Table of contents
2. Analysis of the characteristics of aerogel powder coatings
3. Challenges of high humidity environment to coatings
4. Experimental exploration: aerogel powder coatings under high humidity
In the field of industrial protection and architectural decoration, the moisture-proof performance of coatings plays a key role in the life of facilities and safety of use. As a new type of high-performance coating, aerogel powder coating has become the focus of the industry in recent years due to its unique nanostructure and outstanding properties. Aerogel has an extremely low thermal conductivity and performs well in thermal insulation. Its hydrophobic properties also make the industry have high hopes for the moisture-proof performance of aerogel powder coatings in high humidity environments. However, in reality, high-humidity scenes such as coastal areas, basements, and bathrooms are complex and changeable, and the moisture-proof stability of aerogel powder coatings needs to be verified. If it can stably prevent moisture in high-humidity environments, it will bring more reliable protection solutions to many industries and greatly expand its application space.
2. Analysis of the characteristics of aerogel powder coatings
Aerogel, the core component of aerogel powder coating, has a special nanoporous structure with a porosity of over 95%. This structure effectively inhibits heat conduction, and the thermal resistance value exceeds 0.2m²・K/W, which is at the international advanced level. The thermal insulation effect of a 1mm thick aerogel coating is equivalent to that of a 10-times-thick traditional polystyrene board. In terms of moisture resistance, the internal skeleton of aerogel powder is hydrophobic, with a contact angle with water greater than 130 degrees and a hydrophobicity of ≥99%. In theory, this lays a good foundation for moisture resistance of aerogel powder coating. However, complex factors such as humidity fluctuations and long-term water vapor erosion in actual high-humidity environments may challenge the sustainability and stability of its moisture resistance.
3. Challenges of high humidity environment to coatings
High humidity environment generally refers to the condition where the relative humidity is maintained at more than 60% for a long time. In this environment, ordinary coatings face many problems. Water can easily penetrate into the coating, causing the coating to bubble or even fall off; the hydrophilic pigments or fillers in the coating swell after absorbing water, destroying the coating structure; for breathable coatings, water may also accumulate between the coating and the substrate, reducing the adhesion between the coating and the substrate. For aerogel powder coatings, water may invade its nanoporous structure under high humidity, which may not only change the thermal properties of the aerogel, but also have a negative impact on the moisture resistance, and in severe cases, cause damage to the aerogel structure.
4. Experimental exploration: aerogel powder coatings under high humidity
1.Experimental purpose
This experiment aims to deeply explore the stability of moisture-proof performance of aerogel powder coating in high humidity environment, covering the changes in coating surface state, internal microstructure evolution and dynamic changes in moisture-proof performance indicators.
2.Experimental materials and methods
Experimental materials: Select 3 representative aerogel powder coating products on the market (marked as P, Q, and R respectively), and select ordinary epoxy powder coating as a control (marked as S). The experimental substrate uniformly uses stainless steel plates of the same specifications. Before the experiment, the surface of the steel plate is strictly degreased and passivated to ensure the accuracy and consistency of the experimental results.
Experimental equipment: Use a high-precision constant temperature and humidity test chamber to accurately control temperature and humidity to simulate a complex environment. With the help of an atomic force microscope (AFM), the microstructure of the coating is observed at high resolution. Equipped with a Fourier transform infrared spectrometer (FTIR), the changes in the chemical structure of the coating under high humidity are analyzed. The advanced sessile drop contact angle meter is used to quantitatively evaluate the moisture-proof performance of the coating by measuring the contact angle between the coating surface and water.
Experimental method: Spray the four coatings evenly on the stainless steel plate and cure them according to the curing process of their respective product standards. After curing, place the test plate in a constant temperature and humidity test chamber, set the temperature to 30℃ and the relative humidity to 90% to simulate a high humidity environment. Take out the test plates in the 0th, 2nd, 4th, 6th, and 8th month after the start of the experiment, and conduct comprehensive tests on various performance indicators.
3. Experimental results and analysis
Coating surface state
From the results, it can be seen that in a high humidity environment, the surface state of ordinary epoxy powder coating S deteriorates the fastest, while aerogel powder coatings P, Q, and R have different degrees of change within 8 months, but the overall coating remains relatively intact. Among them, aerogel powder coating Q has outstanding performance in maintaining surface state, with basically no obvious changes within 4 months, and no water droplets have penetrated at 8 months. This shows that aerogel powder coatings have obvious advantages in maintaining coating surface integrity compared with ordinary epoxy powder coatings in a high humidity environment.
