Hydrothermal ageing of hydrophobic nano-calcium carbonate/epoxy nanocomposites
Introduction
Epoxy has been widely used as an adhesive, a coating, and a matrix of advanced composite materials owing to its good mechanical properties, low shrinkage, and high bonding to most materials [1]. A second phase material is often incorporated into epoxy to further improve its properties and achieve the desired properties, such as toughness and good thermal properties. Microparticles have been widely used to improve the stiffness, toughness, and thermal properties of epoxy. However, a large amount of microparticles is required to obtain the desired results, which increases the viscosity of epoxy and reduces the ease of processing. Furthermore, an increase in the microparticle content reduces the tensile strength of epoxy. To overcome these limitations of microparticle addition and to improve the tensile strength, modulus, toughness, and thermal properties of epoxy, the incorporation of nanoparticles such as nano-silica [2,3], nano-silicon carbide [1,4], carbon nano-tubes [5,6], nano-clay [1,7] and graphene [8,9] has been proposed.
Among nanoparticles, nano-calcium carbonate (NCC) is a low-cost filler with good mechanical properties. NCC exhibits low aspect ratio and large surface area, and hence shows strong interfacial interaction with epoxy. As reported by Jin and Park [10], the addition of 2–8 wt% NCC to epoxy improves its fracture toughness and impact strength without compromising its stiffness owing to the high NCC-epoxy interfacial strength. Jain et al. [11] reported that the incorporation of 4 wt% NCC into epoxy improves its rigidity, toughness, and thermal properties significantly. He et al. [12,13] incorporated 4 wt% silane-treated NCC in carbon fibre-reinforced plastic (CFRP) composites and found that the compressive strength, modulus, displacement at break, and fracture energy of the composites increased by 13.5, 6.1, 42.5, and 106.3%, respectively. Furthermore, Eskizeybek et al. [14] reported that the addition of 2 wt% NCC to CFRP composites improves their low-velocity impact properties. Yang et al. [15] evaluated the application of cubic- and rod-shaped NCCs as fillers for epoxy and found that both the types of NCCs improved the mechanical and thermal properties of epoxy. The rod-shaped NCCs showed better dispersion and mechanical and thermal properties than the cube-shaped ones.
The surface treatment of NCC is crucial for improving their dispersion and interfacial strength, leading to improved mechanical properties. He et al. [13], reported that the addition of silane-treated NCC improves the compressive strengths of unfilled cast epoxy and CFRP composites by approximately 13.5% and 14.1%, respectively, owing to its good dispersion. On the other hand, the addition of untreated NCC decreased the compressive strengths of the unfilled cast epoxy by about 8.4% and only improved the compressive strength of the unfilled CFRP composites by approximately 2.7%. Vrsaljko et al. [16] also reported that the addition of silane-treated NCC improves the tensile strength of polyurethane owing to the good NCC/polyurethane interfacial strength. Other researchers, including Shah et al. [17] reported that stearic acid-treated CC derived from eggshells shows good interfacial interaction with epoxy, and hence improves its thermal and tensile properties.
In most applications, epoxy composites are often subjected to moist environments and elevated temperatures. Epoxy can absorb humidity from the surrounding environment, and the absorbed water can have deleterious effects on its physical and mechanical properties. Therefore, the introduction of a secondary phase (either micro or nanoparticles) increases the complexity of the water uptake behaviour of epoxy, particularly the equilibrium water uptake and diffusivity. It is well-known that cement and fly ash particles increase and reduce the water uptake capability of epoxy at short ageing times, respectively. However, after prolonged ageing, both cement and fly ash increase the water uptake capability of epoxy because of their hydrolysis. Meanwhile, micron-sized CC decreases the water uptake capability of epoxy [18,19]. The addition of a small number of inert nanoparticles, such as carbon particles (expanded graphite, carbon black, multi-walled carbon nanotubes (MWCNTs), and nano-platelet graphite), increases the water uptake capability of epoxy. However, these nanoparticles decrease the diffusivity because of the tortuosity effect [20]. The addition of nano-clay, halloysite nanotubes, and nano-silicon carbide (up to 5 wt%) reduce the water uptake capability, diffusivity, and mechanical degradation of epoxy nanocomposites exposed to water [1]. The addition of up to 4 wt% silane-treated NCC also decreases the diffusivity and maximum water uptake capability of epoxy and improves its ageing flexural properties owing to the NCC barrier effect [21].
In addition to the nanoparticle content, the ageing temperature is an essential factor affecting the water uptake behaviour of epoxy. The effect of the ageing temperature on the water uptake behaviours of neat epoxy [22,23], CFRP/bismaleimide composites [24], and MWCNT/epoxy composites has been investigated [20,25]. The ageing temperature mainly increases the diffusivity of such composites, while the equilibrium water uptake capability can be increased or decreased depending on the epoxy system. Hydrophobic NCC can increase the water repellence of epoxy for application in coatings, adhesives, and composite matrices. However, to the best of our knowledge, the combined effect of the content of the hydrophobic NCC and the ageing temperature on the water absorption of epoxy has rarely been investigated. In this study, we investigated the water uptake behaviour of hydrophobic NCC/epoxy nanocomposites at various NCC contents and ageing temperatures. The tensile properties and fracture surfaces of the composites were also investigated.
