The degradation of mechanical properties in halloysite nanoclay–polyester nanocomposites exposed to diluted methanol

Abstract

The degradation of mechanical properties in halloysite nanoclay–polyester nanocomposites was studied after an exposure of 24 h in diluted methanol system by clamping test specimens across steel templates. The glass transition temperature ( Tg) and storage modulus increased steadily with the increase of halloysite nanoclays before and after diluted methanol exposure. The addition of nano-fillers was found to reduce liquid uptake by 0.6% in case of 1 wt% reinforcement compared to monolithic polyester. The mechanical properties of polyester-based nanocomposites were found to decrease as a result of diluted methanol absorption. After diluted methanol exposure, the maximum microhardness, tensile, flexural and impact toughness values were observed at 1 wt% of halloysite nanoclay. The microhardness increased from 203 to 294 HV (45% increase). The Young’s modulus increased from 0.49 to 0.83 GPa (70% increase) and the tensile strength increased from 23 to 27 MPa (17.4% increase). The impact toughness increased from 0.19 to 0.54 kJ/m2 in diluted methanol system (184% increase). Surprisingly, the fracture toughness of all types of nanocomposites was found to increase after exposing to diluted methanol due to plasticization effect. Scanning electron microscope images of the fractured surfaces of tensile specimens revealed that the methanol increased the ductility of the matrix and reduced the mechanical properties of the nanocomposites.

Effect of Short Term Water Exposure on the Mechanical Properties of Halloysite Nanotubes-Multi Layer Graphene Reinforced Polyester Nanocomposites

“…In our previous work, we studied the tensile properties of polyester nanocomposites reinforced with halloysite nanotubes. We found that the incorporation of halloysite nanotubes increased Young's modulus up to 70% compared to unfilled polyester exposed to diluted methanol [13]. Tensile strength and impact toughness increased 17.4% and 184% respectively [13].…”

“…We found that the incorporation of halloysite nanotubes increased Young's modulus up to 70% compared to unfilled polyester exposed to diluted methanol [13]. Tensile strength and impact toughness increased 17.4% and 184% respectively [13]. Other improved physical and engineering properties include fire retardancy [14,15], barrier resistance [16] and ion conductivity [12].…”

“…In particular, all polymer composites absorb moisture and the water molecules can act as a plasticizer by influencing simultaneously the fibres, the matrix and the interface, thus creating regions of poor transfer efficiency, which results in a reduction of mechanical properties [8][9][10]. Several factors are known to affect the way in which composite materials absorb water [8,11], such as temperature, fibre volume fraction, reinforcement architecture, fibre nature (permeable or impermeable), area of exposed surfaces, polarity of the molecular structure, degree of cross-linking and degree of crystallinity [10].…”

Environmental Stress Cracking Resistance of Halloysite Nanoclay-Polyester Nanocomposites

“…The use of nano-particles with polymers could enhance fracture toughness without compromising properties such as strength, modulus, thermal stability, flame retardancy and glass transition temperature [14] [15]. In nature, halloysite nanoclay is nontoxic and has tuneable release rates which make them suitable in biomedical applications [16].…”

“…In this research the polyester resins was used since it is one of the most commonly used thermosetting polymers because of their low cost and versatility [30] [31] [32] [33]. On the other hand, methanol is always a desirable choice as a transportation fuel due to its efficient combustion, ease of availability and distribution [24] [34]. The contact between polyester and methanol is likely to occur in automotive industry.…”