silanol groups in the nanotubes identified the H function as the best functional group in terms of improving the filler-PU compatibility. Transmission electron microscopy, field emission scanning electron microscopy, and atomic force microscopy analyses of the PU nanocomposites containing the three different fillers showed good TNT dispersion. The TNTHA nanotubes functionalized with both groups through the reaction between the H function already anchored on the TNTs and the A group, forming a monourea anchored group, significantly improved the mechanical and thermal properties of PU nanocomposites. POLYM. COMPOS., 40:2292-2300, 2019.
Waterborne polyurethanes (WPUs) are interesting materials for coatings when compared to solvent-based polyurethanes, once that reducing the concentration of volatile organic compounds that are harmful for human health and the environment. however, the WPU has low weathering resistance. In order to improve this behavior among others properties, inorganic fillers has been added in these systems. SiO 2 particles from various sources, mainly, from agro-industrial waste, as rice husk has attracted the scientific and technological interest. In this study, the accelerated weathering essay was performed in waterborne polyurethane (WPU)/ silica (from rice husk ash) composites in order to evaluate the thermal and physical changes in these materials. These composites were prepared by two distinct methods: in situ polymerization and blending method. The highest resistance to thermal degradation and to accelerated weathering was reached with WPU/silica composites obtained by blending method due the interactions between SiO 2 particles and the polymer matrices. Blending method for preparation WPU/silica composites proved to be a simpler and faster method, with no drawback for large scale application.
Nanocomposites of Titanates Nanotubes (TNTs) and waterborne polyurethane were prepared by physical mixture using ultra turrax disperser. TNTs were synthesized by hydrothermal method and added in different contents: 1, 3, and 5% w/w in relation to polymer weight. Films were prepared and characterized by DSC, TGA, DMA and SEM. The increase of fillers content reduced the thermal stability of DPU nanocomposites compared to pure DPU and did not modify the glass transition temperature. To mechanical properties, the addition of 3% and 5% of TNT increased the Young's modulus when compared with pure DPU, but nanocomposite with 1% of TNT presented a decrease in Young's modulus. The stress × strain curves of DPU/TNT 5% presented characteristic behavior of rigid material, with low deformation, unlike other nanocomposites and pure DPU. SEM and TGA analysis proves that the preparation method used promoted the incorporation and good filler dispersion in the polymer matrix.
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