| Waterborne polyurethanes (WPU) are non-toxic, nonflammable and do not pollute the air, and now they are replycing traditional solventborne polyurethanes. Waterborne polyurethanes have been evoked great academic and commercial research interests. However, the thermal stability, insolubility and mechanical properties of the WPU are lower than those of the organic solventborne PU and need to be improved. Using nanoparticle additives is an effective way to alter and enhance the properties of WPU. Using nanoparticle additives is an effective way to alter and enhance the properties of WPU. Various types of fillers have been introduced, and the results showed significant improvement of the performances of the nanocomposite materials such as mechanical properties, thermal stability and others.In this paper, four kinds of WPU nanocomposites have been successfully synthesized by in-situ polymerization from organically modified attapulgite(AT), kaolinite (KAO), multi-walled carbon nanotubes (MWNTs) and ferroferric oxide (Fe3O4). The structure and properties of these nanocomposites have been characterized by Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) and tensile testing, and so on. From these experiments we may come into these conclusions:1. The novel nanocomposites derived from WPU/AT nanocomposites have been successfully synthesized by situ polymerization progress. AT functionalized by chemical modification were incorporated as a crosslinker in prepolymer. The thennal and mechnical properties of WPU/AT nanocomposites were improve greatly because of introduction of AT particles. For example, the onset of the thermal degradation temperature was shifted from 234℃to 256℃and the glass transition temperature was improved from 41℃to 48℃, The Young's modulus inereased from 0.45 GPa to 0.64 GPa and the tensile strength changed from 16.8 MPa to 52.9 MPa.2. Novel nanocomposites of WPU/KAO were prepared, intercalation and in situ polymerization were used in this process. The organo-kaolinote was obtained by refining and chemically modification with solution intercalation step in order to increase the basal plane distance of the original clay. The materials were characterized by FTIR and XRD. The onset of the thermal degradation temperature was shifted from 234℃to 249℃and the glass transition temperature was improved from 41℃to 50℃, The Young's modulus inereased from 0.45 GPa to 0.97 GPa and the tensile strength changed from 16.8 MPa to 80.3 MPa.3. A new aromatic unsymmetrical ether diamine with trifluoromethyl pendent group, 1,4-(2'-trifluoromethyl-4',4"-diaminodiphenoxy)benzene (PAPB), was successfully synthesized in three steps using hydroquinone as starting material. MWNTs functionalized by mixed acid and PAPB were incorporated in prepolymer. The results indicated that the thermal properties, mechanical properties, conductive properties of the two kinds of nanocomposites were improved, but the conductive properties of the PAPB treated MWNTs nanocomposites are better. The volume resistivity and surface resistivity of the acid treated MWNTs nanocomposites were decreased by 7 and 8 orders of magnitude, the volume resistivity and surface resistivity of the PAPB treated MWNTs nanocomposites were decreased by 10 orders of magnitude.4. Oleic acid was used to modify the Fe3O4 nanoparticles to improve their compatibility with monomers. Then the WPU/Fe3O4 nanocomposites were prepared by situ polymerization progress. The results of characterizations indicated that the thermal propertie and conductive properties were obviously improved. The onset of the thermal degradation temperature was shifted from 234℃to 249℃, the volume resistivity and surface resistivity were decreased by 9 and 8 orders of magnitude.
|
PDF Full Text Request