Effect of the dispersive method in the preparation of the polyurethane/hydrotalcite nanocomposites by in situ polymerization

摘要

The dispersions were prepared in the proportion of 1 g LDH to every 100 ml of 1,6-hexamethylenediisocyanate employing four different methodologies. The FTIR results of the dispersions confirmed the presence of monomer in the clay interlayer space, for all methods studied. The XRD analysis showed that the presence of isocyanate contributed to a small structural disorder. Any significant differences between the experimental procedures adopted were observed in TGA results, whereas visual analysis showed that methodology combining ultraturrax and ultrasound bath (TBT) was more effective for dispersion and incorporation of the monomer remaining stable for about a month. The dispersions studied were used in the synthesis of polyurethane nanocomposite. The in situ polymerization step had as objective favor the dispersion of nanofiller during the growth of the polymer chains. The polyurethane obtained was confirmed by the presence of characteristic bands of the urethane group in the FTIR spectrum. The diffraction patterns indicated that in situ polymerization contributed to the structural disorder of the nanocomposites. The strain sweep was carried out by rubber process analyzer (RPA), the lowest values of Payne effect (G_0 - G_∞) were to TBT and T methodologies suggesting a lower filler-filler interaction. The results of the dynamic mechanical thermal analysis (DMTA) showed significant differences that were associated with the dispersion method adopted and also a stoichiometry imbalance due to the interactions of the isocyanate with the hydroxyl groups of the hydrotalcite and/or water molecules within interlayer space and/or air moisture. SEM micrographs revealed better dispersion in the clay polyurethane nanocomposites, whose nanofiller was previously dispersed in the isocyanate monomer.