Mechanical properties of polyester nano-composites exposed to liquid media

Saharudin, Mohd (2017) Mechanical properties of polyester nano-composites exposed to liquid media. Doctoral thesis, Northumbria University.

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Abstract

Halloysite nanotubes (HNTs) offer excellent improvements in wide range of physical and engineering properties at low filler content. Due to their outstanding properties such as large aspect ratio, high surface area, flame retardant and good optical clarity, HNTs polymer nanocomposites are widely used in automotive, coating, packaging and medical devices. The results showed that the incorporation of halloysite nanotubes (HNTs) into polyester significantly improved dynamic mechanical properties of the nanocomposites including the glass transition temperature (Tg), storage moduli, microhardness, tensile properties, flexural properties and impact toughness. The mechanical properties of polyester-based nanocomposites were degraded after water-methanol exposure. The maximum microhardness, tensile, flexural and impact toughness values were measured at 1 wt% of HNTs reinforcement and the results also showed that HNTs improved the liquid barrier properties of polymers due to an increase in the tortuosity path. Several deterioration effects are likely to take place concurrently after seawater exposure. Plasticization reduced the mechanical properties of the nanocomposites and microorganisms such as microbes entered through microvoids to further increase the deterioration in mechanical properties of the nanocomposites. Microbes can cause chemical degradation and the breakage of hydrocarbons using seawater molecules. Nanocomposite biodegradation is highly undesirable for material integrity as these are mostly used in structural designs of marine applications. Structural damage may result in premature weakening which is often translated into system failure and enormous economic losses. The influence of short-term water absorption on the mechanical properties of HNTs-multi layer graphene-reinforced polyester hybrid nanocomposites was also investigated. After short-term water exposure, the maximum microhardness, tensile, flexural and impact toughness values were observed in case of polyester-multi-layer graphene (MLG) nanocomposites. It was also found that synergistic effects were not effective at a concentration of 0.1 wt % in producing considerable improvement in the mechanical properties of the hybrid nanocomposites.

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