Hydrophobicity of Polysilazane Coatings

Polysilazane – A Resin Unlike Any Other

In the field of contemporary materials science, polysilazane, as a ceramic precursor with a silicon-nitrogen alternating framework structure, is increasingly demonstrating its outstanding performance potential and wide range of applications. In recent years, this material has gradually developed into an important component of high-performance resin systems, widely used in vehicle coatings, exterior wall protection for commercial and residential buildings, equipment protection in industrial plants, and many other fields. Compared with other resin materials, polysilazane not only possesses excellent surface hardness and scratch resistance, but its anti-aging and anti-corrosion capabilities are also comparable to or even surpass those of traditional polysiloxanes and fluoropolymers. Furthermore, it also has additional functions such as easy cleaning and anti-graffiti properties, demonstrating multi-dimensional performance advantages.

From a chemical structure perspective, polysilazane can be mainly divided into two categories: inorganic polysilazane and organic polysilazane. The former typically exhibits a fully inorganic silicon-nitrogen backbone, possessing higher thermal stability and ablation resistance; the latter introduces organic side groups into the silicon-nitrogen backbone, thereby maintaining ceramic properties while endowing the material with better flexibility and solubility in organic solvents, broadening its processing and application scenarios. Globally, Merck is one of the few manufacturers capable of commercially producing a full range of organic and inorganic polysilazanes, and its products are recognized by the market for their stable quality and reliable performance. This article will take Merck's Durrazane® 1500, also known as our LS-PA150 organic polysilazane, as an example to deeply analyze the key performance and practical application value of this type of resin.

Excellent Surface Hardness and Scratch Resistance

After curing, polysilazane coatings can form a dense three-dimensional network structure, a characteristic that gives them excellent surface hardness, scratch resistance, and abrasion resistance. Experimental data shows that coatings made with organopolysilazane achieve a pencil hardness of 5H after seven days of curing at room temperature. In contrast, traditional methyl silicone resin coatings only achieve a hardness of B under the same curing conditions, demonstrating a significant performance difference. To further verify its scratch resistance, researchers conducted comparative tests on metal substrates coated with colored paint and polyurethane varnish: the upper half of the substrate was additionally coated with a polysilazane hard coating, while the lower half remained uncoated. After 500 standardized scratch cycles, the area covered with the polysilazane coating remained intact without significant damage; while the unprotected area showed clear scratches after only 10 cycles. This result directly demonstrates the superior ability of polysilazane to protect substrates from mechanical damage.

Besides its use as a transparent hard coating, polysilazane can also be used as a functional resin in colored coating systems to improve the overall scratch resistance of the coating. Related tests show that adding polysilazane resin to white paint containing titanium dioxide significantly enhances its scratch resistance. In scratch tests under identical conditions, the white coating containing polysilazane performed exceptionally well, showing almost no surface damage; while the control group, without polysilazane, exhibited severe scratches. This demonstrates that polysilazane is not only suitable for surface protection, but also, when incorporated as a resin component into paint systems, can effectively improve the overall performance of coatings, providing long-lasting aesthetic protection for various buildings, industrial equipment, and transportation vehicles.

Excellent Cleaning and Anti-Graffiti Properties

Coatings based on organopolysilazane exhibit significant hydrophobic properties, with a water contact angle typically stable between 95° and 105°, classifying them as low surface energy materials. This characteristic enables them to effectively resist the adhesion of various contaminants and demonstrates excellent non-stick, anti-graffiti, and easy-to-clean properties. In practical application tests, researchers used three different colored permanent markers to draw lines on an area extending from the uncoated surface to the polysilazane-coated surface. The results showed that the surface coated with polysilazane exhibited a significant ink repulsion effect; the ink could be easily wiped away with a dry cloth without leaving any trace. In contrast, the untreated surface showed severe ink penetration, making it difficult to remove using conventional cleaning methods.

To systematically evaluate its anti-graffiti level, we conducted a series of tests according to the ASTM D6578 standard. The graffiti media used in the tests included green Eddie 8400 CD/DVD/BD markers, black Eddie 3000 permanent markers, blue crayons, and red "Rico Design" acrylic spray paint. According to the anti-graffiti performance grading system: Level 1 means it can be removed with a dry cloth; Level 2 requires a neutral detergent solution (such as Hartmann Baktolin® sensitive wash); Level 3 requires a limonene-based cleaner (such as 3M Industrial Cleaner - IC Cleaner Spray); Level 4 requires isopropyl alcohol; Level 5 requires a strong solvent such as methyl ethyl ketone; if marked as N.C., it indicates it is not removable. The test results show that the polysilazane coating based on Durazane® 1500, also known as our LS-PA150, can restore the original appearance in most cases with only Level 1-2 cleaning methods, fully demonstrating its excellent anti-graffiti performance. For this reason, Merck's polysilazane materials have been widely used in projects such as the protection of German railway train shells, maintenance of station facilities, and protection of commercial building facades, with remarkable results.