Processing, structure and thermo-mechanical properties of reclaimed nanoclay, and its application in polyamide 6 and low-density polyethylene nanocomposites

Oil-based mud (OBM) wastes are generated every year all over the world, and remain a serious challenge for the oil and gas industry. The potential solution for this global problem is either to destroy these hazardous chemicals completely - a significant challenge - or to use/utilise them for beneficial applications. Therefore, the aim of this thesis is to develop a detailed understanding of the synergistic effects of different clay minerals that exist in OBM waste, in influencing structural, morphological, rheological and thermo-mechanical behaviour of LDPE and PA6 nanocomposite materials. The thesis begins with a critical literature review, covering oil-based mud (OBM) waste treatments, polymer nanocomposites and their manufacturing, thermal degradation behaviour and mechanical performance. This is followed by a detailed characterisation of OBM waste to determine elemental composition, and structural and thermal properties. To evaluate their performance as a filler in polymer composites, both mechanical and thermal properties of polyamide 6 (PA6) and low-density polyethylene (LDPE)-based nanocomposites were manufactured through the process of melt compounding, followed by injection and compression moulding, with different amounts (wt%) of OBM fillers (OBMFs). The study on thermal degradation of LDPE/OBM slurry shows that the nanocomposites with higher percentage filler contents (in case of 7.5 and 10 wt%) decreased the heat capacity value by 33% and 17% in LDPE respectively. OBM slurry shows superior improvements in storage modulus, loss modulus and damping property (tan d) in LDPE matrix, compared to those of LDPE/MMT nanocomposites. However, the study shows a decrease of tensile and flexural properties for the LDPE/OBM slurry nanocomposites. The follow-up study focused on thermally-treated OBM waste in powder form and their effect on thermo-mechanical properties of LDPE matrix. It was observed that OBMFs was compatible with LDPE matrix, which led to a strong interfacial interaction between the clay layers and polymer. Further, the clay minerals present in OBMFs formed chemical bonds in microstructure within the nanocomposites. The OBMFs (10wt %)/LDPE nanocomposite produced the highest onset degradation temperature at 5 wt% loss (TD5%) and 50 wt% loss (TD50%) among the nanocomposites. An enhancement of mechanical properties of composites was identified, which showed a gain of 14% Young's modulus and 18% increase on tensile strength at 10 wt% OBMFs loading, compared to those properties of neat LDPE. The crystallinity and thermal degradation behaviours of polyamide 6/oil-based mud fillers (PA6/OBMFs) nanocomposites were also investigated. TGA indicates the onset decomposition temperature of D1/2 (half-decomposition) for PA6 with 10 wt% of OBMFs is 16oC higher than that of PA6 and also registered a 47% specific heat capacity reduction. The Youngs' moduli were increased by 42% and 35% in PA6 with 7.5 and 10 wt% OBMFs nanocomposites respectively, whereas the tensile strengths were increased by 24% and 16% in PA6 with 7.5 and 10 wt% OBMFs nanocomposites respectively. The flexural strength increased by 26% with the addition of OBMFs from 0 to 10 wt% in PA6 nanocomposites. In conclusion, a loading amount of 10 wt% OBMFs on both polymer matrices was found to be the most desirable enhanced mechanical and thermal stability properties. However, 10 wt% OBMFs showed increased storage modulus and drop in loss modulus in both LDPE and PA6 matrices, leading to the conclusion that OBMFs improves thermo-mechanical properties in LDPE and PA6 matrices in dynamic condition. Considering the findings from this study, this material shows high potential for low-cost structural insulation materials as an alternative to conventional (more expensive) materials. All the proposed treatment techniques presented in the literature and in industrial practices dealing with OBM waste, passes pollution from one stage to another. This study explores the opportunity to utilise the useful reclaimed clay minerals from OBM waste as filler in nanocomposite manufacturing.