Barrier, thermal and mechanical properties of polyurethane-modified clay nanocomposites for thermal insulation material

摘要

In this thesis, the effect of modification through transition metal ions (TMI) on montmorillonite (MMT) clay that was incorporated into thermoplastic polyurethane (PU) was discussed. The TMI modification was intended to achieve a good dispersion of the clay into PU with fewer agglomerates. The modification of the MMT clay was carried out using Copper (II) Chloride and Iron (III) Chloride. The fabrication of the nanocomposites was done via solution intercalation method by employing chloroform as the solvent. The clay content was varied at three different clay loadings (1 to 3 weight percentage). The existences of the TMIs on the modified clay were confirmed through Inductive Couple Plasma Mass Spectrometry (ICP-MS) whereas its morphological structure was tested through Field Emission Scanning Electron Microscope (FESEM) and X-Ray Diffraction (XRD). The morphology of PU-MMT nanocomposites was determined through Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), XRD and FESEM. The mechanical properties of the nanocomposites were studied through its tensile stress and elongation at break whereas its thermal properties were analysed using Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and thermal conduction. Gas and water permeation through the nanocomposites was employed to investigate the nanocomposite’s barrier properties. The modification process was proved successful as high amount of copper and iron ions were detected in the ICP-MS and even distribution of the clay was obtained in FESEM. XRD data with higher d-spacing values was obtained for PU with modified clay which suggests that a good intercalated structure has been achieved. SEM micrographs illustrated lesser agglomerates in PU with modified clay nanocomposites due to the TMI modification that enables an even distribution of the clay into PU. The homogeneous dispersion of the clay strengthened the structure of PU which led to a remarkable improvement in its mechanical properties. The highest increase in tensile stress was obtained in 2% PU-MMT Cu which showed 148% hike in its 1% and 3% clay loading. The thermal stability was also improved in the modified nanocomposites due to its higher thermal degradation temperature however there were no significant effect of the clay on the melting temperature of the nanocomposites. Thermal conductivity of the PU nanocomposites decreased with increasing clay loading which makes it a suitable thermal insulation material. Both the gas and water permeability decreased in PU with modified clay nanocomposites due to the formation of the tortuous path in its matrix. The highest significant decrease in the gas permeation analysis amounted to 68% in 3% PU-MMT Fe and 40 times decrement in water permeation coefficients were obtianed in 1% PU-MMT Fe. The results obtained showed that the incorporation of modified clay into PU has brought significant improvements in its properties.