Abstract:Powder coatings have been receiving attention because they are environmentally friendly. They do not contain solvents in their composition, and their components have decorative and corrosion‐protection functions, among many others. However, the presence of polymers in their composition increases the risk of combustion in adverse situations. In this context, this study aims to develop and characterize acrylic‐based powder paints with the addition of 2 wt % and 4 wt % montmorillonite clays (MMT) as Cloisite 30B … Show more
“…The burning system set-up ( Figure 2 ), according to the assembly proposed by [ 25 ], comprises the painted sample (75 mm × 140 mm) vertically fixed in a test hood chamber.…”
In the shipbuilding sector (cruises, ferries, etc.), the design and control constraints applied to improve the fire safety conditions of naval vessels are acquiring important relevance. Research activities have aimed at enhancing the fire resistance of structures and surface coatings to make ships’ working environments safer, trying to combine performance, durability and low costs. In this context, the aim of this paper is to develop and optimize flame-retardant coatings for naval applications. In particular, in an acrylic carrier, Mg(OH)2 and Al(OH)3 fillers were added to exalt the fire resistance capabilities of the coatings. Furthermore, the effect of the particle size of the hydroxides on the coatings’ fire resistance was investigated. The coatings were studied by structural (XRD), thermo-physical (TG) and morphological (SEM) characterization to evaluate their thermal stability and the damage level due to fire exposition. Specifically, fire reaction tests were applied at different fire exposure times (15 s, 30 s) to estimate the fire resistance of the proposed coatings compared to the commercial reference. The results show that the coatings based on aluminum and magnesium hydroxides exhibit favorable fire resistance. Particularly, effective performances were observed for short times of exposure to direct flames. Furthermore, the temperature monitoring of the steel alloy support during the test allowed us to evaluate the degree of insulation of the coating, highlighting a better result for the specimen filled with Mg(OH)2, making this product promising for its optimization in this context.
“…The burning system set-up ( Figure 2 ), according to the assembly proposed by [ 25 ], comprises the painted sample (75 mm × 140 mm) vertically fixed in a test hood chamber.…”
In the shipbuilding sector (cruises, ferries, etc.), the design and control constraints applied to improve the fire safety conditions of naval vessels are acquiring important relevance. Research activities have aimed at enhancing the fire resistance of structures and surface coatings to make ships’ working environments safer, trying to combine performance, durability and low costs. In this context, the aim of this paper is to develop and optimize flame-retardant coatings for naval applications. In particular, in an acrylic carrier, Mg(OH)2 and Al(OH)3 fillers were added to exalt the fire resistance capabilities of the coatings. Furthermore, the effect of the particle size of the hydroxides on the coatings’ fire resistance was investigated. The coatings were studied by structural (XRD), thermo-physical (TG) and morphological (SEM) characterization to evaluate their thermal stability and the damage level due to fire exposition. Specifically, fire reaction tests were applied at different fire exposure times (15 s, 30 s) to estimate the fire resistance of the proposed coatings compared to the commercial reference. The results show that the coatings based on aluminum and magnesium hydroxides exhibit favorable fire resistance. Particularly, effective performances were observed for short times of exposure to direct flames. Furthermore, the temperature monitoring of the steel alloy support during the test allowed us to evaluate the degree of insulation of the coating, highlighting a better result for the specimen filled with Mg(OH)2, making this product promising for its optimization in this context.
“…Simultaneously, curves do not show a sharp decline, indicating no intense volatilization of organics or matrix decomposition occurred during measurement. Assuming the sample is pure without impurity except for H 2 O, the slight decline could be ascribed to H 2 O volatilization as H 2 O generally exists in clay [34,86] and can be evaporated at 50–500°C [34,87,88]. Figure 5.TGA curves for muscovite under γ -ray irradiation at different doses.…”
Intensive study on structure transformation of muscovite single crystal under high-dose
γ
-ray irradiation is essential for its use in irradiation detection and also beneficial for mechanism cognition on defect formation within a matrix of clay used in the disposal of high-level radioactive waste (HLRW). In this work, muscovite single crystal was irradiated with Co-60
γ
ray in air at a dose rate of 54 Gy min
−1
with doses of 0–1000 kGy. Then, structure transformation and mechanism were explored by Raman spectrum, Fourier-transform infrared spectrum, X-ray diffraction, thermogravimetric analysis, CA, scanning electron microscope and atomic force microscopy. The main results show that variations in the chemical/crystalline structure are dose-dependent. Low-dose irradiation sufficiently destroyed the structure, removing Si–OH, thus declining hydrophilicity. With dose increase up to 100 kGy, CA increased from 20° to 40°. Except for hydrophilicity variation, shrink occurred in the (004) lattice plane which later recovered; the variation range at 500 kGy irradiation was 0.5% close to 0.02 Å. The main mechanisms involved were framework break and H
2
O radiolysis. Framework break results in Si–OH removal and H
2
O radiolysis results in extra OH introduction. The extra introduced OH probably results in Si–OH bond regeneration, lattice plane shrink and recovered surface hydrophilicity. The importance of framework break and H
2
O radiolysis on structure transformation is dose-dependence. At low doses, framework break seems more important while at high doses H
2
O radiolysis is important. Generally, variations in the chemical structure and surface property are nonlinear and less at high doses. This indicates using the chemical structure or surface property variation to describe irradiation is correct at low doses but not at high doses. This finding is meaningful for realizing whether muscovite is suitable for detecting high-dose irradiation or not, and mechanism exploration is efficient for identifying the procedure for defect formation within the matrix of clay used in disposal HLRW in practice.
“…Conventionally, extrusion has been the mixing method for homogenizing organic powder coatings [ 90 , 91 , 92 , 93 , 94 ]. Grigoriev et al [ 89 ] used twin-screw micro extruder for homogenizing epoxy based nanocomposite powders.…”
Epoxy composite coating systems generally find their usage in applications such as, fluid handling systems to protect components from corrosive media. However, their use in demanding tribological applications such as, in sliding components of machines, are known to be limited. This is often attributed to their low load bearing capacity combined with poor thermal stability under severe p-v regimes. Researchers have tried to enhance the tribological properties of the epoxy coatings using a combination of several types of micro/nano sized fillers to produce composite or hybrid composite coatings. Hence, this review paper aims to focus on the recent advances made in developing the epoxy coating systems. Special attention would be paid to the types and properties of nano-fillers that have been commonly used to develop these coatings, different dispersion techniques adopted and the effects that each of these fillers (and their combinations) have on the tribological properties of these coatings.
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