Section snippets
Materials
The epoxy resin used in this study was based on diglycidyl ether bisphenol-A with an equivalent epoxy weight of 189 ± 5 g/eq, a viscosity of 13,000 MPa.s, and a density of 1.15 g/cm3. Polyaminoamide with an amine hydrogen equivalent weight of 120 g/eq, a viscosity of 12,000 MPa.s, and a density of 0.97 g/cm3 was used as the curing agent. Both were purchased from PT. Justus Kimia Raya, Indonesia. Hydrophobic NCC was purchased from RW Chem (China) with a CaCO3 content ≥ 97%, a particle size of
Water uptake
Fig. 2(a)–(c) show the water uptake capability of the NCC/epoxy nanocomposites at various NCC contents and ageing temperatures, where the square root of time was normalised with the specimen thickness. To investigate the effect of the ageing temperature on the water uptake behaviour of the nanocomposites, their water uptake capability vs. normalised ageing time plots were obtained, as shown in Fig. 2(d). The water uptake data were the average of three replicates. The nanocomposites showed a
Conclusions
The water absorption and tensile properties of the hydrophobic NCC/epoxy nanocomposites were investigated. The key findings of this study are summarised below.
- •
The water uptake behaviour of the hydrophobic NCC/epoxy nanocomposites followed the dual-stage diffusion trend; however, at higher ageing temperatures, the second-stage absorption tended to diminish. The addition of a small amount (1–5 wt%) of hydrophobic NCC increased the water uptake capability of the NCC/epoxy nanocomposites. At low
CRediT authorship contribution statement
Sugiman Sugiman: Conceptualization, Methodology, Investigation, Writing – original draft. Salman Salman: Validation, Formal analysis, Visualization. Buan Anshari: Writing – review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgement
This work was funded by the Ministry of Education, Culture, Research and Technology, Republic of Indonesia, under a world-class research scheme for the year 2021.
References (41)
- et al.
Effect of water absorption on the mechanical properties of nanoclay filled recycled cellulose fibre reinforced epoxy hybrid nanocomposites
Compos. Part A
(2013) - et al.
The mechanisms and mechanics of the toughening of epoxy polymers modified with silica nanoparticles
Polymer
(2010) - et al.
Effects of dispersion techniques of carbon nanofibers on the thermo-physical properties of epoxy nanocomposites
Compos. Sci. Technol.
(2008) - et al.
Water transport in epoxy /MWCNT composites
Eur. Polym. J.
(2013) - et al.
Organoclay-modified high performance epoxy nanocomposites
Compos. Sci. Technol.
(2005) - et al.
Mechanical properties and adhesive behavior of epoxy-graphene nanocomposites
Int. J. Adhes. Adhes.
(2018) - et al.
In situ processing of epoxy composites reinforced with graphene nanoplatelets
Compos. Sci. Technol.
(2013) - et al.
Interfacial toughness properties of trifunctional epoxy resins/calcium carbonate nanocomposites
Mater. Sci. Eng. A
(2008) - et al.
Study on thermal and mechanical properties of nano-calcium carbonate/epoxy composites
Mater. Des.
(2011) - et al.
Compressive properties of nano-calcium carbonate/epoxy and its fibre composites
Compos. Part B
(2013)
Static and dynamic mechanical responses of CaCO3 nanoparticle modified epoxy/carbon fiber nanocomposites
Compos. Part B
Effects of volume fraction on water uptake and tensile properties of epoxy filled with inorganic fillers having different reactivity to water
Mater. Today Commun.
Anomalous water diffusion in epoxy /carbon nanoparticle composites
Polym. Degrad. Stab.
Swelling of DGEBA/DDA epoxy resin during hygrothermal ageing
Polymer
Effect of temperature on moisture absorption in a bismaleimide resin and its carbon fiber composites
Polymer
Water uptake of epoxy – clay nanocomposites: experiments and model validation
Compos. Sci. Technol.
Moisture absorption and hygrothermal aging in a bismaleimide resin
Polymer
Hydrothermally resistant thermally reduced graphene oxide and multi-wall carbon nanotube based epoxy nanocomposites
Polym. Degrad. Stab.
Hydrothermal ageing of graphene/carbon nanotubes/epoxy hybrid nanocomposites
Polym. Degrad. Stab.
Water diffusion with temperature enabling predictions for sorption and transport behavior in thermoset materials
Polymer
Cited by (10)
Mechanical properties of aged nanocomposites
2024, Aging and Durability of FRP Composites and NanocompositesSynthesis of highly grafted MWCNTs with epoxy silane to improve curing, thermal and mechanical performances of epoxy nanocomposites
2024, Diamond and Related MaterialsEnhancement of saltwater ageing behavior of nanocomposites and lap joints with boron nanoparticles
2023, International Journal of Adhesion and Adhesives