Abstract
Polyester based polymers are extensively used in aggressive marine environments; however, inadequate data is available on the effects of the seawater on the polyester based nanocomposites mechanical properties. This paper reports the effect of seawater absorption on the mechanical properties degradation of halloysite nanoclay-polyester nanocomposites. Results confirmed that the addition of halloysite nanoclay into polyester matrix was found to increase seawater uptake and reduce mechanical properties compared to monolithic polyester. The maximum decreases in microhardness, tensile and flexural properties, and impact toughness were observed in case of 1 wt% nanoclay. The microhardness decreased from 107 HV to 41.7 HV (61% decrease). Young’s modulus decreased from 0.6 GPa to 0.4 GPa (33% decrease). The flexural modulus decreased from 0.6 GPa to 0.34 GPa (43% decrease). The impact toughness dropped from 0.71 kJ/m2to 0.48 kJ/m2(32% decrease). Interestingly, the fracture toughnessKICincreased with the addition of halloysite nanoclay due to the plasticization effect of the resin matrix. SEM images revealed the significant reduction in mechanical properties in case of 1 wt% reinforcement which is attributed to the degradation of the nanoclay-matrix interface influenced by seawater absorption and agglomeration of halloysite nanoclay.
Highlights
Thermosetting polymers are used in various industrial applications [1]
In case of 0.3 wt% reinforcement, the seawater absorption was 0.12% higher compared to monolithic polyester after 168 h of immersion
In case of 1 wt% reinforcement, the Tg value was slightly lower than nanocomposites of 0.7 wt% reinforcement (3∘C increase compared to monolithic polyester)
Summary
Thermosetting polymers are used in various industrial applications [1]. In the marine environment, complex conditions such as high salinity, high pressure, high humidity, and alkaline corrosion accelerate the degradation of polymers and greatly reduce their reliability [2]. An improvement of Young’s modulus up to 26% was reported by Gabr et al [35] as well Most of these studies agree that the incorporation of nanoclay into epoxy will increase its mechanical properties. Considering these reports, there are great prospects for nanoclay based materials since they are becoming the subject of intense global research. The authors hereby incorporated nanoclay at maximum 1 wt% reinforcement This is based on a study carried out by Sancaktar and Kuznicki [37], where dispersing at higher weight fraction (more than 1 wt% clays) is difficult and agglomerated clay deteriorates the mechanical properties of the composite materials. Asadi et al found that the optimal clay reinforcement should be around 1 wt% for their epoxy-nanotubes nanocomposites samples [38]
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