| Popis: |
Carbon allotropes such as carbon nanotubes, graphene, and carbon black based polymer composites have attracted a huge interest because of their exceptional combination of properties such as lightweight, higher electrical, and mechanical properties over polymers; particularly, their electrical conductivity that falls between semi-conducting and conducting materials is a great interest of ‘Clean energy and Savings’ applications such as electro-magnetic shielding materials, actuators, solar panel compartments, etc. This thesis work majorly covers fabrication and characterisation of five novel polymer nano/microcomposites. Separate sets of single wall carbon nanotubes (SWCNT)-poly (vinyl alcohol) (PVA) and COOH functionalised multi wall carbon nanotubes (MWCNT)-PVA nanocomposite films of 50–80 μm were fabricated through solution-cast; similarly, another two sets adding a cross-linking agent, glutaraldehyde (GA) were also fabricated. These four sets were evaluated for alternating current-electrical conductivity, nano-elastic modulus, nano-hardness, and water resistance properties. At maximum content, 2 wt. % of CNT in PVA/GA-PVA, all nanocomposites showed 11 orders of magnitude improvement in electrical conductivity over blank PVA; 13 and 2.2-folds (SWCNT) and 7 and 5-folds (MWCNT) improvement in nano-elastic modulus; 24 and 2.5-folds (SWCNT), and 6.4 and 6-folds (MWCNT) improvement in nano-hardness were observed. It is noted that most of these findings are novel. FTIR studies confirmed presence of low degree of cross-linking between PVA & GA, which also continued with no significant changes upon continuous additions of both SWCNT and MWCNT in varied quantities. Water resistance of CNT-PVA is improved significantly with the presence of GA. Raman investigation revealed changes in D (disorder) and G (graphite) bands of CNTs due to interaction of wall of CNTs with PVA/GA-PVA. Morphological study by SEM and TEM highlighted excellent wetting of CNTs by PVA and CNT found in both PVA types as uniformly distributed bundles. The remaining is activated charcoal (AC)-epoxy microcomposite, that was fabricated through casting technique and then cured at 60 °C and 120 °C, separately; mechanical properties such as Young’s modulus, UTS, and microhardness of the both were characterised and found over blank epoxy; whereas, strain to failure and toughness were greatly improved due to the strength being maintained at the same level as the neat epoxy. Chemical characterisation with FTIR and Raman confirmed the composite formation and chemical interaction between AC and epoxy. A couple of limited investigations on PMMA reinforced separately with SWCNT and AC showed existence of networks that conduct electrical conductivity in diametrically fractured SWCNT-PMMA and improved thermal stability for AC-PMMA above 260 °C as compared with blank PMMA, respectively; further study with FTIR and Raman confirmed chemical interactions between SWCNT and PMMA, and AC and PMMA. |