Aerogel powder coating P: The surface is flat and smooth at the beginning of the experiment, without abnormalities. After 2 months, there is a very slight haziness, without other defects; at 4 months, the haziness is slightly obvious, without bubbling or shedding; at 6 months, there is a slight whitening phenomenon, and the coating is intact; at 8 months, the whitening area expands, and the coating does not fall off.
Aerogel powder coating Q: The initial surface is uniform and unchanged. There was no significant change within 4 months. At 6 months, a very small amount of water droplets were attached and easy to slide off. At 8 months, the number of water droplets increased, but there was no penetration.
Aerogel powder coating R: The appearance was normal at the beginning. After 2 months, the surface was slightly darkened and there was no blistering. At 4 months, the darkened area expanded and there was no blistering. At 6 months, there was slight peeling, but no shedding. At 8 months, the peeling range increased, and the coating was still intact.
Ordinary epoxy powder coating S: The experiment started normally. After 2 months, a small amount of tiny bubbles appeared. At 4 months, the bubbles increased and some of them broke. At 6 months, the coating had serious blistering and shedding. At 8 months, it fell off over a large area and the substrate was rusted.
Internal structure of coating:
Atomic force microscopy (AFM) observations revealed that the internal structure of ordinary epoxy powder coating S was severely damaged in a high humidity environment, with a large number of voids and cracks. This was due to the disintegration of the coating structure caused by continuous water penetration. In the early stage of the experiment, the internal nanoporous structure of aerogel powder coatings P, Q, and R remained basically intact. However, by the sixth month, a small amount of water accumulated in some pores of aerogel powder coatings P and R, and the regularity of the internal structure was affected to a certain extent. In the eighth month, the internal pore structure of aerogel powder coating Q was still relatively stable, with only a few pores slightly deformed. This shows that the nanoporous structure of aerogel powder coatings can resist erosion in a high humidity environment to a certain extent, but there are differences in the structural stability of different products.
Moisture-proof performance index:
The contact angle between the coating surface and water was measured using a sessile drop contact angle meter. The larger the contact angle, the better the moisture-proof performance.
From the trend of contact angle data, the contact angle of ordinary epoxy powder coating S decreased the most, from the initial 90° to 74° after 8 months, reflecting that its moisture-proof performance deteriorated rapidly in a high humidity environment. Although the contact angles of aerogel powder coatings P, Q, and R also decreased over time, the decrease of aerogel powder coating Q was the smallest, and it still maintained a high contact angle of 126° after 8 months, further confirming that aerogel powder coating Q performed best in terms of moisture-proof performance stability.
Aerogel powder coating P: initial contact angle 131°, dropped to 127° after 2 months, 123° at 4 months, 119° at 6 months, and 115° at 8 months.
Aerogel powder coating Q: initial contact angle 135°, 132° after 2 months, 130° at 4 months, 128° at 6 months, and 126° at 8 months.
Aerogel powder coating R: initial contact angle 133°, 129° after 2 months, 125° at 4 months, 121° at 6 months, 117° at 8 months.
Ordinary epoxy powder coating S: initial contact angle 90°, 86° after 2 months, 82° at 4 months, 78° at 6 months, 74° at 8 months.
Comprehensive experiments show that in high humidity environments, aerogel powder coatings have significant moisture-proof performance advantages over ordinary epoxy powder coatings, and most of them can maintain the integrity of the coating and a certain degree of moisture-proofness for a long time. However, the performance of aerogel powder coatings of different brands and models is different. Over time, the internal structure of some products is affected, the moisture-proof index decreases, and the surface becomes hazy, white, water accumulates in the pores, and the contact angle decreases. This may be related to the purity of the aerogel, the formula additives and the production process.
Looking to the future, to expand the application of aerogel powder coatings in high humidity environments, coating companies need to increase research and development, optimize the formula and process, and improve the moisture-proof stability. In practical applications, for areas with high humidity and high moisture-proof requirements, measures such as adding a waterproof cover layer and pre-treating the substrate can be combined to ensure that the coating can play a long-term role. With the development of material technology, aerogel powder coatings are expected to make greater breakthroughs in high humidity applications and provide more reliable moisture-proof solutions for multiple industries.